WEBVTT 1 00:00:13.140 --> 00:00:13.980 Mark Kushner: Oh. 2 00:00:29.450 --> 00:00:32.040 Mark Kushner: I didn't have. 3 00:00:37.672 --> 00:01:15.309 Mark Kushner: And after that he started working on the energetic part 115. 4 00:01:15.550 --> 00:01:30.529 Mark Kushner: And there is a work on a lot of things which we will talk about today in terms of energetic charge particles in magnetosphere, and 5 00:01:58.360 --> 00:02:03.199 Mark Kushner: he also is the leader of so called ultra 6 00:02:03.450 --> 00:02:26.650 Mark Kushner: for his contributions in understanding the Juvia manosphere and the Jupiter. 7 00:02:26.820 --> 00:02:35.706 Mark Kushner: and with that inform me of welcoming, we have this 8 00:02:37.070 --> 00:02:44.250 Mark Kushner: Oh, thank you very much. Thank. Oh, this is fantastic. Thank you so much. 9 00:02:44.410 --> 00:02:49.668 Mark Kushner: Oh, oh, oh, yes, okay, so so 10 00:02:54.800 --> 00:02:56.808 Mark Kushner: okay, thank you. Thank you. 11 00:02:58.721 --> 00:03:04.148 Mark Kushner: Yeah, thank you so much for the opportunity to come here and talk about some of my research. 12 00:03:04.480 --> 00:03:28.720 Mark Kushner: so a couple of things. One thing I'm heavily involved in instrumentation these days. So this is kind of kind of like a side hobby. It seems at the moment in between deadlines and a lot of paperwork that that goes along with instrumentation. So I like to think about Jupiter's Aurora, and and in particular some of the mysteries pertaining to the polar cap region which we define here, as this region. Here, pull word of the main emissions. 13 00:03:29.030 --> 00:03:51.730 Mark Kushner: And I also just want to apologize ahead of time. I recently got over a flu, and I've been talking a lot today, and so the throat I can feel is is struggling a little bit. So I might be pausing, drinking water and and all that. So just bear with me. So today, like I just said, we'll, we'll focus on this the so-called Polar cap region. I have here. 14 00:03:51.990 --> 00:04:07.850 Mark Kushner: 3 pictures. One of Jupiter's Aurora, one of Earth's, and one of Saturn's. And and the main point that I would like everyone to take away is that it clearly. You can clearly see how different oops. Let me see here. 15 00:04:07.970 --> 00:04:09.050 Mark Kushner: maybe 16 00:04:09.310 --> 00:04:19.379 Mark Kushner: you can clearly see how different at just a high, level perspective. Jupiter is. Compared to the, you know, its counterparts in the solar system, earth and Saturn. 17 00:04:19.707 --> 00:04:35.090 Mark Kushner: You know earth has a void of emissions, not all the time, but most of the time there's lack of emissions inside what's called this open, closed field line boundary that defines the aurora oval here, this region being connected to more of the open field lines. 18 00:04:35.090 --> 00:04:51.290 Mark Kushner: Similar story here at Saturn. But you see a lot of emissions, and they flicker on and off with various timescales, and the question is like, the very fundamental is like, why and what's driving those emissions? And so we'll kind of step through an overview of 19 00:04:52.590 --> 00:05:14.939 Mark Kushner: of Jupiter's aurora and its space environment briefly touch upon some of the main emissions that are not associated with the polar aurora, and then go into some of the major discoveries and open questions about the polar cap and the Aurora missions there, and if there's a little bit of time left, I can talk about the future of Jupiter exploration as well. 20 00:05:16.930 --> 00:05:41.020 Mark Kushner: So I wanted to start this off with kind of the human perspective of Aurora. So of course, this is the Northern lights here on Earth. This was taken in Iceland at this conference several years ago at the outer planet Moon Menesphere Conference. Some of you may have may have been there. This was a fantastic time, because, I remember in the hotel people were just 21 00:05:41.020 --> 00:05:48.329 Mark Kushner: gathering others to go outside. Some people were outside in cold temperatures and just their Pjs because they wanted to cap. They wanted to see this firsthand. 22 00:05:48.370 --> 00:06:11.500 Mark Kushner: So these types of emissions here are a role emissions driven likely by the acceleration of particles into the atmosphere. And so you see colors like green reds depending on what molecule or atom is being stimulated, as well as where that is, in the where it's being excited in the altitude of the earth's atmosphere. 23 00:06:11.500 --> 00:06:36.429 Mark Kushner: And so you see the kind of the dance of the curtain, and what you maybe don't see right away is that this is basically telling you, giving you context or telling you what's going on in the outer magnetosphere of earth. So they are connected to the magnetosphere through magnetic field lines that thread the ionosphere and then go out thousands of kilometers away, and are remotely telling you something about active 24 00:06:36.430 --> 00:06:40.870 Mark Kushner: processes out there that are transporting and energizing particles. 25 00:06:42.160 --> 00:06:43.330 Mark Kushner: So 26 00:06:43.600 --> 00:06:51.780 Mark Kushner: moving from the kind of humans perspective here at Earth, if you look at. You know the kind of context that these auroras provide you. 27 00:06:51.780 --> 00:07:14.570 Mark Kushner: and maybe more fundamentally, what's driving them? You kind of put together a picture like this. And so you have a solar wind, variable solar wind forcing, driving Earth's magnetosphere, and then you have substorm activity that can transport and energize particles and alter the field line current systems here at Earth that will produce those nice, amazing, rolled displays. 28 00:07:14.570 --> 00:07:36.099 Mark Kushner: There's also what I showed you was these discrete aurora arcs. But there's also a diffuse aurora tube, which is a different mechanism, which is usually scattering of plasma and energetic particles of quasi-trapped plasma and magnetic field lines into the atmospheric loss cone, and therefore those particles are interacting with Earth's atmosphere, creating those emissions. 29 00:07:38.460 --> 00:07:57.249 Mark Kushner: moving a little further in. And I apologize. This is going to be hard to read, but maybe I can just talk to it. This is what a space physicist view of Earth's Aurora might look like. And so and by this, I mean, you know, flying a spacecraft with particle instrumentation, wave instrumentation, magnetic field instrumentation and diagnosing 30 00:07:57.250 --> 00:08:17.729 Mark Kushner: the plasma that's associated with these auroral forms. So I even have to look at my computer to walk through this. But I think the main takeaways that I want to point to are these upward current regions, downward current regions, and these so-called Alphanic or broadband acceleration regions. And so these are the type of different flavors that are associated with 31 00:08:17.730 --> 00:08:20.340 Mark Kushner: with Earth's aurora. And so 32 00:08:20.340 --> 00:08:44.410 Mark Kushner: when you have upward current regions here, you see that you have precipitation of electrons that have these. And this red band here is shown as energy as a function of time. This red band is to illustrate that these are electron distributions that are peaked in phase space. So they tend to be monoenergetic. So maybe tens of Kev precipitating. And so that is 33 00:08:44.760 --> 00:09:00.160 Mark Kushner: likely produced by an electrostatic acceleration phenomenon which is outlined here by these kind of v shock potentials that are often drawn to illustrate the the acceleration of particles that are following through these electric fields. 34 00:09:00.160 --> 00:09:27.800 Mark Kushner: And then you also have a downward current region, or where you would not, or you not see emissions, and there you can kind of see the absence of those precipitating monoenergetic electron beams. And then you also have broadband, Alphanic aurora, where now you see that the energy content of the electrons is no longer heathen phase, space, but has these kind of broad energy distributions that are also creating emissions. 35 00:09:29.400 --> 00:09:58.179 Mark Kushner: So why? Why is the why studying Aurora? Why is that important? And it's important? Because the aurora itself, as I already described earlier not only provides context in what we try to understand as the magnetosphere in general, but the aurora also plays a key role of the interface between the ionosphere atmosphere and the magnetosphere. And so, if you want to understand the system of systems that the earth. 36 00:09:58.180 --> 00:10:23.120 Mark Kushner: the earth has, you need to understand the energy deposition into the atmosphere which can be significant from particle precipitation. It is definitely significant at the outer planets. Solar radiance can't account for the kind of so-called energy crisis where you see basically the temperature of the atmosphere. And so what you need, in addition to solar radiance is a lot of energy input into the upper atmosphere. 37 00:10:23.120 --> 00:10:42.389 Mark Kushner: And that has now been confirmed that a world precipitation is a key driver of that. And so at Jupiter, I think it's something like it adds like something 5 times to the heat kind of problem through the redistribution of heat from the precipitation of electrons and over its polar magnetosphere. 38 00:10:44.090 --> 00:11:07.889 Mark Kushner: Of course auroras are not unique to Earth, otherwise I would not be giving this talk focused on Jupiter. But you know we see them at Mars. This is from Maven, and you can kind of see some aurora emissions indicated by these white colors here, and then Hubble has played a big role in our understanding of auroras elsewhere in the planet. So you can kind of see artist renditions of 39 00:11:07.890 --> 00:11:25.639 Mark Kushner: superposing hubble data onto Saturn's southern hemisphere. Also, Jupiter's northern hemisphere. This is from Hubble and Ganymede, too, and so the moons themselves can also have Aurora, because they have tenuous atmospheres and embedded in energetic plasmas as well. 40 00:11:25.640 --> 00:11:26.680 Mark Kushner: And then. 41 00:11:26.840 --> 00:11:48.780 Mark Kushner: finally, you know, there are exosolar examples of possible, you know, brown dwarfs having aurora, too. This is purely an artistic rendition of interpreting radio emissions, and thinking that that might be caused by Aurora. So we definitely cannot resolve that from Earth. So this is just what we may think it might look like. 42 00:11:49.620 --> 00:12:08.450 Mark Kushner: So now, I would like to kind of transition, because there's a lot to get through within the hour like to transition into Jupiter Space environment. Introduce that and also Jupiter's auroras. And so I want to focus on some similarities and differences between Jupiter and Earth and the other planets. So 43 00:12:08.630 --> 00:12:29.119 Mark Kushner: one thing that stands out is Jupiter's magnetosphere is extremely vast. And so this here is a graphic provided by Fran Baganol and and her husband. And so you can kind of see how the magnetospheres the size of the magnetospheres scale with the different planets. And so. 44 00:12:29.120 --> 00:12:50.680 Mark Kushner: you know, Jupiter's subsolar point can be something like 60 to 90 Rj. And then along the flanks. It's hundreds of Rj. And one Rj. Or Jovian radius is roughly 70,000 kilometers. So that gives you a sense of how much space these magnetospheres take up in space. 45 00:12:50.760 --> 00:13:00.340 Mark Kushner: So the Jupiter's magnetosphere is also filled with energetic plasmas, and it has a current sheet that goes out to the magnetopause, and it also has multi mev 46 00:13:00.560 --> 00:13:05.519 Mark Kushner: electrons and ions that also go all the way out to the outer edges of this magnetosphere. 47 00:13:08.000 --> 00:13:35.259 Mark Kushner: Here's a comparison of the composition and the charge state of the plasma at Jupiter. So on the left. Here is Earth Jupiter in the middle, and Saturn on the right. This comes from the same instrument that visited all 3 of these planets. So this is the Cassini chems instrument. So during its Earth flyby it measured Ion composition and charge state that is very well known to be predominantly hydrogen and helium, and being alpha particles sourced by the solar wind. 48 00:13:35.681 --> 00:13:46.239 Mark Kushner: At Jupiter. It had a distant excursion of its magnetosphere, I think, around 100 Rj. On the flank. But it's a nice example, because it illustrates. 49 00:13:46.600 --> 00:14:09.070 Mark Kushner: you know there's a lot of sulfur and oxygen in addition to hydrogen and helium and alpha particles, and the oxygen and sulfur really can have all these charge States. And those charge states are essentially created by the Ion electron temperatures in the inner magnetosphere. But they can also be affected by additional processes of interacting with gases in Jupiter's magnetosphere. 50 00:14:09.070 --> 00:14:21.190 Mark Kushner: And then, of course, Saturn. In looking at Saturn, it compares in comparison. You can see that Saturn has a lot of water group products because of its inner moon, Enceladus, sourcing water via its plumes. 51 00:14:24.100 --> 00:14:48.819 Mark Kushner: So if we look at the inner magnetosphere at Jupiter, what we see are that there are, you know, these Galilean moons. A few of them are icy moons. Ganymede is interesting because it has its own magnetic field strong enough to provide enough pressure to basically form its own Mini magnetosphere within Jupiter's plasma environment, magnetic field and plasma environment. 52 00:14:48.820 --> 00:15:13.769 Mark Kushner: You also have Europa, which is thought to be active. Maybe there's maybe there's some plume activity as well there. I/O, for sure, is a very active world, providing sulfur dioxide through volcanic activity. You know. Sulfur dioxide frost that then gets liberated and added to the Jovian system through many to spheric interactions. And then there's also Callisto as well. 53 00:15:13.770 --> 00:15:14.320 Mark Kushner: So 54 00:15:14.722 --> 00:15:37.280 Mark Kushner: these moons here provide. Especially I/O, is the dominant one in Europa to a lesser extent provide the plasma that fills the Jovian magnetosphere. So it's predominantly sulfur and oxygen and then you also have some hydrogen and other water group products as well, and the moons are also embedded in Jupiter's very energetic radiation environment. 55 00:15:40.970 --> 00:16:01.759 Mark Kushner: So because this is a, you know, physics. Presentation, I figured like equations might be nice, so I don't have a lot of equations, but this one, I thought, is worth worth putting up, because it shows kind of the current systems that arise from those moons in the fast co-rotation of Jupiter's magnetosphere 56 00:16:01.760 --> 00:16:18.440 Mark Kushner: that arise from these kind of interactions. And so what you see here are the perpendicular currents and the various terms that add to that. But of course it's the divergence of that that gives you the field line currents that then cause particles to precipitate creating the aurora. So 57 00:16:18.730 --> 00:16:39.380 Mark Kushner: here is just this schematic, and on the top is an equation that is often applied to Earth's magnetosphere, where you have the pressure gradient and the pressure and isotropy. And then you have basically flows also an acceleration term or a flow term here, and what you do at the outer planets that are more rotationally driven is that you can. You can break this up 58 00:16:39.380 --> 00:17:02.590 Mark Kushner: with some assumption on its time dependence into centrifugal and the Coriolis driven force. So, of course, the centrifugal force has to do with the kind of fast rotation of the Jovian magnetosphere and the Coriolis force is basically the negative, the centripetal force. So this is kind of the outflowing plasma from I/O that is constantly produced, and that flows outward. 59 00:17:02.970 --> 00:17:27.569 Mark Kushner: this whole system, taking those ions that are created at Ion, Europa, and then it has to spin them up to co-rotation there. This whole system tries to do that, but it's not perfect. And one way to kind of communicate stresses between the mass loading of the field lines is through field line currents between the ionosphere and the magnetosphere and those field line currents. And the resulting 60 00:17:27.589 --> 00:17:35.939 Mark Kushner: current system here highlighted in red basically form. This very extended non-dipolar field line geometry. 61 00:17:38.190 --> 00:17:39.014 Mark Kushner: So 62 00:17:40.090 --> 00:18:00.609 Mark Kushner: these kind of currents in the current system produce. You know this amazing display of aurora missions that you would see through a UV telescope staring at Jupiter. And so here it's quite complex in some ways. So you know, here is kind of the main emission of Jupiter's Aurora. 63 00:18:00.990 --> 00:18:11.229 Mark Kushner: Unlike Earth and Saturn, this does not map to an open closed field line boundary where you have the magnetic field lines tied to one end to the solar Imf. 64 00:18:11.250 --> 00:18:20.089 Mark Kushner: But this is rather is indicative of a region of this kind of co-rotation breakdown, or where there's significant. 65 00:18:20.090 --> 00:18:43.300 Mark Kushner: you know, stresses from that kind of mass loading. So this is mapped to the middle magnetosphere, and then you have emissions associated with the moons. And so the moons have their own kind of current system generated through alphane wings that can create, accelerate, and precipitate particles in the upper atmosphere of Jupiter. And then you also in the polar region, which is where we'll focus the rest of the talk 66 00:18:43.340 --> 00:18:47.929 Mark Kushner: you'll have. You can see that there are a lot of patchy, bright emissions there as well. 67 00:18:49.290 --> 00:19:08.460 Mark Kushner: When you look at Hubble, and you, you know, stare at this kind of these emissions long enough, you can break them up and categorize them in many different ways. And so it's quite a complex picture and many physical phenomena that add to this picture. And it's really this kind of. 68 00:19:08.460 --> 00:19:20.829 Mark Kushner: you know. Number 11, ish number 9 and 11 region that we'll focus on where one for reference highlights this kind of main emission 6. Here is the satellite footprints, and so on. 69 00:19:23.520 --> 00:19:44.409 Mark Kushner: It's not just UV, that's important. At Jupiter. X-rays also play a role in the whole current system mainly as tracers of very energetic ion precipitation, or maybe non-thermal electron emissions from Bremstrahn. So here are some early results from Chandra. I think these are both from 70 00:19:44.410 --> 00:20:07.339 Mark Kushner: Chandra. Maybe I can't remember. Nonetheless, you can kind of see that the X-ray emissions here are concentrated in the northern southern hemispheres, kind of co-located where the auroral regions are, and then here's a reprojection of some of that data with the larger dots representing hard X-rays, or likely Bremsstrahn, and the smaller dots representing soft X-rays, which 71 00:20:07.340 --> 00:20:17.709 Mark Kushner: which are basically arise from very energetic ions precipitating into the upper atmosphere, becoming fully stripped, and then giving off X-rays. 72 00:20:18.490 --> 00:20:36.159 Mark Kushner: And so you can kind of see a concentration of these soft X-rays in particular regions in the Polar Cap region, and it's always been wondered, you know, what is accelerating those ions. How are those X-rays really produced? And we can talk about that a little bit too later in the talk. 73 00:20:36.930 --> 00:20:52.059 Mark Kushner: So where do the polar cap Aurora map to? So in the early in the early days. I guess you know, early, 2 thousands, about 20 years ago there was a picture here shown that basically shows the ionospheric flows. 74 00:20:52.070 --> 00:21:13.280 Mark Kushner: And so it might be hard to read. But the point that I want to is this kind of hashed region of the open flux. And so it was thought that the Jupiter's polar region is probably maybe open. So maybe similar to Earth. And maybe this patchy, like emissions, were somehow controlled by solar wind or something like that. 75 00:21:13.550 --> 00:21:25.270 Mark Kushner: although shortly after, in the mid 2 thousands, there was a kind of fundamentally different picture provided about the opening and closing of magnetic flux around Jupiter. And this was by Dave Mccomas and Fran Baganel 76 00:21:25.270 --> 00:21:49.310 Mark Kushner: that showed that. You know there's no need for a dungy like cycle, because you can have solar wind, Imf. Magnetic field lines, kind of draping around the magnetic field of Jupiter, and reconnecting here along the magnetopause flanks and shedding that flux down the tail that way. Unlike, you know, basically adding a lot of pressure and modifying the inner magnetosphere topology. 77 00:21:53.530 --> 00:22:13.639 Mark Kushner: Okay, so that was a fairly quick overview of the Aurora and Jupiter Space environment and some aspects of Jupiter's Aurora. So now I'd like to turn to this wonderful mission that we have called Juno, that has been in orbit around Jupiter since 2016. So Juno is a 78 00:22:14.260 --> 00:22:17.089 Mark Kushner: solar powered spacecraft. It's also a spinner. 79 00:22:17.120 --> 00:22:45.989 Mark Kushner: and on the spacecraft there are a whole instrument suite used to go after the origin, the interior, the atmosphere, and the magnetosphere of Jupiter in particular. I'll be showing data from Jedi, which is a high energy, particle, instrument jade, which are more low energy, thermal particle instrument, and also Uvs and ultraviolet imager and spectrometer and a plasma waves investigation. 80 00:22:47.020 --> 00:22:49.650 Mark Kushner: So do you know 81 00:22:49.990 --> 00:23:00.090 Mark Kushner: Juno has this particular polar orbit, and because of the extreme radiation environment that Jupiter pose a very hazardous risk to spacecraft. 82 00:23:00.230 --> 00:23:16.610 Mark Kushner: you can see that the orbits here at Juno basically skim very close to the planet, and they go underneath these kind of very high energy, trapped regions that are associated with Jupiter's inner radiation belt and synchrotron emission. 83 00:23:16.940 --> 00:23:35.639 Mark Kushner: And so the orbits look like this, and they kind of precess and evolve in this nature. And this is a bit outdated here. We're now at Orbit 70, because the extended mission is still going strong, but you can see the closest approach we've actually been down to roughly 3,000 kilometers or so above the clouds. 84 00:23:35.640 --> 00:23:47.960 Mark Kushner: So we get access to the aurora regions very close to the planet, and we can measure those kind of what's happening in the lost cone. So the particles that are actually creating those aurora emissions. 85 00:23:48.660 --> 00:23:58.702 Mark Kushner: By the way, I I don't know if there's a particular format. But if you want to raise your hand, if something's not clear that's totally fine by me. I'm happy to fill questions along the way. So 86 00:23:59.820 --> 00:24:11.670 Mark Kushner: So here is just another view of that Juno orbit and its evolution. And so this plot here represents basically a bird's eye view 87 00:24:11.670 --> 00:24:37.549 Mark Kushner: where it shows that Juno originally entered on the dusk side, and its evolution has brought the spacecraft to almost all local times in Jupiter's magnetosphere. And we're now looking at another extended mission that would keep bringing it around. What this projection is not showing you, however, is that its line of absidies are moving more and more southern latitudes. 88 00:24:37.710 --> 00:25:05.150 Mark Kushner: That's why you see this kind of odd projection effect here. But this is also what the cylindrical trajectory looks like. This is like Rho and Z, and you can kind of see that again. Jupiter's access in Juno has access to Jupiter very close to the planet. But also, if anyone's interested, it also has these flybys of the moons, and it goes through very interesting regions, and, like the ring region and radiation belts. 89 00:25:05.650 --> 00:25:22.179 Mark Kushner: so part of the extended mission, the 1st extended mission was to tweak the orbit such that we really accessed lower and lower altitudes to try to get at these plasma acceleration regions that we thought were present in generating those patchy emissions that I showed earlier. 90 00:25:24.315 --> 00:25:30.860 Mark Kushner: Before I do that I wanted to. I didn't want to completely. you know. 91 00:25:30.890 --> 00:25:59.270 Mark Kushner: basically disregard the main Aurora region. So I'll talk about this very quickly. But I also would like to give a shout out to Ali Suleiman, who gave a mipsy talk here. Fall of 23. His presentation is online, and he covers these Aurora regions in great detail, and he did a fantastic job. So I recommend that, nonetheless, before we get into the polar region, I will say that Jupiter, like Earth, has these different aurora regions. 92 00:25:59.270 --> 00:26:16.209 Mark Kushner: They have a diffuse auroral region which is primarily due to the precipitation of particles from the radiation belts through wave particle interactions. And then, if you move forward a little bit. You have these more discrete oral arcs, that kind of match, maybe what we saw earlier from that video. 93 00:26:16.460 --> 00:26:28.800 Mark Kushner: And so these are associated like also what I showed earlier, associated with peak energy distributions. So these would be electrons that have, instead of tens of Kev. They now have hundreds of Kev of acceleration. 94 00:26:28.800 --> 00:26:50.239 Mark Kushner: and then, if you keep on moving forward, you have the zone 2, which is now might be analogous to maybe some of the kind of like Alphanic acceleration stuff where you have bidirectional acceleration in this region as well, and and you no longer have this kind of peak energy distributions, but maybe predominantly broadband acceleration. 95 00:26:51.280 --> 00:26:55.919 Mark Kushner: And then, of course, as you move forward of this boundary here, you're now in the so-called polar cap. 96 00:26:58.400 --> 00:27:24.820 Mark Kushner: So 1st off this is what Juno's Aurora looks like from a very high resolution picture of instruments on the Juno spacecraft, so no longer do we have. You know Hubble is a fantastic asset, but there's nothing like being in situ making these measurements. So on the left you have a brightness plot. On the right. You have a color ratio. The color ratio is a ratio of the absorbed versus unabsorbed 97 00:27:24.820 --> 00:27:31.319 Mark Kushner: UV light, and that gives you a sense of how energetic or how deep the emissions are occurring. 98 00:27:31.570 --> 00:27:32.560 Mark Kushner: So 99 00:27:32.860 --> 00:27:58.300 Mark Kushner: you can see that the emissions along the main aural region can be thousands of Kiloraleys, and even in the polar cap they can be hundreds to thousands of Kiloraleys as well, depending on the type of acceleration process generating those emissions. On the right hand side you can see that the Polar Cap region is filled with very high color ratio. So this is indicative of very energetic electrons precipitating 100 00:27:58.360 --> 00:28:14.999 Mark Kushner: one of the big mysteries is that we do not see those. So there might be a hint that we're getting close. But one of the big mysteries is what are causing these deep emissions. If we don't see those very energetic electrons from Geno, as it skims over the low altitude polar Cap region. 101 00:28:17.080 --> 00:28:36.329 Mark Kushner: So one of the 1st major discoveries that Juno made shortly after it arrived at Jupiter is so. Here was these presence of these upward electrons and meb ions, and so to set the stage a little bit. Here are the auroral ovals in this kind of false color. 102 00:28:37.590 --> 00:28:39.330 Mark Kushner: Can I hang up on this person? 103 00:28:40.900 --> 00:28:45.017 Mark Kushner: Okay, someone's calling you on zoom. 104 00:28:47.710 --> 00:28:52.137 Mark Kushner: it's about car insurance. I guarantee it. Yeah. So okay, 105 00:28:52.780 --> 00:29:16.799 Mark Kushner: so here are these false color images from Juno Uvs. And this faint line, if you can make it out, is the magnetic footprint of the Juno spacecraft kind of superimposed on on that particular hemisphere. And so Juno's magnetic footprint. So where where it flew through the Aurora region, is shown here, and then also shown here. 106 00:29:17.160 --> 00:29:37.059 Mark Kushner: Now, if you look below, these are data that kind of correspond to the northern and southern hemisphere, and separated right here. So north, on this side, south on this side what you see this is pitch angle versus time for the very energetic electrons. What you see are these monodirectional upward going electron beams in both the North and the Southern hemisphere. 107 00:29:37.060 --> 00:29:48.920 Mark Kushner: and I don't show every perigove. But I can say with confidence that this is a this is, they're very prevalent. They're almost always there. It's a characteristic of being in the Polar Cap region. 108 00:29:49.300 --> 00:30:11.799 Mark Kushner: Another thing that is also a pretty common picture are the precipitation of Mev ions. And so here are basically the kind of energy versus time of energetic hydrogen and oxygen sulfur. And it's a little hard to tell, but you can kind of see that these color bars shows this increasing intensity. 109 00:30:11.800 --> 00:30:23.429 Mark Kushner: and then it peaks around a couple mev, and then it kind of goes back down, Matt, maybe creating so-called inverted V's, which are a phenomenon known earth. Here is a more 110 00:30:23.740 --> 00:30:36.700 Mark Kushner: recent picture showing these proton acceleration here and then the heavier iron, heavy ion acceleration here. So this would be proton, oxygen sulfur, and a combined oxygen and sulfur channel. 111 00:30:36.890 --> 00:31:02.060 Mark Kushner: And so very clearly. You see that there is ions that are precipitating, due to electrostatic potentials, having these peaked phase based distributions. Now, these distributions here that are likely, the ones that are contributing to the soft X-rays that I showed earlier. They have enough energy to produce the X-rays, and we see them that they tend to fill the Polar cap region. So that's a nice kind of correlation between the 2. 112 00:31:03.960 --> 00:31:18.180 Mark Kushner: So it's natural to kind of ask how how you can create these kind of unidirectional upward electron beams and perhaps downward ions. There have been a couple of theories. So one by Adam Masters that suggests that 113 00:31:18.320 --> 00:31:46.349 Mark Kushner: component reconnection at the low altitudes might be driving, you know, energization where you convert magnetic energy into kinetic particle energy through through reconnection here. And so I would say, this is still very much in the theory realm and hasn't really been, I don't think, proven necessarily through the data, but it's very interesting. And to keep in mind as we look at the observations. 114 00:31:46.350 --> 00:32:01.489 Mark Kushner: One thing to note here is that this is very different than kind of your classical magnetic reconnection, because the guide fields here can be on order of like 10 Gauss or more. So it's not. It's not at all kind of like the reconnection processes that happen. I believe ever 115 00:32:03.960 --> 00:32:27.449 Mark Kushner: another potential mechanism for generating Megav potentials is the fact that maybe you have absence of current carriers in the region that demands current. So if you. If you have a lack of current density carriers, then one way to compensate for that is, by accelerating them, to to maintain some current density that the system requires. And so 116 00:32:27.590 --> 00:32:48.210 Mark Kushner: some studies have shown that when you look at the density profiles of the plasma, and as you move to more and more poleward regions that the density falls off really drastically as you go to the higher magnetic latitudes, and where it falls completely, is kind of unknown. But it could be fraction of a CC. 117 00:32:48.210 --> 00:33:16.549 Mark Kushner: When you take when you look at the kind of current voltage relationships, and you look at how much electric field you need based on the low densities you know you can require. You can very easily compute a megav of acceleration based on something like 0 point 0 1 CC's plasma density, you know, just through a very kind of simple relationship with current density approximated by en times V. 118 00:33:17.870 --> 00:33:47.090 Mark Kushner: other studies have looked at stochastic acceleration and density cavities essentially lower the threshold for alpha dissipation, and could easily create more acceleration in that region. And then also there's an ionospheric alphane resonator formed by rapid decreases in density and phase. Mix and alphane waves. This one I'm less familiar with. But Bob Lysack will tell you that enhances the parallel electric field. 119 00:33:48.400 --> 00:34:07.179 Mark Kushner: So this has been shown many times. This plot here kind of stops right in this inner boundary. But there's been other studies looking at the plasma distributions in the polar cap region. Again, this plot on the left shows electron energy versus time 120 00:34:07.260 --> 00:34:17.290 Mark Kushner: for less than 30 Kv electrons, and it has 3 different regions. And so, or 3 different flavors. It has, you know, highly structured electron events. 121 00:34:17.320 --> 00:34:41.550 Mark Kushner: It has essentially times where it sees no electrons at all, and then, where they're overwhelmed by very energetic particles, causing saturation or radiation effects in their instrument. These 2 here can be thought of as being kind of similar, because in both cases it looks like there's an absence of low energy electrons. And then when you look at how these here map to the Polar Cap region. 122 00:34:41.730 --> 00:35:04.890 Mark Kushner: This blue trace is the main auro region, so anything forward of that is the polar cap, and you can kind of see that the red and light blue box here kind of makes up most of these arcs that the footprint of Juno is making through the Polar Cap region. And then again, if you look at the ions. These were the electrons. But now, if you look at the plasma ions 123 00:35:04.890 --> 00:35:14.909 Mark Kushner: right around here is where you enter the polar Cap region. And again, you can see that due to the sensitivity of the instrument, it basically sees a void of plasma in that region. 124 00:35:14.910 --> 00:35:24.979 Mark Kushner: So it does look like. There's very, very low densities over the polar cap that would necessitate basically strong electric fields to close the current. 125 00:35:26.984 --> 00:35:30.445 Mark Kushner: Moving on to some other major discoveries. 126 00:35:30.960 --> 00:35:49.999 Mark Kushner: it's 4 o'clock, is when it? Oh, 4, 10. Okay, okay. I think we're good. I think we're good. Sorry, even though you do this a lot, you still run into time trouble. So here what we find another thing in the polar cap are observations of significant ion heating and outflow. 127 00:35:50.000 --> 00:36:06.660 Mark Kushner: This is a result by Jamie Solay. So here it looks like when you're at slightly higher altitudes, and Juno is crossing over magnetic field lines. That map to the Polar Cap region. It looks like there is. And this 3rd panel down illustrates it best. 128 00:36:06.660 --> 00:36:15.450 Mark Kushner: It looks like there are proton energy, time, dispersion signatures kind of filling that region. And this is just an example of one. Perigome 129 00:36:15.450 --> 00:36:37.360 Mark Kushner: and Jamie found this for multiple pair of chips. And so the idea here is that there's due to rural processes at the lower altitudes that there's likely significant heating through probably wave particle interactions with the ionospheric ions that are then being heated and forced out, maybe due to the magnetic mirror force, and then they leave the rural region and go out into the main hetosphere. 130 00:36:40.285 --> 00:36:43.964 Mark Kushner: Taking those results and also looking at 131 00:36:44.520 --> 00:37:00.149 Mark Kushner: Looking at other ion data from the more energetic sensor, you can kind of start to get a picture of the kind of composition of the plasma over the polar cap. And that's important. Because earlier, we talked about maybe this debate between open and closed flux. 132 00:37:00.150 --> 00:37:24.870 Mark Kushner: If you have open magnetic flux, you would expect that the composition of the plasma would be more solar wind like, whereas if you're on closed flux tubes, you would expect it to be more magnetospheric like. And so what we find here is that when looking at the composition, we find a lot of oxygen and sulfur ions that have charge states that match what you would see near I/O or the inner magnetosphere. 133 00:37:25.290 --> 00:37:33.319 Mark Kushner: and when you look at where those trace out over the polar cap, you see that they're basically filling almost all regions of magnetospheric plasma. 134 00:37:34.120 --> 00:37:48.089 Mark Kushner: Again, from that Jamie. From that same study they found that those ion outflow events are primarily magneto magnetospheric, and they go up to essentially fill all polar 135 00:37:48.400 --> 00:38:03.960 Mark Kushner: polar cap latitudes and longitudes. So here, being a solar wind type, example of ion composition. And here, being what you see in those outflowing events that match very well with the magnetospheric plasma that is in the outer magnetosphere, Jupiter. 136 00:38:04.240 --> 00:38:15.300 Mark Kushner: so so far it looks like the picture is kind of being painted that the Polar Cap region is unlike Earth, and also is primarily closed. Magnetic flux rather than open. 137 00:38:16.030 --> 00:38:26.729 Mark Kushner: and there's been some modeling to support that recent results by bin zhang using the Gamera Mhd model have shown that 138 00:38:26.760 --> 00:38:44.739 Mark Kushner: have shown that, due to the fast rotation rate of Jupiter, that the amount of open flux appears to be contained in these kind of small swaths in narrow ranges of latitude, and so this would be the green, which is this, Imf open, and you can kind of see this crescent shape here 139 00:38:44.740 --> 00:39:09.250 Mark Kushner: mapped onto the northern hemisphere. And you can kind of see these distant lobe field lines and then these black closed field lines. So it's not as if you just reach a certain latitude, and then it's primarily open. It's much more complex than that. It looks maybe something to do with the rotation rate, and how these things are reconnecting at mid latitudes that would 140 00:39:09.250 --> 00:39:14.930 Mark Kushner: create such a shape of open flux distributed in that region. 141 00:39:16.268 --> 00:39:21.169 Mark Kushner: Peter Delamire, just last year. Was looking at a similar topic. 142 00:39:21.200 --> 00:39:50.390 Mark Kushner: also using the Gamera model. But now plotting things as a function of polar angle here, and L. Shell being the radius. And so you can kind of see here that this color bar represents the percent of open flux in Jupiter's magnetosphere. And again, you can see at the very polar regions the flux appears to be mostly closed, and the and where you see it kind of be more blue, indicating down here you see a lower percentage of open flux, and it's contained to these kind of mid latitudes. 143 00:39:50.630 --> 00:39:59.350 Mark Kushner: Now, looking at the the data, you can see observations from the plasma data and the Juno Jedi more energetic data. So this panel here 144 00:39:59.620 --> 00:40:25.599 Mark Kushner: shows that in correlation with these kind of mid latitudes, you have antico-rotational flows, so you'd expect co-rotational flows to be present as Jupiter's rotate and dragging the magnetic fields with it. However, there seems to be a region of mid latitudes where things are no longer co-rotating, but now are antico-rotating, and that is also indicative of reconnection happening at these middle latitudes with Imf Fields. 145 00:40:26.160 --> 00:40:45.060 Mark Kushner: And then in this region we look at the Ion composition, and we use Helium as a tracer for alpha particles being solar wind origin, and you can kind of see that their abundance also increases at these mid latitudes, further supporting the idea that the amount of open flux is confined to that region. 146 00:40:47.073 --> 00:41:00.729 Mark Kushner: So finally, I think the last like 5 min or so, I'll talk about one more major discovery and some very recent observations that we're making that are kind of exciting. And then we can open the floor for questions. So 147 00:41:00.730 --> 00:41:25.690 Mark Kushner: here one of the big mysteries is, as I've been showing you, these polar capital roll emissions here, showing precipitating of electrons driving UV emissions. However, when you look at the energy content of those precipitating energy. Energetic electrons you find that. And what you need to look for is this black line here? And I'm sorry about this. This black line here represents the energy 148 00:41:25.690 --> 00:41:40.399 Mark Kushner: flux in the particles, and this line here represents the energy flux required to recreate those missions. You can see in the main emission region. There's nice correspondence between the precipitating energy flux and how much is generated through UV. 149 00:41:40.400 --> 00:41:56.309 Mark Kushner: But you can see in the polar cap, that there's a strong disconnect between the stuff precipitating and what we're measuring that also kind of folds into the fact that I showed you earlier that we see mostly upward going things moving away from the planet, and not a lot of precipitation of electrons. 150 00:41:57.570 --> 00:42:08.559 Mark Kushner: So we take advantage of the altitude range of the later orbits at Juno, where we're flying at much lower altitudes over the Polar cap region. 151 00:42:09.370 --> 00:42:20.719 Mark Kushner: And we look at the energetic electron energy and pitch angle distributions at altitudes that are really kind of like 0 point 1 rj, above the one bar level. 152 00:42:21.070 --> 00:42:42.869 Mark Kushner: And so what we're finding here is, you know, here are the energy electron energy versus time. And this is downward downward energy fluxes. And this is the pitch angle distribution. What we're finding here is that we're now in a regime at the low altitudes where things are predominantly precipitating. So it looks like we're below that kind of 153 00:42:42.870 --> 00:43:07.839 Mark Kushner: region where there's precipitating ions and upward electron beams. And we're now entering, perhaps acceleration regions of the most lowest altitudes that are driving precipitation to create those emissions. How this all works in time and space with these kind of contradicting way that the potentials are formed is a little bit beyond me at the moment. But this, so far, is 154 00:43:07.840 --> 00:43:22.689 Mark Kushner: case observationally, and we're seeing that the energy flux carried by these electrons are now starting to get into the tens. And with this case even the hundreds upwards of 100 milliwatts per meter squared. So these can easily drive. 155 00:43:22.900 --> 00:43:38.750 Mark Kushner: you know, hundreds to maybe a thousand kilo Rayleigh like emissions. And so this is exciting, because this is some of the 1st time we've seen such signatures where we're seeing predominantly downward. One electrons now, as opposed to those beams that I showed earlier. 156 00:43:39.280 --> 00:43:49.530 Mark Kushner: And if you look at a very high time resolution of some of these auroral electrons. So here represents just just a minute and a half of data. 157 00:43:49.560 --> 00:44:16.789 Mark Kushner: This is electron energy versus time, and the color bar is flux. And you can kind of see that these particular times right here are when the electrons are precipitating and have the most energy flux, and you can see that their energy distributions are showing some evidence of having peaked phase spaces indicative of perhaps electrostatic acceleration going on above the spacecraft. 158 00:44:16.890 --> 00:44:28.090 Mark Kushner: and that, and they also kind of form these almost inverted V like profiles, which is very characteristic of kind of that V shock profile that I showed very earlier in the presentation here. 159 00:44:32.680 --> 00:44:42.909 Mark Kushner: Finally, we took the oral data and we mapped out where we see the most precipitation, and they seem to be occurring right here on the edge of these polar cap emissions. 160 00:44:43.100 --> 00:44:58.620 Mark Kushner: Why, that is is still a mystery, but they for 3 times now I don't know if it's a coincidence, if it happens 3 times for each time, and right there on the edge of where a thing right before you enter the heart of the polar cab, where all the emissions are occurring. 161 00:45:01.070 --> 00:45:15.090 Mark Kushner: And so, finally, I draw this bar to indicate now the ranges of energy fluxes that we're starting to measure on top of the same plot I showed to show that we're now being able to 162 00:45:15.570 --> 00:45:22.610 Mark Kushner: reconcile the amount of energy you need to drive those ultraviolet emissions. So that's exciting. 163 00:45:24.023 --> 00:45:26.349 Mark Kushner: So I think the 164 00:45:26.650 --> 00:45:47.120 Mark Kushner: big open questions to take away from looking at this plasma phenomenon at Jupiter, especially in the Polar Cap region. Some of the big questions that we have left over, what powers that polar cap, red aurora that I showed earlier, due to the high color ratio. It may be due to some of that energetic electron signatures I showed, but 165 00:45:47.120 --> 00:46:10.790 Mark Kushner: those are so sparse that I would be hesitant to say that we really solved that problem. How are Mav potentials generated? Is it through, you know? Am I coupling processes such as like Alphanic waves. Is it due to these low densities in that region? Is low altitude, component reconnection, playing a role? These are all questions. 166 00:46:11.570 --> 00:46:30.590 Mark Kushner: you know. Can we bring closure to kind of the open, close polar flux polar cap problem. I think we're getting there. But I think there's also more work that can be done between data and models. Model comparison to really nail down where the open flux is at Jupiter, and how that plays a role in its current system. 167 00:46:30.610 --> 00:46:45.719 Mark Kushner: and then Jupiter appears to be I mean Juno appears to have found the low altitude acceleration region, and now we seem to have energy fluxes more commensurate with the UV brightness, you know. Is this the process supplying this patchy emissions? 168 00:46:45.850 --> 00:46:52.970 Mark Kushner: So if you want, I can talk about 2 slides, I think, about Jupiter exploration, or should I stop for questions 169 00:46:53.390 --> 00:47:00.711 Mark Kushner: at the time? Okay, I I can be quick here. So I think, there's 3. There's kind of 3 exciting things. Actually, 170 00:47:01.330 --> 00:47:27.510 Mark Kushner: one is, we're now moving forward with an extended extended mission proposal for Juno. And so Juno has enough fuel and has survived the radiation so far. And we just proposed to the senior review process. And we're hearing back now. But some of the things that we can do is with a new orbit we're afforded with these unique observations, where we can look at the vertical structure of the auroral curtain 171 00:47:27.550 --> 00:47:35.820 Mark Kushner: to understand kind of the energy deposition from those energetic electrons, and how that folds into the whole mi coupling system. 172 00:47:35.820 --> 00:47:58.239 Mark Kushner: The other thing that we can do is leverage Juno's evolving orbit near the boundaries to do, study boundary processes and the nature of the solar wind coupling out there. And so already these yellow and red marks are indicative of times when we cross the magnetosphere or the magneto pause in the Bow shock regions. 173 00:47:58.430 --> 00:48:22.670 Mark Kushner: and they differ from the models greatly. We've had one right here. If you can see this is not an outlier. Apparently Jupiter's magnetosphere was so compressed through a solar event that magnetopause reached around 30 Rj. As opposed to its nominal kind of 100 Rj configuration. So that's very exciting, and maybe we'll see more of those as we move on with the mission. 174 00:48:23.920 --> 00:48:31.939 Mark Kushner: The other thing is juice and clicker will both be in the Jupiter manufacturer at the same time. 175 00:48:32.160 --> 00:49:00.269 Mark Kushner: So we'll have really fantastic opportunity for multipoint observations. And there's been a lot of work that has gone into visualizing the orbits and taking advantage of certain alignments, both in radial and longitudinal distances. And they have some similar instrumentation, too. So we can kind of remove some of these ambiguities you get with single spacecraft and maybe start talking about some real temporal spatial dynamics. 176 00:49:00.910 --> 00:49:12.759 Mark Kushner: So this so essentially, juice gets here in mid 2031, and I think Clipper gets here at the very end of 2030. So Clipper beats us, I think, by roughly, 6 months 177 00:49:13.738 --> 00:49:16.531 Mark Kushner: and finally, something kind of 178 00:49:17.360 --> 00:49:37.889 Mark Kushner: quite passionate about is studying the radiation belts at Jupiter. And so a team of us have offered this mission concept to the Solar and Space Physics Decadal Survey, which is a solar powered mission to kind of go through that inner radiation Belt synchrotron region that most other spacecraft like to avoid. 179 00:49:37.890 --> 00:49:55.619 Mark Kushner: So this mission here was recommended as an example of a mission to go after what the National Academies thinks that heliophysics longer term goal should be which is exploring other planetary magnetospheres. And one thing that we really want to do is outfit this spacecraft with 180 00:49:55.620 --> 00:50:10.359 Mark Kushner: instrumentation to resolve the very, very energetic Ion and electron populations well, above Mev, so we'd like to go up to maybe 75 Ish. Mev. With electrons and hundreds of Gev with ions. 181 00:50:10.710 --> 00:50:36.759 Mark Kushner: The other thing that we want to do is we'll have a dedicated X-ray Imager on the spacecraft, and you can do things you get like 10 to the 7 more sensitivity when you bring an X-ray instrument to Jupiter's magnetosphere, and through this kind of inverse comping, scattering effect through solar ir and multi mev electrons, you can actually image the radiation belts of Jupiter. And so one thing we'd like to do is 182 00:50:36.760 --> 00:50:42.869 Mark Kushner: be able to image kind of the radiation belts of Jupiter with X-rays. To add context to a lot of 183 00:50:42.870 --> 00:50:57.009 Mark Kushner: our observations in situ very much like energetic neutral atom imaging or UV imaging does for other types of science. And so these 3 things right now are kind of the future of Jupiter research. And I think I'll end there. Yeah, thank you. 184 00:51:04.020 --> 00:51:09.300 Mark Kushner: Yeah. I think the floor is open now for questions, comments. 185 00:51:13.200 --> 00:51:13.970 Mark Kushner: Yes. 186 00:51:14.110 --> 00:51:31.599 Mark Kushner: So you mentioned, there's like a location where you get the maximum amount of precipitation. You mapped it somewhere. I mean, it's over the polar cap. Right? Yeah, yeah, that's right. That's right. Have you compared it with the higher, like, you know, hydrocarbon emission regions that people find in the mid 187 00:51:31.780 --> 00:51:51.059 Mark Kushner: spectrum because there's like a hot spot somewhere over there, and we expect particle representation to play a role. But yeah, no, I have not done that kind of detailed like like correlation between those 2 things I know in general, though, that that there 188 00:51:51.670 --> 00:52:10.420 Mark Kushner: particle precipitation does seem to kind of lift that hydro the methane homopause, and it does play effect in the and where the hydrocarbons are distributed. But I can't say for sure with the polar Cap bridge, I know that's more of like a main oral emission kind of effect. So yeah. 189 00:52:11.780 --> 00:52:17.740 Mark Kushner: And Hisaki, by the way, would be a good, a good Hisaki produced some nice measurements on that. 190 00:52:18.220 --> 00:52:19.360 Mark Kushner: Does that reduce 191 00:52:19.470 --> 00:52:27.699 Mark Kushner: spot? The maximum. It seems similar to me when I look at the Ir maps. Oh, okay, okay. Well, yeah. That's that's great to hear. Sure. Okay, okay, yes. 192 00:52:31.240 --> 00:52:46.600 Mark Kushner: Yeah. So in in Earth's atmosphere you can generate these mega volts, potential differences because you have some place to charge store the charge. You know the clouds, ice crystals. And oh, okay, okay. 193 00:52:46.700 --> 00:53:10.559 Mark Kushner: So in the Jupiter atmosphere, is there some place you can store the charge like your charging capacitor that that I don't know. So these these things are much higher altitude things. So these would be, you know, above the ionosphere sort of thing. So that would be where the kind of the impedance region, if you want to call it, that would reside. And so 194 00:53:10.890 --> 00:53:31.809 Mark Kushner: I don't know where, if if similar to you know the clouds supporting Megavolt potentials that that could happen at you. But I suspect there's lightning that happens there. And so I suspect that there's probably similar amounts of energy, because, you know, you need to have that breakdown so. But I can't say with certainty. So 195 00:53:33.830 --> 00:53:47.172 Mark Kushner: on that I remember Juno actually observed lightning events in the atmosphere, those more or less concentrated near the equatorial 196 00:53:48.210 --> 00:54:13.779 Mark Kushner: They were. I know they were distributed in like longitude, but I thought they were maybe kind of like the mid latitudes. But I'm going off a memory of looking at a plot. But I think you know, Bill Kurth, he was looking at Whistler. Mode emissions that I think, are often associated with lightning strikes, generating electrons that stream up. So I think it was those there that he kind of developed a map 197 00:54:14.243 --> 00:54:29.990 Mark Kushner: where the lightning strikes were occurring, and my memory does say kind of more middle attitudes. But I don't know. Maybe. Yes, yes. Please tell me. Okay, okay, thank you. Thank you. Interesting. Yeah. 198 00:54:32.150 --> 00:54:43.520 Mark Kushner: So you might be able to answer next question about the about the Megavolt potentials in the atmosphere? And if so, is the answer, yes, or okay? Okay? 199 00:54:43.680 --> 00:54:44.154 Mark Kushner: No. 200 00:54:47.370 --> 00:54:49.986 Mark Kushner: I have a somewhat related question. Is, 201 00:54:50.800 --> 00:55:04.210 Mark Kushner: You mentioned that during the early phase of, you know, when you guys measure the particle distribution and sort of above the acceleration rate, you're not seeing the full distribution. Yeah. And I figured the 202 00:55:04.330 --> 00:55:08.749 Mark Kushner: the, the location where these region would exist 203 00:55:08.900 --> 00:55:14.349 Mark Kushner: depends on where the density cavity or the density gradient. Yeah, along, yeah. Yeah. 204 00:55:14.680 --> 00:55:26.200 Mark Kushner: And and you show one example where you look at the match. That idea? Yeah. Has anyone looked at this later forwards in terms of enough density profile to kind of confirm 205 00:55:26.210 --> 00:55:49.299 Mark Kushner: now the fact that you're saying you are embedded within the observation. Yeah, I think it's very tricky, because to get a density you need like plasma. And the plasma sensor is not sensitive enough to see kind of like a, you know, to measure a density. And then for the wave instruments you need to look at like characteristic emissions and know where. 206 00:55:49.617 --> 00:56:00.100 Mark Kushner: You know, we're a peak in in frequency, time, space, and how that correlates to a density. And I think there's been some success by Ali and his group looking at omode emissions. 207 00:56:00.566 --> 00:56:02.900 Mark Kushner: And and they found that 208 00:56:03.110 --> 00:56:15.740 Mark Kushner: yeah, there are very. It does support the idea of very low density in the region. I don't think they've done a statistical analysis. I think they've looked at maybe just a few case study events at the at the lower altitudes. So 209 00:56:25.890 --> 00:56:33.280 Mark Kushner: if the Galilean moons weren't there, Jupiter's Aurora be much dimmer. 210 00:56:34.322 --> 00:56:42.080 Mark Kushner: That's a great question. I I don't. 211 00:56:44.440 --> 00:57:06.479 Mark Kushner: Yeah, I think the answer would be yes, and it probably look very, very different. I mean, you wouldn't get the Royal Footprints. You wouldn't have that probably co-rotation breakdown that's supplying a lot of this field line current system. So I think it would be a very different picture if those moons are not actively providing plasma to the system. So yeah, it would be very cool for 212 00:57:06.810 --> 00:57:13.610 Mark Kushner: someone that has modeling tools to kind of play those games and remove the plasma source and all that. Yeah. 213 00:57:19.800 --> 00:57:23.240 Mark Kushner: good questions. Let's thank our speaker again. 214 00:57:27.450 --> 00:57:29.179 Mark Kushner: Okay, thank you all. 215 00:57:34.660 --> 00:57:35.640 Mark Kushner: Oh, we'll see. 216 00:57:36.456 --> 00:57:37.430 Mark Kushner: Thank you.