Affiliation:
1. School of Space Science and Physics Shandong University Weihai China
2. Shandong Key Laboratory of Optical Astronomy and Solar‐Terrestrial Environment Institute of Space Sciences Shandong University Weihai China
3. CAS Key Laboratory of Geospace Environment Department of Geophysics and Planetary Sciences University of Science and Technology of China Hefei China
4. Department of Space Physics School of Electronic Information Wuhan University Wuhan China
5. CAS Center for Excellence in Comparative Planetology Hefei China
6. Staunch Data Analytics Lab Durham NH USA
Abstract
AbstractUsing the data from Van Allen Probes, we statistically study the acceleration conditions of ultrarelativistic electrons (Ek > 3 MeV) in the Earth's outer radiation belt. Based on the different high energy cutoffs of ultrarelativistic electrons, the acceleration events of ultrarelativistic electrons are divided into the four groups of “3.4 MeV events,” “5.2 MeV events,” “6.3 MeV events,” and “7.7 MeV events.” According to different solar wind and substorm conditions during the recovery stage, we classify solar wind into three categories: no high‐speed flows, short‐duration high‐speed flows, and long‐duration high‐speed flows. Substorms are divided into continuous substorm activity and non‐continuous substorm activity. Our statistical results show that (a) The different solar wind speeds can cause enhancements of ultrarelativistic electrons with different energies. The high solar wind speed is more important in the acceleration of ultrarelativistic electrons with higher energies (7.7 MeV) than lower energies (3.4, 5.2, and 6.3 MeV). (b) The different substorm activities during the recovery stage can cause enhancements of ultrarelativistic electrons with different energies. Continuous intense substorms in the early recovery stage can contribute to the rapid recovery and enhancements of ultrarelativistic electrons. The timing, intensity, and duration of substorms during the recovery stage are important to the acceleration of ultrarelativistic electrons. (c) Relativistic (1 MeV) electrons are the direct “source” of ultrarelativistic electrons (3.4, 5.2, and 6.3 MeV) in the outer radiation belt. These can help us further understand the electron dynamics of the Earth’s outer radiation belt.
Publisher
American Geophysical Union (AGU)
Subject
Space and Planetary Science,Geophysics