Effects of the time sampling window on interplanetary shock properties and their associated energetic storm particles

Abstract:

Interplanetary Coronal Mass Ejections (ICMEs) are primary drivers of space weather, they drive fast interplanetary shocks which accelerate particles forming energetic storm particles events (ESPs). ESPs can bring sudden and significant increases to the near-Earth particulate radiation which poses a serious hazard to astronauts and assets in space. Understanding the link between IP shocks and their ESPs is critical to advancing predictions of the physical properties of ESPs, such as arrival time and peak intensities; and will also provide insight for constraints used in space weather prediction models and simulations.

We identify 296 fast forward IP shocks from the Helsinki database (ipshocks.fl) detected by ACE at 1 AU during solar cycles 23 and 24 from 1998 to 2013. Using high resolution solar wind plasma, magnetic field and energetic particle measurements we derive associated shock parameters and ESP properties over different time sampling windows. We find that the IP shock parameters do not vary significantly over the variation of the time sampling windows (up to 20 minutes) and that the ESP spectral indices both upstream and downstream of the shock have little variation over a broad range of sampling windows around the shock (up to few hours). We also find that correlations between the IP shock parameters and some of the ESP properties are unaffected by the time sampling windows. These results provide new insights into the shock structures and ESP formation at CME-driven IP shocks.