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X-ray observations of solar flares routinely reveal an impulsive high-energy and a gradual low-energy emission component, whose relationship is one of the key issues of solar flare study. The gradual and impulsive emission components are…

Solar and Stellar Astrophysics · Physics 2015-05-20 Jingnan Guo , Siming Liu , Lyndsay Fletcher , Eduard P. Kontar

This paper presents measurements of the energy radiated by the lower solar atmosphere, at optical, UV, and EUV wavelengths, during an X-class solar flare (SOL2011-02-15T01:56) in response to an injection of energy assumed to be in the form…

Simultaneous solar flare observations with SDO and RHESSI provide spatially resolved information about hot plasma and energetic particles in flares. RHESSI allows the properties of both hot (> 8 MK) thermal plasma and nonthermal electron…

Solar and Stellar Astrophysics · Physics 2015-06-17 Marina Battaglia , Eduard P. Kontar

All the Extreme Ultraviolet Explorer (EUVE) observations of AD Leo, totalling 1.1 Ms of exposure time, have been employed to analyze the corona of this single M dwarf. The light curves show a well defined quiescent stage, and a distribution…

Astrophysics · Physics 2009-11-07 J. Sanz-Forcada , G. Micela

(Abridged) We investigate the EUV and X-ray flare rate distribution in radiated energy of the late-type active star AD Leo using long EUVE and BeppoSAX observations. We compare the observed light curves with light curves synthesized from…

Astrophysics · Physics 2009-11-07 Manuel Guedel , Marc Audard , Vinay L. Kashyap , Jeremy J. Drake , Edward F. Guinan

We present a new empirical model to predict solar energetic particle (SEP) event-integrated and peak intensity spectra between 10 and 130 MeV at 1 AU, based on multi-point spacecraft measurements from the Solar TErrestrial RElations…

Solar and Stellar Astrophysics · Physics 2021-02-24 Alessandro Bruno , Ian G. Richardson

We study selected properties of Solar Energetic Particle (SEP) events as inferred from their associated radio emissions. We used a catalogue of 115 SEP events that consists of entries of proton intensity enhancements at one AU, with…

Solar and Stellar Astrophysics · Physics 2015-08-12 A. Kouloumvakos , A. Nindos , E. Valtonen , C. E. Alissandrakis , O. Malandraki , P. Tsitsipis , A. Kontogeorgos , X. Moussas , A. Hillaris

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

The abundance of iron is measured from emission line complexes at 6.65 keV (Fe line) and 8 keV (Fe/Ni line) in {\em RHESSI} X-ray spectra during solar flares. Spectra during long-duration flares with steady declines were selected, with an…

Solar and Stellar Astrophysics · Physics 2015-06-03 K. J. H. Phillips , B. R. Dennis

The RS CVn type binary star GT Mus was observed during its quiescence using the Resolve X-ray microcalorimeter spectrometer onboard XRISM. The main and satellite lines of the Fe XXIV--XXVI K-shell transitions were resolved for the first…

We analyse the 30 October, 2004, X1.2/SF solar event that occurred in AR 10691 (N13 W18) at around 11:44 UT. Observations at 212 and 405 GHz of the Solar Submillimeter Telescope (SST), with high time resolution (5 ms), show an intense…

The chromospheric response to the input of flare energy is marked by extended extreme ultraviolet (EUV) ribbons and hard X-ray (HXR) footpoints. These are usually explained as the result of heating and bremsstrahlung emission from…

Solar and Stellar Astrophysics · Physics 2016-01-20 Paulo J. A. Simões , David R. Graham , Lyndsay Fletcher

X-ray and EUV solar flare emission cause increases in the Earth's dayside ionospheric electron density. While the response of the lower ionosphere to X-rays is well studied, the delay between EUV flare emission and the response of the…

Solar and Stellar Astrophysics · Physics 2025-08-06 Aisling N. O'Hare , Susanna Bekker , Harry J. Greatorex , Ryan O. Milligan

The second peak in the Fe XVI 33.5 nm line irradiance observed during solar flares by Extreme ultraviolet Variability Experiment (EVE) is known as Extreme UltraViolet (EUV) late phase. Our previous paper (Liu et al. 2013) found that the…

Solar and Stellar Astrophysics · Physics 2015-04-22 Kai Liu , Yuming Wang , Jie Zhang , Xin Cheng , Rui Liu , Chenglong Shen

We present a statistical study of chromospheric evaporation in solar flares using simultaneous observations by the RHESSI X-ray telescope and the IRIS UV spectrograph. The results are compared with radiation hydrodynamic flare models from…

Solar and Stellar Astrophysics · Physics 2019-01-23 Viacheslav M Sadykov , Alexander G Kosovichev , Ivan N Sharykin , Graham S Kerr

Damped Doppler shift oscillations have been observed in emission lines from ions formed at flare temperatures with the Solar Ultraviolet Measurements of Emitted Radiation spectrometer on the Solar and Heliospheric Observatory and with the…

Astrophysics · Physics 2009-11-13 John T. Mariska , Harry P. Warren , David R. Williams , Tetsuya Watanabe

Flare loops form an integral part of eruptive events, being detected in the range of temperatures from X-rays down to cool chromospheric-like plasmas. While the hot loops are routinely observed by the Solar Dynamics Observatory's…

Solar and Stellar Astrophysics · Physics 2020-01-08 Július Koza , David Kuridze , Petr Heinzel , Sonja Jejčič , Huw Morgan , Maciej Zapiór

We report on multi-wavelength observations spanning radio to X-ray wavelengths of the M dwarf flare star, EV Lacertae, probing the characteristics of the outer atmospheric plasma from the upper chromosphere to the corona. We detect the star…

Astrophysics · Physics 2011-02-11 R. A. Osten , S. L. Hawley , J. Allred , C. M. Johns-Krull , A. Brown , G. M. Harper

Four Fe IX transitions in the wavelength range 188--198 A are identified for the first time in spectra from the EUV Imaging Spectrometer on board the Hinode satellite. In particular the emission line at 197.86 A is unblended and close to…

Astrophysics · Physics 2015-05-13 P. R. Young

In this study we compile for the first time comprehensive data sets of solar and stellar flare parameters, including flare peak temperatures T_p, flare peak volume emission measures EM_p, and flare durations t_f from both solar and stellar…

Astrophysics · Physics 2009-11-13 Markus J. Aschwanden , Robert A. Stern , Manuel Güdel
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