SM21B-2522
Butterfly distribution of outer zone relativistic electrons and their potential connection to the solar wind dynamic pressure
Tuesday, 15 December 2015
Poster Hall (Moscone South)
Binbin Ni1, Zhengyang Zou2, Xudong Gu3, Chen Zhou4, Richard M Thorne5, Jacob Bortnik5, Run Shi6, Zhengyu Zhao7, Daniel N. Baker8, Xinlin Li9, Shri Kanekal10, Harlan E. Spence11 and Geoffrey D Reeves12, (1)Wuhan University, Department of Space Physics, School of Electronic Information, Wuhan, China, (2)Wuhan University, Wuhan, China, (3)Wuhan University Library, Los Angeles, CA, United States, (4)University of California Los Angeles, Department of Atmospheric and Oceanic Sciences, Los Angeles, CA, United States, (5)University of California Los Angeles, Los Angeles, CA, United States, (6)Memorial University of Newfoundland, Dept of Math and Stats, St John's, NL, Canada, (7)Wuhan University, School of Electronic Information, Wuhan, China, (8)University of Colorado at Boulder, Boulder, CO, United States, (9)Univ Colorado at Boulder, Boulder, CO, United States, (10)University of Colorado at Boulder, LASP, Boulder, CO, United States, (11)University of New Hampshire Main Campus, Space Science Center, Durham, NH, United States, (12)Los Alamos National Laboratory, Los Alamos, NM, United States
Abstract:
Butterfly distributions, characterized by flux minima at pitch angles around 90º, are broadly observed in the Earth's magnetosphere. While butterfly distributions have been well recognized for radiation belt electrons below ~ 1 MeV, there is lack of investigation of butterfly distributions for relativistic (> MeV) electrons. We conduct a comprehensive analysis of outer zone (L >= 3) relativistic electron butterfly distribution based upon a survey of over-two-year Van Allen Probes REPT measurements. The global profile of butterfly distribution is investigated in detail for relativistic electrons at REPT energies, along with its dependence on L-shell, MLT, and the level of geomagnetic activity. Furthermore, the occurrence pattern of outer zone relativistic electron butterfly distribution is explored with respect to the solar wind dynamic pressure, which suggests that there exist a good correlation between these two phenomena especially at high L-shells (e.g., L ~ 6) and that some other mechanism(s), besides losses through the magnetopause, should play to contribute to the occurrence of outer zone relativistic electron butterfly distribution at lower L-shells.
