Detailed Thermal and Nonthermal Processes in an A-class Microflare

Li, Zhentong; Su, Yang; Veronig, Astrid; Kong, Shuting; Gan, Weiqun; Chen, Wei

doi:10.3847/1538-4357/ac651c

Cited by 14 publications

(1 citation statement)

References 69 publications

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“…As reported by Glesener et al (2020), even an A5.7-class microflare can be nonthermal as evidenced by the nonthermal hard X-Ray (HXR) emission using direct-focusing NuSTAR observations. The research of an A-class microflare by Li et al (2022) show the existence of a nonthermal component down to 6.5 keV, indicating that accelerated electrons play an important role in microflares, as in large flares.…”

Section: Introductionmentioning

confidence: 99%

Lyα Emission Enhancement Associated with Soft X-Ray Microflares

Tian

et al. 2023

Res. Astron. Astrophys.

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Lyman‐alpha (Lyα, 1216Å) is the strongest emission line in the solar ultraviolet spectrum. In the present work, we obtained a Lyα enhancement catalog covering flares larger than B1 class from the GOES/EUVS data during 2010–2016. We focused on the 242 B-class events which are less investigated, however, show non-negligible Lyα emission enhancement. We found that on average the Lyα peak of B-class flares is 0.85% stronger than the background.For the flare energetics, it is found that the weaker the SXR flare, the larger the ratio of the radiated energy in Lyα to SXR. Using the RHESSI data and multi-wavelength observations taken by SDO-AIA, we diagnose the thermal and non-thermal properties of several flares. Three case studies show that the coincidence of the Lyα peak with the SXR time-derivative peak is not a sufficient condition of the nonthermal property of a Lyα microflare. The Lyα enhancement in the microflares may be caused by the nonthermal electron beams or/and thermal conduction. However for type III events, we found that the delay of the Lyα peak with respect to the SXR peak can be attributed to either the Lyα emission from a filament erupted or the cooling of the thermal plasma in flare loops.Furthermore, interestingly the Lyα emission from filaments can not only occur in the decay phase of the flare, but also in the pre-flare phase. In this case, the Lyα emission was originated from an erupted filament which probably initiated the flare.

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Section: Introductionmentioning

confidence: 99%

Lyα Emission Enhancement Associated with Soft X-Ray Microflares

Tian

et al. 2023

Res. Astron. Astrophys.

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Kink-and-Disconnection Failed Eruption in 3D

Mrozek,

Li,

Karlický

et al. 2024

Sol Phys

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We present a case study of a failed eruption that accompanied an M1.5 GOES class solar flare. It was observed by STIX onboard Solar Orbiter, HXI onboard the Advanced Space-based Solar Observatory, AIA onboard Solar Dynamics Observatory, and WAVES onboard the STEREO-A. The important input is from stereoscopic hard X-ray (HXR) observations obtained by HXI and STIX, whose vantage points were separated by $31.5^{\circ }$ 31.5 ∘ , allowing us to unfold the 3D geometry of the event. The eruption was a two-phase event. First, it started with the rope helical kink and then was slowed down, but with the structure still unstable, it erupted two minutes later due to ongoing reconnection in the interacting legs of the kinked structure. A Type III burst was observed in association with the eruption, indicating the acceleration of semirelativistic electrons into the heliosphere. During the second phase, a hot cloud was disconnected and confined in the overlying magnetic field, where the overlying loops connected two adjacent active regions. The estimated and corrected for real geometry velocities are in the range of 385 – 400 km s−1, whereas acceleration reached 4.78 – 6.33 km s−2. These extreme values are much more demanding from a perspective of conditions that are needed to stop the eruption. Images obtained simultaneously by HXI and STIX located in different vantage points showed that flare-related sources are not lying along a normal to the solar surface. The understanding of the eruption analyzed here has been highly enriched thanks to the stereoscopic information about HXR source locations.

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