3He-Rich SEPs throughout the inner heliosphere

The significance of ³He-rich solar energetic particle (SEP) events, though often overlooked, is threefold: (1) they trace small-scale sites that may serve as precursors to larger eruptive activity, (2) they probe the structure of magnetic connectivity that help refine solar wind and coronal magnetic field models, and (3) they provide constraints on waveparticle interactions and turbulence that influence the acceleration of heavy ions. These ³He-rich events are typically short-lived, exhibit low total particle intensity, and are associated with active region jets and Type III radio bursts. This study presents results from a ³He/⁴He ratio survey using Parker Solar Probe’s IS⊙IS/EPI-Hi instrument from its launch through 2025. We investigate the occurrence, energy spectra, and spatial distribution of ³He-rich SEP events across radial distances. By analyzing the radial distribution of ³He-rich events, we aim to determine whether their characteristic enhancements persist over heliocentric distance or degrade due to transport effects, complementing prior studies focused primarily on longitudinal connectivity. Emphasis is placed on identifying correlations between ³He enrichment and solar source properties, including the differential emission measure (DEM) of active regions and the presence of jets. DEM maps constrain low coronal temperature and density structure, enabling identification of plasma environments where ion cyclotron waves may resonate with ions of specific charge-to-mass ratios, such as the case in which ³He is selectively energized, thus linking in-situ ³He-rich SEP composition via wave-particle processes. We further compare PSP observations with those from other spacecraft (IMAP, ACE, STEREO, Solar Orbiter) during periods of apparent Parker spiral field line alignment to study transport and re-acceleration effects.