Long‐Term Variations of Quasi‐Trapped and Trapped Electrons in the Inner Radiation Belt Observed by DEMETER and SAMPEX

Authors

• Kun Zhang, University of Colorado BoulderFollow
• Xinlin Li, University of Colorado Boulder
• Zheng Xiang, University of Colorado Boulder
• Leng Ying Khoo, University of Colorado Boulder
• Hong Zhao, University of Colorado Boulder
• Mark D. Looper, The Aerospace Corporation
• Michael A. Temerin, University of California, Berkeley
• Jean-Andre Sauvaud, Université de Toulouse

Submitting Campus

Daytona Beach

Department

Physical Sciences

Document Type

Article

Publication/Presentation Date

8-26-2020

Abstract/Description

Electrons in the Earth's radiation belts can be categorized into three populations: precipitating, quasi‐trapped, and trapped. We use data from the Detection of Electro‐Magnetic Emissions Transmitted from Earthquake Regions (DEMETER) and Solar, Anomalous, and Magnetospheric Particle Explorer satellite (SAMPEX) missions and from ground‐based neutron monitors (NM) and sunspot observations to investigate the long‐term variation of quasi‐trapped and trapped sub‐MeV electrons on different L shells in the inner belt. DEMETER and SAMPEX measurements span over 17 years and show that at L ≤ 1.14 the electron flux is anticorrelated with sunspot number, but proportional to the cosmic ray intensity represented by NM count rates, which suggests that electrons at the inner edge of the inner belt are produced by Cosmic Ray Albedo Neutron Decay (CRAND). The solar cycle variation of cosmic rays increased the electron flux at L ≤ 1.14 by a factor of 2 from solar maximum at 2001 to solar minimum at 2009. At L ≥ 1.2, both quasi‐trapped and trapped electrons are enhanced during geomagnetic storms and decay to a background level during extended quiet times. At L > 2, quasi‐trapped electrons resemble trapped electrons, with correlation coefficients as high as 0.97, indicating that pitch angle scattering is the dominant process in this region.

Publication Title

Journal of Geophysical Research: Space Physics

DOI

https://doi.org/ 10.1029/2020JA028086

Publisher

John Wiley & Sons, Inc

Grant or Award Name

National Science Foundation (NSF) Grant AGS 1834971 and NASA Grants NNX17AD85G and 80NSSC17K0429 and by NASA/ RBSPECT funding through JHU/APL Contract 967399 under prime NASA contract NAS5‐01072. Z. X. thanks the support from NSFC Grant 41904143

Additional Information

Dr. Zhang was not affiliated with Embry-Riddle Aeronautical University at the time this paper was published. 

Scholarly Commons Citation

Zhang, K., Li, X., Xiang, Z., Khoo, L. Y., Zhao, H., Looper, M. D., et al. (2021). Long‐term variations of quasi‐trapped and trapped electrons in the inner radiation belt observed by DEMETER and SAMPEX. Journal of Geophysical Research: Space Physics, 125, e2020JA028086. https://doi.org/ 10.1029/2020JA028086