Investigating the Solar Energetic Particle (SEP) Events Occurred During Solar Cycle 24

Abstract:

Solar energetic particle (SEP) events are consequences of acceleration of wide variety of heliospheric particle population by different solar transient eruptions like coronal mass ejections and solar flares. The SEP events are characterized by enhancements in the proton flux at different energy levels. Although solar cycle 24 commenced in 2008, no SEPs were reported till 2010. We investigate the SEP events that occurred during ascending and maximum phase (2010 - June 2015) of solar cycle 24. During this interval, total 37 SEP events were identified by GOES spacecraft at Geosynchronous orbit. Out of 37 events only 5 events exhibited peak proton flux (PF) values between 10⁴ p cm^-2 sr^-1 s^-1 ≤ PF < 10⁴ p cm^-2 sr^-1 s^-1. However, none of the SEP events of current solar cycle registered peak flux value ≥ 10⁴ p cm^-2 sr^-1 s^-1, unlike the previous solar cycles 22 and 23. This confirms weaker solar activity during solar cycle 24 in comparison to previous cycles. We determine the solar source of these events, onset, duration and fluence for protons of energy E > 10 MeV. The SEPs are found to exhibit varying intensities, counts and ionic charges in different elements. Elemental and isotopic variation will also be ascertained for identified SEP events.