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Abstract: Energy conversion between thermal and bulk flow energy in weakly collisional and collisionless plasma processes such as magnetic reconnection and plasma turbulence has recently been the subject of intense scrutiny. This channel of energy conversion is described by the pressure-strain interaction. Typically, it is decomposed into pressure dilatation and Pi-D which isolates compressive and incompressive physics, respectively. We propose an alternative decomposition of pressure-strain interaction isolating bulk flow convergence/divergence from bulk flow shear. This provides an alternative insight into understanding the energy conversion. We furnish a simple example that gives a counterintuitive result for Pi-D but an intuitive result for the alternative decomposition. Moreover, for magnetized plasmas, we write pressure-strain interaction in a magnetic field-aligned coordinate system. This results in its decomposition into eight terms, each with a different physical mechanism that can contribute to changing the thermal energy density. Results from particle-in-cell simulations of two-dimensional magnetic reconnection plotting the decompositions in both Cartesian and magnetic field-aligned coordinates are shown where we identify the mechanisms contributing to heating and cooling during reconnection. The results of this study are readily applicable for interpreting numerical and observational data of pressure-strain interaction (in both Cartesian and field-aligned coordinates) in fundamental plasma processes such as reconnection, turbulence and collisionless shocks.

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https://dartmouth.zoom.us/j/92751420885?pwd=QnIwN0RiSGkzMUtjQVZxRlZLMkcwQT09

Meeting ID: 927 5142 0885
Passcode: Plasma