SEPs Link not Confirmed

From RHESSI Wiki

Introduction   Solar and space scientists have endeavored for years to predict the occurrence of solar energetic particle (SEP) events. These events have the potential for damaging satellite electronics and providing significant radiation doses to astronauts in space. In Nugget 46 entitled “Soft-Hard-Harder” Sam Krucker and Hugh Hudson describe RHESSI observations of five solar flares that occurred in 2005 January. These observations appear to confirm an earlier study done by Alan Kiplinger using Solar Maximum Mission (SMM HXRBS) data from the 1980’s indicating that soft-hard-hard spectral evolution in hard X-ray bursts and soft-hard-harder evolution throughout a flare are indicators of an ensuing SEP event. Both studies have also been published in the Astrophysical Journal. It is important to note that the definition of this spectral hardening is somewhat vague and the analyses have been subjective. If one can find flares associated with SEP events that have no soft-hard-hard characteristics of any kind then the premise can be ruled out.   In this Nugget, we discuss hard X-ray observations of six solar flares between 1991 and 2001 made by Yohkoh that were accompanied by SEP events. We find no evidence for Soft-Hard-Hard evolution in these flares even though four of the SEP events had intensities of >400 MeV protons, sufficiently high to be detected at ground level on Earth (by neutron monitors). A similar conclusion was reached in a Yohkoh Nugget (2001 August 17) by Nariaki Nitta based on much more limited analysis.