Bulletin of the American Physical Society
65th Annual Meeting of the APS Division of Plasma Physics
Monday–Friday, October 30–November 3 2023; Denver, Colorado
Session YM09: Mini-Conference: ELASP III |
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Chair: Paul Bellan, Caltech Room: Governor's Square 16 |
Friday, November 3, 2023 9:30AM - 9:58AM |
YM09.00001: Peculiarities of nonthermal electromagnetic emission spectrum of a continuous ECR discharge plasma in an open magnetic trap Mikhail Viktorov, Mark E Koepke, Ivan Izotov, Elena Kiseleva, Vadim Skalyga We study the stationary stage of plasma turbulence arising in a dense nonequilibrium plasma of an electron cyclotron resonant (ECR) discharge sustained in an open magnetic trap by the continuous microwave radiation. The use of high-power millimeter radiation of modern gyrotrons allows one to create in the laboratory a nonequilibrium two-component plasma characteristic of space conditions and to simulate the physical mechanisms of instabilities developing in space magnetic traps. In the plasma created by continuous gyrotron radiation at a frequency of 28 GHz under ECR conditions in a mirror magnetic trap at the GISMO setup, nonthermal electromagnetic radiation at a frequency of 3-4 GHz was detected as a sequence of bursts with a duration of up to 500 ns. In most cases, bursts of radiation were wave packets with a deep amplitude modulation at a frequency of about 200 MHz, which leads to the formation of multiple "satellites" in the Fourier spectrum. The plasma emission frequency is lower than the electron cyclotron frequency in the source region, which indicates the development of cyclotron instability of whistler waves in dense magnetoactive plasma. We discuss the fine structure of the emission spectrum and the origin of zebra-like structures. |
Friday, November 3, 2023 9:58AM - 10:17AM |
YM09.00002: Inverse currents in current sheets in the Earth magnetosphere and in laboratory experiment Anna G Frank, Anton V Artemyev
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Friday, November 3, 2023 10:17AM - 10:36AM |
YM09.00003: Laboratory Experiments in the Collisionless Kinetic Regime of Magnetic Reconnection Paul Gradney, Jan Egedal, Isaac Barnhill, Rene Flores Garcia, Cameron Kuchta, Joseph Olson, John P Wallace, Xinyu Yu, Cary B Forest The Terrestrial Reconnection EXperiment (TREX)[1] at the Wisconsin Plasma Physics Laboratory (WiPPL)[2] can reliably reach the collisionless kinetic reconnection regime by driving a magnetic field via a cylindrical coil geometry. The most resent upgrade to the TREX configuration is the Drive Cylinder, which creates asymmetric reconnection that generates a ~2m long current layer with a normalized system size of L/di ≈ 13. Compared to the previous TREX systems, the lower inductance of the Drive Cylinder has increased the reconnection rate from Erec ≈ 100V/m to 900V/m. With these improved parameters, the Drive Cylinder produces reconnection events with Lundquist numbers up to S ≈ 105. These upgrades reduce the effects of collisionality in the experiment, such that electron pressure anisotropy is expected to develop unimpeded. By operating in this regime with a highly reproducible plasma, the Drive Cylinder aims to investigate plasma dynamics in the electron diffusion region similar to spacecraft data observed in the Earth's magnetosphere. |
Friday, November 3, 2023 10:36AM - 10:55AM |
YM09.00004: A new look at the Sun's corona as an active medium: implications for coronal seismology Dmitrii Y Kolotkov The hot, 1 million K solar corona exists because of a balance between radiative and conductive energy losses and some yet unknown coronal heating mechanism, which remains one of the major puzzles in solar physics. Such a thermal equilibrium can be readily perturbed by magnetoacoustic waves which are omnipresent in the corona, causing a misbalance between heating and cooling processes. In a series of recent works, it has been shown to lead to a back-reaction causing the wave to either lose or gain energy from the plasma. Thus, the corona acts as an active medium for magnetoacoustic waves (akin to burning gases or gain medium in lasers). In this talk, the recently understood importance of this thermodynamic activity of the corona for the magnetoacoustic wave dynamics and its implication for seismological diagnostics of the enigmatic solar coronal heating function are discussed. For a broad range of coronal conditions, the characteristic timescales of thermal misbalance are shown to be from several to a few tens of minutes, i.e. about the oscillation period of slow magnetoacoustic waves observed in the corona. It causes strong dispersion of slow waves through the modification of the effective coronal adiabatic index and the wave speed. This new dispersion is not connected with the waveguiding effects traditionally considered in the corona. The observed frequency-dependent damping of slow waves in typical thermally stable coronal plasma structures is used for constraining possible coronal heating mechanisms. |
Friday, November 3, 2023 10:55AM - 11:14AM |
YM09.00005: Measuring the Alfvén wave Parametric Decay Instability Growth Rate in the Laboratory Seth Dorfman, Feiyu Li, Xiangrong Fu, Stephen T Vincena, Troy A Carter, Patrick Pribyl Alfvén waves, a fundamental mode of magnetized plasmas, are ubiquitous in lab and space. The non-linear behavior of these modes is thought to play a key role in important problems in space plasma such as the heating of the solar corona and solar wind turbulence. In particular, theoretical predictions show that these Alfvén waves may be unstable to various parametric instabilities, but space observations of these processes are limited. We present an experiment on the Large Plasma Device at UCLA aimed at measuring the Parametric Decay Instability (PDI) growth rate in the laboratory. In these experiments, a high amplitude δB/B0~0.7% pump Alfvén wave is launched from one end of the device and a smaller seed Alfvén wave is launched from the other side. When the frequency of the seed wave is chosen to match the backward wave expected from PDI, damping of the seed wave is reduced. This reduction in damping is well-matched to the theoretically expected PDI growth rate and scales with the pump wave amplitude. Work is underway to expand this result across the accessible LAPD parameter space and compare with related numerical simulations. Results may help validate PDI theories and establish signatures for future space observations. |
Friday, November 3, 2023 11:14AM - 11:33AM |
YM09.00006: Toward Measurement of Electron Pressure Anisotropy in Collisionless Laboratory Reconnection Cameron Kuchta, Paul Gradney, Abhishek Mhatre, Jan Egedal, Joseph Olson, John P Wallace, Xinyu Yu, Samuel Greess, Alexander Millet-Ayala, Rene Flores Garcia, Isaac Barnhill, Cary B Forest The Terrestrial Reconnection EXperiment (TREX) at the Wisconsin Plasma Physics Laboratory (WiPPL) studies collisionless magnetic reconnection [1]. We've developed a new Pressure Anisotropy (PA) probe consisting of 24 langmuir probes; 12 outer tips collect plasma isotropically while the remaining 12 inner tips are shielded and receive plasma directionally. This allows us to measure plasma flows and pressure anisotropy during reconnection. With recent upgrades, we are now able to enter the collisionless kinetic regime of magnetic reconnection in which we expect electron anisotropy effects to dominate the physics in the ion diffusion region. This regime is relevant to reconnection in the magnetosphere. Embedded jets, seen in laboratory data, are driven into the outflow of reconnection as expected from spacecraft observation, theory, and simulations [2]. We’ve also observed signatures of pressure anisotropy with the PA probe. Current progress on probe design and analysis will be presented. |
Friday, November 3, 2023 11:33AM - 11:52AM |
YM09.00007: Magnetic structure formation in super-Alfvénic, quasi-perpendicular expansion of laser-produced plasma into magnetized ambient plasma at high repetition rates Robert S Dorst, Ari Le, Carmen G Constantin, Jessica J Pilgram, David Larson, Derek B Schaeffer, Steve Vincena, Shreekrishna Tripathi, Misa Cowee, Christoph Niemann We present two-dimensional mapping of a super-Alfvénic (MA > 1) carbon, laser produced plasma (LPP) as it expands into an ambient, magnetized helium plasma. The formation and propagation of a magnetic structure is observed in the ambient plasma that separates a relatively large distance (~0.5 di) from the bulk diamagnetic cavity (~di). This structure is observed to coincide with the focusing of the LPP ions into a jet like structure from magnetic pressure forces that act perpendicularly to both the magnetic field and bulk LPP direction of travel. The data was acquired during recent experiments performed on the Large Plasma Device (LAPD) at the University of California, Los Angeles as part of a series of experiments recreating conditions observed in Earth’s magnetosphere for study in the laboratory. The acquisition of this data requires a high repetition rate (~ 1 Hz) as each dataset represent thousands of laser shots in order to fully investigate the two-dimensional region of interest. |
Friday, November 3, 2023 11:52AM - 12:11PM |
YM09.00008: Snow Flakes in the Oven - Cool Material in the Hot Solar Corona and the Thermal Instability Wei Liu, Patrick Antolin, Xudong Sun, Manuel Luna Bennasar, Sijie Yu, Downs Cooper, Viacheslav Titov The Sun's outer atmosphere, the corona, is million-degrees hot and tenuous. Such hot plasma, under certain conditions, can enigmatically undergo a radiative cooling instability and condense into material of 100 times cooler in the form of coronal rain or so-called solar prominences. Where, when, and how such cooling condensation takes place remain poorly understood. Magnetic fields in the magnetized corona undoubtedly play a crucial role (e.g., by trapping the plasma), but where and how? We report recent imaging and spectroscopic observations from NASA's Solar Dynamics Observatory (SDO) and Interface Region Imaging Spectrograph (IRIS) missions that can shed light on this puzzle. Through a systematic survey, we found that a large fraction of quiet-Sun condensations preferentially occur at the dips of coronal loops or funnels. Such dips are located at/near magnetic topological features, such as null points and quasi-separatrix layers (QSLs), which are regions characterized by high values of the squashing factor. We also identified evidence of magnetic reconnection at such locations, which can produce favorable conditions, e.g., density enhancement by compression and/or mass trapping in plasmoids, that can trigger run-away radiative cooling. We present proof-of-concept MHD simulations that demonstrate the role of reconnection in transporting cooled mass from overlying, long loops to underlying, short loops where it slides down as coronal rain. We will discuss the significance and broader implications of these results beyond the Sun, elsewhere in the Universe and in laboratories. |
Friday, November 3, 2023 12:11PM - 12:30PM |
YM09.00009: Generation of laboratory nanoflares from multiple braided plasma loops Yang Zhang, Seth Pree, Paul M Bellan Solar flares are intense bursts of electromagnetic radiation accompanied by energetic particles and hard X-rays. They occur when magnetic flux loops erupt in the solar atmosphere. Solar observations detect energetic particles and hard X-rays but cannot reveal the generating mechanism because the particle acceleration happens at a scale smaller than the observation resolution. Thus, details of the cross-scale physics that explain the generation of energetic particles and hard X-rays remain a mystery. In this talk, I will present observations from a laboratory experiment that simulates solar coronal loop physics. Transient, localized 7.6-keV X-ray bursts and a several-kilovolt voltage spike are observed in braided magnetic flux ropes of a 2-eV plasma when the braid strand radius is choked down to be at the kinetic scale by either magnetohydrodynamic (MHD) kink or magnetic Rayleigh–Taylor instabilities. This sequence of observations reveals a cross-scale coupling from MHD to non-MHD physics that is likely responsible for generating solar energetic particles and X-ray bursts. All the essential components of this mechanism have been separately observed in the solar corona. |
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