Ground level muons coincident with the 20 January 2005 solar flare

Abstract

An array of proportional wire chamber stations, Project GRAND, detects secondary muons produced by hadronic primaries. The muon counting rate at ground level increases above the average background intensity with a statistical significance of 10σ. This ground level event (GLE), caused by solar energetic particles, is detected in close time association with an X7.1 X‐Ray flare on 20 January 2005. The statistical significance of this event rises to 18σ when an angular window of the sky near zenith is studied. These data are compared with data from neutron monitors.