2026/07/27 by Radoslav Bucik, Radoslav Bučík, Raul Gomez-Herrero +6
Physics and Astronomy · #Dust and Plasma Wave Phenomena #Ionosphere and magnetosphere dynamics #Solar and Space Plasma Dynamics #astro-ph.SR
paper · pdf · doi:10.3847/2041-8213/ae8994
published as ApJL 1006, L48 (2026) · 10 pages, 5 figures. Accepted version of the paper. Publisher typeset PDF is provided as ancillary file
openalex publication_date 2026/07/27 · openalex created_date 2026/07/28 · openalex updated_date 2026/07/30 · arxiv created 2026/08/01 · arxiv updated 2026/08/04
Abstract We analyze an impulsive solar energetic particle (SEP) event observed by Solar Orbiter at 0.93 au on 2022 December 24 that exhibits a pronounced intensity dropout between ∼07:15 and 10:00 UT. Pitch-angle distributions show a near-field-aligned beam before the dropout, which disappears abruptly at the dropout onset. At the same time, a weak 100–200 keV component appears at pitch angles of ∼90°–180°; no comparable enhancement over this pitch-angle range is present at MeV energies. The dropout onset is not accompanied by an abrupt change in the in situ magnetic field or solar wind plasma. Solar imaging associates the SEP event with a jet from a compact source. Ballistic back-mapping, together with potential-field source-surface extrapolations and quasi-separatrix-layer proxy diagnostics, indicates that Solar Orbiter nominally connects to the source region but lies close to strong connectivity gradients where small displacement may shift the connection to neighboring open field lines. The in situ measurements show that the event occurs during a magnetic-cloud passage and that additional dropouts occur later in the event. These results favor an interpretation in which the dropout reflects rapid changes in particle access between adjacent flux tubes, while the magnetic cloud may help preserve the sharp SEP intensity gradients between them.