Journal
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
Volume 505, Issue 4, Pages 4857-4873Publisher
OXFORD UNIV PRESS
DOI: 10.1093/mnras/stab1516
Keywords
magnetic reconnection; plasmas; turbulence; solar wind
Categories
Funding
- National Energy Research Scientific Computing Center (NERSC) [DE-AC02-05CH11231]
- National Science Foundation [ACI-1548562]
- NASA High-End Computing (HEC) Program through the NASA Advanced Supercomputing (NAS) Division at Ames Research Center
- NSF EPSCoR RII-Track-1 Cooperative Agreement [OIA-1655280]
- NSF/DOE Partnership in Basic Plasma Science and Engineering via NSF grant [PHY-1707247]
- NSF Atmospheric and Geospace Science Postdoctoral Fellowship [AGS-2019828]
- NSF [PHY-1804428, AGS-1842638]
- NASA [NNX16AG76G, 80NSSC19M0146]
- DOE [DESC0020294]
- EPN [PIM-1901, PII-DFIS-2019-01, PII-DFIS-2019-04]
- Swedish Contingency Agency [2016-2102]
- SNSA [86/20]
- European Union [776262]
- US DOE [DE-SC0019315]
- MMS Theory and Modeling team under NASA grant [80NSSC19K0565]
- U.S. Department of Energy (DOE) [DE-SC0019315] Funding Source: U.S. Department of Energy (DOE)
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This study compares different measures used for characterizing energy dissipation and kinetic-scale conversion in weakly collisional plasmas through kinetic numerical simulations. The results show overall agreement in dissipation measures between particle-in-cell (PIC) and continuum reconnection simulations, with slight differences in details. Distribution function-based measures show a broader width compared to energy-based proxies, indicating that energy transfer occurs in wider regions.
The physical foundations of the dissipation of energy and the associated heating in weakly collisional plasmas are poorly understood. Here, we compare and contrast several measures that have been used to characterize energy dissipation and kinetic-scale conversion in plasmas by means of a suite of kinetic numerical simulations describing both magnetic reconnection and decaying plasma turbulence. We adopt three different numerical codes that can also include interparticle collisions: the fully kinetic particle-in-cell VPIC, the fully kinetic continuum Gkeyll, and the Eulerian Hybrid Vlasov-Maxwell (HVM) code. We differentiate between (i) four energy-based parameters, whose definition is related to energy transfer in a fluid description of a plasma, and (ii) four distribution function-based parameters, requiring knowledge of the particle velocity distribution function. There is an overall agreement between the dissipation measures obtained in the PIC and continuum reconnection simulations, with slight differences due to the presence/absence of secondary islands in the two simulations. There are also many qualitative similarities between the signatures in the reconnection simulations and the self-consistent current sheets that form in turbulence, although the latter exhibits significant variations compared to the reconnection results. All the parameters confirm that dissipation occurs close to regions of intense magnetic stresses, thus exhibiting local correlation. The distribution function-based measures show a broader width compared to energy-based proxies, suggesting that energy transfer is co-localized at coherent structures, but can affect the particle distribution function in wider regions. The effect of interparticle collisions on these parameters is finally discussed.
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