Forecasting Sep Events with Same Active-Region Prior Flares

Abstract:

Forecasting large solar energetic (E > 10 MeV) particle (SEP) events is currently based on observed solar X-ray flare peak fluxes or fluences. Recent work has indicated that the probability of a solar eruptive event in an active region (AR) is enhanced when a large flare has occurred in that AR during the previous day. In addition, peak intensities Sp of SEP events associated with fast CMEs are larger for CMEs with prior CMEs from the same associated ARs in the previous day. This suggests that the associated SEP event probability and/or Sp may be higher for a given solar X-ray flare with a recent prior major flare in the same AR. We use data sets of NOAA flares and SEP events from cycles 23 and 24 to test this idea statistically for periods of prior flares ranging from 12 to 48 hours. The occurrence probabilities of large SEP events are not higher for flares with prior same-AR major flares, hence prior flare occurrence is not a useful SEP event forecasting tool. We show an example of a flare-prolific AR for which the SEP-associated flares are spatially distinct from the numerous non-SEP associated flares, indicating how prior flares may be unrelated to SEP-associated flares.