Astronomy and Astrophysics – Astrophysics
Scientific paper
Jan 1995
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=1995a%26a...293..577s&link_type=abstract
Astronomy and Astrophysics 293, 577-585 (1995)
Astronomy and Astrophysics
Astrophysics
21
Sun: X-Rays, Atomic Data
Scientific paper
The most temporally complete set of solar soft X-ray flux measurements available at the present time is contained in the archive record of 0.5-4A and 1-8A broad-band ion chamber observations from the Geostationary Operational Environmental Satellite (GOES) spacecraft. The archive contains a nearly continuous record of the soft X-ray observations since 1974. Physical analyses of these measurements are often carried out under the isothermal plasma approximation. In this paper we present calculations of the ion chamber current ratio - temperature relationship for soft X-ray detectors onboard four GOES satellites whose data comprise the main historical X-ray record. The present calculations update and extend results obtained by Thomas et al. for the GOES-1 detectors. Our analysis has been performed using two modern sets of theoretical X-ray spectra calculated by Mewe et al. and by Raymond. Comparisons of the detector responses obtained for each of the above theoretical spectra are performed. These analyses indicate that both Mewe et al. and Raymond X-ray spectra provide mutually consistent interpretations of measured GOES X-ray data. Deficiencies in the physical interpretation of a mixture of low-temperature (active region) and high-temperature (flare) plasmas resulting from the isothermal approximation are pointed out and discussed. It is shown that the so called flare "thermodynamic measure", defined here and derived from GOES measurements, compares well with co-temporal values obtained from the analysis of the Yohkoh BCS spectra. It is proposed that the presented method of a thermodynamic measure analysis may be useful in the interpretation of global flare thermodynamics.
Garcia Howard A.
Sylwester Barbara
Sylwester Janusz
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