A1 Refereed original research article in a scientific journal
Very Large and Long-lasting Anisotropies Caused by Sunward Streaming Energetic Ions: Solar Orbiter and STEREO A Observations
Authors: Wei, Wenwen; Lee, Christina O.; Dresing, N.; Khoo, L. Y.; Jian, L. K.; Luhmann, J. G.; Cohen, C. M. S.; Fraschetti, F.; Zhuang, B.; Huang, J.; Nicolaou, G.; Owen, C. J.; Rodriguez-Garcia, L.; Palmerio, E.; Jebaraj, I. C.; Lynch, B. J.; Carcaboso, F.
Publisher: IOP Publishing Ltd
Publishing place: BRISTOL
Publication year: 2024
Journal: Astrophysical Journal Letters
Journal name in source: ASTROPHYSICAL JOURNAL LETTERS
Journal acronym: ASTROPHYS J LETT
Article number: L52
Volume: 973
Issue: 2
Number of pages: 8
ISSN: 2041-8205
eISSN: 2041-8213
DOI: https://doi.org/10.3847/2041-8213/ad78df
Web address : https://doi.org/10.3847/2041-8213/ad78df
Self-archived copy’s web address: https://research.utu.fi/converis/portal/detail/Publication/458580464
The anisotropy of energetic particles provides essential information to help resolve the underlying fundamental physics of their spatial distributions, injection, acceleration, and transport processes. In this work, we report an energetic ion enhancement that is characterized by very large and long-lasting anisotropies observed by STEREO A and Solar Orbiter, which are nearly aligned along the same nominal Parker spiral. This ion enhancement appears at the rising phase of a widespread solar energetic particle event that was associated with the farside coronal mass ejection on 2022 February 15. According to our analysis, the long-lasting anisotropy resulted from the continuous injection of energetic ions from a well-connected particle source located beyond the STEREO A's orbit. Solar Orbiter also observed an interval of very large anisotropy dominated exclusively by sunward streaming ions but with the additional implication that it detected the very early phase of ion injections onto magnetic field lines that newly connected to the particle source, which is likely the first reported event of this kind. These results further illustrate how energetic particle anisotropy information, in particular from multiple observer locations, can be used to disentangle the sources and transport processes of energetic ions, even when their heliospheric context is not simple.
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Funding information in the publication:
We acknowledge the use of the STEREO data provided by the STEREO Science Center (https://stereo-ssc.nascom.nasa. gov/ins_data.shtml) and the Solar Orbiter data from the Solar Orbiter Archive (https://soar.esac.esa.int/soar/). W.W. W. and C.O.L. acknowledge support by NASA grants 80NSSC21K1325 and 80NSSC21K0119. N.D. and I.C.J. acknowledge funding by the European Union’s Horizon 2020 research and innovation program under grant agreement No. 101004159 (SERPENTINE) and No. 101134999 (SOLER), as well as by the Research Council of Finland (SHOCKSEE; grant No. 346902). L.K.J. thanks the support of NASA’s STEREO mission and HGI grant 80NSSC23K0447. B.Z. acknowledges the NASA ECIP grant 80NSSC23K1057 and NSF grant AGS-2301382. J.H. thanks the support of NASA grant 80NSSC23K0737. E.P. acknowledges support from NASA’s LWS (grant No. 80NSSC19K0067) and LWS-SC (grant No. 80NSSC22K0893) programs. B.J.L. acknowledges support from NSF AGS-2147399, NASA HGI 80NSSC21K0731, and XRP 80NSSC22K0674. Solar Orbiter is a space mission run as an international collaboration between ESA and NASA and operated by ESA. Solar Orbiter SWA data were derived from scientific sensors that were designed and created and are operated under funding provided by numerous contracts from UKSA, STFC, the Italian Space Agency, CNES, the French National Centre for Scientific Research, the Czech contribution to the ESA PRODEX program, and NASA. SO SWA work at the UCL/Mullard Space Science Laboratory is currently funded by STFC (grant Nos. ST/W001004/1 and ST/X/002152/1).
