New Insights into Particle Acceleration at Shocks from Parker Solar Probe

Abstract: I will discuss recent insights into the physics of particle acceleration based on spacecraft observations of shocks associated with fast coronal mass ejections (CMEs). The acceleration of charged particles to high energies is a fundamental topic in plasma astrophysics. High energy particles themselves are useful probes of processes occurring far from Earth, either near the solar atmosphere, in the outer heliosphere, or in distant astrophysical sources, such as supernovae blasts. Collisionless shock waves clearly play a critical role. Although we have learned much in the last few decades, there remain puzzles, many of which stem from in situ spacecraft observations. On the one hand, some of the difficulty in understanding relates to the fact that shocks in the solar wind are usually weak, move through energetic particles associated with previous events, and through plasma turbulence, all of which complicate the physics. On the other hand, shocks associated with very fast CMEs, associated with very intense energetic particle events, seem to be more consistent with expectations and provide an excellent laboratory for studying particle acceleration at shocks. In this talk, I will highlight a number of examples, including some recent studies involving observations from the Parker Solar Probe.