Van Allen Probe Observations: Near-Earth injections of Mev Electrons Associated with Intense Substorm Electric Fields

Lei Dai1, John R Wygant2, John W Bonnell3, Cynthia A Cattell2, Craig Kletzing4, Daniel N Baker5, Xinlin Li6, David Malaspina7, J Bernard Blake8, Joseph Fennell9, Seth G Claudepierre10, Kazue Takahashi11, Herbert O Funsten12, Geoffrey D Reeves13, Harlan E Spence14, Vassilis Angelopoulos15, Karl-Heinz Glassmeier16, Drew L Turner17, Scott Thaller2, Aaron W Breneman18, Kris Kersten19, Xiangwei Tang2 and Xin Tao20, (1)University of Minnesota Twin Cities, Minneapolis, United States, (2)University of Minnesota Twin Cities, Minneapolis, MN, United States, (3)University of California Berkeley, Berkeley, CA, United States, (4)University of Iowa, Physics and Astronomy, Iowa City, United States, (5)University of Colorado, Laboratory for Atmospheric and Space Physics, Boulder, United States, (6)University of Colorado Boulder, Boulder, CO, United States, (7)University of Colorado Boulder, Astrophysical and Planetary Sciences Department, Boulder, United States, (8)The Aerospace Corp, Los Angeles, CA, United States, (9)Aerospace Corporation, Los Angeles, CA, United States, (10)The Aerospace Corporation, Los Angeles, CA, United States, (11)Applied Physics Laboratory Johns Hopkins, Laurel, MD, United States, (12)Los Alamos National Laboratory, ISR-DO, Los Alamos, NM, United States, (13)Los Alamos National Laboratory, Los Alamos, United States, (14)University of New Hampshire Main Campus, Durham, NH, United States, (15)University of California Los Angeles, Department of Earth, Planetary, and Space Sciences, Los Angeles, United States, (16)Institute of Geophysics and extraterrestrial Physics, Technical University of Braunschweig, Braunschweig, Germany, (17)University of California Los Angeles, Los Angeles, CA, United States, (18)The University of Minnesota, Minneapolis, United States, (19)University of Minnesota, Minneapolis, MN, United States, (20)University of Science and Technology of China, Hefei, China
Abstract:
With their unique orbit, the Van Allen Probes (RBSP) spacecraft are well suited to investigate near-Earth substorm injections that penetrate into the heart of outer radiation belts. Substorms are generally conceived to inject 10s-100s keV electrons but intense substorm electric fields have been shown capable of injecting ~MeV electrons as well at the geosynchronous altitude. An intriguing question is whether such MeV electron injections can penetrate to lower L shells and directly contribute to the relativistic electron population of the outer radiation belt. In this talk, we present RBSP observations of near-Earth substorm injection of MeV relativistic particles and associated intense dipolarization electric field at L ~5.5. The substorm injection occurred during a moderate storm (DST~-30 to -20) with steady solar wind conditions. RBSP-A observed dispersionless injection of electrons from 10s keV up to 3 MeV in the pre-mid night sector (MLT=22UT). The injection was associated with unusually large (60mV/m) dipolarization electric fields that lasted 1 minute. At about the same time, THEMIS-D observed energy-dispersive injection of electrons at energies as high as at least 720keV at L~6.8 in the pre-dawn sector. Injection of energetic protons (~1MeV) and proton drift echos were observed at RBSP-A as well. RBSP-A observed a broad spectrum of nonlinear electric field structures but no whistler waves at the injection. The properties of the observed dipolarization electric field constrain the acceleration mechanism responsible for the MeV electron injection. We will discuss the implications of these observations on the direct impact of substorms on the outer radiation belt.
Back to: Impact of the Substorm Concept on Space Plasma Research I