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NOAA Active Region (AR) 13664/8 produced the most intense geomagnetic effects since the ``Halloween'' event of 2003. The resulting extreme solar storm is believed to be the consequence of multiple interacting coronal mass ejections (CMEs).…

Solar and Stellar Astrophysics · Physics 2024-12-04 Rui Wang , Ying D. Liu , Xiaowei Zhao , Huidong Hu

The X2.2-class solar flare of February 15, 2011, produced a powerful `sunquake' event, representing a seismic response to the flare impact. The impulsively excited seismic waves formed a compact wavepacket traveling through the solar…

Solar and Stellar Astrophysics · Physics 2011-02-22 A. G. Kosovichev

Between 2017 and 2024, the Helioseismic and Magnetic Imager (HMI) onboard the Solar Dynamics Observatory has observed numerous white-light solar flares (WLFs). HMI spectro-polarimetric observations of certain WLFs, in particular the X9.3…

Solar and Stellar Astrophysics · Physics 2025-07-02 Samuel Granovsky , Alexander G. Kosovichev , Viacheslav M. Sadykov , Graham S. Kerr , Joel C. Allred

To better understand magnetic structure and eruptive process of solar filaments, a solar active-region filament (labeled F2) eruption associated with a B-class flare was investigated by using high-resolution H$\alpha$ data from the 1 m New…

Solar and Stellar Astrophysics · Physics 2020-11-25 X. L. Yan , Q. L. Li , G. R. Chen , Z. K. Xue , L. Feng , J. C. Wang , L. H. Yang , Y. Zhang

Flare ribbons with parallel and circular morphologies are typically associated with different magnetic reconnection models, and the simultaneous observation of both types in a single event remains rare. Using multi-wavelength observations…

Solar and Stellar Astrophysics · Physics 2025-11-03 Ruifei Huang , Hao Ning , Ze Zhong , Ye Qiu , Zhenyong Hou , Yang Su , Chuan Li , Xiangliang Kong , Yao Chen

Solar flares are defined as outbursts on the surface of the Sun. They occur when energy accumulated in magnetic fields enclosing solar active regions (ARs) is abruptly expelled. Solar flares and associated coronal mass ejections are sources…

Solar and Stellar Astrophysics · Physics 2025-02-24 Huseyin Cavus , Jason T. L. Wang , Teja P. S. Singampalli , Gani Caglar Coban , Hongyang Zhang , Abd-ur Raheem , Haimin Wang

Utilizing multiwavelength observations and magnetic field data from SDO/AIA, SDO/HMI, GOES and RHESSI, we investigate a large-scale ejective solar eruption of 2014 December 18 from active region NOAA 12241. This event produced a distinctive…

Solar and Stellar Astrophysics · Physics 2017-08-23 Navin Chandra Joshi , Alphonse C. Sterling , Ronald L. Moore , Tetsuya Magara , Young-Jae Moon

Soar filament eruptions are often associated with solar flares and coronal mass ejections (CMEs), which are the major impacts on space weather. However, the fine structures and the trigger mechanisms of solar filaments are still unclear. To…

Solar and Stellar Astrophysics · Physics 2020-02-12 X. L. Yan , Z. K. Xue , X. Cheng , J. Zhang , J. C. Wang , D. F. Kong , L. H. Yang , G. R. Chen , X. S. Feng

The X2.2-class solar flare of February 15, 2011, produced a powerful sunquake event, representing a helioseismic response to the flare impact in the solar photosphere, which was observed with the HMI instrument on the Solar Dynamics…

Solar and Stellar Astrophysics · Physics 2015-05-28 Alexander G. Kosovichev

The paper presents results of a search for helioseismic events (sunquakes) produced by M-X class solar flares during Solar Cycle 24. The search is performed by analyzing photospheric Dopplergrams from Helioseismic Magnetic Imager (HMI).…

Solar and Stellar Astrophysics · Physics 2020-06-03 I. N. Sharykin , A. G. Kosovichev

Active regions are thought to be one contributor to the slow solar wind. Upflows in EUV coronal spectral lines are routinely osberved at their boundaries, and provide the most direct way for upflowing material to escape into the…

Solar and Stellar Astrophysics · Physics 2021-08-18 David H. Brooks , Louise Harra , Stuart D. Bale , Krzysztof Barczynski , Cristina Mandrini , Vanessa Polito , Harry P. Warren

The emergence of active regions (ARs) closely relates to the solar dynamo and the dynamical atmospheric phenomena.With high-resolution and long-lasting observations from the New Vacuum Solar Telescope, we report a new dynamic activity…

Solar and Stellar Astrophysics · Physics 2019-09-25 Sihui Zhong , Yijun Hou , Leping Li , Jun Zhang , Yongyuan Xiang

We investigate the onsets of three consecutive coronal mass ejection (CME) eruptions in 12 hours from a large bipolar active region (AR) observed by SDO, STEREO, RHESSI, and GOES. Evidently, the AR initially had a triple-decker…

Solar and Stellar Astrophysics · Physics 2020-09-30 Navin Chandra Joshi , Alphonse C. Sterling , Ronald L. Moore , Bhuwan Joshi

In the standard model, magnetic reconnection at a vertical current sheet above the flare arcade is key to explaining many aspects of solar eruptions. The supra-arcade region is where the vertical current sheet is supposedly located, and…

Solar and Stellar Astrophysics · Physics 2025-12-23 Hanya Pan , Astrid M. Veronig , Rui Liu

Extreme solar particle events reveal that the Sun can occasionally produce eruptions significantly more energetic than those observed in the modern era. These events are thought to originate from powerful coronal mass ejections, typically…

Solar and Stellar Astrophysics · Physics 2026-03-11 N. A. Krivova , T. Chatzistergos , M. Kazachenko , E. Isik

In order to understand the flare trigger mechanism, we conducted three-dimensional magnetohydrodynamic simulations using a coronal magnetic field model derived from data observed by the Hinode satellite. Several types of magnetic bipoles…

Solar and Stellar Astrophysics · Physics 2017-06-23 Johan Muhamad , Kanya Kusano , Satoshi Inoue , Daikou Shiota

We present analysis of the magnetic field in seven solar flare regions accompanied by the pulsations of hard X-ray (HXR) emission. These flares were studied by Kuznetsov et al. (2016) (Paper~I), and chosen here because of the availability…

Solar and Stellar Astrophysics · Physics 2018-05-16 I. V. Zimovets , R. Wang , Y. D. Liu , C. C. Wang , S. A. Kuznetsov , I. N. Sharykin , A. B. Struminsky , V. M. Nakariakov

Using HINODE/XRT, GOES, SDO/AIA observations, we study a compact C-1.4 class flare outside a major sunspot of AR 12178 on 4 October 2014. This flare is associated with a peculiar coronal jet, which is erupted in two stages in the overlying…

Solar and Stellar Astrophysics · Physics 2019-01-30 Ritika Solanki , A. K. Srivastava , B. N. Dwivedi

Bald patch (BP) is a magnetic topological feature where U-shaped field lines turn tangent to the photosphere. Field lines threading the BP trace a separatrix surface where reconnection preferentially occurs. Here we study the evolution of…

Solar and Stellar Astrophysics · Physics 2021-11-17 Jonathan H. Lee , Xudong Sun , Maria D. Kazachenko

We examine the cradle-to-grave magnetic evolution of 10 bipolar ephemeral active regions (BEARs) in solar coronal holes, especially aspects of the magnetic evolution leading to each of 43 obvious microflare events. The data are from Solar…

Solar and Stellar Astrophysics · Physics 2022-07-06 Ronald L. Moore , Navdeep K. Panesar , Alphonse C. Sterling , Sanjiv K. Tiwari
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