Balancing the electron Vlasov equation with MMS: Characterizing phase space density gradients during magnetopause reconnection

Abstract:

Widely employed to model collisionless plasma phenomena occurring naturally in Earth’s magnetic environment, throughout the heliosphere, and in laboratory fusion devices, the Vlasov equation self-consistently describes the fundamental kinetic dynamics of plasma particles as they are accelerated through phase space via electric and magnetic forces. Instrumentation comprising the Fast Plasma Investigation onboard NASA's Magnetospheric Multiscale (MMS) four-spacecraft mission sufficiently resolves the seven spatial, temporal, and velocity-space dimensions of phase space necessary for computing terms in the Vlasov equation, as demonstrated by Shuster et al. [2019] in the context of electron-scale current layers embedded in the reconnection exhaust. This technique motivates novel exploration of the types of distinct velocity-space signatures in ∂f/∂t, v⋅∇f, and (E + v×B)⋅∇_vf which are associated with the magnetic reconnection process. Here, we apply this approach to characterize the structure of phase space density gradient terms in the electron Vlasov equation as observed by MMS throughout various dayside reconnection regions, including the inflow, exhaust, separatrices, and ion and electron diffusion regions. We will also discuss how these observations compare with initial predictions from fully kinetic particle-in-cell (PIC) simulations of corresponding asymmetric reconnection regions.