Solar Flare Hard X-ray Spectra Possibly Inconsistent with the Collisional Thick Target Model

Abstract

Recent progress in solar Hard X-ray (HXR) observations with RHESSI data and methods for spectral inversion allow us to study model-independent mean electron flux spectra in solar flares. We report several hard X-ray events observed by RHESSI in which the photon spectra $I(\epsilon )$ are such that the inferred source mean electron spectra are not consistent with the standard model of collisional transport in solar flares. The observed photon spectra are so flat locally that the recovered mean electron flux spectra show a dip around 17-31 keV. While we note that alternative explanations, unrelated to electron transport, have not been ruled out, we focus on the physical implications of this tentative result for the collisional thick-target model.

arXiv comment12 pages, 3 figures, submitted to Advances in Space Research

References in corpus (2)

• Generalized Regularization Techniques With Constraints For The Analysis Of Solar Bremsstrahlung X-Ray Spectra
• Determination Of Electron Flux Spectra In A Solar Flare With An Augmented Regularization Method: Application To Rhessi Data

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• Deducing Electron Properties From Hard X-Ray Observations
• Global Energetics of Solar Flares: III. Non thermal Energies
• Hard X-ray Spectra and Positions of Solar Flares observed by RHESSI: photospheric albedo, directivity and electron spectra
• Simulation of Quiet-Sun Hard X-rays Related to Solar Wind Superhalo Electrons