Validation of Anisotropic Electron Fluid Closure Through In Situ Spacecraft Observations of Magnetic Reconnection

Abstract

A valid fluid model for electrons in collisionless space plasmas is desirable for understanding the structure and evolution of magnetic reconnection geometries. Additionally, such a fluid model would be useful for the simulation of systems too large to be tractable in a fully kinetic model. Using Magnetospheric Multiscale spacecraft observations, we provide direct confirmation of the Lê et al., 2009 (https://doi.org/10.1103/PhysRevLett.102.085001) equations of state for the electron pressure tensor during guide field reconnection and demonstrate how the closure can be applied in efficient numerical simulation, yielding new physical insight to the electron heating problem. Furthermore, we use the Lê et al., 2009 equations of state to predict a scaling of electron heating in the exhaust comparable to the available observational data.

Astrophysical Explosions Revisited: Collisionless Coupling of Debris to Magnetized Plasma

“…where quasi-neutrality is assumed so that not substantially affect the results of these simulations and are in line with previous hybrid simulations that agree with fully kinetic modeling (Le et al, 2016(Le et al, , 2018Wetherton et al, 2019). The electron pressure gradient accounts for electrostatic fields (Bonde et al, 2015), and the electrons are treated as an isothermal fluid.…”

Anisotropic Electron Fluid Closure Validated by in Situ Spacecraft Observations in the far Exhaust of Guide‐field Reconnection

“…The heating provided by the model is clearly anisotropic in favor of T e ‖ . Furthermore, in combination with roughly steady‐state force balance across the exhaust, the model has been shown to predict similar scalings for Δ T e in the exhaust for a variety of guide field regimes (Ohia et al., 2015; Wetherton et al., 2019) as the observed scalings of (Phan et al., 2013). The heating predicted by the EoS in these scalings is primarily regulated by the density and magnetic field strength required in the exhaust for force balance across the layer.…”

Astrophysical explosions revisited: collisionless coupling of debris to magnetized plasma

“…are set to small normalized values in the range of 0.001 to .005, which do not substantially affect the results of these simulations and are in line with previous hybrid simulations that agree with fully kinetic modeling (Le et al, 2016(Le et al, , 2018Wetherton et al, 2019). The electron pressure gradient accounts for electrostatic fields (Bonde et al, 2015), and the electrons are treated as an isothermal fluid.…”