Ring Current Proton Decay Timescales Derived from Van Allen Probe Observations

TL;DR

This study uses Van Allen Probe data to analyze proton decay timescales in Earth's ring current, revealing energy-dependent decay durations that enhance understanding of geomagnetic storm dynamics.

Contribution

It introduces a method to quantify proton decay timescales across different energies and locations, providing new empirical data for ring current modeling.

Findings

Proton decay timescales increase with energy and L-shell.

Decay times range from days at keV energies to over 100 days at higher energies.

Results improve understanding of ring current dynamics and storm recovery processes.

Abstract

The Earth's ring current is highly dynamic and is strongly influenced by the solar wind. The ring current alters the planet's magnetic field, defining geomagnetic storms. In this study, we investigate the decay timescales of ring current protons using observations from the Van Allen Probes. Since proton fluxes typically exhibit exponential decay after big storms, the decay time scales are calculated by performing linear regression on the logarithm of the fluxes. We found that in the central region of the ring current, proton decay timescales generally increase with increasing energies and increasing L-shells. The ~10s keV proton decay timescales are about a few days, while the ~100 keV proton decay time scale is about ~10 days, and protons of 269 keV have decay timescales up to ~118 days. These findings provide valuable insights into the ring current dynamics and can contribute to the development of more accurate ring current models.