Hard X-ray Spectra and Positions of Solar Flares observed by RHESSI: photospheric albedo, directivity and electron spectra

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dc.creatorKasparova, J.
dc.creatorKontar, E. P.
dc.creatorBrown, J. C.
dc.date2007-01-30
dc.date.accessioned2026-07-07T11:00:46Z
dc.date.available2026-07-07T11:00:46Z
dc.descriptionWe 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. Using Ramaty High Energy Solar Spectroscopic Imager (RHESSI) flare data we perform a statistical analysis of spatially integrated spectra and positions of solar flares. We demonstrate clear centre-to-limb variation of photon spectral indices in the 15-20 keV energy range and a weaker dependency in the 20-50 keV range which is consistent with photospheric albedo as the cause. The results also suggest that low-energy cutoffs sometimes inferred in mean electron spectra are an artefact of albedo. We also derive the anisotropy (ratio of downward/observer directed photons) of hard X-ray emission in the 15-20 keV range for various heliocentric angles.
dc.description8 pages, 6 figures, revised manuscript to Astronomy and Astrophysics
dc.identifierhttps://arxiv.org/abs/astro-ph/0701871
dc.identifierhttp://arxiv.org/abs/astro-ph/0701871
dc.identifierAstron.Astrophys.466:705-712,2007
dc.identifierdoi:10.1051/0004-6361:20066689
dc.identifier.urihttp://salesiana.dossiersoluciones.com/handle/123456789/187763
dc.subjectAstrophysics
dc.titleHard X-ray Spectra and Positions of Solar Flares observed by RHESSI: photospheric albedo, directivity and electron spectra
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