Spectral Structures of Type II Solar Radio Bursts and Solar Energetic Particles

TL;DR

This study explores the link between spectral features of type II solar radio bursts and solar energetic particles, revealing correlations that can enhance SEP forecasting accuracy.

Contribution

It provides the first statistical analysis connecting spectral structures of type II bursts with SEP flux, highlighting their shared shock origins.

Findings

Positive correlation between hectometric type II burst bandwidth and SEP peak flux

Spectral structures of type II bursts can improve SEP peak flux predictions

Wider or stronger CME shocks produce more SEPs and longer-lasting shocks

Abstract

We investigated the relationship between the spectral structures of type II solar radio bursts in the hectometric and kilometric wavelength ranges and solar energetic particles (SEPs). To examine the statistical relationship between type II bursts and SEPs, we selected 26 coronal mass ejection (CME) events with similar characteristics (e.g., initial speed, angular width, and location) observed by the Large Angle and Spectrometric Coronagraph (LASCO), regardless of the characteristics of the corresponding type II bursts and the SEP flux. Then, we compared associated type II bursts observed by the Radio and Plasma Wave Experiment (WAVES) onboard the Wind spacecraft and the SEP flux observed by the Geostationary Operational Environmental Satellite (GOES) orbiting around the Earth. We found that the bandwidth of the hectometric type II bursts and the peak flux of the SEPs has a positive correlation (with a correlation coefficient of 0.64). This result supports the idea that the nonthermal electrons of type II bursts and the nonthermal ions of SEPs are generated by the same shock and suggests that more SEPs may be generated for a wider or stronger CME shock with a longer duration. Our result also suggests that considering the spectral structures of type II bursts can improve the forecasting accuracy for the peak flux of gradual SEPs.