We explore the use of centroid coordinates as a means to identify the "locations" of electron–proton bremsstrahlung hard X-ray sources in solar flares. Differences between the coordinates of the electron and photon cen- troids are derived and explained. For electron propagation in a collision-dominated target, with either a uni- form or an...
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2009 (v1)PublicationUploaded on: March 31, 2023
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2004 (v1)Publication
Hard X-ray spectra in solar flares provide knowledge of the electron spectrum that results from acceleration and propagation in the solar atmosphere. However, the inference of the electron spectra from solar X-ray spectra is an ill-posed inverse problem. Here we develop and apply an enhanced regularization algorithm for this process making use...
Uploaded on: March 25, 2023 -
2005 (v1)Publication
Kontar et al. (2004) have shown how to recover mean source electron spectra F(E) in solar flares through a physical constraint regularization analysis of the bremsstrahlung photon spectra I(ε) that they produce. They emphasize the use of non-square inversion techniques, and preconditioning combined with physical properties of the spectra to...
Uploaded on: March 25, 2023 -
2012 (v1)Publication
Aims. To study the acceleration and propagation of bremsstrahlung-producing electrons in solar flares, we analyze the evolution of the flare loop size with respect to energy at a variety of times. A GOESM3.7 loop-structured flare starting around 23:55 on 2002 April 14 is studied in detail using Ramaty High Energy Solar Spectroscopic Imager...
Uploaded on: April 14, 2023 -
2009 (v1)Publication
We develop a formal procedure for the analysis of imaging spectroscopy data, i.e., remote sensing observations of the structure of a radiation source as a function of an observed parameter (e.g., radiation wavelength, frequency, or energy) and two-dimensional location in the observation plane of the instrument used. In general, imaging...
Uploaded on: April 14, 2023 -
2009 (v1)Publication
The Reuven Ramaty High Energy Solar Spectroscopic Imager (RHESSI) produces solar flare images with the finest angular and spectral resolutions ever achieved at hard X-ray energies. Because this instrument uses indirect, collimator-based imaging techniques, the "native" output of which is in the form of "visibilities" (two- dimensional spatial...
Uploaded on: April 14, 2023 -
2004 (v1)Publication
The cross-section for bremsstrahlung photon emission in solar flares is in general a function of the angle θ between the incoming electron and the outgoing photon directions. Thus the electron spectrum required to produce a given pho- ton spectrum is a function of this angle, which is related to the position of the flare on the solar disk and...
Uploaded on: April 14, 2023 -
2003 (v1)Publication
By inverting the Reuven Ramaty High Energy Solar Spectroscopic Imager (RHESSI) hard X-ray photon spectrum with the Tikhonov regularization algorithm, we infer the effective mean electron source spectrum for a time interval near the peak of the 2002 July 23 event. This inverse approach yields the smoothest electron flux spectrum consistent with...
Uploaded on: April 14, 2023 -
2007 (v1)Publication
We introduce a new method for imaging spectroscopy analysis of hard X-ray emission during solar flares. The method avoids the ''traditional'' noise-sensitive step of stacking independent images made in different count-based energy intervals. Rather, it involves regularized inversion of the count visibility spectra (i.e., the two-dimensional...
Uploaded on: March 31, 2023 -
2011 (v1)Publication
Because hard X-rays represent prompt, optically-thin, radiation from energetic electrons, they are a relatively straightforward, and hence valuable, tool in the diagnostic study of °are-accelerated electrons. The observed X-ray °ux (and polarization state) is fundamentally a convolution of the cross-section for the hard X-ray emission...
Uploaded on: March 31, 2023