Acceleration of Relativistic Protons during the 20 January 2005 Flare and CME

TL;DR

This study analyzes the timing and origin of relativistic protons during the 20 January 2005 solar flare and CME, linking their acceleration to specific electromagnetic signatures observed in the solar corona.

Contribution

It provides a detailed comparison of proton profiles with electromagnetic emissions, identifying multiple acceleration episodes during the event.

Findings

Relativistic protons showed two successive peaks in Earth detectors.

Protons and electrons are accelerated during the impulsive flare phase.

A second acceleration episode is associated with coronal signatures near 1 solar radius.

Abstract

The origin of relativistic solar protons during large flare/CME events has not been uniquely identified so far.We perform a detailed comparative analysis of the time profiles of relativistic protons detected by the worldwide network of neutron monitors at Earth with electromagnetic signatures of particle acceleration in the solar corona during the large particle event of 20 January 2005. The intensity-time profile of the relativistic protons derived from the neutron monitor data indicates two successive peaks. We show that microwave, hard X-ray and gamma-ray emissions display several episodes of particle acceleration within the impulsive flare phase. The first relativistic protons detected at Earth are accelerated together with relativistic electrons and with protons that produce pion decay gamma-rays during the second episode. The second peak in the relativistic proton profile at Earth is accompanied by new signatures of particle acceleration in the corona within approximatively 1 solar radius above the photosphere, revealed by hard X-ray and microwave emissions of low intensity, and by the renewed radio emission of electron beams and of a coronal shock wave. We discuss the observations in terms of different scenarios of particle acceleration in the corona.