Stereoscopic electron spectroscopy of solar hard X-ray flares with a single spacecraft

Abstract

Hard X-ray (HXR) spectroscopy is the most direct method of diagnosing energetic electrons in solar flares. Here we present a technique which allows us to use a single HXR spectrum to determine an effectively stereoscopic electron energy distribution. Considering the Sun's surface to act as a 'Compton mirror' allows us to look at emitting electrons also from behind the source, providing vital information on downward-propagating particles. Using this technique we determine simultaneously the electron spectra of downward and upward directed electrons for two solar flares observed by the Ramaty High Energy Solar Spectroscopic Imager (RHESSI). The results reveal surprisingly near-isotropic electron distributions, which contrast strongly with the expectations from the standard model which invokes strong downward beaming, including collisional thick-target model.

7 pages, 3 figures, accepted to Astrophysical Journal Letters

Cited by in corpus (15)

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• Hard X-ray Spectra and Positions of Solar Flares observed by RHESSI: photospheric albedo, directivity and electron spectra
• Low-energy cutoffs in electron spectra of solar flares: statistical survey
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• Understanding breaks in solar flares x-ray spectra: Evaluation of a co-spatial return-current model
• The role of diffusion in the transport of energetic electrons during solar flares
• Data-Constrained Solar Modeling with GX Simulator
• Measurements of electron anisotropy in solar flares using albedo with RHESSI X-ray data
• Connecting solar flare hard X-ray spectra to in situ electron spectra. A comparison of RHESSI and STEREO/SEPT observations
• Physics of collisionless reconnection in a stressed X-point collapse
• Electron plasma wake field acceleration in solar coronal and chromospheric plasmas
• Ramaty High Energy Solar Spectroscopic Imager (RHESSI)