How does the state of the overlying solar corona influence SEP acceleration in CME-driven shocks?

Abstract:

Over the past decade the understanding that solar energetic particles (SEP) are only produced in flares or interplanetary shocks away from the Sun has been continually challenged by a number of observational and modeling studies. The lower and middle corona up to about 30 solar radii is now thought to be an important region for early acceleration and transport of SEPs by coronal mass ejection-driven shock waves. There, these waves propagate into a highly variable dynamic medium with steep gradients and rapidly expanding coronal magnetic fields, which modulates the acceleration near the shock/wave surfaces, and the way SEPs spread into the heliosphere. In this study, we modeled the interaction of over 20 coronal shocks and compressive waves with the coronal plasma. We analyzed coronal bright front (CBF) observations from the SDO/AIA EUV telescope to drive geometric models, and a combination of MHD and data-based (DEM) models. The goal was to find typical parameters of SEP shock acceleration modulation by the volumetric coronal regions, through which shocks/waves propagate. We summarize our findings and present implications for nowcasting SEP acceleration and heliospheric connectivity.