HORNET - A New Measure of Kinetic-Scale Energy Conversion
Presentation Type
Talk
Presenter Format
Virtual Meeting Talk
Topic
Fundamental Processes in Comparative Magnetospheres
Start Date
13-5-2022 4:00 PM
Abstract
Kinetic-scale energy conversion and dissipation play a crucial role in the dynamics of magnetic reconnection and turbulence. The pressure-strain interaction recently reintroduced [Y. Yang et al., Phys.Plasmas 24, 072306 (2017)] is the only channel for energy conversion into internal energy and compression (because heat flux has no net contribution); it has thus been employed as a diagnostic in numerical simulations of reconnection and turbulence and in satellite observations to identify the power density of plasma heating or cooling. The pressure-strain interaction term can be decomposed into pressure dilatation which deals with the conversion of energy due to compression (changing the density) and Pi-D which describes incompressible conversion to or from internal energy (changing the temperature). We present a new measure on the same footing as the pressure-strain interaction dubbed “higher order non-equilibrium term” (HORNET), which gives the power density of energy conversion to all moments of the phase space density beyond temperature, thus describing energy going into changing the shape of the phase space density. We perform particle-in-cell simulations of symmetric magnetic reconnection and compare HORNET to the pressure-strain and heat flux terms. We find that HORNET identifies regions where kinetic-scale energy conversion is taking place and we find that energy going into higher order moments can be a significant fraction of the total energy conversion in and near the diffusion region. We furthermore show that while the heat flux divergence does not contribute to the net heating, it can be important locally and can even dominate over Pi-D.
HORNET - A New Measure of Kinetic-Scale Energy Conversion
Kinetic-scale energy conversion and dissipation play a crucial role in the dynamics of magnetic reconnection and turbulence. The pressure-strain interaction recently reintroduced [Y. Yang et al., Phys.Plasmas 24, 072306 (2017)] is the only channel for energy conversion into internal energy and compression (because heat flux has no net contribution); it has thus been employed as a diagnostic in numerical simulations of reconnection and turbulence and in satellite observations to identify the power density of plasma heating or cooling. The pressure-strain interaction term can be decomposed into pressure dilatation which deals with the conversion of energy due to compression (changing the density) and Pi-D which describes incompressible conversion to or from internal energy (changing the temperature). We present a new measure on the same footing as the pressure-strain interaction dubbed “higher order non-equilibrium term” (HORNET), which gives the power density of energy conversion to all moments of the phase space density beyond temperature, thus describing energy going into changing the shape of the phase space density. We perform particle-in-cell simulations of symmetric magnetic reconnection and compare HORNET to the pressure-strain and heat flux terms. We find that HORNET identifies regions where kinetic-scale energy conversion is taking place and we find that energy going into higher order moments can be a significant fraction of the total energy conversion in and near the diffusion region. We furthermore show that while the heat flux divergence does not contribute to the net heating, it can be important locally and can even dominate over Pi-D.
