Plasma Turbulence in Earth’s Magnetosheath Observed by the Magnetospheric Multiscale Mission over the First Sub-Solar Apogee Pass

Abstract:

Magnetic reconnection, a process in which the magnetic topology undergoes multi-scale changes, is a significant mechanism for particle energization as well as energy dissipation. Reconnection occurs in thin current sheets generated between two regions of magnetized plasma merging with a non-zero shear angle. The plasma becomes demagnetized as field lines transform before becoming frozen-in again and accelerated out of the electron diffusion region. Turbulence is another fundamental process in collision-less plasmas. Turbulence in both plasmas and fluids has a fundamental property in that it follows an energy cascade into smaller scales. Energy introduced into a fluid or plasma through turbulence can cause intermittency and vorticity, merging into increasingly smaller eddies. Turbulent energy in magnetized plasmas is hypothesized to be dissipated by magnetic reconnection, just as viscosity dissipates energy in neutral fluid turbulence. Additionally it has been observed that plasma intermittency in the magnetosheath increases when the solar wind is quasi-parallel to the bow shock normal. The focus of this study is to use the high temporal resolution suite of instruments on board the Magnetospheric MultiScale (MMS) mission to explore this hypothesis. We use highly accurate (0.1 nT) Flux Gate Magnetometer (FGM) data to observe the intermittency of 20 burst periods spread out over the first sub-solar pass of MMS. The burst periods are selected because they were observed to contain thin current sheets. We apply the auto-correlation method of Partial Variance of Increments (PVI) to search for localized intermittency within a burst period. The maximum PVI per period is then correlated with the angle between the solar wind and the bow shock normal.