3 He-rich Solar Energetic Particle Events at Solar Orbiter and L1: New Results from IMAP/CoDICE

We present multispacecraft observations of a series of 3 He-rich solar energetic particle (SEP) events observed by Solar Orbiter/Solar Isotope Spectrometer (SIS), Advanced Composition Explorer (ACE)/Ultra-Low-Energy Isotope Spectrometer (ULEIS), and the recently launched Interstellar Mapping and Acceleration Probe (IMAP)/Compact Dual Ion Composition Explorer (CoDICE) between 2026 February 5 and 9. The three spacecraft were very closely magnetically aligned, with their magnetic footpoints at 2.5 R ⊙ separated by less than 4°, providing a rare opportunity to investigate SEP evolution with minimal uncertainties due to longitudinal and latitudinal connectivity. Using the February 5 events, we measure the radial evolution of 3 He fluences between 0.57 and 1 au and find a radial scaling of J ( R ) ∝ R −2.72 , consistent with a combination of spherical expansion and interplanetary transport effects. The February 8 events are associated with two SEP dropouts. First, ACE/ULEIS observes an SEP dropout coincident with a change in interplanetary magnetic field orientation. CoDICE observations instead reveal a corresponding shift in the incident SEP streaming direction. Second, Solar Orbiter observes a separate dropout at −10 . ° 6 Carrington latitude associated with changing solar wind plasma and magnetic field properties, suggesting a transition between filled and empty magnetic flux tubes. Whether the changing magnetic connectivity is latitude-dependent remains inconclusive. These observations demonstrate the importance of combining multispacecraft measurements with broad angular coverage to distinguish radial transport, magnetic connectivity, and particle anisotropy effects in 3 He-rich SEP populations.