Chen, Xiaomin;
Li, Chuan;
Xu, Zigong;
Nicolaou, Georgios;
Kollhoff, Alexander;
Ho, George C;
Wimmer-Schweingruber, Robert F;
(2025)
Local Particle Acceleration in an ICME-in-Sheath Structure Observed by Solar Orbiter.
The Astrophysical Journal
, 994
(2)
, Article 211. 10.3847/1538-4357/ae1476.
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Abstract
Local particle acceleration in the shock sheath region formed during the interaction between multiple coronal mass ejections (CMEs) is a complicated process that is still under investigation. On 2024 March 23, the successive eruption of two magnetic flux ropes from the solar active region 3614 produced twin CMEs, as identified in coronagraph images. By analyzing in situ data from Solar Orbiter and Wind, it is found that the primary interplanetary CME (ICME)-driven shock overtook the preceding ICME, trapping it in the sheath between the shock and the primary ICME, forming the ICME-in-sheath (IIS) structure. Using Solar Orbiter observations, we show that both electrons and ions are accelerated within the IIS. A clear enhancement of suprathermal electrons was observed at the IIS boundary, where strong flow shear and large magnetic field variation suggest possible local electron acceleration. Electrons (>38 keV) exhibit a long-lasting enhancement in the IIS with a spectral index of ∼2.2, similar to that in the shock sheath and the primary ICME, indicating a similar solar origin. Inside both the sheath and IIS, spectra of protons and 4He are generally consistent with the prediction of the diffusive shock acceleration, whereas Fe and O present a double power-law shape. Additionally, the Fe/O ratio in the IIS is higher than that in the sheath, and closer to the abundance of the flare-related particles, suggesting the remnant particles of flare confined in the IIS.
| Type: | Article |
|---|---|
| Title: | Local Particle Acceleration in an ICME-in-Sheath Structure Observed by Solar Orbiter |
| Open access status: | An open access version is available from UCL Discovery |
| DOI: | 10.3847/1538-4357/ae1476 |
| Publisher version: | https://doi.org/10.3847/1538-4357/ae1476 |
| Language: | English |
| Additional information: | Original content from this work may be used under the terms of the Creative Commons Attribution 4.0 licence (https://creativecommons.org/licenses/by/4.0/). Any further distribution of this work must maintain attribution to the author(s) and the title of the work, journal citation and DOI. |
| UCL classification: | UCL UCL > Provost and Vice Provost Offices > UCL BEAMS UCL > Provost and Vice Provost Offices > UCL BEAMS > Faculty of Maths and Physical Sciences UCL > Provost and Vice Provost Offices > UCL BEAMS > Faculty of Maths and Physical Sciences > Dept of Space and Climate Physics |
| URI: | https://discovery.ucl.ac.uk/id/eprint/10218286 |
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