The potential for plasma diagnostics from stellar extreme-ultraviolet observations

Abstract

Based on 20 years of solar investigations, the extreme-ultraviolet (EUV) spectrum in the range 50-500 Â has proved to be extraordinarily rich in providing information on the density, temperature, and element abundances of the plasma in the Sun's chromosphere and corona, especially when observed with high spectral resolution. With the advent of new instruments using multilayer optics and CCD detectors, similar measurements with a spectral resolution of about 10,000 become possible on large numbers of nearby stars, in contrast with lower resolution instruments now scheduled for space flight. In this paper we provide a description of the lines from the most abundant ions in this spectral region that have special diagnostic significance. These lines are from plasmas in the temperature range from 10 5 to 10 7 K. We demonstrate their utility for determining temperature, density, and abundances. We also describe an objective grating spectrometer, based on the Naval Research Laboratory Skylab slitless spectrograph, for making celestial observations in the EUV spectral region with high spectral resolution.

Transition Region Abundance Measurements During Impulsive Heating Events

“…We carry out these calculations assuming both photospheric abundances (Caffau et al 2011) and our approximation to the abundances of Feldman et al (1992) that have the low-FIP elements enriched by a factor of 4 and the values for the high-FIP elements left at their photospheric values. The EM loci curves can be interpreted as an approximate envelope to the differential EM distribution, which is the best-fit solution to the ill-posed integral equation …”

“…The photospheric abundances (A p ) are those tabulated by Caffau et al (2011). For coronal abundances (A c ) we approximate the tabulation of Feldman et al (1992) by scaling the photospheric abundances of the low-FIP elements by a factor of 4 and leaving the abundances of the high-FIP elements unchanged. Because of telemetry constraints, EIS observations are usually structured such that only a subset of the full detector exposures are read out and telemetered to the ground.…”

Coronal-Temperature-Diagnostic Capability of the Hinode/X-Ray Telescope Based on Self-Consistent Calibration

“…The differences between our estimate and that of Kano and Tsuneta (1995) are the adopted solar spectrum database and its units. We adopt solar photon-number spectra in units of [photon cm −2 sec −1 sr −1Å−1 ] from the CHIANTI atomic database version 6.0.1 (Dere et al, 1997;: which is the latest version, when we analyzed) with ionization equilibrium from chianti.ioneq (Dere, 2007) and abundance from sun coronal ext.abund (Feldman et al, 1992;Landi, Feldman, and Dere, 2002), while Kano and Tsuneta (1995) used solar emissivity [erg cm −2 sec −1 sr −1Å−1 ] from Mewe's spectral data (Mewe, Gronenschild, and van den Oord, 1985;Mewe, Lemen, and van den Oord, 1986 First, we derive two conversion factors as preparation for the error estimate. When XRT observes an isothermal corona at a temperature of T and a volume emission measure of V EM with p pixels of the CCD and t [sec] exposure, the incident photon number in a range of wavelength from λ to λ + dλ is…”

Observations and modeling of the ultraviolet emission of solar flares

“…The silicon abundances are A(Si) = 7.53 ± 0.08. Carbon abundances (A(C) = 8.59) were taken from Feldman et al (1992). For this conditions we calculated synthetic UV spectra in ranges corresponding to both IRIS FUV channels.…”