WEBVTT

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Mark Kushner: I think it's, it's really difficult.

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Mark Kushner: Yeah, right?

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Mark Kushner: Alright, really good views. Powder Tower…

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Mark Kushner: This thing on? I don't know how the… Total battery? Hello? Hello? I don't even know. Thanks.

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Mark Kushner: All right, I think we're ready to start. Dear friends of Plasma Science, it's my great pleasure to introduce today's speaker, Dr. Michael Hesse from the Naval Postgraduate School in Monterey, California.

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Mark Kushner: I had to step out from another meeting to come to here, and the comment when I was leaving was, well, Michael Hesse doesn't need an introduction. But I'm gonna give one anyway.

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Mark Kushner: So Michael got his PhD from, Rural University in Bochum, in his native Germany in 1988.

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Mark Kushner: After that, he was a post-doctoral fellow at Los Alamos National Laboratory in New Mexico. He then joined the NASA Goddard Space Flight Center, and during 1999-1912,

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Mark Kushner: Through 2012, Michael was the founding director of the Community Coordinated Modeling Center, or CCMC as we know it today.

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Mark Kushner: That center provides models and model results for, not only modeling experts, but those who,

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Mark Kushner: work in problems of space, space physics in different realms, and want to use models, and so it's proven to be a very valuable tool, so I think we all very much appreciate the work that Michael did there.

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Mark Kushner: CCMC has also become broadly the home of NASA space weather activities, which, of course, are increasing in importance as we see men and women orbiting the moon once again.

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Mark Kushner: He,

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Mark Kushner: Following his career at NASA Goddard, he served 4 years as the Heliophysics Science Division Director at Goddard, and then, spent 3 years at the University of Bergen in Norway, where he led the Geomagnetic Expert Service Center, a multinational consortium providing space weather services to the European Space Agency this time.

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Mark Kushner: Upon returning to the U.S, he served as the Director of Science Directorate at NASA's Ames Research Center before joining the Naval Postgraduate School just last year.

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Mark Kushner: So I first met Michael, in my very, very first conference trip to a magnetic, appropriately magnetic reconnection workshop in Potsdam, then East Germany, in 1988.

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Mark Kushner: At that time, Michael had already established a strong record of studying magnetic reconnection.

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Mark Kushner: using numerical models. And over the course of his career, he has published over 300, scientific articles, many of which relate to, various aspects of magnetic reconnection,

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Mark Kushner: and, various problems in space plasma physics, using, numerical models that range from, MHD to kinetic and, approaches that cover both analytical considerations and numerical simulations, as well as observations.

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Mark Kushner: Michael's contributions have been significant, both for the basic understanding of the behavior of current sheets in the magnetotail, and the application of those theories to space weather problems.

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Mark Kushner: His contributions have been widely recognized in the community. He's a fellow of the American Geophysical Union, of which,

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Mark Kushner: Which is a, select group of only 2% of the membership at any given time.

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Mark Kushner: He's a member of Academia Europe, and has received several, awards, including NASA Outstanding Leadership Medal, NASA Distinguished Service Medal, and AGU Space Weather and Nonlinear Waves and Processes Prize.

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Mark Kushner: Please, join me in welcoming Dr. Michael Hess.

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Mark Kushner: Well, thank you, Tuya, for those incredibly kind words.

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Mark Kushner: Let me… let me also thank you, thank Mark, and…

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Mark Kushner: Julia and Tuya and everybody else was involved in getting me here. It's a real pleasure to be here at a place that, quite evidently, values plasma physics very highly.

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Mark Kushner: Which is exactly as highly as it should be valued, and a place that has so many, so many old friends that I've already had an opportunity to chat with, throughout the day, and perhaps one day was not enough. I'll learn next time I'll be here a little bit longer, okay? So…

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Mark Kushner: So it's a…

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Mark Kushner: It's a great opportunity for me to basically meet the charge that Mark gave me, which is to give you an introduction to what magnetic connection is. So…

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Mark Kushner: We had a… we had a very nice space mission here called MMS that,

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Mark Kushner: I worked on also for many years that, basically developed

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Mark Kushner: new knowledge of the basic foundation of reconnection. What I'm going to do now, here in this presentation, is walk you through the basic idea of reconnection. For those of you who are not familiar with it, for those of you who are, I apologize to

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Mark Kushner: hopefully not bore you too much, but then we get into a little bit more of the physical foundation, which may be… may be new to more of you. So, without further ado.

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Mark Kushner: So I'm going to talk about what it is, first of all, and then also motivate a little bit why it's important. You heard about space weather.

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Mark Kushner: There's very little space weather or reconnection, that's my belief, at least, and I think many would agree. Then, before we flew MMS, we had some expectations of what we should be seeing once we get that mission, and we'll talk about that, and what, some examples of that.

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Mark Kushner: some key examples of that. And then what we actually found once that mission flew, and…

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Mark Kushner: And we look a little bit on open questions and future research, we'll sum up, and hopefully that will stay within time. Do my best. So a lot of people involved here, colleagues, former postdocs and so on, and grad students, and even undergrad students who played a role in this.

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Mark Kushner: all of them are listed there, and then there's all MMS team, of course. So…

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Mark Kushner: Let's… let's talk about reconnections. So you're all… you're a plasma physicists at some level, and you probably believe me when I say space is not a vacuum, it's largely a class.

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Mark Kushner: And cosmos, as you well know, is the dynamic shape by the interaction of electromagnetic fields with charged particles.

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Mark Kushner: And there are rules governing such interactions, you know that. Maxwell's equations are the rule, but we're going to talk about a different one, and then we talk about breaking that, because it's so much fun to break rules.

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Mark Kushner: That's going to lead us to the reconnection discussion. So, let's do that.

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Mark Kushner: Start with a rule.

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Mark Kushner: So, for those of you who like… like MHD, you're very familiar with that.

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Mark Kushner: Throughout space, most of space, Not all of it, but most of it.

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Mark Kushner: the plasma and the magnetic fields kind of behave like a magneto fluid, like an MHD fluid, so fairly simple, waves, relatively easily predictable on the large scales.

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Mark Kushner: You know, and what that means in such a situation.

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Mark Kushner: Is that if you have two plasma mass elements, this could be blobs of ions or electrons or so, and you can treat those individually, that at some point, connected by a magnetic field line, gear, and then they move.

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Mark Kushner: Okay.

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Mark Kushner: some velocity. S is a species. As I said, you can make this for ions or electrons.

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Mark Kushner: And then at some neater time.

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Mark Kushner: You find that no matter which ones you started with that were initially connected, they're still connected by a magnetic field line afterwards, okay?

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Mark Kushner: That's… that's a condition that holds in most of space.

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Mark Kushner: Right? It holds in what we call ideal MHD, and we'll get to that in a minute.

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Mark Kushner: And we call that frozen influx, or line conservation. The experts of you know that those things are not exactly the same, but for the sake of the discussion, let's call that,

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Mark Kushner: the scene, and it preserves topology, you know? If you have

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Mark Kushner: one field line and its entity mapped by plasma elements, and you follow that around, follow those plasma elements around, you still get a field line, so you preserve the topology of the magnetic field, quite simply. Okay?

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Mark Kushner: And that is a situation we There's no reconnection, that was.

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Mark Kushner: That may sound kind of… trivial.

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Mark Kushner: But that condition has some pretty dramatic consequences.

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Mark Kushner: So let's look at Zach a little bit.

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Mark Kushner: Oh yeah, forgot to mention that.

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Mark Kushner: So you can convince yourself, I'm not going to prove that to you.

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Mark Kushner: But if this condition holds, E plus V cross B equal to 0,

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Mark Kushner: V is the velocity of these plasma elements, then this condition holds, okay? It's not… the reverse isn't true, you can have something on the right-hand side, a few things that preserve it too, but… but for the sake of the discussion, we won't talk about that, at least not yet.

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Mark Kushner: Okay, so… So if we have that, then this is true.

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Mark Kushner: So if we're going to violate that, something has to be on the right-hand side. We'll get to that in a minute. Okay, so here's…

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Mark Kushner: A lot of us' favorite playground, the magnetosphere.

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Mark Kushner: It's really that beautiful, I assure you. So you got the… the sun is on the left here somewhere, okay? You get the magnetic field of the Earth, which is compressed at the day side. Here's… it's, like, distended into a long tail on the night side with the current sheet in the middle.

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Mark Kushner: Okay, you've got magnetic field and plasma streaming at it, at, super critical speeds here, and then you get a bow shock in the middle here before, before the magnetosphere. Then you get interaction with this magnetic field.

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Mark Kushner: and the geomagnetic field. So…

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Mark Kushner: Let's say we have two of these plasma elements.

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Mark Kushner: They sit on a field line here.

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Mark Kushner: Okay.

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Mark Kushner: I come from the sun.

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Mark Kushner: And then… A little bit later, they sit like that.

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Mark Kushner: This one sits inside the magnetosphere, this one sits on this field, and that is only connected to the Earth on one end.

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Mark Kushner: And you can see here they were magnetically connected. Here, they're quite evidently not magnetically connected anymore.

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Mark Kushner: So… If our condition holds, This can't happen.

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Mark Kushner: Okay.

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Mark Kushner: Now, we do know this happens.

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Mark Kushner: Okay, this does actually happen. So we find plasma from the solar wind inside the magnetosphere all the time, so that condition cannot hold.

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Mark Kushner: everywhere.

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Mark Kushner: So, okay.

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Mark Kushner: What you do, if you know…

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Mark Kushner: you have to violate that condition. You define, hey, we violate that condition by something, Okay.

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Mark Kushner: So we call… define magnetic connection, a process by which plasma elements changes connection through a localized, non-ideal field. And that definition, by the way, is much more general than the scenario that I'm talking to you about now, but again, for simplicity, I'm going to just focus on this one.

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Mark Kushner: So, in that scenario that we had before, We want that, right?

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Mark Kushner: Here's… this is a somewhat abstract depiction of what's coming from the sun. This is a geomagnetic field here, and then something magic happens here, and these things can lose their magnetic connection.

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Mark Kushner: Only there, not everywhere else. I'm maintaining.

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Mark Kushner: Okay.

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Mark Kushner: So… And, obviously, that would… if the condition

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Mark Kushner: E plus V cos B equal to 0 prevents that from happening. We have to have something on the right-hand side.

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Mark Kushner: We're gonna talk about what that is in a little bit.

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Mark Kushner: And, the key question is, what's going on in here?

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Mark Kushner: what is happening? And we're going to see in a minute that this is a multi-scale problem.

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Mark Kushner: Okay, this region here is way, way, way smaller than all the other parts of this system that are affected by this reconnection process.

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Mark Kushner: And we can really only measure that in space, because of the scale sizes. So…

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Mark Kushner: So if we do that… The connection opens the magnetosphere, and then our

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Mark Kushner: Little plasma blob has no problems getting in there.

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Mark Kushner: But the question still remains, Okay, I mean, this is a very simplified introduction, on the…

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Mark Kushner: concept of reconnection that we had as important before the MMS mission, because we had no clue

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Mark Kushner: No clue what happens here, for example, what happens on the nights.

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Mark Kushner: Okay, we're gonna get to that.

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Mark Kushner: But before we get to that,

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Mark Kushner: I love preaching to the choir, at least some of you are the choir. Some others, hopefully, convinced and joined the choir afterwards. Why is reconnection important? I'll just give you a few examples, very quickly.

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Mark Kushner: First, a little… Simulation that I did some years ago here.

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Mark Kushner: Here we have a current sheet in the middle, we have a magnetic energy reservoir here, okay, on both ends, magnetic field directed that way, it's directed the other way, so we have a current sheet in the middle.

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Mark Kushner: And this currently gets disrupted by some magic process here. Okay, and then these plasma elements get shut out, just like we had in our cartoon.

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Mark Kushner: But at the same time, we have flows here, and we have no magnetic field component that's weaker than this one.

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Mark Kushner: And we have internal heating. And you can see this here, this is actually done… taken from the simulation. Time is shown here. And we integrate the energy contributions to

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Mark Kushner: out of that simulation, there's a particle cell simulation, with the magnetic energy here that drops from here to here, okay? It drops.

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Mark Kushner: And the kinetic energy goes up, so we have stuff flying out to the left and to the right. Okay, that's the bulk kinetic energy of the plasma, not the individual kinetic energy of the particles. It's the average kinetic energy. And then we have the internal energy, that's heat, like a heater.

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Mark Kushner: the atmosphere, okay, that increases, and there's actually more energy going into heat than into kinetic energy. That's something that most people

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Mark Kushner: who don't work on reconnection don't appreciate, okay? But the key point that I want to make, it's an energy conversion process, and it takes magnetic energy and converts it to particle energy, both in form of kinetic belt motion and internal energy.

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Mark Kushner: So that can do a lot of stuff, not just transport, which you see there in terms of our little yellow blobs, but it can also do energy conversion, and that, therefore, can power things.

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Mark Kushner: So one thing it's believed to power is… are these emissions here that you see from the Crab Nebula.

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Mark Kushner: Yeah, that apparently I'm not an astrophysicist, okay, maybe some of you as an astrophysics physicists, and you can comment on this better, that, were believed to be caused by shocks.

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Mark Kushner: But modern understanding says these are much more likely explainable, the spectra that you see here, by the particle acceleration that you get as a result of a reconnection process. So the belief is in the Crab Nebula here that the emissions that you're seeing there are caused by reconnection.

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Mark Kushner: There are many, many other astrophysical examples. Don't want to go through those.

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Mark Kushner: When I go here, this is closer to home.

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Mark Kushner: Okay, this is a permanence eruption.

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Mark Kushner: You only play once? Huh.

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Mark Kushner: Sorry, I'd fix that, sorry about that. Let me play one more time.

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Mark Kushner: It's even more annoying if it doesn't stop… okay, here's…

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Mark Kushner: There you go. So, a permanence, which is now gone, forgive me for that, is a magnetic structure that's suspended over the sun that has some mass in it, and that's why it's darker.

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Mark Kushner: Okay? It's basically… and then you have stored energy here in the

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Mark Kushner: in the surrounding atmosphere, magnetic energy, through the convective fields and the solar corona… in the photosphere, they bring magnetic fields together, they store them, and then all of a sudden, this can erupt and fly out into space, okay? There are also other eruptions that are not prominence-related, that are similarly related to stored magnetic energy suddenly explosively being released.

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Mark Kushner: And shooting these big things out into space, and… and…

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Mark Kushner: Remember, this is, like, 10 million aircraft carriers worth of mass flying out there at a couple of thousand kilometers per second or so. Now, they're spread out in space, so you don't duck and cover because aircraft carriers are going to rain down on you, but they still have remarkable effects on anything that's in their way, including the magnetosphere.

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Mark Kushner: Here's what, the magnetosphere does, and this is actually a space for a modeling framework simulation, TAMAS.

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Mark Kushner: You should love this. Okay. Here, impact of a CME onto the structure, but it erodes, it's a magnetic field on the day side. I always like anybody who's a Trekkie here, like I am, you know, this is our magnetic shield, okay? The Earth has a shield, it protects us.

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Mark Kushner: From harmful radiation that our space environment is throwing at us, and

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Mark Kushner: But what… what this interaction does, this stops, no? It wasn't supposed to do that.

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Mark Kushner: Go back.

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Mark Kushner: So…

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Mark Kushner: You see, this is our normal magnetic shield, and then gets eroded, and then you see activity on the night side also, reconnection-type activity, where the fields that you…

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Mark Kushner: It's not the best visualization. It gets stored up and down, gets disrupted and propagated this way. Yeah, so reconnection is a key.

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Mark Kushner: contributor to the way the solar wind… the solar wind impacts the magnetosphere, and then how the energy gets transported inside of the magnetosphere. And it powers all these fine things, like radiation, aurora, you know, atmospheric heating, and all these wonderful things that we all call space weather.

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Mark Kushner: And by and large, they're not the ones that you like to have.

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Mark Kushner: astronauts going to the moon, okay?

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Mark Kushner: So… Good idea to try to understand them.

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Mark Kushner: I just want to point out that reconnection is a multi-scale process. That is something that we expected, at least based on theory and modeling.

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Mark Kushner: So this is…

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Mark Kushner: And I swear I didn't do that because I'm here, but this is another picture of the… of a simulation of the space modeling framework, but taken from the CCMC this time.

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Mark Kushner: So here's the day side again. I need a pause. The connection occurs here, in this… in this little region. I got about 100,000 kilometers across here.

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Mark Kushner: You see, things change on that scale, and if you blow it up, you get something that's about 500 kilometers across, and if you blow that up, you get a current sheet that's less than 10 kilometers across.

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Mark Kushner: And the process, it kind of,

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Mark Kushner: So what you have is clear links of 1 to 5 kilometers that

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Mark Kushner: enable effects on a 100,000 kilometer scale. So we have several orders of magnitude scale difference here, which makes this a particularly challenging process to study, but also particularly interesting.

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Mark Kushner: So, this is…

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Mark Kushner: the electron diffusion region, basically this magic region where the electrons, violate E plus V cross B over 0. You can see how tiny that is, and finding that is

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Mark Kushner: It's very, very difficult. But we needed to do that in order to get an insight on what's going on in the region.

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Mark Kushner: So I'm going to tell you a little bit about… well, I'm showing a couple more examples, but I want to tell you a little bit about

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Mark Kushner: what we expected to go in that region, go on in that region as one example, and then we'll talk about MMS observations, and then we look a little bit

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Mark Kushner: Further out into the future.

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Mark Kushner: So, in the laboratory, some of you might be working in laboratory plasmas.

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Mark Kushner: Reconnection is generally something that you don't want to have, because it destroys your confinement, right? If you use magnetic fields to confine plasmas, and a process eats your magnetic field and kicks the plasma out, that's exactly what you want to avoid, right? So you don't want to have that. So what you do instead.

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Mark Kushner: well, is find ways to prevent it from happening, but for that, you want to study it in the laboratory as well, and that's what our principal friends did here, is a paper from Hunter OG, which basically looks at

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Mark Kushner: Let's find MRX machine here, which is now called Flare, to look at asymmetric and symmetrical connection, and they get flow patterns all over there, and so on. But, I mean, this is an extremely useful, wonderful tool.

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Mark Kushner: But to get into the core of this thing is very, very difficult, because the scale sizes are millimeters, okay? And you cannot easily build millimeter-sized detectors and not destroy

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Mark Kushner: The environment that you're studying, and the same…

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Mark Kushner: was in this, you know, spacecraft is still so tiny compared to kilometers, right? So your perturbation to your environment that a spacecraft causes is much, much smaller.

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Mark Kushner: So, it's a really key multi-scale process in plasmas, and anything that's not totally collisional, it plays a major role, okay, and it's collisionless enough.

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Mark Kushner: Then you really need to look at kinetic processes to enable it.

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Mark Kushner: And therefore, it has been an important thing to study, basically, since it's been discovered on the Sun. This is the old Giovanni paper, which most of you weren't even born, was written.

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Mark Kushner: But…

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Mark Kushner: And it's cool, we know this unknown physics of the electron diffusion region. And so if… I mean, just imagine, if the electrons weren't getting unmagnetized.

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Mark Kushner: Right? They would stick to the field lines, the ions would move, and what would that do? Generate a huge charge separation, and you pump so… ultimately pump so much electrostatic energy into the system that it can't continue.

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Mark Kushner: Right? So what you're going to have to do is demagnetize the electrons also. The ions are heavier, so it's easier to do, and so we study the most difficult thing, how do electrons do that?

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Mark Kushner: And MMS was designed to do that, and so let's talk about what we expected, how this might work.

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Mark Kushner: Before the MMS mission.

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Mark Kushner: So… Let's talk about the reconnection electric fields.

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Mark Kushner: I mean, you all know Maxwell's equations.

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Mark Kushner: Since you're a plasma physicist, right? You can do them in your sleep.

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Mark Kushner: So if you want to… Move magnetic flux from Up here, okay.

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Mark Kushner: 2… Here.

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Mark Kushner: Right? In an electric field, right?

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Mark Kushner: And let's see… see, electric field needs to point out of the plane. By the way, both my coordinates. X is horizontal, Z is up, and Y is out of the plane. That's something…

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Mark Kushner: magnetospheric people like to do, and I just can't stop doing it. But you need an electric field here, and basically the electric field tells you the rate of flux transport from here to here.

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Mark Kushner: Let's just mixed with equations, there's nothing magic about that.

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Mark Kushner: But there's something interesting about it.

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Mark Kushner: here.

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Mark Kushner: In the simplest case, you have no magnetic field, it's an X-type structure, or you have a magnetic field that's only sticking out of the plane, and you've got an electric field there, so it will accelerate particles, right?

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Mark Kushner: In that region.

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Mark Kushner: So what I'm going to do is, I'm going to study very, very qualitatively the ways,

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Mark Kushner: electrons can get accelerated, and the acceleration can be balanced, right? So something has to balance this. The electric force has to be balanced by something. So for that, we're going to turn that sideways, and now the fine graph is going to get a lot simpler.

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Mark Kushner: So, here the magnetic field is now sticking out of the plane. You see my Y is now horizontal, my Z is up. Here's magnetic field sticking out of the plane and into the plane, and here's an electric field.

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Mark Kushner: Alright, that's our reconnection electric field at that X point.

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Mark Kushner: So we have some electrons in there, and they're going to feel that electric field. What's going to happen to those electrons?

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Mark Kushner: Okay, what balance is the force of…

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Mark Kushner: of this electric field. It's like electrons in a voltage drop or something, and a capacitor is… not capacitor, of course.

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Mark Kushner: But, it's kind of similar to this. So I'm not leaving out the magnetic field, too, to make it even more simple.

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Mark Kushner: So, first option is straight line acceleration, right? The electrons are sitting there, and they're just going to get faster, faster, faster, faster.

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Mark Kushner: It basically means inertia will balance the electric field.

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Mark Kushner: But there's a little bit of a problem with that.

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Mark Kushner: First of all, the electrons are light.

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Mark Kushner: Even though we sometimes modeled somewhat heavier electrons, in order to do it in a particle,

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Mark Kushner: all things limited by the system size, because they're fast, right? They get… they get relativistic very quickly if your electric field is

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Mark Kushner: is significantly enough, and then they just leave your system, they're gone, okay? If you do that with relativistic electrons, this effect can play a role.

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Mark Kushner: But you have to be in a pretty relativistic system for that to matter. In a classical system, this can't really work, because you will deplete this region of electrons very quickly, yeah?

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Mark Kushner: So… Not the right approach.

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Mark Kushner: So the next one is…

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Mark Kushner: what happens in many, many cases in plasmas that are collisional, right, is that you have classical collisions, you got some ions here, or you could have another electron species that's not moving, although it's kind of difficult in an electric field, but ions could be sitting there, and you could do Coulomb scattering, or something like this.

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Mark Kushner: But in many space plasmas, that's not nearly frequently enough to matter.

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Mark Kushner: Okay.

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Mark Kushner: And lab plasmas aren't want that either, because what you're losing is you want to energize, and you don't want to lose your energies through collisions, and you don't want to cause diffusion through collisions either. In collisional plasma regimes, this can play a role, but I'm not going to talk about that.

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Mark Kushner: You can do resistive MHD for that. It works quite well.

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Mark Kushner: So, the third one is wave-particle interactions.

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Mark Kushner: Let's see, we've got… We accelerate these electrons here.

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Mark Kushner: And then we have fluctuating electromagnetic fields, so this can be…

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Mark Kushner: Just electrostatic, so that the electric field wobbles around here, or usually in these systems, it's electromagnetic, so you get

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Mark Kushner: electromagnetic fluctuations, and if they interact with these electrons, they will scatter them in whichever direction, which is the same as removing that momentum that you've just built up through the electric field, so it's like a break on this acceleration, and it could, in principle, work, right?

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Mark Kushner: So…

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Mark Kushner: It involves special plasma conditions, so you need typically instabilities to get these fluctuations to go. There's a variety of possible mechanisms, find them in the magnetopause. There are lots of instabilities that could play a role there, but

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Mark Kushner: The connection isn't occurring everywhere.

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Mark Kushner: But it's… it's a possibility, principle.

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Mark Kushner: Okay, let's… let's do a little…

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Mark Kushner: Little game here to see what…

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Mark Kushner: This will look like. This is a basic idea, this is a perspective view of an X point here.

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Mark Kushner: Here's one… the one typical electron, okay? It's feeling the electric field, but at the same time, its world is

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Mark Kushner: bubbling around.

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Mark Kushner: Okay, and this poor electron is…

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Mark Kushner: Maybe getting seasick, but it's getting kicked around and ultimately ejected, okay?

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Mark Kushner: So, that could work, right? But one thing I want you to take away from that is, if that were to occur.

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Mark Kushner: if you've…

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Mark Kushner: the electron orbits are all over the place, right? So if you look at which way the electrons are moving with which probability, you shouldn't see any significant structure in the distributions, because, you know.

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Mark Kushner: you're basically… I mean, instabilities have a tendency to… to, thermalize distributions, right? Because that's where the free energy is sitting. So your electron distribution shouldn't have structure.

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Mark Kushner: Yeah.

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Mark Kushner: Okay.

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Mark Kushner: Fine. No.

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Mark Kushner: Is there anything else?

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Mark Kushner: Okay, let's look at a fourth option. There's another great… I got Chef GPT to do that for me. It's sort of work, but let's… let's look at…

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Mark Kushner: Something different.

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Mark Kushner: I mean… Imagine for a moment a sandblaster, right?

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Mark Kushner: I don't know if anybody works on cars or something, repaints stuff or so, a sandblaster has a jet of gas, right? A jut of… and what you do is you drop sand into that.

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Mark Kushner: Okay, the sand gets accelerated by this… by this gas and flies out and hits your target and takes the paint off, right? What if we apply that same principle to the electrons?

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Mark Kushner: All right, we have electrons that drop in from

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Mark Kushner: Dropped… a drop in from above, okay, from both sides, above and below, they get into this region, here they may do something, we'll see what they do there in a minute, but they get accelerated, and as they get accelerated, they disappear.

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Mark Kushner: This is a…

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Mark Kushner: conceptually the same as the… as the disappearance that we had, through… through fluctuations, okay? But… but the disappearance here is regular, and I'll show you in a minute what that means, okay? So we have bulk-structured electrons coming in here.

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Mark Kushner: getting accelerated.

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Mark Kushner: hitting the electric field, and then you have a mixture here of electrons that have been accelerated and not so accelerated. They get a kick, and then somehow they leave.

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Mark Kushner: Okay, I'm going to show you the same thing.

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Mark Kushner: In a prospect… in the same perspective view, So, electrons coming in here.

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Mark Kushner: They get accelerated, you see the color change, it's supposed to indicate that. They bounce around a couple of times, and we'll see later that they bounce at most twice.

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Mark Kushner: Okay, almost twice.

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Mark Kushner: And then they get kicked out here through the interaction with the adjacent magnetic field.

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Mark Kushner: Yeah? And if you believe that…

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Mark Kushner: Let me play it one more time. Took me quite a while to get ChatGPT to do that. I mean, AI is not that smart, I can tell you that.

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Mark Kushner: of… So it bounces around, and then…

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Mark Kushner: And then they fly out. And…

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Mark Kushner: These orbits are fairly regular, right? Because they actually bounce around a couple of times, and then eventually they get defected to the side by… So if that's true.

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Mark Kushner: The distribution, for instance, should be…

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Mark Kushner: Much more structured. I should show some evidence of these orbits.

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Mark Kushner: Because all electrons are doing something like that, we should see that.

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Mark Kushner: Okay.

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Mark Kushner: All right.

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Mark Kushner: Okay, well…

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Mark Kushner: I'm harping on this. That's, of course, what happens, right? But we didn't know that yet. That was…

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Mark Kushner: There was something we predicted, but had no idea whether it was going to be true or not.

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Mark Kushner: So that's the case, and the central diffusion region should be laminar, in the sense that these orbits are nice and

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Mark Kushner: Alright.

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Mark Kushner: and predictable. Turbence is locally important… unimportant locally, mind you, in that region.

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Mark Kushner: I can even tell you why. There's a very good reason for it, not to be important.

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Mark Kushner: The electron orbits are fairly undisturbed.

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Mark Kushner: But they can have… can be complex, they can bounce around, and you don't know whether they go to the left or the right, so there's some sort of significant dependence on initial conditions, if you think in terms of Lapino exponents. And you should see that, okay? So…

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Mark Kushner: So let's… let's now go and construct a distribution function from scratch.

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Mark Kushner: Okay.

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Mark Kushner: And then we'll see where we find that in observation. So what should we actually see

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Mark Kushner: If this happened in… real life.

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Mark Kushner: Okay.

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Mark Kushner: Yeah, we designed this mission.

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Mark Kushner: Based on that. So you have this fine…

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Mark Kushner: structure again. We had the electric field here, okay? And we're going to turn…

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Mark Kushner: Oops, no, we're not going to turn this around. We're going to look at an equation first. Sorry.

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Mark Kushner: So the electric field here, okay, for those of you who are familiar with,

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Mark Kushner: a second moment of the Vlasso equation for this electromotentum equation solved for the electric field. We have the convective terms here, okay, and we have pressure terms, and then we have inertia terms.

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Mark Kushner: Nothing magic about that.

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Mark Kushner: So, at… at this central point, at this X point.

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Mark Kushner: we have the magnetic field going to zero, and we have, if we have a stagnation point, the flow is going in and out like this, the velocity is also zero, so this thing, the convective term, the V cos B term, is quadratically zero.

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Mark Kushner: Well, so that cannot give us an electric field there.

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Mark Kushner: Let's look at the inertia terms next.

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Mark Kushner: So you have electrovelocity over time term. That's basically a quick time change of the electron velocity that we're not really seeing, because what we're seeing in the region is that the system evolves on ion scales.

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Mark Kushner: which is much slower, and therefore, electron inertia term of this kind cannot be very important. And this one.

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Mark Kushner: It's something that we propose to be unimportant, that's,

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Mark Kushner: The pressure grad… electron pressure gradient into the plane here.

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Mark Kushner: Okay, I convinced yourself very quickly that

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Mark Kushner: All you can get out of reconnection based on that pressure term is basically the thermal energy of the electrons. That's not very much. That's not enough to explain magnetospheric reconnection.

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Mark Kushner: So it's probably also not important.

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Mark Kushner: And here we have the convective inertia term, the Vigrad V term.

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Mark Kushner: Okay, this is the inflow velocity, this is the outer plane velocity. This one is large, but this one goes to zero, because the flow stagnation point, and at least in the symmetric system, this thing actually has a local maximum.

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Mark Kushner: So the gradient also goes to zero. So, in other words, this cannot be happened, playing a role, and then the only thing that you're stuck with are those, and these are…

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Mark Kushner: Press a tensor terms.

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Mark Kushner: Right? Not… it's not even isotropic, it's not… not even gyrotropic, it's a non-gyrotropic pressure that plays a role. Non-gyrotropic, yeah? So.

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Mark Kushner: That's kind of messy, but also cool.

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Mark Kushner: So this pressure tensor here has to be non-gerotropic, which means it has no symmetry about the magnetic field.

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Mark Kushner: order that to work. So normally, electrons run around the magnetic field like this, and they make everything nice and symmetric. In order for that to work.

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Mark Kushner: That cannot be the whole story.

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Mark Kushner: And I'll show you why that it indeed isn't a whole story.

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Mark Kushner: Okay, now let's look a little bit about… let's try to construct a distribution function. This is a simulation I did.

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Mark Kushner: a few years ago, about magnetopause reconnection, here's the magneto sheath, here's the magnetosphere. I turned this around, sorry about that.

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Mark Kushner: Well, I think you can follow me anyway.

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Mark Kushner: And,

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Mark Kushner: So we're going to look at this. So here we have… this is just one picture of this.

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Mark Kushner: Here we have strong magnetic field and less plasma density, and here weaker magnetic field and more particle density.

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Mark Kushner: Okay.

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Mark Kushner: And here we have this mixing region. So now we're going to turn this around again.

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Mark Kushner: Okay, now I made a little bit…

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Mark Kushner: Add a little bit more electric, magnetic field here.

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Mark Kushner: To make a point. Here's the current, here's also an electric field, and not so hot electrons.

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Mark Kushner: Okay?

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Mark Kushner: So we got lots of hot electrons there, and these electrons

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Mark Kushner: By and large, bounce around, okay?

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Mark Kushner: Let's consider that bounce mode, real quick.

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Mark Kushner: So, electrons coming from down here, you know, they're…

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Mark Kushner: execute some sort of partial LAMO orbit here, when they penetrate into the magnetic barrier, and they get turned back.

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Mark Kushner: Alright, so it's very simple.

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Mark Kushner: Here we have an upward velocity. Here, the velocity is horizontal.

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Mark Kushner: Okay, at the peak of this little arch, and here it goes down again.

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Mark Kushner: So now what we can do is we can add higher energies to that.

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Mark Kushner: High energies penetrate deeper.

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Mark Kushner: So we tick one here.

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Mark Kushner: You have to imagine this thing being extended here, this way and this way. So this electron here enters here.

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Mark Kushner: And it comes down here, but…

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Mark Kushner: Where this orbit is horizontal, with an orbit that's much… with an orbital element that's much steeper.

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Mark Kushner: And it does it both ways. Here, there's also one that originates here and goes up at the same time. Then we get at even higher energies.

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Mark Kushner: Okay, and they do like this.

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Mark Kushner: And if you know, measure here…

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Mark Kushner: So if you're flying a spacecraft, and you measure here, then you're going to get a mixture of electrons that are sort of turning around here, and they have the lowest energies.

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Mark Kushner: Okay, and then you have electrons that are going up and down with increasing, increasingly steeper

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Mark Kushner: Ascent or descend angle, depending on their energy.

334
00:40:44.790 --> 00:40:46.390
Mark Kushner: Yeah? Yep.

335
00:40:46.640 --> 00:40:47.930
Mark Kushner: Bog, log.

336
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Mark Kushner: More aligned with the z-axis, the larger the energy is.

337
00:40:52.090 --> 00:40:53.740
Mark Kushner: Does that make sense, right?

338
00:40:53.980 --> 00:40:55.859
Mark Kushner: Okay, very good.

339
00:40:57.950 --> 00:40:59.310
Mark Kushner: So, that's good.

340
00:41:00.630 --> 00:41:02.750
Mark Kushner: Here's what that looks like.

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00:41:04.730 --> 00:41:11.869
Mark Kushner: So here's the upper… so this is now a probability distribution of those electrons constructed… taken from a peak simulation.

342
00:41:12.220 --> 00:41:17.609
Mark Kushner: Here's the up and down velocity, up and down direction, and here's the horizontal direction.

343
00:41:17.760 --> 00:41:25.889
Mark Kushner: the Y direction, yeah? Just taking straight from the… Sketch I did.

344
00:41:26.850 --> 00:41:30.430
Mark Kushner: So at the peak here, We have the maximum…

345
00:41:30.680 --> 00:41:41.500
Mark Kushner: velocity in the Y direction, okay, no velocity in the Z direction, and the lowest energy, and you can kind of see that, because the energy is proportional to V squared in this

346
00:41:41.850 --> 00:41:47.320
Mark Kushner: In this diagram. And if you're going here, then we are still in the upward.

347
00:41:48.270 --> 00:41:53.979
Mark Kushner: part of the… part of the trajectory. These electrons are going to a higher Z, and they have higher energy.

348
00:41:54.450 --> 00:41:55.540
Mark Kushner: Okay.

349
00:41:56.630 --> 00:42:03.730
Mark Kushner: And equally, These electrons here are returning from hyazine with high energy.

350
00:42:04.450 --> 00:42:09.989
Mark Kushner: Yeah? Makes perfect sense. You can even verify that in a peak simulation is actually what they're doing.

351
00:42:10.880 --> 00:42:11.760
Mark Kushner: But it…

352
00:42:12.090 --> 00:42:19.380
Mark Kushner: But it's… it's because you're sampling loc… you're doing a local measurement, which means you're sampling orbits that are going far out.

353
00:42:20.440 --> 00:42:21.330
Mark Kushner: Okay.

354
00:42:22.350 --> 00:42:24.399
Mark Kushner: So we need to add one thing to that.

355
00:42:24.970 --> 00:42:27.559
Mark Kushner: And that's electrons that are coming in from above.

356
00:42:28.770 --> 00:42:32.890
Mark Kushner: We're measuring here somewhere. And they're just fairly benign, they're just…

357
00:42:33.040 --> 00:42:40.570
Mark Kushner: gyrate an E cross B drift, with an E cross B drift velocity that's much smaller than the summer velocity, so it's kind of hard to see.

358
00:42:40.890 --> 00:42:42.230
Mark Kushner: But I do that.

359
00:42:43.760 --> 00:42:47.840
Mark Kushner: And if you put that all together, you get this… Fine thing here.

360
00:42:48.280 --> 00:42:52.139
Mark Kushner: So here's our…

361
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Mark Kushner: crescent, as we call that. And here's our incoming distribution. And the local magnetic field here is, if you want, sticking out of the plane.

362
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Mark Kushner: Okay, and you can… I mean, it's rather obvious that this distribution is not gyotropic.

363
00:43:09.160 --> 00:43:14.850
Mark Kushner: It's not symmetric in this plane, in any which way, yeah?

364
00:43:15.570 --> 00:43:22.250
Mark Kushner: So… So if this works, and we get a non-gerotropic distribution on the silver platter, and…

365
00:43:22.390 --> 00:43:24.449
Mark Kushner: Well, bear that tear.

366
00:43:24.900 --> 00:43:27.569
Mark Kushner: Okay, and this is the incoming part from above.

367
00:43:27.860 --> 00:43:35.030
Mark Kushner: Yeah, so that was a prediction that was done in 2014, two years before MMS was launched.

368
00:43:35.330 --> 00:43:37.819
Mark Kushner: Okay, and

369
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Mark Kushner: Yeah, that was a prediction. I was taken in, actually, this simulation at roughly this location, the distribution function.

370
00:43:47.450 --> 00:43:53.100
Mark Kushner: So… That's… what am I doing this time, by the way?

371
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Mark Kushner: About 15 minutes.

372
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Mark Kushner: Boom.

373
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Mark Kushner: Okay, so… Back to that small needle in the haystack problem.

374
00:44:06.350 --> 00:44:10.470
Mark Kushner: So you're flying a mission out there, you don't really know where this

375
00:44:11.190 --> 00:44:21.990
Mark Kushner: is supposed to occur here, and you need to resolve that region at the same time. You can design your orbit to maximize like you've encountered this region, but

376
00:44:21.990 --> 00:44:32.349
Mark Kushner: it's a tricky business, and… and you need to do this really fast, because these current sheets here move… they're 1 to 5 kilometers thick, and they move at about 20 kilometers a second. We know that, but…

377
00:44:32.490 --> 00:44:41.350
Mark Kushner: other spacecraft observations. That means you have to… in order to get a couple of measurements across that, you need 30 millisecond time resolution.

378
00:44:41.350 --> 00:44:55.579
Mark Kushner: For a full electron distribution, 30 milliseconds. That's two orders of magnitude faster than anything that was done before. And nowadays we can even, on occasions, do 7.5 milliseconds, which is just insanely fast, but beautiful for science.

379
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Mark Kushner: purposes. And the mission was designed based on these parameters.

380
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Mark Kushner: Okay, it was designed so it can do that. It was designed to be a heretofore, unavailable and totally out of, out of

381
00:45:12.760 --> 00:45:20.700
Mark Kushner: possible microscope to study kinetic processes. Okay, so what first target was what happens there?

382
00:45:21.540 --> 00:45:25.480
Mark Kushner: So, I'm trying to spend too much time on this.

383
00:45:25.610 --> 00:45:26.400
Mark Kushner: Listen.

384
00:45:27.280 --> 00:45:28.710
Mark Kushner: This was a launch.

385
00:45:29.100 --> 00:45:47.770
Mark Kushner: And I mentioned to some of you before, I've seen a lot of launches over my life, being at NASA, but if you spend a lot of years working on that mission, and you see that, that's a very different feeling. I mean, you get goosebumps, seriously. And you're like, how is it gonna work? Is it gonna work, you know? And it did.

386
00:45:48.170 --> 00:45:58.069
Mark Kushner: And it did exactly what you're seeing in this animation here. See a stack of four spacecraft, they get separated, and then you see unfolding of various booms.

387
00:45:58.380 --> 00:46:02.670
Mark Kushner: Actually, instruments here.

388
00:46:02.840 --> 00:46:08.589
Mark Kushner: particle instruments. We have, 16 detectors for each spacecraft.

389
00:46:08.710 --> 00:46:25.900
Mark Kushner: four electrons for ion detectors, so we don't depend on the spin of the spacecraft in order to get a 4-piecester radiant distribution. That was also never, never been done before. You see the wire booms to measure electric fields coming out.

390
00:46:26.010 --> 00:46:45.230
Mark Kushner: And you will later see that the Z boom coming out here, here we go, is to measure electric fields in the orthogonal direction, so we can 3-axis magnetic field… electric fields, I'm sorry. These are magnetic field booms here, and then we got four of those things, flying in formation.

391
00:46:45.460 --> 00:46:47.380
Mark Kushner: At…

392
00:46:47.660 --> 00:46:57.239
Mark Kushner: down to interspacecraft distances of only 10 kilometers, and in one case was 7 or so. That was a little bit risky, because it, you have to

393
00:46:57.490 --> 00:47:00.440
Mark Kushner: You know, for collision avoidance reasons.

394
00:47:01.090 --> 00:47:04.200
Mark Kushner: And they, they served us well, okay?

395
00:47:05.430 --> 00:47:06.540
Mark Kushner: So…

396
00:47:06.720 --> 00:47:14.760
Mark Kushner: The mission continues to be a huge success and has tremendous additional potential, but… but just shortly after launch.

397
00:47:16.020 --> 00:47:21.909
Mark Kushner: I'm sorry, the launch was in 2015, not 2016. I misspoke earlier.

398
00:47:22.140 --> 00:47:27.059
Mark Kushner: Here we have a schedule of magnetosphere, here's the day side.

399
00:47:27.180 --> 00:47:34.599
Mark Kushner: Here's the night side, and why did I do that? Because I want to put a sketch of the orbit in here, as it roughly was doing that

400
00:47:34.730 --> 00:47:45.290
Mark Kushner: Today in 2015, so it's reaching the magnetopause here in Apogee, which is where the spacecraft are the slowest, and we designed it so we have that tetrahil configuration, so we can actually

401
00:47:45.490 --> 00:47:49.230
Mark Kushner: Measure things there as designed.

402
00:47:50.590 --> 00:47:58.620
Mark Kushner: And in a paper that Jim Birch published in 2016, we had this situation here.

403
00:47:59.010 --> 00:48:07.549
Mark Kushner: There's our magnetosphere. Sorry, the sun is on the right here, both of the inflow regions, and then they measured these electron distributions.

404
00:48:07.790 --> 00:48:16.150
Mark Kushner: Okay, and… The key, electron distribution, It's this one here.

405
00:48:17.400 --> 00:48:22.109
Mark Kushner: So this measures the direction here perpendicular to the magnetic field here.

406
00:48:22.310 --> 00:48:25.850
Mark Kushner: Okay, so this is this direction.

407
00:48:25.960 --> 00:48:34.689
Mark Kushner: Okay, and what you're seeing here are the crescents, and you see simulations, you get more beautiful crescents, but nevertheless, they're here too.

408
00:48:34.950 --> 00:48:54.059
Mark Kushner: the incoming distribution is this here, this hot halo, because in reality, the temperature of the incoming distribution is quite a bit higher than what I have in my simulation. But it is essentially the same thing. It's coming in here, and these penetrate from below, and cause this crescent distinction.

409
00:48:54.520 --> 00:49:00.959
Mark Kushner: So that was the first indication. There were quite a few more later on, that indeed that concept was

410
00:49:01.260 --> 00:49:02.670
Mark Kushner: is correct.

411
00:49:04.670 --> 00:49:06.969
Mark Kushner: Okay, that was a day sign.

412
00:49:07.320 --> 00:49:12.000
Mark Kushner: Now, the night side, things are more anti-perall, right?

413
00:49:12.270 --> 00:49:15.259
Mark Kushner: So what happens there?

414
00:49:15.570 --> 00:49:17.390
Mark Kushner: In 2017,

415
00:49:17.630 --> 00:49:27.159
Mark Kushner: a little bit later, not too much later, how we had raised the apogee considerably to further out here. Sorry, my eye is not perfect, but

416
00:49:27.440 --> 00:49:37.479
Mark Kushner: But anyway, we have the upper GRT and the tail, and we can position our spacecraft there with a small interspacecraft separation to measure, again, the same quantities.

417
00:49:38.830 --> 00:49:42.140
Mark Kushner: And here's what data looks like.

418
00:49:42.500 --> 00:49:46.260
Mark Kushner: So up here you have the magnetic field components.

419
00:49:46.500 --> 00:49:52.590
Mark Kushner: BX is the blue one, here's the direction it goes to the… to the Earth and back, if you want.

420
00:49:52.700 --> 00:50:04.459
Mark Kushner: Okay, then, BZ here is the red one, is that normal component that we create if reconnection occurs, and the green one is sticking out of the plane. That's the

421
00:50:04.850 --> 00:50:06.260
Mark Kushner: by component.

422
00:50:06.390 --> 00:50:09.370
Mark Kushner: And I want to draw your attention to this part here.

423
00:50:11.280 --> 00:50:18.499
Mark Kushner: which is where the… where the reconnection, where the magnetic field goes close to zero. Okay, that's a nice candidate for…

424
00:50:18.780 --> 00:50:21.739
Mark Kushner: For a reconnection event.

425
00:50:22.010 --> 00:50:23.910
Mark Kushner: And if you look down here.

426
00:50:27.000 --> 00:50:29.920
Mark Kushner: These are the electron flow velocities.

427
00:50:30.510 --> 00:50:35.780
Mark Kushner: The… X component, here's the blue one.

428
00:50:36.010 --> 00:50:38.280
Mark Kushner: So it's moving to the left here.

429
00:50:38.950 --> 00:50:43.250
Mark Kushner: Before you encounter this zero here, and then it's moving to the right.

430
00:50:43.360 --> 00:50:59.300
Mark Kushner: Okay, so basically you see the electron ejection that we had. Remember the conversion of energy to kinetic and so on? Well, it's doing the stat for us. And then here, the green one is the electrons moving out of the plane, and that's that acceleration of the electric field that we talked about.

431
00:50:59.510 --> 00:51:02.880
Mark Kushner: Right? So you see all that, it all fits together.

432
00:51:03.170 --> 00:51:14.620
Mark Kushner: Here the ions are doing their thing, too. They're also moving left and right, but for focus on the electrons. And nicely, because the mission was designed for that, we can take distribution functions.

433
00:51:15.460 --> 00:51:20.500
Mark Kushner: And that's what Roy Tolbert did. One thing I wanted to point out is that gradient here.

434
00:51:21.470 --> 00:51:26.680
Mark Kushner: There's actually a nice gradient of this hot flow velocity. We'll get back to that in a minute.

435
00:51:27.830 --> 00:51:33.089
Mark Kushner: So here's what the distribution functions look like. That's a little bit messy.

436
00:51:33.560 --> 00:51:39.089
Mark Kushner: But the one that's perpendicular to the magnetic field is this one here.

437
00:51:40.770 --> 00:51:44.170
Mark Kushner: And what you're seeing there… R.

438
00:51:45.460 --> 00:51:49.790
Mark Kushner: One, two crises, right? Two, at different energies.

439
00:51:50.120 --> 00:51:53.620
Mark Kushner: And why are you seeing two? It's because electrons bounce twice.

440
00:51:53.780 --> 00:51:58.849
Mark Kushner: Right? If they bounce once, you see that? Okay, and if they bounce again, you see a second crescent.

441
00:51:59.370 --> 00:52:01.730
Mark Kushner: Okay, but can we see a third one?

442
00:52:02.060 --> 00:52:06.490
Mark Kushner: Which means that… Very little, if any, bonds, more than twice.

443
00:52:08.380 --> 00:52:12.290
Mark Kushner: Okay, and the cool thing is, if you model this.

444
00:52:12.750 --> 00:52:14.750
Mark Kushner: Like I did for that paper.

445
00:52:15.170 --> 00:52:18.530
Mark Kushner: And you actually also saw two crescents here, right?

446
00:52:19.210 --> 00:52:21.010
Mark Kushner: It's a little faint, but…

447
00:52:21.110 --> 00:52:39.360
Mark Kushner: But you can see. So, in the model, nicely enough, you get the same result. And I used a simulation that was roughly consistent with the parameters. Later, some folks had actually set up a simulation to look exactly like this event, and they got an even better match than what I had.

448
00:52:41.920 --> 00:52:43.910
Mark Kushner: So here's a gradient again.

449
00:52:44.390 --> 00:52:54.420
Mark Kushner: So what Rumi Nakamura, who some of you know very, very well, did, she went back to that event and looked at measurements of this flow velocity.

450
00:52:54.960 --> 00:53:03.129
Mark Kushner: This is the… in her… it's called VL, that's the outflow to the left and to the right, and put a… put a gradient to that.

451
00:53:05.250 --> 00:53:10.979
Mark Kushner: which looks like this, and if you plug that gradient into a formula that I developed a while ago.

452
00:53:11.120 --> 00:53:14.489
Mark Kushner: Based on a model for this non-gyrotropic pressure.

453
00:53:14.670 --> 00:53:20.470
Mark Kushner: Then you get an electric field here, which basically coincides with the measurements here rather well.

454
00:53:20.940 --> 00:53:25.480
Mark Kushner: Okay, so it's another proof that this seems to be all fitting together.

455
00:53:25.620 --> 00:53:26.760
Mark Kushner: Pretty live.

456
00:53:27.880 --> 00:53:28.810
Mark Kushner: Okay.

457
00:53:29.160 --> 00:53:40.070
Mark Kushner: Now, let's talk about a… so we understand a lot, okay? A lot, a lot more than we ever did. Hugely more than we ever did, but that doesn't mean we understand everything. So there's lots to do in reconnection.

458
00:53:40.960 --> 00:53:43.530
Mark Kushner: So the diffusion region is laminar, right?

459
00:53:43.710 --> 00:53:45.590
Mark Kushner: Is it always lemon?

460
00:53:46.280 --> 00:53:48.780
Mark Kushner: Probably yes.

461
00:53:49.130 --> 00:54:01.039
Mark Kushner: for the simple reason that the electrons don't hang around enough for an instability to develop. You need… you need the instability, you need at least a growth time, or a couple of growth times.

462
00:54:01.220 --> 00:54:21.069
Mark Kushner: residence time of the electrons for an instability to hold, okay, to grow. The electrons are gone before that, and replaced by some with no memory, no correlation with anything that might be going on there, might be wanting to grow there. So, probably not. And any 3D effects that play a role?

463
00:54:22.480 --> 00:54:25.310
Mark Kushner: Physics of the asymmetric diffusion region.

464
00:54:26.200 --> 00:54:35.140
Mark Kushner: We talked largely about planar things, but asymmetric with guide fields, very tricky. What is dissipation here, anyway?

465
00:54:35.340 --> 00:54:49.710
Mark Kushner: particle orbits with large Lyapunov coefficients that are not integral, information loss, you know, how does it actually work? It's a… I mean, it's… it's a… some mathematical folks among you might… might love that kind of question.

466
00:54:50.280 --> 00:55:08.529
Mark Kushner: So here's something that I'm working on right now, can't say I understand it yet, but this is the diffusion region, if you have a strong guide field here, this is a color, a BY, that's out of the plane, which is about the same size as in-plane magnetic field, and you can see what that does to the electron flow patterns here.

467
00:55:08.530 --> 00:55:11.379
Mark Kushner: They're coming in at some angle here, and then if…

468
00:55:11.430 --> 00:55:29.220
Mark Kushner: flying… flowing around here along the magnetic field, you get a strong acceleration here. This looks like more of a usual reconnection pattern, but it's all a big mess. So you don't have a flow stagnation point here in the middle, okay? And so we're still trying to understand how that actually works.

469
00:55:33.120 --> 00:55:42.920
Mark Kushner: The rate… So… Simulations always show a reconnection rate of 0.1 to 0.2 times VLFA in V0.

470
00:55:43.230 --> 00:55:51.010
Mark Kushner: Right? Invariably. If you put enough dissipation in there, it will do it for you, and a pig simulation does that in any case.

471
00:55:51.170 --> 00:55:56.590
Mark Kushner: Now, why is that, okay? Isshin, actually,

472
00:55:57.140 --> 00:56:15.829
Mark Kushner: put together a theory that's both based on a local geometry to predict that that is indeed the maximum you should expect. Now, there's more discussion about that, because it's local, and the question is what happens to the larger-scale system, but it's certainly a highly promising, explanation.

473
00:56:17.020 --> 00:56:21.759
Mark Kushner: Coupling to the larger environment is a multi-scale process, right? We look at…

474
00:56:21.940 --> 00:56:34.259
Mark Kushner: And we have a pretty good understanding of this local scale, but there's much bigger scales, okay? So here, we got our electron diffusion region that we measured here with MS. Around that is an ion diffusion region, it's already

475
00:56:34.530 --> 00:56:37.739
Mark Kushner: Hugely bigger, typically 40 times as large or so.

476
00:56:38.100 --> 00:56:50.409
Mark Kushner: Because of the mass difference, where the ions get unmagnetized, right? What's the physics of that, and how do these things fit together? Okay, and then way out there, well, I'm not saying that because

477
00:56:50.530 --> 00:57:06.540
Mark Kushner: I'm here, but I firmly believe that physics is, to a large degree, dominated by MHD. So how do we… how does it all work together and operate consistently as a multi-scale problem? Something you need to understand. If you just compare ions and electrons.

478
00:57:07.520 --> 00:57:25.810
Mark Kushner: And as for the fun of it, we can express electric fields through the electrons, like we did before. We can equally, well, express it through the ions, right? It's just another… such the ion loss of equation taken the second moment off. Okay, but there's only one electric field, so these things have to be equal.

479
00:57:27.020 --> 00:57:36.020
Mark Kushner: Okay, and to a good approximation, if we neglect some inertia effects or so, this means that the divergence of this ion pressure tensor

480
00:57:36.270 --> 00:57:43.030
Mark Kushner: has to be equal to the divergence of the electron pressure tensor, and then the whole term here, the J cross B term.

481
00:57:43.710 --> 00:58:03.279
Mark Kushner: Yeah? So there is some implicit coupling between the ions and electrons that has to take place in order for this to be operating consistently, even on that multiscale, relatively benign multiscale interaction, okay? And think about what that means if you extend that to MHD.

482
00:58:03.810 --> 00:58:06.349
Mark Kushner: So there's a lot of good work that can be done here.

483
00:58:07.830 --> 00:58:13.049
Mark Kushner: Okay, in MHD, we have slow shocks and beautiful things like that that heat up.

484
00:58:13.270 --> 00:58:25.109
Mark Kushner: plasma might come from inflow to outflow on the large scale. Those things don't seem to exist very often in real life, okay? But we still have energy conversion on the large scale. What is that?

485
00:58:25.840 --> 00:58:40.610
Mark Kushner: This is some work that, Cecilia Norger and I did, looking at electrostatic turbulence at the… at the, separatrix here, facilitating that, electron heating here. This is… this is turbulence here, this is,

486
00:58:40.950 --> 00:58:47.589
Mark Kushner: electron velocity and current density. Here we have electron heating, and you can see there's a clear correlation.

487
00:58:47.760 --> 00:59:05.129
Mark Kushner: with that turbulence, and then Cecilia went in, in her unique skills and looked at MMS data and found that heating, associated with, turbulence in the same way. And then there's iron acceleration that involves pickup, and acceleration by normal,

488
00:59:05.380 --> 00:59:06.920
Mark Kushner: Electric fields.

489
00:59:07.030 --> 00:59:17.809
Mark Kushner: And all of that works in sync, somehow, yeah? So we want to understand how that energy conversion occurs, and then how it syncs up with the process in the other scan.

490
00:59:19.910 --> 00:59:39.229
Mark Kushner: Okay, then taking this further out, how does this recon actually depend on inflow conditions? Geometry on inflow is particularly important in the magnetopause. Our geomagnetic field is nice, it's always north, doesn't bobular, but our field here does this, right? Magneto sheath field. So what happens if that changes?

491
00:59:39.400 --> 00:59:40.220
Mark Kushner: Right?

492
00:59:40.430 --> 00:59:47.130
Mark Kushner: And then, if you have a reconnection, it can change its own inflow. What's that feedback?

493
00:59:47.510 --> 01:00:00.390
Mark Kushner: And how long are we reconnection lines, and why? You know, we got flow bursts in the magnetos tail that are on our E long, or something like that, and similar FTE sizes on the magnetopods, and sometimes we get

494
01:00:00.610 --> 01:00:06.329
Mark Kushner: reconnection lines that are quite evidently much larger, hens of RAE hormone.

495
01:00:07.100 --> 01:00:10.969
Mark Kushner: Or does it… why is it long sometimes, and why is it short?

496
01:00:11.260 --> 01:00:12.170
Mark Kushner: Don't know.

497
01:00:13.880 --> 01:00:15.710
Mark Kushner: Okay, and then,

498
01:00:16.530 --> 01:00:31.819
Mark Kushner: This is… this is, AL, for those of you who know that. It's a geomagnetic index that basically shows how active the magnetosphere is, and you see it's active, and then it stops, right? So how does recon… reconnections drive? How does it stop?

499
01:00:32.550 --> 01:00:38.760
Mark Kushner: And that's… that's something… this is one possibility, and that's basically heavy, heavy,

500
01:00:39.140 --> 01:00:49.079
Mark Kushner: high-density material coming in from the inflow region, like from the plasma mantle or something like this. I can facilitate something study by our tent floor.

501
01:00:49.630 --> 01:00:58.250
Mark Kushner: A few years ago. But there are other ways, like rotating magnetic fields, or pileup, or whatnot.

502
01:00:58.370 --> 01:01:04.239
Mark Kushner: probably a zoo of possible mechanisms, you know, which one applies where, but we know reconnection stops at some point.

503
01:01:04.980 --> 01:01:11.150
Mark Kushner: If you want to assess how important it is, we also got to understand how long it's going to run, and how far.

504
01:01:11.880 --> 01:01:14.770
Mark Kushner: And then, yeah, we talked about,

505
01:01:15.240 --> 01:01:26.189
Mark Kushner: How do we get very small things in the solar corona, they're even smaller compared to the system size. How do we get them to organize and form a big breakup, okay? Substore, how do…

506
01:01:26.430 --> 01:01:38.880
Mark Kushner: We get a large-scale substance phenomena. Is it an aggregation of many, many, many little things that suddenly are curled together, or is it… is it a little thing turning into something really big, okay?

507
01:01:39.060 --> 01:01:48.250
Mark Kushner: Is it, like, one reconnection line, even a little contorted, or is it just increasing the frequency of small bursts, and why, right? And then…

508
01:01:49.030 --> 01:01:51.300
Mark Kushner: And one reason to believe that,

509
01:01:51.940 --> 01:01:58.740
Mark Kushner: It may be a region getting larger, is that we get very well-organized current systems that form as a result.

510
01:01:58.860 --> 01:02:18.220
Mark Kushner: Okay, that's what you… you wouldn't expect that out of a lot of small events, and… and so how does that actually work? When… when do we get a large event, or do we not? And if you want to predict space weather, besides your scientific interests alone, that's a very compelling topic.

511
01:02:18.400 --> 01:02:35.300
Mark Kushner: And I'm really running out of time, but I'm almost done. The last thing is very dear to my heart, the oral acceleration reach. So I'm one of these people who believe that the aura is nothing but a result of reconnection, okay? It's very strong guide field reconnection, you have magnetic field going to the Earth, right?

512
01:02:35.810 --> 01:02:53.919
Mark Kushner: And… and… but what you're doing out there in the magnetosphere is introducing a shear, okay? If you have a magnetic shear, you get a current, and if you're in a low beta system like that, then your current density goes like B, right? And B goes crazy up as you come closer to the Earth, so your current density is larger, larger, larger.

513
01:02:53.920 --> 01:03:09.310
Mark Kushner: It's all likely that this will disrupt at some point, and give you a reconnection, which gives you electron acceleration, which you can then see in… in… from the aurora. And there's actually a simulation that Ishi and Liu did with a student.

514
01:03:09.580 --> 01:03:13.149
Mark Kushner: To show that that might be a possibility. So…

515
01:03:15.360 --> 01:03:20.960
Mark Kushner: Done. The connection powers explosions, right? That's…

516
01:03:21.900 --> 01:03:26.709
Mark Kushner: The most dramatic effect of reconnection is also believed to eat the solar corona and so on.

517
01:03:26.870 --> 01:03:32.500
Mark Kushner: We have resolved how reconnection works on the most fundamental level.

518
01:03:32.710 --> 01:03:34.150
Mark Kushner: Okay,

519
01:03:35.040 --> 01:03:44.239
Mark Kushner: seems to be correct that this diffusion region is laminar, and the caudic orbits are not very important. It does not mean that,

520
01:03:45.260 --> 01:04:02.460
Mark Kushner: you know, turbulence is not important, it probably plays a big role in plasma heating on the large scale, actually. And we can really look at the next steps now, coupling between micro and macro scales, taking the knowledge to other environments, and I think there's still lots to do, okay?

521
01:04:02.590 --> 01:04:14.919
Mark Kushner: And if you're interested in that, you've got good people here to work with, and obviously I'm interested in it too, if you want. And this… I want to finish with this. As I said I'm collecting this from the space station.

522
01:04:15.050 --> 01:04:19.389
Mark Kushner: Years ago, I'm… I'm quite…

523
01:04:19.580 --> 01:04:26.560
Mark Kushner: quite certain, you know, be 100%, right? But that this is the result of reconnection. So with that.

524
01:04:26.870 --> 01:04:31.639
Mark Kushner: I want to thank you for your attention, and for having me here, and I'm happy to take any questions.

525
01:04:39.620 --> 01:04:54.209
Mark Kushner: Well, thank you for that wonderful thought. Before we go to breakfast, I'll just present you with the lips in mind. Oh, wow. The infamous Lipsy mod. Wow! Infamous. It's beautiful. Thank you.

526
01:04:54.450 --> 01:04:55.460
Mark Kushner: Thank you.

527
01:04:55.660 --> 01:05:08.939
Mark Kushner: I will treat it with respect. Thank you. Oh! With a mic. With this size, or this size? Thank you very much.

528
01:05:09.440 --> 01:05:12.819
Mark Kushner: Thank you. You're very welcome. Thank you.

529
01:05:13.130 --> 01:05:14.350
Mark Kushner: Questions?

530
01:05:14.810 --> 01:05:15.819
Mark Kushner: One of them.

531
01:05:17.390 --> 01:05:20.869
Mark Kushner: Let's see…

532
01:05:20.970 --> 01:05:27.699
Mark Kushner: Are they, has physics been fully realized? You capture all the relevant length scales, time scales.

533
01:05:27.780 --> 01:05:44.429
Mark Kushner: electron-proton mass ratio, you feel like you have all the relevant simply a matter of figuring out what's happening in the simulations to characterize the rotation? Or is it still have issues with the simulations? Well, I mean, there are always issues with simulations, as you well know, right?

534
01:05:44.430 --> 01:05:51.290
Mark Kushner: So, I mean, what we do here is… in this case, I think I ran a mass ratio of 100, or…

535
01:05:52.680 --> 01:05:56.440
Mark Kushner: About 200, I don't quite remember, okay?

536
01:05:56.580 --> 01:06:08.750
Mark Kushner: And that's what you need to do in order to resolve a sufficiently large system. Now you can actually do 1836 or so. But even in those simulations, you have an unrealistically low ratio between the speed of light

537
01:06:08.930 --> 01:06:11.770
Mark Kushner: And… and the other things, okay?

538
01:06:11.990 --> 01:06:16.949
Mark Kushner: So, that's much larger in reality, at least in those systems, than we can do in a simulation.

539
01:06:17.120 --> 01:06:18.439
Mark Kushner: So, input.

540
01:06:18.850 --> 01:06:31.149
Mark Kushner: If we want to execute in any reasonable amount of time, okay? So you cheat, okay? So what you need to do is you need to convince yourself that your results are resilient against that kind of cheating.

541
01:06:31.450 --> 01:06:34.899
Mark Kushner: Yeah, so for instabilities, for example, it can be…

542
01:06:35.220 --> 01:06:39.669
Mark Kushner: You know, it can impact your growth rates and so on, depending on what you're doing, yeah.

543
01:06:41.120 --> 01:06:50.539
Mark Kushner: You know, if you get close to relativistic, if your electrons get too fast or so, you run into a relativistic regime, which is totally artificial, because the speed of light is so small.

544
01:06:50.900 --> 01:06:58.610
Mark Kushner: Okay, that's another thing you need to take into account. So, what you do is you go into your results and you verify that you are

545
01:06:58.710 --> 01:07:00.250
Mark Kushner: clean enough.

546
01:07:00.350 --> 01:07:04.390
Mark Kushner: Okay, to believe the results, yeah? And that you… if you…

547
01:07:04.470 --> 01:07:22.309
Mark Kushner: if you find a phenomenology like I did here, or the mathematics for it, which I did not show you, which exists too, you know, that you can scale that to the correct mass ratio without any problems. And we can do that. And by the way, reality seems to show the same thing, which is a

548
01:07:22.350 --> 01:07:25.359
Mark Kushner: very convincing argument, right? But…

549
01:07:25.360 --> 01:07:43.199
Mark Kushner: But I mean, in any simulation, you make approximations, like, an instrument, even a space measurement, is an approximation of reality, because you're not measuring everything, you have counting statistics and so on, you're running out of counts at high energies and so on, so you need to know that you have

550
01:07:43.200 --> 01:07:47.749
Mark Kushner: You represent the information that you're interested in correctly enough.

551
01:07:48.290 --> 01:08:04.879
Mark Kushner: Okay? And it's… it's a bit of an art form to make sure that this is done right, and if any of you are interested in doing pig simulations, I strongly encourage you, or any simulation for that matter, I strongly encourage you to spend time to put your physical understanding

552
01:08:04.960 --> 01:08:14.229
Mark Kushner: apply it to the results of the simulations to make sure that things are consistent, because otherwise you can run afoul very badly.

553
01:08:14.630 --> 01:08:19.960
Mark Kushner: Okay, very bad. So, you know, we spent a lot of time Validating this.

554
01:08:20.240 --> 01:08:27.319
Mark Kushner: Yeah, that is an excellent question. Can I ask you a couple of follow-on questions, then? Of course, yeah. It's one-on-one.

555
01:08:29.109 --> 01:08:43.200
Mark Kushner: Yes, go ahead. You mentioned the double crescents that were observed and were also produced in the simulations. Do you think that that is a limit for just Earth's magnetosphere, or do you think that it could change depending on the regime?

556
01:08:43.590 --> 01:08:44.260
Mark Kushner: Soon.

557
01:08:46.470 --> 01:08:50.650
Mark Kushner: That is a good question.

558
01:08:51.370 --> 01:08:55.689
Mark Kushner: I suspect it is… It is…

559
01:08:56.189 --> 01:08:59.779
Mark Kushner: It is difficult to get more bounces, okay?

560
01:09:00.020 --> 01:09:01.260
Mark Kushner: Because…

561
01:09:02.490 --> 01:09:18.590
Mark Kushner: you know, you… each bounce is a result of electrons getting more acceleration, right? And more accelerate… stronger accelerated electrons react stronger with the magnetic field component that wants to jar turn them around and kick them out of the

562
01:09:18.750 --> 01:09:20.200
Mark Kushner: Out of the,

563
01:09:20.830 --> 01:09:30.599
Mark Kushner: out of the system, out of the export region, right? So, it's maybe conceivable that you… if you had a very flat

564
01:09:30.800 --> 01:09:34.399
Mark Kushner: Current sheet, very flatway connection region for some reason.

565
01:09:34.410 --> 01:09:53.839
Mark Kushner: that electrons could bounce more often, but you probably… it's very flat, you also get less, reconnection rate, because the electric field will be weaker, and the aspect ratio is smaller. So, you can't say it will never happen, okay, but I wouldn't bet money on it, okay?

566
01:09:55.770 --> 01:09:59.950
Mark Kushner: There's too many. Yeah, on the… so, on the multi-scale coupling,

567
01:10:00.000 --> 01:10:18.719
Mark Kushner: you know, a lot of recent reconnection physics has been about the interaction between the ion diffusion region and the electron diffusion region. Yes. Conceivably, if your environment is… has a lot of, say, heavier ions, like oxygen, then you could have a much bigger oxygen diffusion region. So, what effect would that have on the reconnection process?

568
01:10:19.340 --> 01:10:37.600
Mark Kushner: So, yeah, that's a really good question. So, in principle, if your scales are large enough, okay, then you have another consistency problem here, okay? You need to have the electric field expressed through the oxygen ions, which you can, right? Be consistent with all the other electric fields, which

569
01:10:38.090 --> 01:10:47.159
Mark Kushner: creates another equation. What we have shown is that for a limited amount of time, when we were still in Bergen studying this, that

570
01:10:47.310 --> 01:10:50.380
Mark Kushner: Reconnection proceeds almost unaffected.

571
01:10:50.440 --> 01:10:59.060
Mark Kushner: by the oxygen, because the oxygen is so heavy that it just doesn't react on those scales, okay? But if you run long enough, then the

572
01:10:59.100 --> 01:11:12.449
Mark Kushner: oxygen will have to couple into this just like any other ion, okay? And you're going to have mass loading, and things will slow down as a result, okay? And until you come to a reconnection rate that's,

573
01:11:12.490 --> 01:11:32.199
Mark Kushner: basically consistent with the… with the oxygen, or the combined alpha in speed, right, of all the species, which by mass is largely oxygen. So we did some studies on that that seemed to bear… bear that out, based on pig simulations, and you're absolutely right, you need to have that consistency as well.

574
01:11:33.710 --> 01:11:40.889
Mark Kushner: Sure. Take the delivery of taking the last question. Of course. Have you thought about… I mean, you presented the,

575
01:11:41.480 --> 01:12:01.110
Mark Kushner: the, reasoning how you couple the electron to ion scales, have you thought about what is the physics of coupling that to the global scales when we see this very coherent process that involves higher magnetosphere? Yeah, that is a really… So, I mean, on the very large scale, of course, the communication medium

576
01:12:01.270 --> 01:12:04.010
Mark Kushner: alternate waves, right? So you can…

577
01:12:04.020 --> 01:12:20.519
Mark Kushner: This is… this is my… one of my favorite pet peeves with those people who say we have a null point on each side of the nitosphere, and they control what reconnection happens on the… on the day side. It can possibly be happening because it can communicate fast enough.

578
01:12:20.530 --> 01:12:29.139
Mark Kushner: Right? The fact that something changes in this inner region here can only be communicated with something that's further away by… if I send a wave out, it's…

579
01:12:29.380 --> 01:12:38.730
Mark Kushner: It's like a sound wave, you know, you cannot hear what I'm saying until you hear the sound wave that I'm sending out, right? So,

580
01:12:39.290 --> 01:12:52.989
Mark Kushner: So… so if you're too far away, then you have to wait. You get a delayed reaction, because it takes a while for the wave to propagate out. So I'm very convinced that alphan waves are going to play a key role in this. Now.

581
01:12:53.400 --> 01:12:59.099
Mark Kushner: The details of the physics, you know, we need… we need to work out, okay? Because…

582
01:12:59.480 --> 01:13:15.110
Mark Kushner: This electron diffusion region is this tiny little thing, okay? And we're converting huge amounts of energy that can't all go through this tiny little region. No physical system would ever do that. Instead, it's converted all the way along this outflow region.

583
01:13:15.280 --> 01:13:21.650
Mark Kushner: Yeah? That's where the energy… I mean, energetically, this little effusion region is totally irrelevant.

584
01:13:21.760 --> 01:13:30.440
Mark Kushner: Yeah? Totally irrelevant. We still need it, and we can work without it, okay, but it's totally irrelevant. So we have that conversion on the large scale, and

585
01:13:31.000 --> 01:13:54.680
Mark Kushner: you know, when that starts, and what it's supposed to do, has to rely on this communication by alphan waves. But how exactly it does that is still something we need to understand, and how that communication works, you know, that we don't… don't run ahead of each other, yeah? And how it runs so quickly. How it runs so quickly, exactly. I think there's a class starting in 30 seconds here, so I think we need to start. Okay.

586
01:13:54.680 --> 01:13:57.010
Mark Kushner: Very much. Thank you.

587
01:13:57.980 --> 01:13:59.619
Mark Kushner: Don't they very much.