Donald L. Turcotte Award: Pathways to Dissipation in Weakly Collisional Plasmas

Abstract:

A familiar problem in space and astrophysical plasmas is to understand how dissipation and heating occurs. These effects are often attributed to the cascade of broadband turbulence which transports energy from large scale reservoirs to small scale kinetic degrees of freedom. When collisions are infrequent, local thermodynamic equilibrium is not established. In this case the final stage of energy conversion becomes more complex than in the fluid case, and both pressure-dilatation and pressure strain interactions (Pi-D) become relevant and potentially important [1]. Pi-D in plasma turbulence has been studied so far primarily using simulations [2,3], or selected individual events [4]. Here, we report a statistical analysis of Pi-D in the Earth’s magnetosheath using the unique measurement capabilities of the Magnetospheric Multiscale (MMS) mission. The statistics of Pi-D in this naturally occurring plasma environment strongly resemble results from previously published fully kinetic simulations. The conversion into internal energy is concentrated in small regions of space and occurs near intense current sheets, but not within them [5]. This supports recent suggestions that the chain of energy transfer channels involves regional, rather than pointwise, correlations.

[1] Y. Yang et al., PRE, 95, 061201 (2017)

[2] O. Pezzi et al., PoP, 26, 072301 (2019)

[3] Y. Yang et al., MNRAS, 482, 4933 (2019)

[4] A. Chasapis et al., ApJ, 862, 32 (2018)

[5] R. Bandyopadhyay et al., PRL, 124, 255101 (2020)