Investigation on spectral behavior of Solar Transients and their Interrelationship

TL;DR

This study investigates the spectral hardening of solar flare emissions and their relationship with solar proton events and CMEs, revealing correlations that suggest re-acceleration processes in interplanetary space.

Contribution

It provides new insights into the spectral behavior of solar flares and their association with SEPs and CMEs, highlighting a re-acceleration mechanism beyond standard models.

Findings

Good association of SHH spectral behavior with SEPs

Correlation between SEP spectral hardening and CME velocity

Protons and CMEs are accelerated at the flare site and re-accelerated in interplanetary space

Abstract

We probe the spectral hardening of solar flares emission in view of associated solar proton events (SEPs) at earth and coronal mass ejection (CME) acceleration as a consequence. In this investigation we undertake 60 SEPs of the Solar Cycle 23 alongwith associated Solar Flares and CMEs. We employ the X-ray emission in Solar flares observed by Reuven Ramaty Higly Energy Solar Spectroscopic Imager (RHESSI) in order to estimate flare plasma parameters. Further, we employ the observations from Geo-stationary Operational Environmental Satellites (GOES) and Large Angle and Spectrometric Coronagraph (LASCO), for SEPs and CMEs parameter estimation respectively. We report a good association of soft-hard-harder (SHH) spectral behavior of Flares with occurrence of Solar Proton Events for 16 Events (observed by RHESSI associated with protons). In addition, we have found a good correlation (R=0.71) in SEPs spectral hardening and CME velocity. We conclude that the Protons as well as CMEs gets accelerated at the Flare site and travel all the way in interplanetary space and then by re-acceleration in interplanetary space CMEs produce Geomagnetic Storms in geospace. This seems to be a statistically significant mechanism of the SEPs and initial CME acceleration in addition to the standard scenario of SEP acceleration at the shock front of CMEs.