Authors: Fan Guo (LANL), Joe Giacalone (University of Arizona), Christina Cohen (Caltech), Xiaohang Chen (U of Michigan), George Ho (SWRI), R. A. Leske (Caltech), Maher Dayeh (SWRI), Lulu Zhao (U of Michigan), Yu Chen (UNH), Qiang Hu (UAH), Meiqi Wang (NJIT)

We present fine-scale abrupt changes (dropouts) of solar energetic particle (SEP) intensities observed by Parker Solar Probe (PSP) and supported by new numerical simulations designed to study the dropouts observed in the inner heliosphere (PSP+Solar Orbiter). PSP is shown to detect dropouts near the Sun and is capable of measuring SEPs from Sunward and anti-Sunward directions. In the 2021 Aug 23 event, it displayed several dropouts and an odd onset feature. We also show the dropout in the 2022 Feb 27 event. We present theoretical estimates and numerical simulations on how dropout durations change as a function of the distance from the source region. In our simulations, dropouts are modeled as energetic particles from a compact source region propagate in a turbulent magnetic field. In addition, we have included SEP intensities in directions toward and away from the source region, similar to the Sunward and anti-sunward directions. We find that dropouts may explain the anomalous onset and sharp variations in particle SEP intensities of observed by PSP. We have also done simulations with a dropout feature simultaneously across multiple release SEP times. The implications of these events to interplanetary magnetic fields will be discussed.