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 (6)

• Chromospheric magnetic field and density structure measurements using hard X-rays in a flaring coronal loop
• Combined Modeling of Acceleration, Transport, and Hydrodynamic Response in Solar Flares: I. The Numerical Model
• 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
• Electron-Electron Bremsstrahlung Emission and the Inference of Electron Flux Spectra in Solar Flares
• Physics of collisionless reconnection in a stressed X-point collapse