Results 21 to 30 of about 18,154 (212)

Hard X-ray spectra and positions of solar flares observed by RHESSI: photospheric albedo, directivity and electron spectra [PDF]

, 2007
<p><b>Aims</b>: We investigate the signature of the photospheric albedo contribution in solar flare hard X-ray spectra, the effect of low energy cutoffs in electron spectra, and the directivity of hard X-ray emission.</p> <p&
Brown, J.C., Kašparová, J., Kontar, E.P.   +2 more
core   +2 more sources

Temporal and spectral variations of the photoelectron flux and solar irradiance during an X class solar flare

Geophysical Research Letters, 2008
Photoelectrons are the main energy source of airglow used to diagnose the state of the ionosphere‐thermosphere system. Because of measurement uncertainties and substantial gaps in the historical record, parameterized models of the EUV irradiance and ...
W. K. Peterson, P. C. Chamberlin, T. N. Woods, P. G. Richards   +3 more
doaj   +1 more source

Tracking X-Ray Source Movement in a Retracting Flux Tube

The Astrophysical Journal, 2023
Solar flares produce sources of localized, enhanced X-ray emission, thought to be due to the acceleration of nonthermal electrons and the transport of energy away from the reconnection site.
John Unverferth, Jeffrey W. Reep
doaj   +1 more source

Temporal variations of the CaXIX spectra in solar flares [PDF]

Astronomy & Astrophysics, 2009
Standard model of solar flares comprises a bulk expansion and rise of abruptly heated plasma (the chromospheric evaporation). Emission from plasma ascending along loops rooted on the visible solar disk should be often dominated, at least temporally, by a blue-shifted emission.
Falewicz, R., Rudawy, P., Siarkowski, M.
openaire   +2 more sources

Imaging Spectroscopy of a White-Light Solar Flare [PDF]

, 2010
We report observations of a white-light solar flare (SOL2010-06-12T00:57, M2.0) observed by the Helioseismic Magnetic Imager (HMI) on the Solar Dynamics Observatory (SDO) and the Reuven Ramaty High-Energy Solar Spectroscopic Imager (RHESSI). The HMI data
A. Donea, A.G. Kosovichev, A.G. Kosovichev, A.G. Kosovichev, A.N. Babin, A.Y. Shih, C. Lindsey, C. Lindsey, C. Liu, C.L. Wolff, D. Beşliu-Ionescu, D.B. Jess, D.F. Neidig, D.F. Neidig, D.M. Rust, H. Hudson, H. Potts, H. S. Hudson, H. Wang, H.S. Hudson, H.S. Hudson, H.S. Hudson, J. Birn, J. C. Martínez Oliveros, J. Hénoux, J. Schou, J.C. Brown, J.J. Sudol, L. Fletcher, L. Fletcher, M.E. Machado, M.S. Giampapa, P. Scherrer, R.C. Carrington, R.O. Milligan, S. Couvidat, S. Krucker, T.N. Woods, Y. Xu, Z. Švestka   +39 more
core   +2 more sources

Solar flare soft X-ray spectra from Diogeness observations [PDF]

Proceedings of the International Astronomical Union, 2015
AbstractDiogeness was an uncollimated scanning flat crystal spectrometer observing solar flare X-ray spectra in four narrow wavelength bands in the vicinity of Ca xix, S xv and Si xiii He-like line ‘triplets’ around 3.18 Å, 5.04 Å and 6.65 Å. In two of the spectral channels, emission lines around the Ca xix 3.178 Å resonance line were scanned in ...
Marek Stȩślicki, Janusz Sylwester, Barbara Sylwester, Żaneta Szaforz, Zbigniew Kordylewski, Stefan Płocieniak, Marek Siarkowski, Kenneth J. H. Phillips   +7 more
openaire   +1 more source

Transient ionization and solar flare X-ray spectra

The Astrophysical Journal, 1987
In this paper the effects of a transiently ionizing solar flare plasma on the X-ray spectrum of iron between 1.85 and 1.92 A are considered. The atomic physics of the nonequilibrium spectrum is discussed, and reasons for differences in appearance from ionization equilibrium spectra are explained.
G. A. Doschek, K. Tanaka
openaire   +1 more source

Optical Spectral Observations of a Flickering White-Light Kernel in a C1 Solar Flare [PDF]

, 2014
We analyze optical spectra of a two-ribbon, long duration C1.1 flare that occurred on 18 Aug 2011 within AR 11271 (SOL2011-08-18T15:15). The impulsive phase of the flare was observed with a comprehensive set of space-borne and ground-based instruments ...
Cauzzi, Gianna, Fletcher, Lyndsay, Kowalski, Adam F.   +2 more
core   +3 more sources

HIGH DIELECTRONIC SATELLITE LINES IN SOLAR FLARE SPECTRA

Le Journal de Physique Colloques, 1979
Resonance lines of highly ionized H and He-like ions and their associated satellite lines are used to determine the electron temperature and the transient state of the plasma in solar flares. The intensity ratio of the satellite lines 1s2nl-1s2pnl to the resonance line 1s2-1s2p has been calculated for the n = 2, 3 and 4 shells of Fe XXIV.
Steenman-Clark, L., Bely Dubau, F., Dubau, J., Faucher, P., Gabriel, Aurélie, Loulergue, M., Volonté, S.   +6 more
openaire   +1 more source

Plasma heating in the very early phase of solar flares

, 2009
In this paper we analyze soft and hard X-ray emission of the 2002 September 20 M1.8 GOES class solar flare observed by RHESSI and GOES satellites. In this flare event, soft X-ray emission precedes the onset of the main bulk hard X-ray emission by ~5 min.
Asai, Brosius, Feldman, Landi, M. Siarkowski, McTiernan, P. Rudawy, R. Falewicz, Schmahl, Warren   +9 more
core   +1 more source