Description:

For over 50 years, space-based measurements of cosmic rays have been used to better understand the acceleration and transport of particles within the confines of our own stellar astrosphere, the “heliosphere”. These measurements have led to many insights about the interactions of the Sun with its surrounding interstellar environment, the size and structure of the heliosphere, as well the physics of particle-plasma interactions applicable to many astrophysical applications. Most in-situ measurements to date have been made by outward-moving spacecraft located 1 AU from the Sun and beyond. However, since 2018, Parker Solar Probe has been sampling a largely unexplored regime (from ~1 AU to < 0.05 AU), providing new insights into particle transport and acceleration near the Sun. Here we highlight observations of cosmic rays measured by the Integrated Science Investigation of the Sun (ISOIS) instrument onboard Parker Solar Probe, including unexpectedly large radial gradients in the transition from Solar Cycle 24 to 25, evolution of spectra as a function of radial distance, and the search for anisotropic signatures near the Sun. We show new results for Protons, Helium, and Oxygen and evaluate these findings in the light of past observations of the inner heliosphere. Finally, we discuss the implications for current and future models of cosmic ray transport near the Sun.

Jamie Rankin, Associate Research Scholar, Princeton University

Host: Elena Murchikova