Journal article
The Acceleration of Ultrarelativistic Electrons During a Small to Moderate Storm of 21 April 2017
Geophysical research letters, Vol.45(12), pp.5818-5825
06/28/2018
DOI: 10.1029/2018GL078582
Abstract
The ultrarelativistic electrons (E > ~3 MeV) in the outer radiation belt received limited attention in the past due to sparse measurements. Nowadays, the Van Allen Probes measurements of ultrarelativistic electrons with high energy resolution provide an unprecedented opportunity to study the dynamics of this population. In this study, using data from the Van Allen Probes, we report significant flux enhancements of ultrarelativistic electrons with energies up to 7.7 MeV during a small to moderate geomagnetic storm. The underlying physical mechanisms are investigated by analyzing and simulating the evolution of electron phase space density. The results suggest that during this storm, the acceleration mechanism for ultrarelativistic electrons in the outer belt is energy‐dependent: local acceleration plays the most important role in the flux enhancements of ~3–5 MeV electrons, while inward radial diffusion is the main acceleration mechanism for ~7 MeV electrons at the center of the outer radiation belt.
Plain Language Summary
The Earth's radiation belt electrons exhibit frequent flux variations under the effect of various physical mechanisms. The inward radial diffusion and local acceleration by whistler mode waves are recognized to be the most important acceleration mechanisms for outer belt electrons, while their effectiveness and relative importance are still under considerable debate. In the past decades, intensive studies have been performed on the acceleration of energetic and relativistic electrons (hundreds of keV to ~2 MeV). However, ultrarelativistic electrons (> ~3 MeV) received limited attention due to sparse measurements. The Van Allen Probes provide high‐resolution measurements of ultrarelativistic electrons and thus an unprecedented opportunity to study the dynamics of this population. In this study, using data from Van Allen Probes, we report significant flux enhancements of ultrarelativistic electrons with energies up to 7.7 MeV during a small to moderate storm. The analysis and simulation of electron phase space density evolution indicate that the acceleration mechanism for ultrarelativistic electrons during this storm is energy‐dependent: local acceleration plays the most important role for ~3–5 MeV electron acceleration, while the inward radial diffusion is the most important mechanism causing ~7 MeV electron acceleration at the center of outer belt.
Key Points
Significant flux enhancements of electrons with energies up to 7.7 MeV are reported during a small to moderate storm
The phase space density evolution of ultrarelativistic electrons during this storm is analyzed and simulated using a radial diffusion model
The results suggest that the physical mechanism causing ultrarelativistic electron flux enhancements during this storm is energy‐dependent
Details
- Title: Subtitle
- The Acceleration of Ultrarelativistic Electrons During a Small to Moderate Storm of 21 April 2017
- Creators
- H Zhao - University of Colorado BoulderD. N Baker - University of Colorado BoulderX Li - University of Colorado BoulderA. N Jaynes - University of IowaS. G Kanekal - Goddard Space Flight Center
- Resource Type
- Journal article
- Publication Details
- Geophysical research letters, Vol.45(12), pp.5818-5825
- DOI
- 10.1029/2018GL078582
- ISSN
- 0094-8276
- eISSN
- 1944-8007
- Number of pages
- 8
- Grant note
- NASA (NAS5‐01072)
- Language
- English
- Date published
- 06/28/2018
- Academic Unit
- Physics and Astronomy; University College Courses
- Record Identifier
- 9984199695402771
Metrics
13 Record Views