Did the 2000 November 8 solar flare accelerate protons to >=40 GeV?

TL;DR

This study analyzes muon data during the November 2000 solar flare and finds evidence suggesting that even non-GLE class M solar flares can accelerate protons to energies exceeding 40 GeV.

Contribution

It provides the first evidence that a Class M solar flare may accelerate protons to energies above 40 GeV, expanding understanding of solar particle acceleration.

Findings

Detected a 4.7sigma muon excess coincident with the flare

Muons indicate primary protons above 40 GeV

Suggests non-GLE flares can accelerate high-energy protons

Abstract

It has been reported that a 5.7sigma directional muon excess coincident with the 2000 July 14 solar flare was registered by the L3 precision muon spectrometer [Ruiguang Wang, Astroparticle Phys., 31(2009) 149]. Using a same analysis method and similar criteria of event selection, we have analyzed the L3 precision muon spectrometer data during November 2000. The result shows that a 4.7sigma muon excess appeared at a time coincident with the solar flare of 8 of November 2000. This muon excess corresponds to above 40 GeV primary protons which came from a sky cell of solid angle 0.048 sr. The probability of being a background fluctuation is estimated to be about 0.1%. It has been convinced that solar protons could be accelerated to tens of GeV in those Class X solar flares which usually arose solar cosmic ray ground level enhancement (GLE) events. However, whether a Class M solar flare like the non-GLE event of 8 November 2000 may also accelerate solar protons to such high energies? It is interesting and noteworthy.