Plasmaspheric Plume Turbulence: Signature of an Electrostatic Corotation-Convection Shear-Layer Instability

IMAGE-EUV observations have demonstrated that plasmaspheric drainage plumes are a common feature emanating from the plasmasphere during periods of enhanced convection. While IMAGE-EUV remote imaging may give the impression that plasmaspheric plumes are a quasi-uniform density structure extending out toward geosynchronous orbit, in–situ LANL-MPA observations reveal a large spatial-scale ensamble populated by small-scale density structures suggestive of the presence of a turbulent process. We investigate the occurrence and nature of plasmaspheric drainage plumes as observed by concurrent EUV-MPA observations and explore the possibility that the observed in–situ small-scale density structures are the signature of an instability produced by the sheared velocity found within the plasmaspheric layers separating the corotation of the main plasmasphere from the convection-driven flow generating the plume. Particle-in-cell simulations indicate that the generation of shear-flow driven instabilities is possible under plasmaspheric plasma conditions. The initial results of these simulations indicate that the plasmaspheric instabilities generated are electrostatic in nature, consistent with in–situ plume observations.