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The Solar Flare 4-10 keV X-ray Spectrum View all project descriptions by submitter

Ken Phillips Submitted: 22-Aug-2003 14:55

The 4-10 keV solar flare spectrum includes highly excited lines of stripped Ca, Fe, and Ni ions as well as a continuum steeply falling with energy. Groups of lines at ~7keV and ~8keV, observed during flares by RHESSI and which I call the Fe-line and Fe/Ni-line features, are formed mostly of Fe lines but with Ni lines contributing to the ~8keV feature. I have investigated these lines from a theoretical point of view, using atomic data to find diagnostic potential for application to RHESSI data. Thus, I point out possible temperature indicators of these line features -- the peak or centroid energies of the Fe-line feature, the line ratio of the Fe-line to the Fe/Ni-line features, and the equivalent width of the Fe-line feature. The equivalent width is by far the most sensitive to temperature. However, results will be confused if, as is commonly believed, the abundance of Fe varies from flare to flare, even during the course of a single flare. With temperature determined from the thermal continuum, the Fe-line feature becomes a diagnostic of the Fe abundance in flare plasmas. The results I have obtained are of interest for other hot plasmas in coronal ionization equilibrium such as stellar flare plasmas, hot gas in galaxies, and older supernova remnants. I have written up this work as a preprint. This is available from my web site, and clicking on to the postscript file (approx. 1MB long).

Participants: Ken Phillips

Project Status: Work completed and paper submitted to ApJ Go to main RHESSI project descriptions page  Evidence for the Formation of Large-Scale Current Sheets  Edit Entry  Submitter's Homepage

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