WEBVTT 1 00:00:00.000 --> 00:00:01.210 Mark Kushner: on magnitude. 2 00:00:02.190 --> 00:00:05.389 Mark Kushner: Dynamo and charged particle acceleration. 3 00:00:05.630 --> 00:00:14.469 Mark Kushner: He holds visiting and guest appointments at the University of Oxford, Lawrence Livermore National Laboratory, and Los Alamos National Laboratory. 4 00:00:14.640 --> 00:00:28.440 Mark Kushner: Petros received the APS John Dawson Award for Excellence in Plasma Physics Research in 2019, an Early Career Award from the U.S. Department of Energy of Office of Science in 2021, 5 00:00:28.610 --> 00:00:34.560 Mark Kushner: and the Presidential Early Career Award for Scientists and Engineers in 2025. 6 00:00:34.820 --> 00:00:41.869 Mark Kushner: The title of this talk today is Laboratory Experiments of Astrophysical Processes and Magnetized Turbulence. 7 00:00:42.090 --> 00:00:45.389 Mark Kushner: But before he gives his talk. 8 00:00:45.800 --> 00:00:52.790 Mark Kushner: We are pleased to present Petros with the MIPSE mug. Excellent. We need to memorialize this. 9 00:00:54.140 --> 00:00:55.459 Mark Kushner: Oh, it'll be screwed. 10 00:00:59.000 --> 00:01:03.190 Mark Kushner: And thank you for making the trek, and I want everybody to know that 11 00:01:03.190 --> 00:01:15.329 Mark Kushner: Echo spent the night in a DC hotel because his flight was canceled, and he's working on minimum sleep, so be gentle with your questions. Or give me coffee and then ask the question. I think that's the… 12 00:01:15.330 --> 00:01:29.970 Mark Kushner: That's the appropriate level of response here. So, thank you so much for the opportunity, thank you for this fantastic opportunity to come to the University of Michigan, to come to MIPSE, and learn about your work, and then share with you the things that we do. 13 00:01:29.970 --> 00:01:49.010 Mark Kushner: The talk today will, will focus on a combination, essentially, of what we have been doing in the context of the Turbulent Dynamo Collaboration, which is a collaboration that we are co-leading with the University of Oxford that does laboratory astrophysics experiments 14 00:01:49.030 --> 00:01:51.940 Mark Kushner: In the context of trying to understand 15 00:01:51.980 --> 00:02:03.239 Mark Kushner: fundamental processes like fluctuation dynamo, charged particle transport in astrophysical environments using laser-driven laboratory experiments. And then. 16 00:02:03.530 --> 00:02:07.539 Mark Kushner: I want to turn this around and see what we can… 17 00:02:08.190 --> 00:02:12.209 Mark Kushner: Learn from the experiments, and incited by the experiments. 18 00:02:12.270 --> 00:02:31.129 Mark Kushner: Try to go back to the foundational simulation approach that we've had for magnetized turbulence up until now, fundamentally driven turbulence in magnetized plasmas, central turbulence and box type of simulations, and then try to bring all of the extra 19 00:02:31.130 --> 00:02:36.749 Mark Kushner: And interesting physics that we're doing in the laboratory into that 20 00:02:36.840 --> 00:02:46.899 Mark Kushner: framework, like, the idealized framework of driven turbulence simulations. The… Work is being funded by… 21 00:02:47.000 --> 00:03:00.980 Mark Kushner: primarily by the National Agriculture Security Administration, the U.S. Department of Energy and Office of Science. Support has been received from the Lifeline Science Foundation, and in general, the Placent on Science 22 00:03:00.980 --> 00:03:10.709 Mark Kushner: is supported by NSA directly, but also from the national labs, like the Salamo National Lab, as well as the Laboratory for Laser and Genetics. 23 00:03:10.740 --> 00:03:18.629 Mark Kushner: The work that I'm showing is part of the Dyna collaboration, so this is an international collaboration that involves 24 00:03:18.630 --> 00:03:31.989 Mark Kushner: multiple institutions from the University of Rochester, the University of Oxford, Queens, University of Belfast, Gettysburg College, Lawrence Livermore, MIT, and UChicago. 25 00:03:32.320 --> 00:03:40.509 Mark Kushner: You can see some of the folks that are, part of the collaboration here. But the work that I'm showing is primarily done by 26 00:03:40.510 --> 00:03:57.550 Mark Kushner: Dr. Hanapool, and, who is, up until recently, was a postdoctoral scholar with the University of Rochester, now she's back in the UK. And, Ananya Mohapatra, who is a graduate student that is about to graduate this, fall, and is very interested in finding 27 00:03:57.550 --> 00:04:11.529 Mark Kushner: new opportunities. She's already interviewing for a few, but the work that she's done is amazing, so I cannot recommend her enough. If you're looking for a brilliant scientist to do theoretical, fundamental research. 28 00:04:11.580 --> 00:04:14.689 Mark Kushner: This is it. Okay. 29 00:04:14.720 --> 00:04:30.359 Mark Kushner: So, let's contextualize a little bit what we're going to be talking about today. The target is going to be magnetized turbulence, which is a process that is ubiquitous in the universe in the sense that wherever you look, you will find, essentially. 30 00:04:30.360 --> 00:04:40.019 Mark Kushner: plasma conditions whose non-dimensional Reynolds number and magnetic Reynolds number are exorbitantly large. 31 00:04:40.390 --> 00:04:51.790 Mark Kushner: What does that mean? These are essentially the way that we characterize the timescales associated with diffusion versus the ones associated with adjection. 32 00:04:52.160 --> 00:05:00.649 Mark Kushner: That means that if my Reynolds number is very, very large, that means that my advection timescale is tiny compared to my diffusion timescale. 33 00:05:00.810 --> 00:05:10.660 Mark Kushner: And whereas in the magnetic Reynolds case, the same is true for the, for the resistivity. So, for… 34 00:05:11.080 --> 00:05:27.810 Mark Kushner: The thing to keep in mind when looking at Reynolds numbers and magnetic Reynolds numbers is to think, if my fluid Reynolds number is very, very large, my flow will be turbulent. If my magnetic Reynolds number is very, very large, my magnetic field will tend to not diffuse 35 00:05:27.810 --> 00:05:32.070 Mark Kushner: Rather, it will be very well flux-frozen into what 36 00:05:32.220 --> 00:05:37.410 Mark Kushner: that turbulence of the large magnetic… the large fluid Reynolds number implies. 37 00:05:37.790 --> 00:05:42.919 Mark Kushner: Okay, so now, what can we… 38 00:05:43.070 --> 00:05:53.939 Mark Kushner: say about these astrophysical environments, to try to motivate laboratory astrophysics research. So we're looking at systems that are 39 00:05:54.640 --> 00:06:07.899 Mark Kushner: highly turbulent, that they're magnetized, so the question then becomes, what does this combination, this unique combination of magnetized fluctuations, result in? And, this 40 00:06:07.900 --> 00:06:16.809 Mark Kushner: this, sort of platform, astronomical platform, is a key agent in several astrophysical processes, right? So, if you think about 41 00:06:16.810 --> 00:06:23.190 Mark Kushner: how we understand the origin of cognitive magnetic fields, we could look at the seminal work by 42 00:06:23.190 --> 00:06:37.020 Mark Kushner: Kolstrode and, and Zweibel, looking at, essentially, how, small-scale fluctuation dynamo, can, account for the change in scales, 43 00:06:37.230 --> 00:06:53.480 Mark Kushner: in magnitude scales, from the tiny seeds that you have generated at early times in the story of the universe, to the micro Gao that we observe now in galactic… in extragalactic scales. 44 00:06:53.700 --> 00:07:11.280 Mark Kushner: So this process, fluctuation dynamo, is a key part of what we're trying to understand. Essentially, think of it as a… as a way of transferring energy from the fluctuations of the turbulence, so kinetic energy moving flax-frozen magnetic fields about. 45 00:07:11.290 --> 00:07:21.030 Mark Kushner: And then those fluctuations result in topological transformation of magnetic felines, and therefore you can imagine that those transformations 46 00:07:22.720 --> 00:07:34.200 Mark Kushner: Steal a little bit of kinetic energy from the turbulence and put it into the, the magnetic energy, the tension, the fields that are being, carried by that turbulence. 47 00:07:34.200 --> 00:07:42.949 Mark Kushner: Now, this process, kind of shown, it is an exponential process, so provided that the magnetic field is weak, that growth will be exponential. 48 00:07:43.320 --> 00:07:48.530 Mark Kushner: And that is a very economical way to account for cold magnetic fields. 49 00:07:49.100 --> 00:08:02.509 Mark Kushner: Now, magnetized surveillance is also a platform where we can study the transport and acceleration of cosmic rays, right? Essentially, if you go back to your understanding of Badmin acceleration, essentially you can think of 50 00:08:02.590 --> 00:08:15.170 Mark Kushner: the magnetic, fluctuating magnetic fields as potential magnetic mirrors, where you can have the second-order Fermi. There are other processes that can occur as well, so this allows us to 51 00:08:15.390 --> 00:08:22.620 Mark Kushner: study how carbonic rays, can interplay with With magnetized surveillance. 52 00:08:22.830 --> 00:08:35.189 Mark Kushner: There's also the aspects of the transport of heat that we have in galaxy clusters. There is a well-known cooling flow problem that has been 53 00:08:35.260 --> 00:08:43.260 Mark Kushner: Under continuous study for many years in the phenomenology world of just doing simulations of galaxy clusters. 54 00:08:43.289 --> 00:08:57.900 Mark Kushner: As well as, questions regarding the star formation rate, the efficiency, the stellar mass distribution. There are essentially big questions that can be, tackled with this sort of, two entities thing that is 55 00:08:57.940 --> 00:09:00.689 Mark Kushner: Fluctuating magnetic fields and fluctuating plaus blows. 56 00:09:02.150 --> 00:09:13.300 Mark Kushner: Okay, so what can we do about that in the laboratory? The TDNA collaboration essentially has been around, for quite a while now. We are… we just, 57 00:09:13.790 --> 00:09:31.160 Mark Kushner: We just made it 10 years into this collaboration, so it's a long-lasting collaboration that tries to study magnetized turbulence, fluctuation, dynamo, cosmic rate transport and acceleration using laboratory experiments. And the way that this happens is, essentially, we use 58 00:09:31.370 --> 00:09:40.600 Mark Kushner: simulations to design platforms that we can then deploy at facilities like the Omega Laser facility, and come up with ideas of creating 59 00:09:40.710 --> 00:09:54.549 Mark Kushner: scaled replicas, essentially, of plasma conditions that one finds in astrophysical environment in a very, very small volume, right? Essentially, you can, with the capabilities that we have now in these flagsuit facilities. 60 00:09:54.550 --> 00:10:02.590 Mark Kushner: we can generate plasmas at magnetic Reynolds numbers, and Reynolds numbers, and other non-dimensional, 61 00:10:02.740 --> 00:10:11.140 Mark Kushner: numbers associated with what you would use to describe, essentially, an emits the plasma or a two-fluid plasma. 62 00:10:11.860 --> 00:10:29.379 Mark Kushner: to a great extent, matching or tending to match what we actually see in astrophysical environments. So this was our big first breakthrough, where we essentially took the flash code, this is the simulation code that we developed at the Flash Center for Computational Science. 63 00:10:29.420 --> 00:10:47.480 Mark Kushner: It's been around now for almost 25 years with continuous evolution. It's now being used to do high-end density science research throughout the U.S. and the world, and it's currently being used by more than 5,500 users around the world. 64 00:10:48.150 --> 00:10:56.879 Mark Kushner: So, we are using Flask, essentially, to come up with these new designs that we can then deploy at Omega and demonstrate these processes. 65 00:10:57.430 --> 00:11:16.720 Mark Kushner: This particular one was the first experimental demonstration of fluctuation dynamo in the laboratory, which we achieved at the Omega Laser facility, by, sort of, like, blue sky simulations that we came up with using Flash, where we had counter-streaming plasma plumes propagating through grids. 66 00:11:16.720 --> 00:11:21.280 Mark Kushner: Colliding, creating a turbine region that had high enough magnetic Kranos numbers. 67 00:11:21.400 --> 00:11:25.139 Mark Kushner: for the dynamo action to actually kick in. 68 00:11:25.270 --> 00:11:42.279 Mark Kushner: Now, these were the simulations of that, but the experimental results were what sealed the deal. Essentially, we were able to demonstrate, looking at X-ray imaging and analyzing the fluctuations of the intensity, the power spectrum of the turbulence, we were able to demonstrate the amplification of the magnetic field. 69 00:11:42.280 --> 00:11:47.099 Mark Kushner: And that sort of created a credible… the first credible 70 00:11:47.200 --> 00:11:53.789 Mark Kushner: crack at Dynamo in the laboratory, something that folks have been trying to do, since the 90s. 71 00:11:53.890 --> 00:12:06.909 Mark Kushner: Now, that is what sort of made us famous in that space, and it resulted in the John Dawson Award that Mark mentioned. But the most important thing is the thing that I highlighted here. 72 00:12:06.910 --> 00:12:14.120 Mark Kushner: So this opens up a path to laboratory investigation of other ostrophysical processes, and that is the key thing that 73 00:12:14.210 --> 00:12:17.159 Mark Kushner: I want folks to come away from this meeting with 74 00:12:17.350 --> 00:12:20.009 Mark Kushner: The fact that we are now at the… 75 00:12:20.580 --> 00:12:32.890 Mark Kushner: CAASP, essentially, of a new era of laboratory astrophysics that can come in and be an equal partner to decades-long research that has been done in, 76 00:12:32.890 --> 00:12:49.289 Mark Kushner: in astronomy, in astronomical observations, in the theoretical models that describe astrophysical processes, and then medical simulations. We made it feel like it stool into a table onto which we can build a lot of new science on top of that. 77 00:12:51.480 --> 00:13:10.530 Mark Kushner: So, with this breakthrough, we took and run with it. Essentially, we've been trying to apply similar platforms that access different plasma regimes that are applicable for different plasma environments, from galaxy clusters to interstellar medium and so on. 78 00:13:10.610 --> 00:13:16.479 Mark Kushner: And answering questions that have been lingering in, in, in the, 79 00:13:16.610 --> 00:13:20.629 Mark Kushner: in the, in the literature. 80 00:13:20.810 --> 00:13:23.969 Mark Kushner: some highlights, essentially here I have, 81 00:13:23.980 --> 00:13:28.549 Mark Kushner: The first, time-resolved characterization of fluctuation dynamo 82 00:13:28.550 --> 00:13:44.469 Mark Kushner: Where we can actually see how the magnetic field grows as a function of time, and how the magnetic field saturates. The interplay that I talked about when the fluctuations of the plasma result in the amplification of the magnetic field. 83 00:13:44.470 --> 00:13:53.859 Mark Kushner: This will go on all the way to the point where there is a back reaction from the Lorentz force to the turbulence itself. Therefore, you cannot go all the way to… 84 00:13:53.880 --> 00:14:07.930 Mark Kushner: however high values you want, there will be a balance that will be stricken at the very end, the saturation phase, where this is how much energy you can actually move into magnetic energy before you have that back reaction. 85 00:14:08.010 --> 00:14:20.929 Mark Kushner: So we're able to demonstrate, essentially, the saturation levels, the growth rates that we have seen in studies that were done before in purely idealized configurations. 86 00:14:21.270 --> 00:14:31.190 Mark Kushner: We were also able to demonstrate, heat, conduction suppression, similar to what we observed now in galaxy clusters. 87 00:14:31.190 --> 00:14:50.370 Mark Kushner: in the presence of very strong magnetic field fluctuations. And this is essentially the porting of our platform at the National Immigration Facility, where, through a painstaking campaign of multiple years, we accumulated enough data to be able to make claims about how much thermal conduction is suppressed in the presence of stochastic magnetic fields. 88 00:14:50.680 --> 00:14:56.149 Mark Kushner: More recently, we have been doing experiments at the GSI. This is the German… 89 00:14:56.400 --> 00:15:03.579 Mark Kushner: it's the, it's, the Center for, it's a… 90 00:15:03.700 --> 00:15:22.949 Mark Kushner: I'm blanking on the acronym, but it's essentially a unique facility in Darmstadt where you have the ability to combine lasers with a linear accelerator. So, essentially, a particle gun that can act as cosmic rays 91 00:15:22.950 --> 00:15:33.450 Mark Kushner: In our attempt to emulate, essentially, how cold micrade interact with micro surveillance. And we did… we did a number of experiments there. We had two experimental campaigns, demonstrating 92 00:15:33.450 --> 00:15:53.240 Mark Kushner: effects like, particle acceleration through, through lower hybrid, lower hybrid drift instability, figuring out what type of energizations we are getting from that interaction. This is the simulation paper that Cassie Machulski, wrote, on, on the flash simulations, which was recently followed up with a Nature Communications paper. 93 00:15:53.240 --> 00:15:59.479 Mark Kushner: That just came out, and I would invite you to take a look at. 94 00:16:00.580 --> 00:16:09.349 Mark Kushner: The main thing that I will focus in today's talk regarding our dyno advancements will be supersonic dynamo. Now. 95 00:16:10.950 --> 00:16:28.359 Mark Kushner: being able to demonstrate fluctuation dynamo in the supersonic regime becomes a Goldilocks problem. Why is that? Because, essentially, we are required to get a high enough temperature for the magnetic Reynolds number to be large, and therefore have dynamo operating. 96 00:16:28.820 --> 00:16:47.120 Mark Kushner: But high temperature works against us in terms of the sound speed. So you want to create a configuration in which you are above critical direct grounds number, but you have a sound speed that is small enough to be smaller than the turbulent velocity that you have in your plasma. 97 00:16:47.410 --> 00:17:02.200 Mark Kushner: So, a lot of design work went in, a lot of failed experiments went in, but in the end, we were able to show the things that I'll show. Now, what happens when you have fluctuation dynamo in the supersonic turbulence case? 98 00:17:02.310 --> 00:17:21.129 Mark Kushner: The first thing that you will notice is that fluctuation dynamo is less efficient. So, essentially, the magnetic field that you will get in the end is lower than the subsonic counter. You also see that in terms of growth rates, you see that in saturation values, both of these guys decrease with increasing Mach number. 99 00:17:21.819 --> 00:17:34.050 Mark Kushner: On top of that, the critical RM, so essentially the threshold that we expect for a dynamo to operate, turns out to be 3 times larger than that of equivalent subsonic cases. 100 00:17:34.530 --> 00:17:52.600 Mark Kushner: Now, all of that comes from the literature of driven turbulence simulations. So, folks like Gusto Federev and Nadita have done a lot of work in essentially running, actually, flash simulations of driven turbulence to do studies like this to understand 101 00:17:52.600 --> 00:17:59.330 Mark Kushner: How these processes change in supersonic environments like those you encounter in the interstellar medium. 102 00:18:00.600 --> 00:18:19.650 Mark Kushner: We tried to do this on multiple campaigns. The first one was actually one that happened back in, I think it was 2018 when we did the experiments in 2019 when we published the paper, where we deployed, essentially, a similar platform than the one that we had at, 103 00:18:19.650 --> 00:18:21.449 Mark Kushner: like the one that we had at Omega. 104 00:18:21.670 --> 00:18:37.399 Mark Kushner: on Balkan, where we use external magnets to create, essentially, a magnetized turbulence in, again, counter-propagic flows. However, because of the scale of the facility, we're only able to get 105 00:18:37.520 --> 00:18:49.190 Mark Kushner: magnetic Reynolds numbers over unity, and therefore dynamo could not really operate. But what we did demonstrate, though, which is why we actually got a nature communications paper out of it, was a supersonic 106 00:18:49.220 --> 00:19:05.239 Mark Kushner: turbulence, like freestanding turbulence, which we're able to characterize and demonstrate the Berger spectrum that one expects in, in, in, in a steady-state, supersonic, turbulence. Is this the same setup as your original 107 00:19:05.240 --> 00:19:25.210 Mark Kushner: You were showing earlier? I was actually wondering what the seed was for that. So, there we had the permanent magnets to provide the field, because we didn't have enough B1 battery field to bring in into the interaction region, and then the turbulence itself was picking up that external field, and we were using the field as a tracer. 108 00:19:25.270 --> 00:19:27.510 Mark Kushner: So it was not really, 109 00:19:27.850 --> 00:19:39.080 Mark Kushner: we didn't see any amplification of the field itself, because when you have magnetic Reynolds numbers of order unity, and you end up having a spectrum, say, a Komogoro spectrum. 110 00:19:39.090 --> 00:19:54.069 Mark Kushner: you can sort of create a balance between the diffusion term and the advection term, and figure out what power spectrum you will be getting for RM or the Unity. And what you get is the Golitsyn spectrum. It's a rather sharp spectrum that, 111 00:19:54.130 --> 00:19:59.130 Mark Kushner: is, is indicative of, essentially, this balance between a RAM and a B. 112 00:19:59.330 --> 00:20:14.209 Mark Kushner: So it's… The original setup that you're showing did not have a… No, it did not. So the Omega one, the original one actually, used the Piedmont battery field that was generating the laser targeting direction. 113 00:20:14.210 --> 00:20:20.439 Mark Kushner: as an initial seed that would be advectored into the center. As the seed comes in. 114 00:20:20.440 --> 00:20:28.519 Mark Kushner: Expands, becomes smaller, goes down to the, like, less than kilogauss range, and then comes to the center and is amplified exponentially. 115 00:20:29.160 --> 00:20:34.740 Mark Kushner: I'll… Won't talk about this here, but there is an ongoing, 116 00:20:34.990 --> 00:20:52.969 Mark Kushner: effort to study more, configurations, including MIFED's magnetic fields, to try to understand, essentially anisotropic, turbulence, ideally in the strong alphanic regime, which is 117 00:20:53.310 --> 00:21:04.110 Mark Kushner: something that my, my graduate student, J, is, Cats is working on right now, and we have experiments lined up for later this year. 118 00:21:04.340 --> 00:21:10.240 Mark Kushner: And, we have some really cool results there that she will be presenting at APS. 119 00:21:10.520 --> 00:21:12.460 Mark Kushner: Okay, so, 120 00:21:13.260 --> 00:21:28.170 Mark Kushner: The follow-on experiment that we did was to go at LMJ. We were actually the first academic team that got time at the Laser MegaJewel, which is, the, essentially the NIF of France. 121 00:21:28.170 --> 00:21:36.239 Mark Kushner: It's a… it's an amazing facility. However, we got in too early, so they didn't have enough beams to… 122 00:21:36.300 --> 00:21:43.240 Mark Kushner: get to the high enough magnetic Reynolds numbers to clearly state that we had dynamo. So it was… 123 00:21:43.370 --> 00:22:02.939 Mark Kushner: better than one, but it was essentially some nonlinear amplification that was, again, very cool to see, because we essentially demonstrated that the amplification is less efficient in supersonic, low parameter turbulence as compared to moderate parameter subsonic turbulence. So… 124 00:22:03.090 --> 00:22:17.680 Mark Kushner: We're building, essentially, knowledge and know-how by doing these experiments, and then we can go and come back to Omega and actually do experiments that will allow us to demonstrate fluctuation dynamo in the supersonic region. 125 00:22:18.020 --> 00:22:23.699 Mark Kushner: Now, this was done using a variant of the original platform. 126 00:22:23.810 --> 00:22:27.460 Mark Kushner: By essentially tweaking, using flash simulations. 127 00:22:27.510 --> 00:22:40.910 Mark Kushner: to sort of get this Goldilocks condition right, essentially making it so that the magnetic Reynolds number and the sound speed were such that it would be super critical 128 00:22:40.910 --> 00:22:59.969 Mark Kushner: but be supersonic as well. So, here I'm showing the simulations that went into the design problem, and what we're… I'm showing here is, it's the Mach number on the top and the magnetic field on the bottom, and I'm only showing magnetic fields that are above unity. 129 00:23:00.480 --> 00:23:06.830 Mark Kushner: Sorry, Mach numbers that are above United. So, a key thing to demonstrate in our experiments is 130 00:23:06.830 --> 00:23:24.269 Mark Kushner: the whole process of the amplification should happen with magnums above unity. Otherwise, you might be getting a subsonic amplification, tainting, essentially, a later on, supersonic turbulence. 131 00:23:24.730 --> 00:23:31.730 Mark Kushner: The idea here is to use the properties of the plasma and make it so that 132 00:23:31.990 --> 00:23:39.479 Mark Kushner: You cool sufficiently the turbulent interaction region immediately after that first delusion happens. 133 00:23:41.440 --> 00:23:48.779 Mark Kushner: So, the, design that we came up, was fielded at Omega. 134 00:23:49.210 --> 00:23:56.920 Mark Kushner: And use the somewhat different pulse profile, and some… some modifications in the… in the… in the target itself. 135 00:23:57.180 --> 00:24:09.670 Mark Kushner: And we fielded it successfully on June 8th, 2023, and since we have been essentially analyzing meticulously the results in order to make the big claim that I'm about to make. 136 00:24:09.910 --> 00:24:12.429 Mark Kushner: So, how do we… 137 00:24:12.810 --> 00:24:20.770 Mark Kushner: Try to demonstrate that we have, in fact, the conditions that we want to achieve. 138 00:24:20.880 --> 00:24:37.140 Mark Kushner: We use X-ray imaging to capture the fluctuations in intensity. This can give us the density fluctuations in turbine plasma, and we can also create maps of the electron temperature by using a two-color free-that approach that you essentially bring in 139 00:24:37.140 --> 00:24:45.030 Mark Kushner: the, the response of the instrument to, to get Bath-integrated, density weight temperature maps. 140 00:24:45.300 --> 00:24:58.170 Mark Kushner: Now, these have the benefit of not being affected by anything else, but what is actually going on in the turbulence. We use optical Thompson scattering to get all the plasma properties inside a small box 141 00:24:58.310 --> 00:25:06.789 Mark Kushner: in, in the, in the, in the, in the turbulent region. So, through the ion acoustic array, we can get things like. 142 00:25:06.810 --> 00:25:15.179 Mark Kushner: the, the, the temperature, the amp temperature, the, the, the velocity, we're gonna get the turbulent velocity as well. 143 00:25:15.190 --> 00:25:31.370 Mark Kushner: We will see that in a bit. We use the APW to get the density. So all of these are things that can be extracted in a small subset of the turbulence, so we can essentially inspect a particular scale 144 00:25:31.380 --> 00:25:36.969 Mark Kushner: Of the turbulent cascade that we create, and a particular scale of the magnetic field cascade that we create. 145 00:25:38.060 --> 00:25:46.700 Mark Kushner: And then, in order to measure the magnetic fields, we're using proton radiography. This is essentially another experiment that happens on the side of the experiment, where you 146 00:25:46.700 --> 00:26:01.680 Mark Kushner: implode a capsule to generate 3 and 14 MeVV protons that fly everywhere in the chamber. Some of them go through the interaction region and then are captured into a radio chromic film to actually create, like, a 147 00:26:01.970 --> 00:26:04.999 Mark Kushner: a proton polaroid of your magnetic structures. 201 00:34:07.390 --> 00:34:15.889 Mark Kushner: What I wanted to pivot now, and for the rest of my talk, is to see how that can go back and inform astrophysical 202 00:34:16.060 --> 00:34:20.519 Mark Kushner: research, and just being cognizant of time. 203 00:34:26.320 --> 00:34:28.500 Mark Kushner: 10 minutes or so. Excellent. 204 00:34:28.630 --> 00:34:29.610 Mark Kushner: So… 205 00:34:30.550 --> 00:34:49.359 Mark Kushner: Mark mentioned, the Early Career and PKs Award. These are essentially one thing. The Early Career was awarded in 2021 to start the research, and then the PKs Award came, with a slight delay at the end of the last administration. And, the… 206 00:34:49.710 --> 00:35:02.939 Mark Kushner: it's, of course, a fantastic honor and a huge boon, because essentially what this has allowed us to do is take all of the extended MHD and HDD capabilities that we have in Clash. 207 00:35:03.090 --> 00:35:11.920 Mark Kushner: and propagate them back into the driven turbulence scenario of studying magnetized turbulence. How this works is essentially… 208 00:35:13.050 --> 00:35:24.929 Mark Kushner: just use the code that is being used already for driven turbulence with all the things that we put for HD, right? I mean, the beauty of a code like Flash is that it is already 209 00:35:25.130 --> 00:35:27.930 Mark Kushner: A workhorse for astrophysical research. 210 00:35:28.150 --> 00:35:39.360 Mark Kushner: We're just using the same infrastructure, the same algorithms, with extra extensions that have to do with X and MSD and high energy density science. 211 00:35:40.030 --> 00:35:45.580 Mark Kushner: Now, the idea here is, can we create, essentially, a new set of theory 212 00:35:45.810 --> 00:35:53.790 Mark Kushner: that will incorporate the effects of extended MHC and HD in the driven turbulence scenario, and then use that 213 00:35:53.940 --> 00:35:59.909 Mark Kushner: To create new experiments, create a virtuous cycle, essentially, of new research that can be opened up. 214 00:36:00.080 --> 00:36:01.540 Mark Kushner: From that effort. 215 00:36:02.810 --> 00:36:11.970 Mark Kushner: Now, I want to motivate what was the first thing that we tried to do in terms of extended MHC. 216 00:36:12.410 --> 00:36:16.990 Mark Kushner: I've shown flash matching experimental data in multiple talks. 217 00:36:17.600 --> 00:36:33.060 Mark Kushner: there are things that flash cannot produce, right? One big thing that we found when we did our 2021 paper on the temporal evolution of the magnetic field was that you had consistently 218 00:36:33.430 --> 00:36:40.809 Mark Kushner: the integral scale in the flat simulations be significantly smaller than the experimental one. 219 00:36:41.280 --> 00:36:42.600 Mark Kushner: By a factor of 3. 220 00:36:43.210 --> 00:36:45.909 Mark Kushner: I mean, it's not a small difference. 221 00:36:46.050 --> 00:36:51.319 Mark Kushner: And what we found was, essentially, Flash was able to… 222 00:36:51.380 --> 00:36:56.169 Mark Kushner: Give the same predictions that we were getting from periodic bulk simulation, so if you were to 223 00:36:56.170 --> 00:37:12.619 Mark Kushner: compare, essentially, flash simulations of the design to turbulence and box simulations with similar magnetic radius numbers, we would be getting the same… the same power spectra, and therefore the same peaking of that power spectrum, which is 224 00:37:12.620 --> 00:37:15.469 Mark Kushner: Where you expect these structures to live, right? 225 00:37:16.040 --> 00:37:17.070 Mark Kushner: So… 226 00:37:17.900 --> 00:37:30.529 Mark Kushner: That was not the case in the experiment. The experiment had chunky, essentially, structures that persisted, and we had to find a way to sort of speculate in our paper. 227 00:37:30.530 --> 00:37:42.290 Mark Kushner: And the first speculation that we did was actually the order unity hull parameter. Essentially, the idea that whole physics can come in and change where the peak of the power spectrum is. 228 00:37:43.250 --> 00:37:50.690 Mark Kushner: This was sort of, stipulated by Haines in 1986, but it's sort of like a theoretical argument. 229 00:37:50.940 --> 00:38:03.879 Mark Kushner: There might also be differences in the… in the power spectrum of the initial migrating fetals, which Amit Seta and Christoph Feder have found that had some effect in the end result, but also differences in the actual dissipation mechanisms 230 00:38:03.880 --> 00:38:11.310 Mark Kushner: We're missing a lot of the kinetic physics that occur in real plasmas, and are not included in a complex launch. 231 00:38:11.790 --> 00:38:25.459 Mark Kushner: Now, this is interesting, because the discrepancy that we're seeing between experiment and simulation is actually a long-standing problem in explaining the scale of tangent magnetic fields that are present in the ICN. 232 00:38:25.820 --> 00:38:33.380 Mark Kushner: So, there, they also find larger peaking compared to what they do in their simulations of those environments. 233 00:38:34.420 --> 00:38:48.760 Mark Kushner: And you see it clearly as day in the power spectra, right? Essentially, you have the peak of the power spectrum of the magnetic energy from the experimental data way… to way smaller wave numbers than what we get in the flask simulations. 234 00:38:49.000 --> 00:38:59.519 Mark Kushner: Okay, so what did we do to try to understand this? We took… driven turbulence calculations using flash. 235 00:38:59.730 --> 00:39:04.720 Mark Kushner: But we took, essentially, the extended MHD version of our generalized on slow. 236 00:39:04.910 --> 00:39:11.710 Mark Kushner: We got rid of most of the terms and included only the advection term, the whole term. 237 00:39:11.820 --> 00:39:24.919 Mark Kushner: And a uniform resistivity, so essentially this is… sorry, not an isotropic resistivity, so not this formalism, but the one that is just one eta throughout. 238 00:39:25.310 --> 00:39:38.380 Mark Kushner: Now, these simulations are done at a 1 centimeter domain. They are using the stereo unit that has been used in astrophysics for many years, where, essentially, you're injecting a velocity, sorry, a force field 239 00:39:38.380 --> 00:39:47.199 Mark Kushner: Which evolves in time to keep, sort of prodding your turbulence and introducing energy at the larger scales. 240 00:39:47.200 --> 00:40:00.520 Mark Kushner: to create the turbulent cascade, and then take a seed magnetic field and amplify it, as we're seeing in the simulation. So, starts with very, very low magnetic fields, grows exponentially, and then saturates at some level. 241 00:40:01.110 --> 00:40:18.670 Mark Kushner: The simulation includes viscosity, resistivity, and the whole term, and they were done in a rather low, grid, because we were looking, actually, at low magnetic Reynolds numbers of the order of a few hundreds, so we don't actually need to go to very high resolutions to get there. 242 00:40:19.670 --> 00:40:29.980 Mark Kushner: the plasma conditions that we were trying to do was to emulate what we had in our, in our 2021 paper. So, essentially. 243 00:40:30.020 --> 00:40:41.230 Mark Kushner: Reynolds and magnetic Reynolds numbers of 300 to 650, Mach numbers of 0.2 to 0.6, Prundle numbers of order unity, and then this whole ratio 244 00:40:41.440 --> 00:40:53.350 Mark Kushner: So the inverse of the whole ratio, essentially 1 over H, which gives you an indication of how important is the whole term in your dynamics. 245 00:40:54.330 --> 00:41:09.119 Mark Kushner: The parameterization that we did was actually on the hull parameter, so that was essentially our knob to change the effect of the hull physics. And then we started running, essentially, a set of simulations, increasing from zero hull to 246 00:41:09.120 --> 00:41:16.100 Mark Kushner: A hole that… a whole effect that is comparable to what we had in the experiments, to see what the whole term does. 247 00:41:16.760 --> 00:41:23.129 Mark Kushner: Now, the first thing that we saw was… Surprising We saw that… 248 00:41:23.420 --> 00:41:28.229 Mark Kushner: By increasing the ion inertial rate, and therefore increasing the whole parameter. 249 00:41:28.650 --> 00:41:34.260 Mark Kushner: The magnetic field saturation level is lower Than in the null holder. 250 00:41:35.470 --> 00:41:41.599 Mark Kushner: So, Hall is acting as a new way To saturate the magnetic field. 251 00:41:41.800 --> 00:41:44.779 Mark Kushner: At late times, in a dynamo process. 252 00:41:46.200 --> 00:41:58.060 Mark Kushner: It is a substantial difference, and it's… and you find. We're not expecting that. Previous studies that had been done with whole MHC had claimed that there was no difference in the saturation. 253 00:41:59.390 --> 00:42:01.770 Mark Kushner: We also found out that 254 00:42:02.130 --> 00:42:12.499 Mark Kushner: The growth rate itself, so the rate with which this part happens, does not really depend on the presence of hole or not. We can fit, essentially, the growth rates with the flood line. 255 00:42:13.680 --> 00:42:17.179 Mark Kushner: Interestingly, we found that this 256 00:42:17.450 --> 00:42:28.710 Mark Kushner: Dependence that we have between the saturated magnetic to kinetic energy, essentially, at what ratio of the two the magnetic field saturates, 257 00:42:29.240 --> 00:42:32.520 Mark Kushner: With the, with the whole parameter. 258 00:42:32.610 --> 00:42:39.440 Mark Kushner: can be derived analytically. If you go and compare, in the smallest of scales. 259 00:42:39.440 --> 00:42:57.429 Mark Kushner: essentially the characteristic timescale of Hall-induced field line drift with the turbulent stretching, and you can essentially do an order of magnitude argument and find that the scaling is supposed to go as a lie over L to the minus 2. 260 00:42:57.620 --> 00:43:06.020 Mark Kushner: This is already exciting, right? I mean, we're finding new physics in fluctuation dynamo just by the inclusion of Hall. 261 00:43:06.830 --> 00:43:11.830 Mark Kushner: Okay, what else did we find? We find… that… 262 00:43:12.160 --> 00:43:14.760 Mark Kushner: In order for the Hall effect 263 00:43:15.110 --> 00:43:18.640 Mark Kushner: To be a dominant player in the saturation process. 264 00:43:18.840 --> 00:43:31.409 Mark Kushner: Well, of course, you need to get to a point where the majority field has become strong enough, right? But it turns out that it will happen when this ratio becomes smaller than 1. 265 00:43:31.510 --> 00:43:35.610 Mark Kushner: What is this ratio? It is the ratio, essentially, of how 266 00:43:35.800 --> 00:43:40.240 Mark Kushner: local detection at the scale of the grid. 267 00:43:40.690 --> 00:43:46.599 Mark Kushner: versus the Hall effect compares to the ratio of local advection to resistive diffusion. 268 00:43:46.800 --> 00:43:51.529 Mark Kushner: So it's kind of like a Prandle number per hole. 269 00:43:51.820 --> 00:43:58.239 Mark Kushner: Jokingly, I call it the Ananya number, because she found it, but, 270 00:43:58.530 --> 00:44:04.100 Mark Kushner: We'll see if that will stick. So… That comparison, essentially, is what 271 00:44:05.290 --> 00:44:12.360 Mark Kushner: sort of demarcates this deviation between saturation due to resistivity versus saturation due to hull. 272 00:44:14.020 --> 00:44:30.050 Mark Kushner: It also changes the power spectrum significantly. What we find is, of course, you have less magnetic energy as you saturate lower, but overall, the magnetic energy in the inertial range becomes more spread out. 273 00:44:30.170 --> 00:44:40.049 Mark Kushner: In the total magnetic range, inertial range. And therefore, we have a more efficient transfer of energy from the larger scales to the smaller scales. 274 00:44:40.210 --> 00:44:41.170 Mark Kushner: So… 275 00:44:41.890 --> 00:45:01.890 Mark Kushner: Can we say, then, that the whole term explains the difference that we see in the experimental results? What we need to be focusing on is, essentially, what happens at the scale of the peak of the inertial range, right? Essentially, what happens close to this area, and we need to be thinking that we're comparing proton radiographs to proton radiographs. 276 00:45:02.290 --> 00:45:09.800 Mark Kushner: Like, visually, so we better normalize that and make that comparison like we did in the experimental data. 277 00:45:09.980 --> 00:45:18.359 Mark Kushner: Now, the thing to realize is, when you're doing proton radiography, what you're actually visualizing is not the magnetic field. 278 00:45:19.280 --> 00:45:27.610 Mark Kushner: It is actually the MHT current that the protons find as they're propagating towards their target. 279 00:45:28.330 --> 00:45:44.650 Mark Kushner: So, what we decided to look at first was, how does the Hall term change the magnetic structures that come into this magnetized surveillance? And what we find is that the Hall term actually broadens the current spectrum. 280 00:45:45.050 --> 00:45:50.140 Mark Kushner: And has the peak of the current moved to lower k. 281 00:45:51.580 --> 00:45:56.029 Mark Kushner: This is interesting, because this is exactly what we were hoping to… to see. 282 00:45:56.150 --> 00:46:09.989 Mark Kushner: And also, we know that we have also lower total current and more intermittent structures that you can sort of see when you're comparing the normalized isosurfaces. And that… 283 00:46:10.700 --> 00:46:14.640 Mark Kushner: takes us now to the piece de resistance, which is. 284 00:46:14.750 --> 00:46:29.550 Mark Kushner: Well, let's look at what happens at the peak. Let's make sure that we normalize everything to one, so that we can actually compare, and what we find is that this crossing that happens between the two 285 00:46:29.750 --> 00:46:40.939 Mark Kushner: the one that we saw in the experimental results is actually happening in our simulations. It's not as pronounced as here. This is sort of like the same ranges that we were looking at between the two. 286 00:46:41.420 --> 00:46:47.629 Mark Kushner: But we have, essentially, a consistent behavior that seems to indicate that 287 00:46:48.010 --> 00:46:50.359 Mark Kushner: The structures that one can expect. 288 00:46:50.450 --> 00:46:57.869 Mark Kushner: The current structures that one can expect. And the magnetic energy relative peak for a normalized 289 00:46:57.900 --> 00:47:05.739 Mark Kushner: Magnetic power distribution is, in fact, moving to smaller wavelengths, and therefore larger scales. 290 00:47:05.750 --> 00:47:22.609 Mark Kushner: It is consistent, essentially, with the trend that we saw. So we think that, in part, this whole effect is actually playing a role in explaining what we saw in terms of that discrepancy, at least within the experiment and the simulation. Now, the thing to ask ourselves is. 291 00:47:22.990 --> 00:47:27.720 Mark Kushner: Should we be using Hall when modeling the guys that we've been modeling for so long? 292 00:47:28.300 --> 00:47:30.489 Mark Kushner: Okay, so here's the summary. 293 00:47:31.110 --> 00:47:42.370 Mark Kushner: The advent of high-power lasers is now opening this new field of plasma physics research that allows us to reproduce astrophysical environments in the lab. 294 00:47:43.170 --> 00:47:56.379 Mark Kushner: The turbulent dynamo platform that we have developed with the University of Oxford was done using flash simulations to demonstrate fluctuation dynamo for the first time at the Omega Laser facility at the Laboratory for Laser Energetics. 295 00:47:56.590 --> 00:48:15.820 Mark Kushner: This platform has allowed us to do a number of things, and the most recent one is the generation of a supersonic turbulent interaction region, in which our measurements from Thomson scattering, x-ray emission imaging, and proton radiography seem to indicate that, in fact, we have supersonic turbulent dynamo demonstrated in the lab. 296 00:48:16.330 --> 00:48:18.480 Mark Kushner: Now, this… 297 00:48:18.720 --> 00:48:28.989 Mark Kushner: set of experimental results motivated, in part, the development of new theories in HD magnetized turbulence, where we can actually go and ask ourselves. 298 00:48:29.140 --> 00:48:35.760 Mark Kushner: How does the extra physics that exist in the plasmas of our laboratory go and change 299 00:48:35.890 --> 00:48:40.780 Mark Kushner: the, simplified approximation of resistive MHC that we've been doing all along. 300 00:48:41.050 --> 00:48:54.999 Mark Kushner: Now, the fluctuation dynamo, whole MST simulations that we did revealed that the whole MSD term can alter the saturation level, introducing a new way to saturate dynamo of late times. 301 00:48:55.170 --> 00:49:05.890 Mark Kushner: And also, changes the magnetic energy power spectrum and the properties of the current structures that one can expect from such a configuration. 302 00:49:06.280 --> 00:49:15.279 Mark Kushner: All of this is consistent with the TIDAN experimental findings, and this is just one of the things that we have done. So there's a number of other… 303 00:49:15.400 --> 00:49:19.760 Mark Kushner: Research thrust that we're looking at, including, 304 00:49:20.050 --> 00:49:35.000 Mark Kushner: transitional, turbulence from subsonic to supersonic, with the inclusion of HCD terms, heat exchange, and isotropic resistivity, which has, resulted in very interesting outcomes. 305 00:49:35.000 --> 00:49:46.419 Mark Kushner: So, there is a lot to unpack and uncover and study in this field of research, and we hope to pursue this in the future with 306 00:49:46.420 --> 00:50:03.169 Mark Kushner: The combination of the experiments that we've been doing, motivated now by new theory, but also with going back and doing the due diligence and propagating what we know from the experiments back to our driven turbulence simulations. 307 00:50:03.740 --> 00:50:06.620 Mark Kushner: With that, I will thank you all, and take any questions. 308 00:50:11.070 --> 00:50:13.489 Mark Kushner: Thank you very much. Are there questions? 309 00:50:14.270 --> 00:50:19.490 Mark Kushner: Yes, thank you for a very nice talk. I just wanted to, if I understood… 310 00:50:19.710 --> 00:50:37.269 Mark Kushner: the corrections you added, it was a scalar resistivity and no thermoelectric contributions. That is correct, yes. That wouldn't include the NERT defects. That is correct. So these are just, without, any of the… all of the other terms that I included. Would, 311 00:50:37.630 --> 00:50:43.289 Mark Kushner: would the coefficients be small for that? I mean, normally you think of the Hall term and the pressure 312 00:50:43.430 --> 00:50:55.430 Mark Kushner: to be of similar order. So, that's a very… that's a very good point. So, the way that we are doing the runs, is, is sort of, enforcing an isothermal behavior 313 00:50:55.430 --> 00:51:05.979 Mark Kushner: In, in, in the, in the plasma itself. So these guys… so when you have it, when… one of the complexities of… of doing HD-like things 314 00:51:05.980 --> 00:51:19.720 Mark Kushner: in a box is, what do you do with the energy that is being generated, right? And the way that it has been solved in the astrophysical community is to have, essentially, an equation of state closure that will take away the extra energy and keep things 315 00:51:19.720 --> 00:51:27.639 Mark Kushner: In the same temperature. So, there are no gradients in the temperature, which is unphysical compared to what we have in the experiment, because 316 00:51:27.640 --> 00:51:40.950 Mark Kushner: In the experiment, we have a freestanding turbulence that can radiate, can expand, so we have essentially the whole thing, and not the periodic box that we need to do special magic to get rid of extra energy from. Now. 317 00:51:41.190 --> 00:51:55.170 Mark Kushner: It is true that we have done simulations with all of the physics of the extra heating and so on, and of course, what we find is that if you let, you know, compressibility and shock heating and all of the things come into play. 318 00:51:55.710 --> 00:52:04.220 Mark Kushner: the temperature goes up, the Mach number will go down, and therefore you can find yourself 319 00:52:04.540 --> 00:52:14.010 Mark Kushner: changing regimes from a supersonic to subsonic, and then study interesting stuff, right? I mean, there are cases where 320 00:52:14.520 --> 00:52:18.729 Mark Kushner: In the long scheme of things, a saturated… 321 00:52:18.970 --> 00:52:25.119 Mark Kushner: turbulent magnetic field come cool enough to become a different thing. So. 322 00:52:25.890 --> 00:52:29.520 Mark Kushner: I think there is a lot… to, sort of. 323 00:52:30.260 --> 00:52:43.120 Mark Kushner: Try to pull together and try to create a different picture that includes more physics and allows us to ask bigger questions than what we have been asking up until now. 324 00:52:45.290 --> 00:52:50.470 Mark Kushner: I have a quick question about your, Thompson scattering data. Yes. 325 00:52:50.740 --> 00:52:54.690 Mark Kushner: So, when you're looking at the… The two colliding flows. 326 00:52:54.940 --> 00:53:02.210 Mark Kushner: Do you have a reason to believe that it's going to be in thermal equilibrium there, so we can actually just do… use Thompson scattering at all? 327 00:53:03.310 --> 00:53:11.120 Mark Kushner: So let's go back to that, and a reminder to myself that I will need to remove that, real quick. 328 00:53:11.800 --> 00:53:14.479 Mark Kushner: It's just… Who's confident. 329 00:53:17.850 --> 00:53:20.549 Mark Kushner: So, let's use this as a stand-in. 330 00:53:22.220 --> 00:53:23.700 Mark Kushner: Which I don't have to remove. 331 00:53:30.930 --> 00:53:34.170 Mark Kushner: So the question is, Essentially. 332 00:53:34.770 --> 00:53:52.230 Mark Kushner: Can you repeat the question? Yeah, so, when you were, in your collection volume, do you have a reason to believe that your plasma there is in sufficient thermal equilibrium to be able to use Thompson scattering? Oh, yeah, absolutely, absolutely. So the way that you, so these are, 333 00:53:52.510 --> 00:54:12.010 Mark Kushner: The way that you should think of these plasmas coming together is, essentially, they are the outcome of what you've driven from the back. So these guys are pretty dense already. They're pretty slow, it takes them, like, 18, 20 nanoseconds to actually travel those 4 millimeters in order to meet at the center. 334 00:54:12.780 --> 00:54:32.620 Mark Kushner: And the collision, you know, initially it will be a little bit collision-less, because it is actually sort of like a Rao Faction moving into a rough faction, but quickly the density becomes so high that with the low velocities that you have, your intra-jet mean-free path 335 00:54:32.960 --> 00:54:40.839 Mark Kushner: is such that it stops everything. So it is both ions and electrons stopping at the center. Now. 336 00:54:41.680 --> 00:54:45.230 Mark Kushner: Initially, what we find is that the ion temperature 337 00:54:45.440 --> 00:55:01.860 Mark Kushner: is not in equilibrium with the electron one. So it takes a little time, about a nanosecond or two, for the two to come together, because I am heated, right? So there is also the thing of the heat exchange that one needs to keep into account. 338 00:55:02.030 --> 00:55:05.600 Mark Kushner: These are the times where things are interesting, right? So… 339 00:55:05.810 --> 00:55:18.549 Mark Kushner: There is a way to calculate an effective temperature at the early beginning that allows you to make claims about sound speeds, but in reality, what you care about is the measurements that you have afterwards. 340 00:55:18.770 --> 00:55:21.830 Mark Kushner: And are consistent with what we… what we see. 341 00:55:24.960 --> 00:55:37.079 Mark Kushner: In the experiment and simulation comparison, did the initial BIM and battery fields match in Flash in the experiment? Yes, they did. They did. So the, the, 342 00:55:38.710 --> 00:55:42.220 Mark Kushner: That was the comparison that we did way back there. 343 00:55:46.910 --> 00:55:48.710 Mark Kushner: Sorry, at this moment. 344 00:55:51.690 --> 00:55:53.380 Mark Kushner: So, this comparison here. 345 00:55:53.600 --> 00:55:56.570 Mark Kushner: Yeah, so essentially, the… 346 00:55:57.410 --> 00:56:08.990 Mark Kushner: This is sort of like an upper limit that we're able to provide in the BRMS. The flash simulations were predicting something… I think it was either 2 or 3 kilogafs. 347 00:56:09.230 --> 00:56:16.479 Mark Kushner: With the… with the… when you change the platforms, the… You don't expect the… 348 00:56:16.680 --> 00:56:31.790 Mark Kushner: That is correct, yes, but we take advantage of, essentially, the big thing that we take advantage of here in all of these platforms is the distance, because the laser target interaction, depending on what you're shooting, you will get a different result. 349 00:56:31.930 --> 00:56:34.490 Mark Kushner: However, if you wait long enough. 350 00:56:34.710 --> 00:56:50.990 Mark Kushner: that seed has to expand adiabatically into… into… to fill the volume, essentially, that it needs to fill until it gets to the interaction region of the center. So that time, so this distance here, is what takes us from 351 00:56:51.130 --> 00:56:58.230 Mark Kushner: a… an interesting field to begin with into a seed field that we can then amplify. 352 00:56:58.780 --> 00:57:02.680 Mark Kushner: Now, we have also done experiments with MIFEDs. 353 00:57:02.900 --> 00:57:09.530 Mark Kushner: That was back in 2018, to see how much the initial field strength 354 00:57:09.900 --> 00:57:21.580 Mark Kushner: changes the saturation value at the end. So essentially, we started with a MIFAS that was much larger than this for kilogauss, and we ended up saturating at the same level. 355 00:57:21.710 --> 00:57:23.819 Mark Kushner: So, it appears that it does not… 356 00:57:24.740 --> 00:57:28.870 Mark Kushner: matters so much. What happens fundamentally is, if you think about it. 357 00:57:29.850 --> 00:57:33.640 Mark Kushner: With the proviso that you are still in the… 358 00:57:34.400 --> 00:57:39.239 Mark Kushner: In this part of the amplification, you're just starting up higher, right? 359 00:57:39.890 --> 00:57:49.719 Mark Kushner: You just have a… less of a… less of a headroom in the kinematic phase of the dynamo to… to actually capture that growth. 360 00:57:50.280 --> 00:57:51.810 Mark Kushner: Which kind of makes sense. 361 00:57:55.370 --> 00:57:56.720 Mark Kushner: Yes, it is spam. 362 00:57:56.920 --> 00:57:59.739 Mark Kushner: Yes, a nice talk. 363 00:58:00.010 --> 00:58:05.960 Mark Kushner: If you… this might be a naive question, but if you had the ability to build your own 364 00:58:06.470 --> 00:58:22.440 Mark Kushner: laser facility for these experiments. What is missing right now? What would you do next, or what would you make? I would, very much like for us to put a linear accelerator in all of our facilities so we can have charged particles to do stuff with. 365 00:58:22.930 --> 00:58:37.070 Mark Kushner: It's, I mean, if you can have, like, an ion gun and an electron gun… Or a cosmic, right? Yeah, it would be fantastic. We could have something that we could share, even. I mean, you could have something that moves around, like, 366 00:58:37.110 --> 00:58:44.310 Mark Kushner: like, Pierre Gordon's experiment was just coming here. So, it would be very fun to do something like that. So the GSI… 367 00:58:44.660 --> 00:58:58.780 Mark Kushner: That would be amazing. I mean, the GSI essentially has a unilug that you can specify what type of ions you're shooting, and they shoot throughout your experiment. So essentially, you're doing an experiment around that ion beam. 368 00:58:58.900 --> 00:59:01.370 Mark Kushner: And you can do a lot of cool things around it. 369 00:59:04.460 --> 00:59:06.930 Mark Kushner: Scott? And then we'll finish up with Charlotte. 370 00:59:07.480 --> 00:59:29.339 Mark Kushner: Yeah, so you had this observation that the Hall… turning on the Hall effect in the flash simulations caused the dynamo magnetic field to saturate at a lower value. Yes. Do you have a physical picture for what's happening? Yes, so I will… so I was debating if I wanted to put it in the… in the presentation or not, but essentially it's, like, two pages of math that you can do 371 00:59:29.350 --> 00:59:34.510 Mark Kushner: That will convince you that this is, in fact, sensible. Essentially. 372 00:59:34.920 --> 00:59:53.069 Mark Kushner: take… the… it's the argument that I was making here, this, this sort of cryptic thing in the bottom. Check out… check out the archive one. It has, like, a one-page, derivation of why that dependence is valid, and, that sort of… 373 00:59:53.180 --> 01:00:05.000 Mark Kushner: this dependence in the, in the, in the LI over L will give you the, will give you, sort of, like, how this value changes. Now, in terms of 374 01:00:05.330 --> 01:00:13.369 Mark Kushner: why the hole is… Providing, sort of, like, a lower value earlier? 375 01:00:13.760 --> 01:00:16.739 Mark Kushner: You can go, and we do this in the paper. 376 01:00:16.890 --> 01:00:23.150 Mark Kushner: You can go and analyze the contribution to the DBDT and the DDT of the various terms. 377 01:00:23.290 --> 01:00:31.320 Mark Kushner: And you can track them in the process. And what we find is that as soon as the contribution to the magnetic field 378 01:00:31.690 --> 01:00:39.350 Mark Kushner: Of the whole term reaches the level of the resistivity one. Essentially, it provides it with 379 01:00:39.470 --> 01:00:42.280 Mark Kushner: A new way to… 380 01:00:42.800 --> 01:00:50.700 Mark Kushner: do the same thing that the resistivity does earlier. So it's acting like a different saturation channel, if you will. 381 01:00:50.860 --> 01:00:55.930 Mark Kushner: that, competes with resistivity. So it allows us to, sort of. 382 01:00:56.030 --> 01:01:12.909 Mark Kushner: cup it a bit earlier than if you did not have that. So it's a balance of the various terms in the induction and the energy equation, ultimately. But, like, unlike resistivity, the Hall effect is non-dissipative, so… Correct. Saturated by reflecting the currents in a different direction. That's right. 383 01:01:12.960 --> 01:01:23.609 Mark Kushner: No, but essentially, it is coming, though, as an extra term in that balance, right? So, if you have the time, we can look at it together and can show you. 384 01:01:25.180 --> 01:01:39.490 Mark Kushner: And Carolyn? So, to piggyback off of Artis' question, what about a high-intensity laser, like, I don't know, 3 petawatt laser, if you have one. So, who's got one of those? I don't know. 385 01:01:39.800 --> 01:01:51.909 Mark Kushner: So we're building it, so… it's going ahead. I think there are a lot of flagship experiments that we can try and do there, and it is exciting to try to 386 01:01:52.200 --> 01:01:54.329 Mark Kushner: Come up with new ideas. 387 01:01:54.710 --> 01:02:08.719 Mark Kushner: to deploy this high intensity. Definitely, I would very much like to, to explore applications in which you can use high intensities in conjunction with 388 01:02:08.880 --> 01:02:15.400 Mark Kushner: Our lower, intensity drive beams to set things up, and then have 389 01:02:16.230 --> 01:02:35.979 Mark Kushner: ultra-high energy cosmic rays, essentially, zipping through that thing. I mean, there are many things that… all the new capabilities that we're building create a playground that we had no idea existed, right? So, we need to keep thinking in a blue sky type of way to 390 01:02:36.130 --> 01:02:38.130 Mark Kushner: Push this thing forward. 391 01:02:40.880 --> 01:03:00.109 Mark Kushner: I mean, the cosmic rays going through the turbulent magnet, so what would you think would happen to them? So, there is a paper that we published on UpJ, in 2020. This was essentially the last paper I submitted from Chicago before I went to Rochester, and 392 01:03:00.220 --> 01:03:12.659 Mark Kushner: It was, when the pandemic started, so it has not been cited at all, because we could not publicize it. But what we were able to do there, was to actually try to understand 393 01:03:12.740 --> 01:03:35.710 Mark Kushner: the type of diffusion that happens in these charged particles as they're going through, through magnetic fields. And, this will work out with, Ellen Zweibel, who has done a lot of work on the, on the field, to sort of understand if we were doing… if we were encountering, essentially, a subdiffusion, super diffusion, or a regular Markov chain diffusion in, in, 394 01:03:35.710 --> 01:03:42.520 Mark Kushner: In these particles that we were shooting through. 395 01:03:42.780 --> 01:03:50.650 Mark Kushner: fundamentally the proton radiography. So, the way that we had it set up, we had essentially very energetic particles. 396 01:03:50.760 --> 01:03:58.749 Mark Kushner: Which were a good stand-in in terms of their rigidity to their ultra-high energy cognate rays. 397 01:03:59.140 --> 01:04:11.320 Mark Kushner: And they were getting a little bit deflected. So from that deflection, we had a pinhole that allowed us to measure, essentially, the deflection properly in the proton radiograph. 398 01:04:11.340 --> 01:04:25.350 Mark Kushner: And from that measurement, we could then figure out what is the diffusion coefficient associated with the diffusion process of those particles, had they propagated through a larger extent of turbulence. So, there are… 399 01:04:25.910 --> 01:04:41.210 Mark Kushner: quantifiable things that you can eke out of these things, the problem becomes a bit more complicated when you have lower energy particles that are getting tangled up there. There are cool things that you can do there. I think there was a 400 01:04:41.780 --> 01:04:48.210 Mark Kushner: a recent presentation at the, the Eclipse meeting, was showing, 401 01:04:48.350 --> 01:04:55.840 Mark Kushner: Showing acceleration in, in, in, in sort of, like, loaded particles by, 402 01:04:56.960 --> 01:05:06.000 Mark Kushner: I'm blanking on the name, but I can bring it up. There's new physics behind it. Definitely, it's something that… 403 01:05:06.130 --> 01:05:12.679 Mark Kushner: our Astro colleagues are doing a lot of work on, and I think it would be foolish for us not to help them. 404 01:05:15.140 --> 01:05:17.580 Mark Kushner: Mr. Thank you so much. Thank you. 405 01:05:20.950 --> 01:05:21.860 Mark Kushner: Housing? 406 01:05:22.420 --> 01:05:23.479 Mark Kushner: Work history.