Identification of Spectral Lines in the 500–1600 A Wavelength Range of Highly Ionized Ne, Na, Mg, Ar, K, Ca, Ti, Cr, Mn, Fe, Co, and Ni Emitted by Flares (T_e≥ 3 x 10⁶K) and Their Potential Use in Plasma Diagnostics

Abstract

On 1999 May 9 the Solar Ultraviolet Measurements of Emitted Radiation (SUMER) spectrometer on the Solar and Heliospheric Observatory (SOHO) recorded spectra from a high-temperature region located in the solar corona above the west limb. These spectra contain lines from rather less-abundant elements in solar plasmas. In this paper we present identiÐcations of the high-temperature K) Ne, (T e º 3 ] 106 Na, Mg, Ar, K, Ca, Ti, Cr, Mn, Fe, Co, and Ni lines that were detected in the 500È1600 spectral range A of SUMER. In addition, accurate wavelength measurements have been obtained with uncertainties varying between 0.015 and 0.040(1 p). Making use of the newly measured wavelengths, we derive A energy levels in the ground conÐguration of a number of highly charged ions. We present intensity ratio calculations of lines in the SUMER range that could be used to measure electron densities in hightemperature solar plasmas. We also provide emissivities for Ca XIIIÈCa XV and Fe XVIIIÈFe XXIII lines that could be used to determine emission measures and electron temperatures of high-temperature plasmas. We discuss a method for measuring elemental abundance variations in high-temperature solar plasmas using lines presented in the paper. A list of spectral lines spanning the 300È30000 wavelength A range and their branching ratios that are suitable for efficiency calibration of space-borne spectrographs is provided.

Large Doppler Shifts in X-Ray Plasma: An Explosive Start to Coronal Mass Ejection

“…SUMER is able to observe simultaneously any selected 40 Å window within its 660-1600 Å wavelength range. SUMER was in the middle of obtaining a spectral scan of the hot active region corona (described in Feldman et al 2000) when the flare erupted. During the spectral scan, the spectrometer slit was held at a fixed position while the wavelength range was stepped in increments of 20 Å .…”

Observations of the Sun at Vacuum-Ultraviolet Wavelengths from Space. Part II: Results and Interpretations

“…Temperatures above 10 MK are quite common in strong flares and lead to spectra with lines of highly ionized species extending into the X-ray range. Flare spectral observations from Skylab instruments S082A and S082B and from SUMER can be found, for instance, in Doschek et al (1975b), Dere (1978), Cohen et al (1978), and Feldman et al (2000b). A class M2 flare was observed by the S082A spectrograph in the He II lines at 25.6 nm and 30.4 nm, and Fe XV at 28.4 nm (Tousey et al 1977).…”

Mass Motions and Plasma Properties in the 107K Flare Solar Corona

“…In addition, allowed lines between levels of the second and first excited configurations in Helike ions (1s2s-1s2p) for elements between Ne and Ca are also expected in the SUMER spectral range. A detailed list of lines that were observed by SUMER and are emitted by flaring plasmas and their wavelengths and identifications is given in Curdt et al (2000) and Feldman et al (2000). Most of these lines are suitable for studies of flare temperatures and dynamics.…”

“…Figure 6 shows plasma velocities measured in a sample of coronal and flare lines observed after the flare onset. Velocities are calculated as absolute values, taking as the rest wavelengths of the flare lines the values listed in Feldman et al (2000). Positive velocities in the figure indicate redshifts, and negative velocities indicate blueshifts.…”