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Context.The 2003 October 28 (X17.2) eruptive flare was a unique event. The coronal electric field and theπ-decayγ-ray emission flux displayed the highest values ever inferred for solar flares. Aims.Our aim is to reveal physical links between the magnetic reconnection process, energy release, and acceleration of electrons and ions to high energies in the chain of the magnetic energy transformations in the impulsive phase of the solar flare. Methods.The global reconnection rate,φ̇(t), and the local reconnection rate (coronal electric field strength),Ec(r, t), were calculated from flare ribbon separation in Hαfiltergrams and photospheric magnetic field maps. Then, HXRs measured by CORONAS-F/SPR-N and the derivative of the GOES SXR flux,İSXR(t) were used as proxies of the flare energy release evolution. The flare early rise phase, main raise phase, and main energy release phase were defined based on temporal profiles of the above proxies. The available results of INTEGRAL and CORONAS-F/SONG observations were combined with Konus-Wind data to quantify the time behavior of electron and proton acceleration. Promptγ-ray lines and delayed 2.2 MeV line temporal profiles observed with Konus-Wind and INTEGRAL/SPI were used to detect and quantify the nuclei with energies of 10−70 MeV. Results.The magnetic-reconnection rates,φ̇(t) andEc(r, t), follow a common evolutionary pattern with the proxies of the flare energy released into high-energy electrons. The global and local reconnection rates reach their peaks at the end of the main rise phase of the flare. The spectral analysis of the high-energyγ-ray emission revealed a close association between the acceleration process efficiency and the reconnection rates. High-energy bremsstrahlung continuum and narrowγ-ray lines were observed in the main rise phase whenEc(r, t) of the positive (negative) polarity reached values of ∼120 V cm−1(∼80 V cm−1). In the main energy release phase, the upper energy of the bremsstrahlung spectrum was significantly reduced and the pion-decayγ-ray emission appeared abruptly. We discuss the reasons why the change of the acceleration regime occurred along with the large-scale magnetic field restructuration of this flare. Conclusions.The similarities between the proxies of the flare energy release withφ̇(t) andEc(r, t) in the flare’s main rise phase are in accordance with the reconnection models. We argue that the main energy release and proton acceleration up to subrelativistic energies began just when the reconnection rate was going through the maximum, that is, following a major change of the flare topology.
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Impact of tearing instability on the global quadrupole Hall magnetic field in an anti-parallel magnetic reconnection
Hall effect generates a global quadrupole Hall magnetic field, which plays a crucial role in facilitating fast magnetic reconnection (MR). Tearing instability often arises in MR due to the increasing magnetic shear during the thinning of the current sheet, triggering multiple fast local spontaneous MRs. A critical question that naturally emerges is how these local spontaneous MRs interact with the global Hall magnetic field and affect the reconnection energy release processes. Using a 2.5D particle-in-cell simulation, we investigate this problem in an MR with a Harris current sheet under the guide field-free condition. Our results show that the global MR evolves through two distinct phases: an initial laminar phase marked by a slow magnetic field dissipation, followed by a phase dominated by spontaneous MRs that significantly accelerate the magnetic energy release by driving multiple local spontaneous MRs. We reveal that the Hall magnetic fields produced by the local spontaneous MRs also exhibit quadrupole structures, which reinforce or weaken the global Hall magnetic field locally. The local enhanced Hall field is found to be associated with a faster spontaneous MR with a rate up to 0.3, which exceeds the laminar MR rate upper-limit 0.2, suggesting that the Hall field interactions may be able to break the bottleneck of the onset of fast MR.
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- Award ID(s):
- 2144324
- PAR ID:
- 10675472
- Publisher / Repository:
- AIP
- Date Published:
- Journal Name:
- Physics of Plasmas
- Volume:
- 32
- Issue:
- 7
- ISSN:
- 1070-664X
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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- Free Publicly Accessible Full Text
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Accepted Manuscript
- Journal Article:
- https://doi.org/10.1063/5.0259029
