Cross-Scale Wave Coupling Processes in Kelvin-Helmholtz Structures
PI Heidi Nykyri
Project investigates cross-scale wave coupling processes and their role on ion heating, mixing and diffusion.
One of the pending problems in collisionless plasmas is to understand the plasma heating and transport across three fundamental scales: fluid, ion and electron. The plasma inside Earth’s magnetotail plasma sheet is ~50 times hotter than in the magnetosheath. Furthermore, the specific entropy increases by two orders of magnitude from the magnetosheath to the magnetosphere, which is a signature of a strong non-adiabatic heating. Also, the cold component ions are hotter by ~30 % at the dawnside compared to those measured on the duskside. Our recent statistical study using THEMIS data indicates that the magnetosheath seed population is not responsible for this asymmetry so additional physical mechanisms at the magnetopause or plasma sheet must be at work to explain this asymmetric heating. Recent works suggest that dawn-flank magnetopause boundary is more prone to the fluid-scale Kelvin-Helmholtz instability (KHI) as well as to the ion-scale electromagnetic wave activity, which may help explain the observed plasma sheet asymmetry. Project uses numerical simulations, plasma theory and spacecraft observations to understand relation of small-scale waves to large-scale velocity driven modes and evaluate their role in mixing, diffusion, and heating of ions.
11/01/2017 to 08/31/2022