A Comparative Study of Energy Conversions Associated with Collisionless Shocks and Magnetic Reconnection in the near-Earth Environment

Collisionless shocks are ubiquitous in space plasmas. The mechanisms responsible for energy conversion and particle acceleration in collisionless shocks remain elusive and central to many astrophysical problems. Here we propose to analyze and compare terms of the energy equation during Earth bow shock and magnetopause Electron Diffusion Region (EDR) crossings using the high-resolution, multi-spacecraft Magnetospheric MultiScale (MMS) mission. Direct derivations from the Vlasov-Maxwell equation provide the equation that describes the temporal evolution of the kinetic energy. In this study, we investigate, in a multifluid framework, the terms that quantify the acceleration or deceleration of ions and electrons, i.e., pressure-gradient force term, and the electromagnetic energy term. The former accounts for plasma acceleration/deceleration from a pressure-gradient, while the latter accounts for plasma acceleration/deceleration from an electric field. While global average balance between the terms is expected, deviations from zero are sources of accelerations or decelerations. We use in-situ observations from MMS to determine statistically the dominant terms responsible for electrons and ions acceleration in association with these two key phenomena: shocks and reconnection. In this ongoing work, we present the probability distribution functions of the relevant terms. We classify our results with respect to the Alfvènic Mach number and the plasma beta. We discuss the role of each term in accelerating, heating the plasma and producing or annihilating magnetic energy.