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- Title
Simulating the Earth's Outer Radiation Belt Electron Fluxes and Their Upper Limit: A Unified Physics‐Based Model Driven by the AL Index.
- Authors
Ma, Donglai; Bortnik, Jacob; Ma, Qianli; Hua, Man; Chu, Xiangning
- Abstract
Using particle and wave measurements from the Van Allen Probes, a 2‐D Fokker‐Planck simulation model driven by the time‐integrated auroral index (AL) value is developed. Simulations for a large sample of 186 storm‐time events are conducted, demonstrating that the AL‐driven model can reproduce flux enhancement of the MeV electrons. More importantly, the relativistic electron flux enhancement is determined by the sustained strong substorm activity. Enhanced substorm activity results in increased chorus wave intensity and reduced background electron density, which creates the required condition for local electron acceleration by chorus waves to MeV energies. The appearance of higher energy electrons in radiation belts requires a higher level of cumulative AL activity after the storm commencement, which acts as a type of switch, turning on progressively higher energies for longer and more intense substorms, at critical thresholds. Plain Language Summary: The Earth's radiation belts are filled with high‐energy electrons (100s keV–10 MeV) that can damage satellites and impact the expanding human presence in space. The flux of these electrons can change by several orders of magnitude in less than a day. Thus, predicting and understanding their dynamics is crucial. We have developed a physical model driven by the integral auroral index (AL), which influences the amplitude of plasma waves and the density of the background plasma. We simulated a large sample of 186 events from 2012 to 2018 for the first time. The results show that this model not only simulates the acceleration of electrons at high energy levels but also reveals that sustained strong substorms act as a switch. High energy electrons are accelerated only when the intensity of sustained substorms exceeds a certain threshold. Key Points: An AL‐driven radiation belt model reproduces the observed MeV electron fluxes for 186 storm‐time events with good performancePost‐storm flux enhancement requires sufficient integrated substorm strength which increases wave activity and decreases plasma densityAccumulated substorm activity is shown to act as a switch, turning on progressively higher energies at certain critical thresholds
- Subjects
RADIATION belts; PLASMA waves; ELECTRONS; ELECTRON density; RELATIVISTIC electrons; TERRESTRIAL radiation
- Publication
Geophysical Research Letters, 2024, Vol 51, Issue 10, p1
- ISSN
0094-8276
- Publication type
Article
- DOI
10.1029/2024GL109169