Bulletin of the American Physical Society
62nd Annual Meeting of the APS Division of Plasma Physics
Volume 65, Number 11
Monday–Friday, November 9–13, 2020; Remote; Time Zone: Central Standard Time, USA
Session NO04: Fundamental Plasmas: Reconnection ILive
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Chair: Gregory Howe, University of Iowa |
Wednesday, November 11, 2020 9:30AM - 9:42AM Live |
NO04.00001: Laboratory study of X-ray jets from coronal hole in the sun and initial simulation study Masaaki Yamada, Elena Belova, Joshua Latham A laboratory study is being planned for plasma jets from sun’s coronal hole observed through X-ray by Yohkoh and Hinode satellites. A scenario for X-ray jets from coronal hole was first suggested based on magnetic reconnection by Shibata et al. from the Anemone structure [1]. A new model was developed and has been further analyzed initially by numerical simulation by the present authors. This model is based on a tilt instability of a spheromak-like configuration formed in the coronal hole of the sun. As the spheromak is elongated upward due to a slow emergence of flux from the solar surface, this half-spheromak becomes unstable to a tilt mode. As the inner configuration tilts, a current sheet develops near a tilted top null point and reconnection takes place. As the reconnected field lines expand towards the exhaust, a plasma jet is ejected with bursts. This talk presents recent results from numerical simulation which was carried out on HYM code. A laboratory experiment is being planned to verify the results. [1] Shibata, K et al, Science 318, 1591 (2007). [Preview Abstract] |
Wednesday, November 11, 2020 9:42AM - 9:54AM Live |
NO04.00002: Collisional Effects on the Lower Hybrid Drift Wave Inside the Reconnecting Current Sheet of a Laboratory Plasma Jongsoo Yoo, Yibo Hu, Jeong-Young Ji, Hantao Ji, Jonathan Jara-Almonte, Sayak Bose, Aaron Goodman, Masaaki Yamada, Andrew Alt, Will Fox Lower hybrid drift waves (LHDWs) have been observed near the electron region of the Magnetic Reconnection Experiment (MRX), where finite Coulomb collisions exist. To address possible collisional effects on LHDW, we have developed a theoretical framework, which is based on a local linear model and electron fluid equations. Unlike the previous model for collisionless plasma [1], we have modified the expression for electron heat flux and added the effects due to heat generation by collisions with known fluid closures [2,3]. In addition, the first-order perpendicular temperature is included. Preliminary results show that collisional effects with typical MRX parameters are negligible, although the growth rate decreases. For parameters measured in MRX during high guide field reconnection, the quasi electrostatic LHDW propagating almost perpendicular to the magnetic field is unstable. This quasi electrostatic LHDW is capable of generating density fluctuations correlated with fluctuations in the electric field, potentially leading to anomalous electron heating. [1] J. Yoo et al. Lower hybrid drift waves during guide field reconnection, submitted. [2] J. Ji and E. D. Held, phys. plasmas 20, 042114 (2013). [3] J. Ji and I. Joseph, phys. plasmas 25, 032117 (2018). [Preview Abstract] |
Wednesday, November 11, 2020 9:54AM - 10:06AM Live |
NO04.00003: Stability Properties and Intermittent Failed Eruptions of Arched, Line-Tied Magnetic Flux Ropes Andrew Alt, Hantao Ji, Jonathan Jara-Almonte, Jongsoo Yoo, Sayak Bose, Masaaki Yamada Coronal mass ejections occur when long-lived magnetic flux ropes (MFR) anchored to the solar surface destabilize and erupt away from the Sun. These eruptions are considered to be driven by ideal MHD instabilities such as the kink and torus instabilities. These instabilities have long been considered in axisymmetric fusion devices where the instability criteria are given in terms of the edge safety factor and confining magnetic field decay index, respectively. Laboratory experiments have been performed in the Magnetic Reconnection Experiment (MRX), where the stability properties of the ropes were controlled via the external fields. A recent observation in these experiments is the existence of ropes which intermittently erupt. These ropes have stable periods, lasting longer than an Alfv\`en time, interrupted by quick rises which end when the rope falls back down to the stable height before it fully erupts. This repeated behavior is similar to the storage and release in homologous events on the Sun. The work presented here investigates several potential causes for both the initiation of the eruptive events and the collapse back to stability. Understanding the trigger mechanism for the intermittent ropes also gives insight into the stability criteria for other MFR experiments in MRX. [Preview Abstract] |
Wednesday, November 11, 2020 10:06AM - 10:18AM Live |
NO04.00004: Thermodynamics of the Collisional-Collisionless Phase Transition in Magnetic Reconnection Jonathan Jara-Almonte, Hantao Ji The transition between collisional and collisionless magnetic reconnection is of critical importance in understanding how and when fast magnetic reconnection is triggered. By examining a fully kinetic simulation, it is shown that this transition may be viewed as a second-order thermodynamic phase transition that occurs when the current sheet reaches a critical temperature, $T_c = m_i\Omega_i^2\delta^2/k_B$. At the phase transition, the transport coefficients and thermodynamic properties change character, and critical behavior is identified. The high-temperature ordered phase is described by a non-zero viscous electric field, efficient thermal transport across the separatrix, and entropy production due to thermal mixing. Finally, a model for the thermodynamic collapse of an isolated Sweet-Parker current sheet is derived and it is shown that any isolated current sheet will eventually collapse down to kinetic scales, regardless of initial thickness. Implications for the onset of kinetic reconnection in both single and multi X-line scenarios is discussed. [Preview Abstract] |
Wednesday, November 11, 2020 10:18AM - 10:30AM Live |
NO04.00005: Guide Field Plasmoid Statistics and Fast Electrons in MRX Stephen Majeski, Hantao Ji, Jonathan Jara-Almonte, Jongsoo Yoo, Will Fox Understanding the behaviors of a plasmoid unstable current sheet can provide insight into how reconnection generates fast electrons in processes from solar flares to sawtooth crashes. To extend the work of Huang and Bhattacharjee\footnote{Yi-Min Huang and A. Bhattacharjee. Distribution of plasmoids in high-lundquist number magnetic reconnection. Physical Review Letters, 109(26), 2012. }, a model for the distribution of plasmoids in a moderate guide field is presented based on the concepts of helicity and Taylor relaxation. Following their approach, a statistical equation is developed to determine the distribution of cylindrical plasmoids as a function of helicity assuming that it is conserved in plasmoid collisions. The in-plane flux distribution differs only slightly from the non-relaxing -2 power law, but the guide field flux distributions for the relaxing and non-relaxing cases are distinct, with -1 and -3/2 power laws respectively. The design of a non-swept multi-channel electron energy analyzer is also presented, with the goal of measuring fast electrons produced from plasmoid mergers in the Magnetic Reconnection Experiment. [Preview Abstract] |
Wednesday, November 11, 2020 10:30AM - 10:42AM Live |
NO04.00006: Particle Acceleration in Magnetic Reconnection Using Laser-Powered Capacitor Coils Abraham Chien, Lan Gao, Hantao Ji, Kenneth Hill, William Daughton, Ari Le, Adam Stanier, Eric Blackman Magnetic reconnection is a ubiquitous astrophysical phenomenon at low plasma $\beta $ that rapidly converts magnetic energy into some combination of flow energy, thermal energy, and non-thermal energetic particles. The latter is often an observational signature of magnetic reconnection environments, which can be more efficient accelerators than competing processes such as isolated collisionless shocks. Experimental diagnostics capabilities have long limited most reconnection experiments to focus on the generation of plasma flow or thermal energy, leaving the acceleration of non-thermal particles unknown. To overcome this limitation, we have developed a robust platform for generating and measuring non-thermal energetic electrons from magnetically driven, quasi-axisymmetric reconnection using laser-powered capacitor coils and demonstrated this setup on the OMEGA EP laser facility at the Laboratory for Laser Energetics. The experimental conditions were simulated using a 2D particle-in-cell code (VPIC). Detailed experimental and numerical results will be presented, including their comparisons in both reconnection electromagnetic fields and the resulting accelerated particle spectrum. Implications to the acceleration mechanisms and observations will be discussed. [Preview Abstract] |
Wednesday, November 11, 2020 10:42AM - 10:54AM Live |
NO04.00007: Ion acceleration in 3D guide field magnetic reconnection Qile Zhang, James Drake, Marc Swisdak, Joel Dahlin Magnetic reconnection can acceleration ions to up to GeV energy in solar flares but the ion acceleration mechanism is still unclear. Previous 3D particle-in-cell guide field reconnection simulations suggest that electrons have stronger acceleration in 3D than 2D due to enhanced 3D transport to access more fermi reflection regions, but mysteriously ions acceleration in 3D is suppressed compared to 2D. By further analysis and particle tracking in these simulations, we find that the fermi slingshot effect in 3D is weaker than 2D due to the 3D entangled turbulent field lines, which reduces the energy conversion from the fermi mechanism of both ions and electrons. Energetic ions are accelerated by the fermi mechanism like energetic electrons, but they travel much slower than electrons and thus they cannot make full use of the 3D transport like energetic electrons to overcome the weaker slingshot effect in 3D, resulting in a reduced acceleration than 2D. [Preview Abstract] |
Wednesday, November 11, 2020 10:54AM - 11:06AM Live |
NO04.00008: FLARE: a collaborative research facility to study magnetic reconnection and related phenomena H. Ji, J. Yoo, J. Jara-Almonte, A. Goodman, Y. Ren, M. Yamada, A. Bhattacharjee, W. Fox, W. Daughton, A. Stanier The FLARE device (Facility for LAboratory Reconnection Experiments; flare.pppl.gov) is a new experimental device constructed at Princeton University for the study of magnetic reconnection in the multiple X-line regimes, directly relevant to space, solar, astrophysical, and fusion plasmas. The first plasma operation was successfully conducted to validate the engineering design and to demonstrate access to parameter space beyond its predecessor, MRX. The device has been relocated to PPPL while the power supplies are being upgraded to access new multiple X-line regimes in the reconnection phase diagram. The construction activity has been affected by the COVID-19 pandemic and currently is being re-started. A progress update including available diagnostics and the operation plan as a DoE collaborative research facility will be presented. Numerical predictions using the state-of-the-art particle-in-cell code, VPIC, will be discussed to guide the first physics operation of FLARE. [Preview Abstract] |
Wednesday, November 11, 2020 11:06AM - 11:18AM Live |
NO04.00009: Laboratory verification of electron-scale diffusion regions modulated by a three-dimensional instability Samuel Greess, Jan Egedal, Adam Stanier, Joseph Olson, William Daughton, Rachel Myers, Alexander Millet-Ayala, Ari Le, Michael Clark, John Wallace, Douglass Endrizzi, Cary Forest During magnetic reconnection, the electron fluid decouples from the magnetic field within narrow current layers, and theoretical models for the process can be distinguished in terms of their predicted current layer widths. In agreement with numerical and theoretical results, we present laboratory observations that confirm the presence of electron scale current layer widths. Although the layers are modulated by a current-driven instability, the narrow experimental current layers are consistent with a 3D simulation for which off-diagonal stress in the electron pressure tensor is responsible for fast reconnection. [Preview Abstract] |
Wednesday, November 11, 2020 11:18AM - 11:30AM Live |
NO04.00010: Enhanced Thomson Scattering from Ion Acoustic Waves in a Magnetic Reconnection Current Sheet L.G. Suttle, S.V. Lebedev, J.W.D. Halliday, J.D. Hare, D.R. Russell, E.R. Tubman, V. Valenzuela-Villaseca, C. Bruulsema, W. Rozmus, N.F. Loureiro, M. Koepke We present Thomson scattering (TS) measurements probing the ion acoustic waves (IAWs) inside a magnetic reconnection current sheet, produced by super-Alfvenic magnetized plasma flows from ablating wire arrays [Suttle PRL 2016]. We measure the TS spectra of IAWs at spatially-resolved positions across the current sheet and upstream flows. Multiple simultaneous observation directions allow us to independently probe waves along different scattering vectors. In the direction parallel to the reconnection electric field we detect large current drift velocities, exceeding the local sound speed in the current sheet. We also observe a strong enhancement to the TS intensity in the sheet from IAWs propagating parallel to the current, compared to the predicted Spectral Density function S($\omega $,K). However, the enhancement is observed across both forward and backward propagating waves, contrary to the expectation for current-driven ion acoustic turbulence (IAT). We assess the stability of the layer to IAT and discuss other potential sources for the IAW enhancement. [Preview Abstract] |
Wednesday, November 11, 2020 11:30AM - 11:42AM Live |
NO04.00011: Spiky electric potential structures in flux rope experiments Shawn Wenjie Tang, Walter Gekelman, Patrick Pribyl, Stephen Vincena Spiky structures have been observed in measurements of the electric potential in a magnetized flux rope experiment at UCLA's LArge Plasma Device (LAPD). They are reminiscent of Time Domain Structures (TDS) -- narrow, intense electric field spikes that appear in space observations of the aurora and planetary magnetospheres, and are associated with non-linear processes related to plasma instabilities and the end state of turbulence. In the LAPD, two 11~m long kink-unstable flux ropes were created by a lanthanum hexaboride (LaB$_6$) source and are encapsulated within a 18~m long background plasma produced by a barium oxide (BaO) cathode. The spikes appear near the surface of the two ropes and are highly correlated with the rope motion, only appearing when the ropes are kink unstable. They also seem to emanate from the reconnection region and migrate to the periphery of the ropes at the start of the experiment. In addition, the spikes appear to be driven by deterministic behavior and have characteristics of Lorentzian pulsed signals. A primitive model of the system is presented in an attempt to explain the spikes' occurrence. [Preview Abstract] |
Wednesday, November 11, 2020 11:42AM - 11:54AM Live |
NO04.00012: Global field evolution in magnetic reconnection experiments using laser-powered capacitor coils Shu Zhang, A. Chien, L. Gao, H. Ji, K. Hill, J. Fuchs, S. Chen, A. Fazzini, P. Bleotu, R. Takizawa, A. Rasmus, S. Klein, X.X. Yuan, H. Chen Magnetic reconnection is a plasma process that leads to the explosive release of magnetic energy from the sudden change of the magnetic field topology. Using capacitor coils driven by $3\times10^{15}$~W/cm$^2$ high-intensity Titan laser at the Jupiter Laser Facility, we have conducted experiments to study magnetic reconnection in a low-beta plasma with 10s-T magnetic field. The flexibility of this platform enabled us to scan the system size of the reconnection region by changing the coil distance. The plasma profiles between the coils were simulated using radiation-magnetohydrodynamics code (FLASH) and compared with the interferometry measurements. We also used wide-spectrum proton beams (3--20 MeV) to probe the global evolution of the magnetic and electric fields. Electric and magnetic fields were reconstructed and distinguished from the proton radiography images. Details of the experiments, simulations, and the field reconstruction will be presented. [Preview Abstract] |
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