[P-EM13] Dynamics of the Inner Magnetospheric System

[PEM13-07] Energetic Particle Precipitation in Sub-Auroral Polarization Streams

*Anton Artemyev¹, Ying Zou², Xiaojia Zhang³, Xing Meng⁴, Vassilis Angelopoulos¹ (1.Institute of Geophysics and Planetary Physics at UCLA, 2.Applied Physics Laboratory, Johns Hopkins University, Laurel, United States, 3.Department of Physics, University of Texas at Dallas, Richardson, TX, USA, 4.Jet Propulsion Laboratory, California Institute of Technology, Pasadena, United States of America)

Keywords:Sub-Auroral Polarization Streams, Energetic Electron Precipitations, Plasma Sheet Injections

Sub-auroral polarization streams (SAPS) are one of the most intense manifestations of magnetosphere-ionosphere coupling. Magnetospheric energy transport to the ionosphere within SAPS is commonly attributed to Poynting flux and the precipitation of thermal energy (0.03-30 keV) plasma sheet particles. However, much less is known about the precipitation of high-energy (>50 keV) ions and electrons and their contribution to the low-altitude SAPS physics. This study examines particle precipitation within SAPS using a combination of equatorial (THEMIS and ERG) and low-altitude (DMSP and ELFIN) observations, which, jointly, cover the entire energy range of interest from a few eV up to a few MeV. We show that the observed SAPS are embedding the ion isotropy boundary, which includes strong 300-1000 keV ion precipitation. We find that SAPS are associated with intense precipitation of relativistic electrons (< 3MeV), well equatorward of the electron isotropy boundary. Such relativistic electron precipitation is likely due to electron scattering by electromagnetic ion cyclotron waves at the equator. We also show that relativistic electron precipitation within SAPS is accompanied by sub-relativistic (<500keV) electron injections into the plasmasphere. We discuss observational evidence of such injections observed by ELFIN at low altitudes and ERG near the equatorial plane.