Relationship of solar flare accelerated particles to solar energetic particles (SEPs) observed in the interplanetary medium

Abstract

Observations of hard X‐ray (HXR)/gamma‐ray continuum and gamma‐ray lines produced by energetic electrons and ions, respectively, colliding with the solar atmosphere, have shown that large solar flares can accelerate ions up to many GeV and electrons up to hundreds of MeV. Solar energetic particles (SEPs) are observed by spacecraft near 1 AU and by ground‐based instrumentation to extend up to similar energies, but these appear to be accelerated by shocks associated with fast Coronal Mass Ejections (CMEs). The Ramaty High Energy Solar Spectroscopic Imager (RHESSI) mission provides high‐resolution spectroscopy and imaging of flare HXRs and gamma‐rays. Here we review RHESSI observations for large solar flares and SEP events. The 23 July gamma‐ray line flare was associated with a fast, wide CME but no SEPs were observed, while the 21 April 2002 flare had no detectable gamma‐ray line emission but a fast CME and strong SEP event were observed. The October– November 2003 series of large flares and associated fast CMEs produced both gamma‐ray line emission and strong SEP events. The spectra of flare‐accelerated protons, inferred from the gamma‐ray line emission observed by RHESSI, is found to be essentially identical to the spectra of the SEPs observed near 1 AU for the well‐connected 2 November and 20 January events.