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The CHIANTI atomic database contains atomic energy levels, wavelengths, radia-tive transition probabilities and electron excitation data for a large number of ions of astrophysical interest. Version 4 has been released, and proton excitation data is now included, principally for ground configuration levels that are close in energy. The fitting procedure for(More)
Quiet Sun and active region spectra from the Hinode/EIS instrument are presented , and the strongest lines from different temperature regions discussed. A list of emission lines recommended to be included in EIS observation studies is presented based on analysis of blending and diagnostic potential using the CHIANTI atomic database. In addition we identify(More)
The frequency distribution of the extreme ultraviolet (EUV) emission line intensities in the quiet Sun has in the past often been modelled using two Gaussians. This gives adequate fits to observed distributions of average statistical significance. In this paper we test this and other distribution functions against observed distributions with exceptional(More)
The SUMER (Solar Ultraviolet Measurements of Emitted Radiation) instrument on SOHO (Solar and Helio-spheric Observatory) provides an opportunity to observe and study the solar transition region with high spatial and spectral resolution. We present new evidence to confirm that the emission from the quiet Sun at 2 × 10 5 K is dominated by cool loop-like fine(More)
We study the Differential Emission Measure distribution of two pairs of active and quiet regions of the solar atmosphere , observed by CDS Normal Incidence Spectrometer (NIS) on SOHO, and investigate their temperature and density structure. Use is made of the Arcetri Method (Landi & Landini 1997) for DEM and density diagnostics. An iterative method for(More)
By examining solar observations using the Normal Incidence Spectrometer (NIS) within the Coronal Diagnostic Spectrometer (CDS) on board SOHO, an isothermal region in the lower solar corona was chosen for analysis by three different temperature diagnostic techniques. These techniques are the line-ratio method, the Differential Emission Measure and the(More)