A multi-spacecraft view of solar-energetic-particle onsets in the 1977 november 22 event

Abstract

We examine the onset timing of solar energetic particles in the large ground-level event (GLE) of 1977 November 22 as observed from six spacecraft at four distinct solar longitudes. In most cases, it was possible to use velocity dispersion of the energetic protons to fix the solar particle release (SPR) time and the path length traveled by the initial particle burst from each solar longitude. We find that the SPR times do depend upon solar longitude, being earliest for spacecraft that are magnetically well connected to the source region, and later for longitudes on the flanks of the outward-driven shock wave. The earliest SPR time occurs well after peak photon emission from the associated Há flare. These observations are consistent with conclusions derived from single-longitude observations of different GLE events. They are consistent with shock acceleration over a broad spatial region with heights rising, and/or shock speeds falling, for longitudes on the flanks of the shock. © 2010. The American Astronomical Society.