Small impulsive events dominated by ~1-100 keV (sometimes down to ~0.1 keV) solar electrons are detected hundreds of times a year at ~1 AU near solar maximum (see Lin 1985). Over the last solar cycle the occurrence frequency rate for impulsive electron events observed at ~ 1AU varies with the electron peak flux as a power law with average exponent -1.4, suggesting that many more events are likely below present detection thresholds. Associated increases in ~0.01 to 1 MeV/nuc ions are often observed (may always be present, but with fluxes too low to be always detected), with factors of 10-10000 enrichments of 3He (sometimes 3He/4He >1) along with factors of ~10 enrichment of heavy ions up to Fe, together with high charge states. Curiously, analysis of the nuclear lines and continuum for the large γ-ray flares that accelerate ions to >~100 MeV shows that those flares often also have high e/p ratios, enhanced heavy ions, and enhanced He/p ratios (Ramaty et al. 1993), even though impulsive SEP events at 1 AU are almost never associated with such large flares.
Relevant SOOPs:
+ other SOOPs in sub-objectives: