EUV Spectra of the Full Solar Disk: Analysis and Results of the Cosmic Hot Interstellar Plasma Spectrometer (CHIPS)
arXiv:1007.2439 · doi:10.1007/s11207-010-9591-7
Abstract
We analyze EUV spectra of the full solar disk from the Cosmic Hot Interstellar Plasma Spectrometer (CHIPS) spanning a period of two years. The observations were obtained via a fortuitous off-axis light path in the 140 -- 270 Angstrom passband. The general appearance of the spectra remained relatively stable over the two-year time period, but did show significant variations of up to 25% between two sets of Fe lines that show peak emission at 1 MK and 2 MK. The variations occur at a measured period of 27.2 days and are caused by regions of hotter and cooler plasma rotating into, and out of, the field of view. The CHIANTI spectral code is employed to determine plasma temperatures, densities, and emission measures. A set of five isothermal plasmas fit the full disk spectra well. A 1 -- 2 MK plasma of Fe contributes 85% of the total emission in the CHIPS passband. The standard Differential Emission Measures (DEMs) supplied with the CHIANTI package do not fit the CHIPS spectra well as they over-predict emission at temperatures below log(T) = 6.0 and above log(T) = 6.3. The results are important for cross-calibrating TIMED, SORCE, SOHO/EIT, and CDS/GIS, as well as the recently launched Solar Dynamics Observatory.
arXiv comment27 Pages, 13 Figures
References in corpus (5)
- Ionization balance for optically thin plasmas: rate coefficients for all atoms and ions of the elements H to Ni
- High precision density measurements in the solar corona: I. Analysis methods and results for Fe XII and Fe XIII
- Observations of Active Region Loops with the EUV Imaging Spectrometer on Hinode
- Observations of Diffuse EUV Emission with the Cosmic Hot Interstellar Plasma Spectrometer (CHIPS)
- A Search for EUV Emission from Comets with the Cosmic Hot Interstellar Plasma Spectrometer (CHIPS)