The longitudinal dependence of SEP events on associated Solar Flare parameters

Abstract

The dependence of the solar energetic particle event (SEP) properties, viz. proton fluence and proton peak flux, in the two proton energy values, ∼25 MeV/n and ∼68 MeV/n, on the solar flare (SF) parameters, viz. SXR fluence and SF peak flux were examined for three western longitudinal areas, W0–W39, W40–W70 and W71–W90. The analysis used SEP events observed by the SOHO ERNE during the 23rd and 24th solar cycles and associated with solar flares originated from the western hemisphere of the sun. It is observed that the correlation coefficient of proton parameters with solar flare parameters is highest in the W40–W70 longitudinal area, except in the case of the correlation between proton fluence/peak flux and solar flare peak flux in the ∼25MeV/n energy particles. It is also observed that the SF fluence has a greater influence on the SEP parameters than the SF peak flux. Furthermore, of the two properties of SEP, the SEP fluence is more correlated with both SF parameters than the SEP peak flux. The influence of impulsive time (the time difference between the flare start time and peak time), on the correlation coefficient between SEP parameters and solar flare parameters indicates that in category 1 (events with an impulsive time ≤0.3hr.), the events occurring from the W40–W70 longitudinal area show higher correlation than those from the rest of the area, whereas in category 2 (events with an impulsive time >0.3hr.), the events originating from the W71–W90 longitudinal area show greater correlation. The dependence between impulsive time and SEP parameters is very weak.