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We demonstrate that for weak flares the dependence on spottedness can be rather weak. The fact is that such flares can occur both in small and large active regions. At the same time, powerful large flares of classes M and X occur much more…

Solar and Stellar Astrophysics · Physics 2022-09-07 M. M. Katsova , V. N. Obridko , D. D. Sokoloff , I. M. Livshits

The sunspot-associated sources at the frequency of 17 GHz give information on plasma parameters in the regions of magnetic field about B=2000 G at the level of the chromosphere-corona transition region. The observations of short period…

Solar and Stellar Astrophysics · Physics 2015-03-19 Vladimir E. Abramov-Maximov , George B. Gelfreikh , Kiyoto Shibasaki

Solar flares and coronal mass ejections are the largest energy release phenomena in the current solar system. They cause drastic enhancements of electromagnetic waves of various wavelengths and sometimes eject coronal material into the…

Solar and Stellar Astrophysics · Physics 2022-04-14 Shin Toriumi , Sung-Hong Park

Rapid increase of horizontal magnetic field ($B_h$) around the flaring polarity inversion line is the most prominent photospheric field change during flares. It is considered to be caused by the contraction of flare loops, the details…

Solar and Stellar Astrophysics · Physics 2022-08-17 Lijuan Liu , Zhenjun Zhou , Yuming Wang , Xudong Sun , Guoqiang Wang

Most models of solar eruptions assume that coronal field lines are anchored in the dense photosphere and thus the photospheric magnetic fields would not have rapid, irreversible changes associated with eruptions resulted from the coronal…

Solar and Stellar Astrophysics · Physics 2015-05-19 Haimin Wang , Chang Liu

Solar flares are intense bursts of electromagnetic radiation, which occur due to a rapid destabilization and reconnection of the magnetic field. While pre-flare signatures and trends have been investigated from magnetic observations prior…

Solar and Stellar Astrophysics · Physics 2025-06-18 Kara L. Kniezewski , Emily I. Mason , Daniel J. Emmons , Kyle E. Fitch , Seth H. Garland

This publication provides an overview of magnetic fields in the solar atmosphere with the focus lying on the corona. The solar magnetic field couples the solar interior with the visible surface of the Sun and with its atmosphere. It is also…

Solar and Stellar Astrophysics · Physics 2015-06-23 Thomas Wiegelmann , Julia K. Thalmann , Sami K. Solanki

We analyze high-cadence vector magnetograms (135~s) and flare-ribbon observations of 37 flares from the Solar Dynamics Observatory to understand the spatial and temporal properties of changes in the photospheric vector magnetic field and…

Solar and Stellar Astrophysics · Physics 2023-03-08 Rahul Yadav , Maria D. Kazachenko

We investigate the orientation of the photospheric magnetic fields in the solar polar region using observations from the Helioseismic and Magnetic Imager (HMI). Inside small patches of significant polarization, the inferred magnetic field…

Solar and Stellar Astrophysics · Physics 2021-06-04 Xudong Sun , Yang Liu , Ivan Milić , Ana Belén Griñón Marín

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

Active regions (AR) appearing on the surface of the Sun are classified into $\alpha$, $\beta$, $\gamma$, and $\delta$ by the rules of the Mount Wilson Observatory, California on the basis of their topological complexity. Amongst these, the…

Solar and Stellar Astrophysics · Physics 2016-03-09 Piyali Chatterjee , Viggo Hansteen , Mats Carlsson

Solar flares may be the best-known examples of the explosive conversion of magnetic energy into bulk motion, plasma heating, and particle acceleration via magnetic reconnection. The energy source for all flares is the highly sheared…

Solar and Stellar Astrophysics · Physics 2022-08-02 Joel T. Dahlin , Spiro K. Antiochos , Jiong Qiu , C. Richard DeVore

Aims: Changes of the magnetic field and the line-of-sight velocities in the photosphere are being reported for an M-class flare that originated at a $\delta$-spot belonging to active region NOAA 11865. Methods: High-resolution ground-based…

Solar activity can be witnessed in the form of sunspots and active regions, where the magnetic field is enhanced by up to a factor 1000 as compared to that of the quiet Sun. In addition, solar activity manifests itself in terms of flares,…

Solar and Stellar Astrophysics · Physics 2025-07-25 Gottfried Mann , Frédéric Schuller

The results of the microwave observations of the Sun made with the RATAN-600 have shown the existence of many types of spectral peculiarities in polarized emission of active regions, which produce powerful flares. These phenomena happen at…

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

Solar flares are a fundamental component of solar eruptive events (SEEs; along with solar energetic particles, SEPs, and coronal mass ejections, CMEs). Flares are the first component of the SEE to impact our atmosphere, which can set the…

Magnetic storms on stars manifest as remarkable, randomly occurring changes of the luminosity over durations that are tiny in comparison to the normal evolution of stars. These stellar flares are bursts of electromagnetic radiation from…

Solar and Stellar Astrophysics · Physics 2024-02-13 Adam F. Kowalski

Many previous studies have shown that magnetic fields as well as sunspot structures present rapid and irreversible changes associated with solar flares. In this paper we first use five X-class flares observed by SDO/HMI to show that not…

Solar and Stellar Astrophysics · Physics 2016-08-17 Yongliang Song , Mei Zhang

Besides their causal connection with long and short-term magnetic variability, solar bipolar magnetic regions are our chief source of insight into the location, size, and properties of large-scale toroidal magnetic structures in the solar…

Solar and Stellar Astrophysics · Physics 2022-03-23 A. Munoz-Jaramillo , B. Navarrete , L. E. Campusano