Relations between Microwave Bursts and near-Earth High-Energy Proton Enhancements and their Origin

TL;DR

This study analyzes 25 years of microwave burst data at 35 GHz to understand their relation to near-Earth high-energy proton enhancements, revealing that flare-related processes significantly contribute to proton fluxes and proposing diagnostic relations.

Contribution

It provides new empirical relations linking microwave burst parameters to high-energy proton enhancements, emphasizing the role of flare processes over shock acceleration.

Findings

Higher correlation between microwave and proton fluences than peak fluxes.

Flare processes contribute more to high-energy proton fluxes than shock acceleration.

Proposed empirical diagnostic relations for predicting proton enhancements.

Abstract

We further study the relations between parameters of bursts at 35 GHz recorded with the Nobeyama Radio Polarimeters during 25 years, on the one hand, and solar proton events, on the other hand (Grechnev et al. in Publ. Astron. Soc. Japan 65, S4, 2013a). Here we address the relations between the microwave fluences at 35 GHz and near-Earth proton fluences above 100 MeV in order to find information on their sources and evaluate their diagnostic potential. A correlation was found to be pronouncedly higher between the microwave and proton fluences than between their peak fluxes. This fact probably reflects a dependence of the total number of protons on the duration of the acceleration process. In events with strong flares, the correlation coefficients of high-energy proton fluences with microwave and soft X-ray fluences are higher than those with the speeds of coronal mass ejections. The results indicate a statistically larger contribution of flare processes to high-energy proton fluxes. Acceleration by shock waves seems to be less important at high energies in events associated with strong flares, although its contribution is probable and possibly prevails in weaker events. The probability of a detectable proton enhancement was found to directly depend on the peak flux, duration, and fluence of the 35 GHz burst, while the role of the Big Flare Syndrome might be overestimated previously. Empirical diagnostic relations are proposed.