34th Solar Physics Division Meeting, June 2003
Session 16 Flares and Microflares II
Poster, Wednesday, June 18, 2003, 3:30-5:00pm, Mezzanine

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[16.22] Solar Flare Abundances of Potassium, Argon, and Sulphur

K.J.H. Phillips (NRC Senior Research Associate, Goddard Space Flight Center), J. Sylwester, B. Sylwester (Space Research Center, Polish Academy of Sciences), E. Landi (Artep, Inc., Ellicott City, MD and US Naval Research Laboratory)

The absolute coronal abundances of potassium, argon, and sulphur are determined from X-ray solar flare spectra using the RESIK bent crystal spectrometer on the Coronas-F space observatory. A differential emission measure of the form exp(-\alpha Te) was found to be appropriate for describing the fluxes of the lines due to K XVIII (\lambda 3.53Å), Ar XVIII (\lambda 3.73Å), Ar XVII (\lambda 3.95Å), S XV (\lambda\lambda 4.09, 4.30Å), Si XIV (\lambda 5.22Å), and Si XIII (\lambda\lambda 5.40, 5.68Å) which are observed by RESIK over a period of several hours in four long-duration flares. The continuum in two of the four RESIK channels appears to be uncontaminated by crystal fluorescence or other instrumental effects, allowing abundances relative to H to be determined. We estimate the following abundances relative to H: [K/H] = 4.7 X 10-7; [S/H] = 2.9 X 10-5; [Ar/H] = 2.0 X 10-6. These values agree with a pattern that depends on the first ionization potential (FIP) of an element in which the coronal abundances of low-FIP elements (like K) are enhanced over their photospheric abundances by a factor 3 and high-FIP elements (like Ar) are depleted by a factor 2. The coronal abundance of sulphur (medium-FIP) is slightly enhanced (factor of 1.5) compared with its photospheric abundance. The exponential temperature dependence of the differential emission measure is applied to simultaneous X-ray data from the RHESSI mission which sees a thermal spectrum (continuum plus Fe lines at 6.7 keV) for some of these flares. Results of this will be discussed.

We acknowledge support for this research from the National Research Council (KJHP), Polish Committee for Scientific Research (JS, BS), and from the Office of Naval Research (EL).

The author(s) of this abstract have provided an email address for comments about the abstract: phillips@stars.gsfc.nasa.gov

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