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X-ray and EUV observations are an important diagnostic of various plasma parameters of the solar atmosphere during solar flares. Soft X-ray and EUV observations often show coronal sources near the top of flaring loops, while hard X-ray…

Solar and Stellar Astrophysics · Physics 2015-06-11 Marina Battaglia , Eduard P. Kontar

The large (X-ray class > M1) and very large (X-ray class >X1) flares (according to the observations of GOES-15 and Preliminary data from Current Catalog of Flare Events) in solar activity cycle 24 were analyzed. The monthly average values…

Solar and Stellar Astrophysics · Physics 2018-03-21 E. A. Bruevich , T. V. Kazachevskaya , G. V. Yakunina

Context. The variability of Solar Spectral Irradiance over the rotational period and its trend over the solar activity cycle are important for understanding the Sun-Earth connection as well as for observational constraints for solar models.…

Solar and Stellar Astrophysics · Physics 2015-06-16 C. Wehrli , W. Schmutz , A. I. Shapiro

We investigate accelerated electron energy spectra for different sources in a large flare using simultaneous observations obtained with two instruments, the Nobeyama Radio Heliograph (NoRH) at 17 and 34 GHz, and the Reuven Ramaty High…

Solar and Stellar Astrophysics · Physics 2015-05-13 M. R. Kundu , V. V. Grechnev , S. M. White , E. J. Schmahl , N. S. Meshalkina , L. K. Kashapova

We study the electron energy spectra of two powerful solar flares SOL2003-10-28T 11:06:16 (GOES class X17.2) and SOL2002-07-23T00:18:16 (X4.8) on the basis of HXR and gamma-ray spectra obtained from RHESSI data. Electron-electron (e-e)…

Solar and Stellar Astrophysics · Physics 2020-12-16 I. D. Oparin , Yu. E. Charikov , E. P. Ovchinnikova , A. N. Shabalin

The extreme ultraviolet portion of the solar spectrum contains a wealth of diagnostic tools for probing the lower solar atmosphere in response to an injection of energy, particularly during the impulsive phase of solar flares. These include…

Solar and Stellar Astrophysics · Physics 2015-09-16 Ryan O. Milligan

We investigate the X-ray and UV emission detected by RHESSI and TRACE in the context of a solar flare on the 16th November 2002 with the goal of better understanding the evolution of the flare. We analysed the characteristics of the X-ray…

Solar and Stellar Astrophysics · Physics 2015-06-11 Hamish A. S. Reid , Nicole Vilmer , Guillaume Aulanier , Etienne Pariat

Nanoflares, the basic unit of impulsive energy release may produce much of the solar background emission. Extrapolation of the energy frequency distribution of observed microflares, which follows a power law to lower energies can give an…

Solar and Stellar Astrophysics · Physics 2011-12-22 E. Tajfirouze , H. Safari

In addition to X-rays, extreme ultraviolet (EUV) rays radiated from solar flares can cause serious problems, such as communication failures and satellite drag. Therefore, methods for forecasting EUV dynamic spectra during flares are…

Solar and Stellar Astrophysics · Physics 2020-05-14 Toshiki Kawai , Shinsuke Imada , Shohei Nishimoto , Kyoko Watanabe , Tomoko Kawate

Aims The possible influence of solar superflares on the near-Earth space radiation environment are assessed through the investigation of scaling laws between the peak proton flux and fluence of Solar Energetic Particle (SEP) events with the…

Solar and Stellar Astrophysics · Physics 2023-03-08 Athanasios Papaioannou , Konstantin Herbst , Tobias Ramm , Edward W. Cliver , David Lario , Astrid M. Veronig

The statistical characteristic of stellar flares at optical bands has received an extensive study, but it remains to be studied at soft X-ray bands, in particular for solar-type stars. Here, we present a statistical study of soft X-ray…

Solar and Stellar Astrophysics · Physics 2024-01-19 Zhanhao Zhao , Ziqian Hua , Xin Cheng , Zhiyuan Li , Mingde Ding

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

Solar flares significantly impact the conditions of the Earth's ionosphere. In particular, the sudden increase in X-ray flux during a flare penetrates down to the lowest-lying D-region and dominates ionization at these altitudes (60-100…

Solar and Stellar Astrophysics · Physics 2021-11-17 Laura A. Hayes , Oscar S. D. O'Hara , Sophie A. Murray , Peter T. Gallagher

We analyze here variations of the position and the vertical extent of the energy deposition layer (EDL) inthe C1.6 GOES-class solar flare observed at 10:20 UT on 2012 September 10. The variations of the EDL arecontrasted with the variations…

Solar and Stellar Astrophysics · Physics 2020-11-04 Krzysztof Radziszewski , Robert Falewicz , Pawel Rudawy

The Total Irradiance Monitor (TIM) from NASA's SOlar Radiation and Climate Experiment (SORCE) can detect changes in the Total Solar Irradiance (TSI) to a precision of 2 ppm, allowing observations of variations due to the largest X-Class…

Instrumentation and Methods for Astrophysics · Physics 2015-09-22 Christopher Samuel Moore , Phillip Clyde Chamberlin , Rachel Hock

The sites of chromospheric excitation during solar flares are marked by extended extreme ultraviolet ribbons and hard X-ray footpoints. The standard interpretation is that these are the result of heating and bremsstrahlung emission from…

Solar and Stellar Astrophysics · Physics 2014-01-28 L. Fletcher , I. G. Hannah , H. S. Hudson , D. E. Innes

We present measurements of elemental abundances in solar flares with the EUV Variability Experiment (EVE) on the Solar Dynamics Observatory (SDO). EVE observes both high temperature Fe emission lines (Fe XV-Fe XXIV) and continuum emission…

Solar and Stellar Astrophysics · Physics 2015-06-17 Harry P. Warren

The Sun's proximity offers us a unique opportunity to study in detail the physical processes on a star's surface; however, the highly dynamic nature of the stellar surface -- in particular, energetic eruptions such as flares and coronal…

Instrumentation and Methods for Astrophysics · Physics 2023-10-31 Haosheng Lin , Tetsu Anan , Gianna Cauzzi , Lyndsay Fletcher , Pei Huang , Adam Kowalski , Maxim Kramar , Jiong Qiu , Jenna Samra , Constance Spittler , Takashi Sukegawa , Gregory Wirth

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

Total solar irradiance and UV spectral solar irradiance have been monitored since 1978 through a succession of space missions. This is accompanied by the development of models aimed at replicating solar irradiance by relating the…

Solar and Stellar Astrophysics · Physics 2015-07-07 K. L. Yeo , W. T. Ball , N. A. Krivova , S. K. Solanki , Y. C. Unruh , J. Morrill