MMS observations of the multiscale wave structures and parallel electron heating in the vicinity of the southern exterior cusp

The counter-streaming electron intervals were associated with large-magnitude field-aligned Poynting fluxes. Burst mode data at the large Alfven velocity gradient revealed a strong correlation between counter streaming electrons, enhanced parallel electron temperatures, strong anti-field aligned wave Poynting fluxes, and wave activity from sub-proton cyclotron frequencies extending to electron cyclotron frequency. Waves were identified as Kinetic Alfven waves but their contribution to parallel electron heating was not sufficient to explain the >100 eV electrons, and rapid nonadiabatic heating of the boundary layer as determined by the characteristic heating frequency, derived here for the first time.