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We detected a giant X-ray flare from the RS-CVn type binary star UX Ari using MAXI on 2020 August 17 and started a series of NICER observations 89 minutes later. For a week, the entire duration of the flare was covered with 32 snapshot…

Solar flares are known to be prolific electron accelerators, yet identifying the mechanism(s) for such efficient electron acceleration in solar flare (and similar astrophysical settings) presents a major challenge. This is due in part to a…

Solar and Stellar Astrophysics · Physics 2023-04-18 Eduard P. Kontar , A. Gordon Emslie , Galina G. Motorina , Brian R. Dennis

We probe the spectral hardening of solar flares emission in view of associated solar proton events (SEPs) at earth and coronal mass ejection (CME) acceleration as a consequence. In this investigation we undertake 60 SEPs of the Solar Cycle…

Solar and Stellar Astrophysics · Physics 2013-10-22 Sharad C Tripathi , Parvaiz A Khan , Aslam A M , A K Gwal , P K Purohit , Rajmal Jain

We have compiled a catalog of solar flares as observed by the Extreme ultraviolet Imaging Telescope (EIT) aboard the Solar and Heliospheric Observatory (SOHO) spacecraft and the GOES spacecraft over a span from 1997 to 2010. During…

Solar and Stellar Astrophysics · Physics 2020-08-05 Sumanth A. Rotti , Petrus C. H. Martens , Berkay Aydin

The calcium abundance in flare plasmas is estimated using X-ray spectra from the Solar Maximum Mission Bent Crystal Spectrometer (BCS) during the decays of 194 flares (GOES classifications from B6.4 to X13) occurring between 1980 and 1989.…

Solar and Stellar Astrophysics · Physics 2022-05-18 J. Sylwester , B. Sylwester , K. J. H. Phillips , A. Kepa

On October 3rd, 2024, the Sun emitted an X9.0-class flare from active region NOAA 13842. The event was recorded by multiple space-based instruments, beginning hours before the eruption, granting a unique opportunity to provide insight into…

Solar and Stellar Astrophysics · Physics 2026-05-28 Louis Seyfritz , Maria Kazachenko , Ryan French

Solar flares are events of intense scientific interest. Although certain solar conditions are known to be associated with flare activity, the exact location and timing of an individual flare on the Sun cannot as yet be predicted with…

Solar and Stellar Astrophysics · Physics 2021-11-03 Andrew R. Inglis , Jack Ireland , Albert Y. Shih , Steven D. Christe

We analyze 19 bright variable X-ray sources detected in the XMM-Newton Extended Survey of the Taurus Molecular Cloud (XEST), in order to characterize the variations with time of their coronal properties and to derive informations on the…

Doppler shifts in chromospheric and transition-region lines during solar flares are often interpreted as chromospheric condensation or evaporation. However, alternative sources of Doppler-shifted emission have been suggested, such as…

Solar and Stellar Astrophysics · Physics 2025-09-08 Luke H. Majury , Ryan O. Milligan

We present a multiwavelength analysis of the long duration flare observed on 15 April 2002 (soft X-ray peak time at 03:55 UT, SOL2002-04-15T03:55). This flare occurred on the disk (S15W01) in NOAA 9906 and was observed by a number of space…

Solar and Stellar Astrophysics · Physics 2020-03-11 A. Kepa , B. Sylwester , J. Sylwester , T. Mrozek , M. Siarkowski

A statistical analysis of almost 50000 soft X-ray (SXR) flares observed by GOES during the period 1976-2000 is presented. On the basis of this extensive data set, statistics on temporal properties of soft X-ray flares, such as duration,…

Astrophysics · Physics 2009-11-07 A. Veronig , M. Temmer , A. Hanslmeier , W. Otruba , M. Messerotti

The thick-target model predicts that in flare foot points, we should observe lowering of HXR sources' altitude with increasing energy. The foot point of HXR sources result from the direct interaction of non-thermal electron beams with…

Solar and Stellar Astrophysics · Physics 2022-03-14 T. Mrozek , R. Falewicz , S. Kolomanski , M. Litwicka

The disparate nature of thermal-nonthermal energy partition during flares, particularly during weak flares, is still an open issue. Following the Neupert effect, quantifying the relative yield of X-ray emission in different energy bands can…

Solar and Stellar Astrophysics · Physics 2024-02-06 Arun Kumar Awasthi , Tomasz Mrozek , Sylwester Kołomański , Michalina Litwicka , Marek Stęślicki , Karol Kułaga

Context: Solar flares release a large fraction of their energy into non-thermal electrons, but it is not clear where and how. Bremsstrahlung X-rays are observed from the corona and chromosphere. Aims: We aim to characterize the acceleration…

Astrophysics · Physics 2009-11-11 Marina Battaglia , Arnold O. Benz

Context: On 2022 May 4, an M5.7 flare erupted in the active region NOAA 13004, which was the target of a coordinated campaign between GREGOR, IRIS, Hinode, and ground-based instruments at the Ond\v{r}ejov observatory. A flare kernel located…

Solar and Stellar Astrophysics · Physics 2024-08-21 M. García-Rivas , J. Kašparová , A. Berlicki , M. Švanda , J. Dudík , D. Čtvrtečka , M. Zapiór , W. Liu , M. Sobotka , M. Pavelková , G. G. Motorina

NuSTAR is a highly sensitive focusing hard X-ray (HXR) telescope and has observed several small microflares in its initial solar pointings. In this paper, we present the first joint observation of a microflare with NuSTAR and Hinode/XRT on…

Soft X-ray spectra 3.33 A - 6.15 A from the RESIK instrument on CORONAS-F constitute a unique database for the study of the physical conditions of solar flare plasmas, enabling the calculation of differential emission measures. The two…

Solar and Stellar Astrophysics · Physics 2020-10-14 A. Kepa , R. Falewicz , M. Siarkowski , M. Pietras

We report the detection of emission from a non-thermal electron distribution in a small solar microflare (GOES class A5.7) observed by the Nuclear Spectroscopic Telescope Array (NuSTAR), with supporting observation by the Reuven Ramaty High…

The microwave spectrum contains valuable information about solar flares. Yet, the present spectral coverage is far from complete and broad data gaps exist above 20 GHz. Here we report the first flare (the X2.2 flare on 2022 April 20)…

Solar and Stellar Astrophysics · Physics 2023-01-11 F. Yan , Z. Wu , Z. Shang , B. Wang , L. Zhang , Y. Chen