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 TP14: Poster Session: Fundamental Plasmas: Reconnection (9:30am 12:30pm)On Demand

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TP14.00001: Annihilation of Magnetic Field in Relativistic LaserPlasma Interaction and Electromagnetic Burst Generation Francesco Pegoraro, Y.J. Gu, P.V. Sasorov, D. Golovin, A. Yogo, G. Korn, S.V. Bulanov We investigate the formation and evolution of a relativistic current sheet in a collisionless plasma during magnetic reconnection driven by parallel laser pulses interacting with an underdense plasma target (Electromagnetic Burst Generation during Annihilation of Magnetic Field in Relativistic LaserPlasma Interaction. Sci Rep 9, 19462 (2019).). Annihilation of the magnetic field of opposite polarity generates a strong nonstationary electric field accelerating charged particles within the current sheet. This laserplasma target configuration is relevant to the modeling of charged particle acceleration and gamma flash generation in astrophysics. [Preview Abstract] 

TP14.00002: Nonlinear error field response in the presence of plasma rotation and real frequencies due to favorable curvature John Finn, Cihan Akcay, Andrew Cole, Dylan Brennan We present NL NIMROD resistive MHD simulations of a rotating plasma with error fields for a plasma with weakly damped linear tearing modes (TM's), stabilized by favorable curvature. Favorable curvature leads to the Glasser effect, real frequencies and stabilization with positive Delta'. Hollow pressure in a cylinder models the toroidal favorable curvature. Linear simulations with rotation and an error field show, in agreement with analysis, that the peak reconnected flux occurs for rotation near the TM phase velocity. NL simulations show that the Glasser effect disappears due to a NL effect for thin islands: flattening of the pressure across the island due to sound wave propagation. This causes the disappearance of real frequencies and destabilization, allowing the mode to grow like a zero beta unstable TM. The flattening of the current for larger islands saturates the mode nonlinearly; the interaction of the error field with the rotating spontaneous tearing mode leads to oscillations in the Maxwell torque and therefore modulations in the plasma rotation. The islands also rotate with modulated phase velocity, undergoing smallamplitude oscillations due to these modulations. We present a quasilinear model with a TM, rotation and error fields, showing similar oscillations. [Preview Abstract] 

TP14.00003: Nonlinear magnetic reconnection analysis and effective longitudinal electron thermal conductivity Dario Borgogno, Daniela Grasso, Bruno Coppi Since the onset of magnetic islands on rational surfaces can affect the effective longitudinal electron thermal conductivity, a non linear twofluid model has been derived for the analysis of modes producing magnetic reconnection including the pressure gradient contribution to the longitudinal electron momentum conservation equation. Numerical solutions of the model, reproducing results obtained from the linear analysis starting from a one dimensional plane geometry $^{\mathrm{1}}$, are presented. $^{\mathrm{1}}$ B. Coppi, B. Basu et al. Nucl. Fusion (2019) [Preview Abstract] 

TP14.00004: PIC Simulations of particle energization during magnetic reconnection of laser produced plasma bubbles Kai Germaschewski, John Donaghy, Will Fox, Derek Schaeffer, Amitava Bhattacharjee, Jackson Matteucci, Gennady Fiksel We perform and analyze particleincell simulations of colliding laserproduced plasma bubbles. These endtoend simulations model generation and heating of the bubbles, which by means of the Biermann battery effect selfconsistently generate magnetic fields. The antiparallel fields then collide and reconnect. Previous 2D simulations in the reconnection plane demonstrate the formation of an energized electron population during reconnection [W. Fox, PoP 24, 092901 (2017)]. Here we expand the calculations to the full 3D evolution of colliding plasmas to determine the conditions required in this more complete system to accelerate particles. We also investigate the effect of a preheated electron population on particle energization. Simulations are performed using the GPUenabled PSC particleincell code on ORNL's Summit supercomputer. [Preview Abstract] 

TP14.00005: Asymmetric Magnetic Island Dynamics with Curvature Effects M. Stefany Cancino, Julio J. Martinell, Fran\c{c}ois L. Waelbroeck Magnetic islands allow heat and particle flow within the separatrix along the closed flux surfaces, thus establishing a connection between inner and outer plasma regions in the toroidal plasma, which in turn deteriorates confinement. In general, magnetic islands are not symmetric, as they can have a certain degree of asymmetry in the radial direction. Such asymmetry affects in turn the stability of tearing modes, through a modification of the temperature profiles. Previous works have studied the influence of the magnetic island asymmetry on density and temperature profiles, but there are some discrepancies among the various results over the actual effect produced. On the other hand, previous studies have shown that the magnetic field line curvature has an influence on the tearing mode instability, modifying the width of the island given by the Rutherford equation. The curvature centrifugal term can have a stabilizing or destabilizing effect, depending on the direction of the average curvature. The present work studies the magnetic island dynamics when it has radial asymmetry taking into account magnetic curvature effects in a slab model complementing the existing discussion about the influence of these effects on the profiles of plasma parameters such as density and temperature. [Preview Abstract] 

TP14.00006: Identifying the scales of energy transfer due to plasmoidmediation in 2D MHD turbulence Liang Wang MHD turbulence plays a critical role in energy transfer in numerous space and astrophysical plasma systems. MHD turbulence tends to form thin electrical current sheets where copious plasmoids could form at sufficiently high magnetic Reynolds numbers and consequently disrupt the current sheets. Recent theoretical and numerical studies have reported a new energy cascade regime in MHD turbulence, mediated by the plasmoid instability and the consequent fast magnetic reconnection. A number of theories predicted that the disruption of current sheet structures would facilitate the energy cascade towards small scales. Later, Dong et al.[1] reported the first direct numerical simulation evidence on this topic in the context of 2D MHD turbulence. In particular, the breaking and steepening of the energy spectrum was confirmed using simulations of unprecedented high resolution and large magnetic Reynolds number (Re=1e6). In this work, we further explore aspects of plasmoidmediated turbulence using similar largescale, 2d simulations and quantify the scales at which the plasmoid and reconnection effects set in. [1] Dong, Wang, Huang, Comisso, Bhattacharjee. Role of the plasmoid instability in magnetohydrodynamic turbulence. Physical review letters. 2018 17;121(16):165101 [Preview Abstract] 

TP14.00007: Mode Converting Alfv\'{e}n Waves from Magnetic Reconnection Enhancing the Energy Source for the Aurora Borealis Harsha Gurram, Jan Egedal, William Daughton Previous studies have concluded that the Hall magnetic field structures generated during magnetic reconnection are carried away by kinetic Alfv\'{e}n waves (KAW) for distances $\sim 10R_e$. However, from our study of Hall field profiles obtained from domain $200d_i \times 30d_i$, we observe that the large scale structure is carried by waves which are superAlfv\'{e}nic ($\sim 2V_a$ ) near the Xline where they are generated, but as they travel into the exhaust for $\sim 5R_e$ their propagation velocity decreases and become Shear Alfv\'{e}nic ( $\sim 1V_a$ ). Owing to the dispersive nature of KAW as they propagate their wavenumber, $k_{\bot}$, decreases, corresponding to a mode conversion into ShearAlfv\'{e}n waves(SAW). This mode conversion, away from the Xline becomes important as it eliminates the energy attenuation of 99\% due to Landau damping, expected when KAWs propagate towards Earth without conversion. The SAWs permit a substantial transfer of Poynting flux to the auroral regions, enhanced by a factor of $10^3$ above previous estimates. This may lead to particle acceleration and help account for auroral brightening at locations magnetically conjugate to spacecraft observations. [Preview Abstract] 

TP14.00008: Dependence of Kinetic Entropy~on Plasma Temperature~and Density in ParticleinCell Simulations of~Antiparallel Reconnection Mahmud Hasan Barbhuiya, Haoming Liang, Paul Cassak, Marc Swisdak, Vadim Roytershteyn Kineticscale energy conversion and dissipation plays a crucial role during magnetic reconnection. Many theoretical approaches have been used to identify energy conversion and dissipation in reconnection. We focus our investigation on kinetic entropy, related to the phase space integral of ``f ln f'', where f is the distribution function. The motivation behind using kinetic entropy as a diagnostic is that it is the most natural quantity to identify and quantify dissipation in a closed physical system [e.g., Liang et al., Phys. Plasmas, 26, 082903, 2019]. We use particleincell simulations using the P3D code that are twodimensional in physical space and threedimensional in velocity space to study the generation, spatial structure and time evolution of kinetic entropy in antiparallel magnetic reconnection. We perform a parametric study varying the temperature and density of the electrons and ions to investigate their impact on kinetic entropy and the usage of kinetic entropy to identify regions of adiabatic and irreversible processes. [Preview Abstract] 

TP14.00009: An examination of Reconnection Suppression in Asymmetric Guide Field Reconnection on MRX Aaron Goodman, Jongsoo Yoo, Jonathan JaraAlmonte, Sayak Bose, Hantao Ji Data is presented from reconnection experiments on MRX with large density asymmetry across the current sheet in the presence of a large guide field ($\frac{B_g}{B_{rec}} > 2$). Swisdak (2003) and Liu (2016) have both reported simulation results showing that reconnection with strong density asymmetry can be suppressed in the presence of a guide field due to Alfvenic motion of the Xline. Phan has reported observations of reconnection suppression due to the diamagnetic electron current in space (2013). In MRX it is seen that fast reconnection may proceed even when beta varies significantly across the current sheet, in violation of the suppression condition reported for THEMIS data. A 2D pressure profile has been reconstructed and it is found that the diamagnetic drift speed in MRX is much smaller than the alfven velocity due to small pressure gradients around the Xline. The discrepancy between MRX and space observations is most likely caused by the different boundary conditions in the two cases or finite collisionality contributing to small pressure gradients near the Xline. Further research is required to resolve this point. Finally, a limited energy budget and energy analysis is presented for this reconnection regime. [Preview Abstract] 
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