Radiation belt electron dynamics at low L (<4): Van Allen Probes era versus previous two solar cycles
Abstract
Long‐term (>2 solar cycles) measurements reveal that MeV electron fluxes, solar wind speed, and geomagnetic activity have been extremely low during this current solar cycle, including years before and during the Van Allen Probes era. This study examines solar wind speed, the geomagnetic storm index (Dst), >2 MeV electrons at geostationary orbit, and ~2 MeV electrons across various L shells measured by Solar Anomalous Magnetospheric Particle Explorer in low Earth orbit (LEO) and by the Van Allen Probes/Relativistic Electron and Proton Telescope (REPT) in a geotransfer‐like orbit; the latter measurements are normalized to LEO based on comparison with Colorado Student Space Weather Experiment/Relativistic Electron and Proton Telescope integrated little experiment (REPTile) measurements in LEO. The average ratio of REPTile/REPT varies in a systematic manner with L, ~16% at L = 2.7, decreasing with L and reaching ~0.7% at L = 4.7, and increasing again with L though with greater uncertainty. We show that there have been no ~2 MeV electron enhancements inside L ~ 2.6 since 2006, prior to which numerous penetrations of ~2 MeV electrons into L B, and a sustained southward Bz) and thus stronger geomagnetic activity. We conclude that results from the Van Allen Probes, which have been providing the finest measurements but in operation during a quiet solar activity period, may not be representative of radiation belt dynamics, particularly for the inner edge of the outer belt, during other solar cycle phases.
Document Details
- Document Type
- Pub Defense Publication
- Publication Date
- May 01, 2017
- Source ID
- 10.1002/2017ja023924
Entities
People
- Allison Jaynes
- Bernard Blake
- Daniel N. Baker
- Hong Zhao
- Kunyi Zhang
- M. Temerin
- Q. Schiller
- S. G. Kanekal
- Xinlin Li
Organizations
- Air Force Research Laboratory
- National Aeronautics and Space Administration
- National Science Foundation
- The Aerospace Corporation