TY - JOUR
T1 - Coupling between magnetic reconnection, energy release, and particle acceleration in the X17.2 2003 October 28 solar flare
AU - Kurt, Victoria G.
AU - Veronig, Astrid M.
AU - Fleishman, Gregory D.
AU - Hinterreiter, Jürgen
AU - Tschernitz, Johannes
AU - Lysenko, Alexandra L.
N1 - Publisher Copyright:
© The Authors 2024.
PY - 2024/6/1
Y1 - 2024/6/1
N2 - Context. The 2003 October 28 (X17.2) eruptive flare was a unique event. The coronal electric field and the π-decay γ-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, σ(t), and the local reconnection rate (coronal electric field strength), Ec(r, t), were calculated from flare ribbon separation in Hα filtergrams 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. Prompt γ-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, σ(t) and Ec(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-energy γ-ray emission revealed a close association between the acceleration process efficiency and the reconnection rates. High-energy bremsstrahlung continuum and narrow γ-ray lines were observed in the main rise phase when Ec(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-decay γ-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 with σ(t) and Ec(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.
AB - Context. The 2003 October 28 (X17.2) eruptive flare was a unique event. The coronal electric field and the π-decay γ-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, σ(t), and the local reconnection rate (coronal electric field strength), Ec(r, t), were calculated from flare ribbon separation in Hα filtergrams 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. Prompt γ-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, σ(t) and Ec(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-energy γ-ray emission revealed a close association between the acceleration process efficiency and the reconnection rates. High-energy bremsstrahlung continuum and narrow γ-ray lines were observed in the main rise phase when Ec(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-decay γ-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 with σ(t) and Ec(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.
KW - Gamma rays
KW - Sun: activity
KW - Sun: flares
KW - Sun: magnetic fields
KW - Sun: X-rays
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U2 - 10.1051/0004-6361/202349130
DO - 10.1051/0004-6361/202349130
M3 - Article
AN - SCOPUS:85196303046
SN - 0004-6361
VL - 686
JO - Astronomy and Astrophysics
JF - Astronomy and Astrophysics
M1 - A195
ER -