Patterns of X-ray line emission variability as observed by the RESIK Bragg spectrometer
Abstract
RESIK is a unique Bragg bent crystal spectrometer operating continuously since August 2001. By now, it has collected ~10 GB of solar flare and active region spectra in a very much unexplored spectral region between 3.2 Å and 6.1 Å. In this paper we present a number of representative observations covering periods of various solar activity: from the most active level (M+ flares) to exceptionally quiet corona. We present also a tentative list of the spectral features observed. In the wavelength range observed by RESIK there are a number of strong emission lines corresponding to H- and He-like resonance transitions of Si, S, Ar and K ions. These lines are formed by thermal plasma of temperature between 5 and 50 MK, and therefore their analysis reveal the distribution of hot plasma over this interval. RESIK sees lines from a number of different elements, so it is possible to do abundance analyses. The elements concerned have a wide range of first ionisation potentials (FIPs) so it has been possible to examine the dependence of coronal or flare abundances on FIP. We have observed substantial variations of the K/Ar line ratio, and respective line/continuum ratios, which can be best explained by allowing for changes in the chemical composition of the coronal plasma
- Publication:
-
Solar Variability as an Input to the Earth's Environment
- Pub Date:
- September 2003
- Bibcode:
- 2003ESASP.535..733S
- Keywords:
-
- Solar Physics;
- X-Rays;
- Spectra;
- Instruments: RESIK