Browsing by Author "Daou, Antoun Georges"
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Item Nonthermal hard X-ray flux saturation in solar flares(2005) Daou, Antoun Georges; Alexander, DavidWe use the unprecedented spectral and spatial resolution of RHESSI to explore the behavior of electrons and their associated currents in solar flares. Spectral images are used to determine an estimate of the effective surface area for the different independent substructures within each event. The incident electron spectra at those flaring footpoints are derived from the RHESSI photon spectra. We find that, over a wide range of flare X-ray magnitudes, the integrated photon flux above 20 keV asymptotically approaches a limiting value, suggesting a saturation of the photon production in flares. The inferred particle fluxes in the beam, together with this saturation limit, are used to determine the energy loss mechanism dominating the energetic particle transport in solar flares.Item Observational and theoretical interpretation of energetic particle transport in solar flares(2008) Daou, Antoun Georges; Alexander, DavidThe combination of excellent space-based remote sensing, and image reconstruction techniques, as well as improvements in numerical modeling, help enhance our understanding of particle transport in solar flares. We conduct a rigorous analysis of flare hard X-ray emission using the unprecedented spectral and spatial resolution of the RHESSI telescope data in order to better understand the spectral properties of the emitting electron population in solar flares. We complete our study with a forward-fit to the data using a Fokker-Planck kinetic code, to numerically model the particle transport in phase-space in realistic magnetic geometries and for different particle injection profiles.