TEMPERATURE AND HARD X-RAY SIGNATURES FOR ENERGETIC PROTON EVENTS

The temperature distributions of flares associated with solar energetic protons (SEPs) have been found to differ significantly from those of normal (non-SEP-associated) flares. At high temperature (greater than or similar to 20 MK) and high X-ray intensity, the two temperature distributions merge. At lower temperature (less than or similar to 20 MK) and low X-ray intensity, the distributions separate; the SEP-associated flares tend to exhibit temperatures anomalously lower than those of normal flares. At high X-ray intensity, gradual hard X-ray flares are highly correlated with SEPs; at low-to-moderate X-ray intensities, this correlation is much weaker. These two properties, a low-temperature signature for weak flares and a gradual hard X-ray signature for intense flares, may prove useful in identifying events potentially productive of SEPs for all levels of intensity above soft X-ray class M1.