SM21A-2468
Van Allen Probes observations of EMIC events triggered by solar wind dynamic pressure enhancements
Tuesday, 15 December 2015
Poster Hall (Moscone South)
Junghee Cho1, Dae-Young Lee2, Sung-Jun Roh1, Dae-Kyu Shin2, Junga Hwang3, Kyung-Chan Kim3, Cheongrim Choi4, Craig Kletzing5, John R Wygant6, Scott A Thaller6, Brian Larsen7 and Ruth M Skoug8, (1)Chungbuk National University, Department of Astronomy and Space Science, Cheongju, South Korea, (2)Chungbuk National University, Cheongju, South Korea, (3)KASI Korea Astronomy and Space Science Institute, Daejeon, South Korea, (4)KAIST Korea Advanced Institute of Science and Technology, Daejeon, South Korea, (5)University of Iowa, Iowa City, IA, United States, (6)University of Minnesota Twin Cities, Minneapolis, MN, United States, (7)The New Mexico Consortium, Los Alamos, NM, United States, (8)Los Alamos Natl Lab, Los Alamos, NM, United States
Abstract:
Electromagnetic ion cyclotron (EMIC) waves are one of the key plasma waves that can affect charged particle dynamics in the Earth’s inner magnetosphere. One of the generation mechanisms of EMIC waves has long been known to be due to magnetospheric compression due to impact by enhanced solar wind dynamic pressure Pdyn. With the Van Allen Probes observations, we have identified 4 EMIC wave events that are triggered by Pdyn enhancements under northward IMF, prolonged quiet time conditions. We find the following features of the EMIC events. (1) They are triggered immediately at the Pdyn impact and remain active during the same period as the enhanced Pdyn duration. (2) They occur in either H band or He band or both. (3) Two events occur inside the plasmasphere and the other two outside the plasmasphere. (4) The wave polarization, either R or L, are highly elliptical, being close to be linear. (5) The wave normal angles are quite large, well away from being field-aligned. (6) About 10 – 50 keV proton fluxes indicate enhanced flux state with ~90 deg-peaked anisotropy in velocity distribution after the Pdyn impact. (7) From low altitude NOAA POES satellite observations of particles we find no obvious evidence for relativistic electron precipitation due to these Pdyn-triggered EMIC events. We will discuss implications of these observations on wave generation mechanism and interaction with radiation belt electrons.
