SHINE: Solar Energetic Particles Mediating Interplanetary Shocks Close to the Sun

Solar energetic particles (SEPs) are high-energy particles that can propagate from the Sun all the way to the surface of the Earth, which can cause significant disruptions to communication systems. Their generation mechanisms remain a subject of much debate, with strong coronal and interplanetary discontinuities or shocks driven by coronal mass ejections (CME) being likely responsible. Previous observations studied these shocks at different solar distances from the Earth’s orbit to the outer heliosphere, but were limited to distances mostly outside the Earth’s orbit (>1 au). Currently, however, observations with Parker Solar Probe (PSP) and Solar Orbiter (SolO) allow us to build a more complete picture by probing extensively distances below 1 au. A key consequence of studying this region, which is the goal of this project, is that these in-situ observations will provide SEP and shock measurements that are dramatically less affected by transport effects as the spacecraft progressively get closer to the Sun. The data from PSP and SolO will be analyzed for periods when these spacecraft observe shock events with exceptionally high SEP intensities. The results will address the significant issue of energetic particle acceleration by shocks near the Sun and how the particles affect the structure of these young shocks. Additionally, as energetic-particle-mediated shocks are predicted to occur in various astrophysical settings across a broad range of spatial and temporal scales, our comprehensive search for such structures very close to our Sun may fundamentally contribute to our understanding of well-known ‘cosmic ray’-mediated collisionless shocks. The science goals of this project are to (1) quantify SEP-mediated shocks, (2) assess SEP impact on shock mediation, and (3) explore shock-SEP relationships. This project will support students from the APL CIRCUIT Program to work on this project which will be promoting research and education. This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.