@article{Ogasawara:2026:1538-4357/ae9153,
author = {Ogasawara,  K and Dewey, RM and Allegrini, F and Alterman, BL and Galvin, A and Horbury, TS and Kistler, L and Lepri, ST and Livi, SA and Louarn, P and Owen, CJ and Raines, JM and Spitzer, SA},
doi = {1538-4357/ae9153},
journal = {The Astrophysical Journal},
pages = {90--90},
title = {Resolving Compositional Features of Solar Wind Source Regions near the Heliospheric Current Sheet at 0.3 au},
url = {http://dx.doi.org/10.3847/1538-4357/ae9153},
volume = {1008},
year = {2026}
}

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TY  - JOUR
AB  - <jats:title>Abstract</jats:title>                  <jats:p>                    The Heavy Ion Sensor in Solar Wind Analyser suite on Solar Orbiter has provided unprecedented high-resolution elemental and ionic signatures around the heliospheric current sheet (HCS) from a vantage point near the Sun. Its high cadence time-series observations are used to determine the magnetic connectivity and map these complex transitions, revealing embedded processes of the observed signatures around the HCS crossing at ∼0.3 au. Electron strahl dropouts observed before the HCS crossing are accompanied by distinct local drops in the oxygen–proton temperature ratio (                    <jats:italic>T</jats:italic>                    <jats:sub>O</jats:sub>                    /                    <jats:italic>T</jats:italic>                    <jats:sub>p</jats:sub>                    ), while carbon and oxygen charge-state ratios remain nearly invariant, with at most slight reductions depending on the interval. In contrast, near the true sector boundary (TSB) the heavy-ion composition profiles remain nearly constant, despite marked changes in magnetic and strahl topology. These measurements show that small-scale HCS-related structures at 0.3 au can be systematically matched with their heavy-ion thermal and compositional signatures. A gradual decrease of the Fe/O ratio toward the TSB is observed, reaching a minimum of (4.54 ± 0.54) × 10                    <jats:sup>−2</jats:sup>                    at the sector boundary and recovering within a few hours, establishing a clear association between Fe/O depletion and the HCS. After the HCS crossing,                    <jats:italic>T</jats:italic>                    <jats:sub>O</jats:sub>                    /                    <jats:italic>T</jats:italic>                    <
AU  - Ogasawara, K
AU  - Dewey,RM
AU  - Allegrini,F
AU  - Alterman,BL
AU  - Galvin,A
AU  - Horbury,TS
AU  - Kistler,L
AU  - Lepri,ST
AU  - Livi,SA
AU  - Louarn,P
AU  - Owen,CJ
AU  - Raines,JM
AU  - Spitzer,SA
DO  - 1538-4357/ae9153
EP  - 90
PY  - 2026///
SN  - 0004-637X
SP  - 90
TI  - Resolving Compositional Features of Solar Wind Source Regions near the Heliospheric Current Sheet at 0.3 au
T2  - The Astrophysical Journal
UR  - http://dx.doi.org/10.3847/1538-4357/ae9153
UR  - https://doi.org/10.3847/1538-4357/ae9153
VL  - 1008
ER  - 

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