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This paper reports the results of a survey of Doppler shift oscillations measured during solar flares in emission lines of S XV and Ca XIX with the Bragg Crystal Spectrometer (BCS) on Yohkoh. Data from 20 flares that show oscillatory…

Astrophysics · Physics 2009-11-13 John T. Mariska

We detect rapid downflows of 150-217 km/s in IRIS Si IV 1402.77 nm measurements of an X9-class solar flare on 2024 October 3rd. The fast redshift values persist for over 15 minutes from flare onset, and can be split into two distinct stages…

In this work, we studied X-ray source SRGe~J021932.4$-$040154 (SRGe J021932), which we associated with a single X-ray active star of spectral class G2V-G4V and the rotational period $\rm P_{rot} < 9.3$ days. Additional analysis of TESS…

High Energy Astrophysical Phenomena · Physics 2024-12-13 Andrey Mukhin , Roman Krivonos , Ilfan Bikmaev , Mark Gorbachev , Irek Khamitov , Sergey Sazonov , Marat Gilfanov , Rashid Sunyaev

The solar active region NOAA 11719 produced a large two-ribbon flare on 11 April 2013. We have investigated the sudden variations in the photospheric magnetic fields in this active region during the flare employing the magnetograms obtained…

Solar and Stellar Astrophysics · Physics 2016-10-27 Brajesh Kumar , A. Raja Bayanna , P. Venkatakrishnan , Shibu K. Mathew

The explanation of the coronal heating problem potentially lies in the existence of nanoflares, numerous small-scale heating events occuring across the whole solar disk. In this paper, we present the first imaging spectroscopy X-ray…

We investigate the spatial, temporal, and spectral properties of 10 microflares from AR12721 on 2018 September 9 and 10 observed in X-rays using the Nuclear Spectroscopic Telescope ARray (NuSTAR) and the Solar Dynamic Observatory's…

The existence of time-energy correlations in flare occurrence is still an open and much debated problem. This study addresses the question whether statistically significant correlations are present between energies of successive flares as…

Solar and Stellar Astrophysics · Physics 2010-03-02 Eugenio Lippiello , Lucilla de Arcangelis , Cataldo Godano

Mercury mission MESSENGER's %(MErcury Surface, Space ENvironment, GEochemistry, and Ranging Solar Assembly for X-rays (SAX) observed almost 700 solar flares between May 28, 2007 and August 19, 2013, as cataloged by…

Solar and Stellar Astrophysics · Physics 2021-01-06 Erica Lastufka , Säm Krucker

We study the temporal evolution of coronal loops using data from the Solar X-ray Imager (SXI) on board of GOES-12. This instrument allows us to follow in detail the full lifetime of coronal loops. The observed light curves suggest three…

Astrophysics · Physics 2008-11-26 M. C. Lopez Fuentes , J. A. Klimchuk , C. H. Mandrini

Using data from the Geostationary Operational Environmental Satellites (GOES) spacecraft in the 1-8 \AA\ wavelength range for Solar Cycles 23, 24, and part of Cycles 21 and 22, we compare mean temporal parameters (rising, decay times,…

Solar and Stellar Astrophysics · Physics 2017-10-19 I. M. Chertok , A. V. Belov

Aims: This work aims to identify the mechanism driving pulsations in hard X-ray (HXR) and microwave emission during solar flares. Here, by using combined HXR and microwave observations from Solar Orbiter/STIX and EOVSA we investigate an…

Solar and Stellar Astrophysics · Physics 2024-05-01 Hannah Collier , Laura A. Hayes , Sijie Yu , Andrea F. Battaglia , William Ashfield , Vanessa Polito , Louise K. Harra , Säm Krucker

Short timescale flux variations are closely related to the energy release process of magnetic reconnection during solar flares. Radio light curves at 1, 2, 3.75, 9.4, and 17 GHz of 209 flares observed by the Nobeyama Radio Polarimeter from…

Solar and Stellar Astrophysics · Physics 2020-06-04 Wang Lu , Liu Si-ming , Ning Zong-jun

Investigate particle acceleration and heating in a solar microflare. In a microflare with non-thermal emission to remarkably high energies ($>50$ keV), we investigate the hard X-rays with RHESSI imaging and spectroscopy and the resulting…

Astrophysics · Physics 2010-09-17 I. G. Hannah , S. Krucker , H. S. Hudson , S. Christe , R. P. Lin

Using a new type of oscillation map, made from the radio spectra by the wavelet technique, we study the 18 April 2014 M7.3 flare (SOL2014-04-18T13:03:00L245C017). We find a quasi-periodic character of this flare with periods in the range…

Solar and Stellar Astrophysics · Physics 2017-07-19 M. Karlicky , J. Rybak , C. Monstein

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

Introducing thresholds to analyze time series of emission from the Sun enables a new and simple definition of solar flare events, and their interoccurrence times. Rescaling time by the rate of events, the waiting and quiet time…

Statistical Mechanics · Physics 2007-05-23 Marco Baiesi , Maya Paczuski , Attilio L. Stella

Solar flares stronger than X10 (S-flares, >X10) are the highest class flares which significantly impact on the Sun's evolution and space weather. Based on observations of Geostationary Orbiting Environmental Satellites (GOES) at soft X-ray…

Solar and Stellar Astrophysics · Physics 2025-01-10 Baolin Tan , Yin Zhang , Jing Huang , Kaifan Ji

From the observing campaigns of a number of helioseismic telescope networks such as the Global Oscillation Network Group (GONG) and also from the Solar Heliospheric Observatory satellite (SoHO), helioseismologists now have data on in excess…

Astrophysics · Physics 2007-05-23 Frank P. Pijpers

We present a multi-instrument study of the two precursor brightenings prior to the M6.5 flare (SOL2015-06-22T18:23) in the NOAA Active Region 12371, with a focus on the temperature (T), electron number density (n), and emission measure…

Solar and Stellar Astrophysics · Physics 2023-02-15 Nian Liu , Ju Jing , Yan Xu , Haimin Wang