Energy Dependence of SEP Electron and Proton Onset Times

TL;DR

This study analyzes the timing and correlation of solar energetic particle events, revealing near-simultaneous release of electrons and protons in most cases and examining measurement errors and delays in particle acceleration.

Contribution

It provides a detailed comparison of electron and proton release times using multiple analysis methods and evaluates scattering effects during SEP events.

Findings

Most electrons and protons are released within 8 minutes of each other.

Strong correlation between electron and proton profiles and acceleration.

Measurement errors vary with energy and analysis method.

Abstract

We study the large solar energetic particle (SEP) events that were detected by GOES in the $>$ 10 MeV energy channel during December 2006 to March 2014. We derive and compare solar particle release (SPR) times for the 0.25--10.4 MeV electrons and 10--100 MeV protons for the 28 SEP events. In the study, the electron SPR times are derived with the time-shifting analysis (TSA) and the proton SPR times are derived using both the TSA and the velocity dispersion analysis (VDA). Electron anisotropies are computed to evaluate the amount of scattering for the events under study. Our main results include: 1)near-relativistic electrons and high-energy protons are released at the same time within 8 min for most (16 of 23) SEP events. 2)There exists a good correlation between electron and proton acceleration, peak intensity and intensity time profiles. 3) The TSA SPR times for 90.5 MeV and 57.4 MeV protons have maximum errors of 6 min and 10 min compared to the proton VDA release times, respectively, while the maximum error for 15.4 MeV protons can reach to 32 min. 4) For 7 low-intensity events of the 23, large delays occurred between 6.5 MeV electrons and 90.5 MeV protons relative to 0.5 MeV electrons. Whether these delays are due to times needed for the evolving shock to be strengthened or due to particle transport effects remains unresolved.