Extreme Ultraviolet Spectra of Solar Flares From the Extreme Ultraviolet Spectroheliograph Spirit Onboard the Coronas-F Satellite

Abstract

We present detailed EUV spectra of 4 large solar flares: M5.6, X1.3, X3.4, and X17 classes in the spectral ranges 176-207Å and 280-330Å. These spectra were obtained by the slitless spectroheliograph SPIRIT aboard the CORONAS-F satellite. To our knowledge these are the first detailed EUV spectra of large flares obtained with spectral resolution of ∼ 0.1Å. We performed a comprehensive analysis of the obtained spectra and provide identification of the observed spectral lines. The identification was performed based on the calculation of synthetic spectra (CHIANTI database was used), with simultaneous calculations of DEM and density of the emitting plasma. More than 50 intense lines are present in the spectra that correspond to a temperature range of T = 0.5 − 16 MK; most of the lines belong to Fe, Ni, Ca, Mg, Si ions. In all the considered flares intense hot lines from Ca XVII, Ca XVIII, Fe XX, Fe XXII, and Fe XXIV are observed. The calculated DEMs have a peak at T ∼ 10 MK. The densities were determined using Fe XI-Fe XIII lines and averaged 6.5 × 10 9 cm −3 . We also discuss the identification, accuracy and major discrepancies of the spectral line intensity prediction. Subject headings: Sun: activity -Sun: flare -Sun: UV radiation 280 290 300 310 320 330 λ, A 0.000 0.001 0.002 0.003 0.004 0.005 Intensity, erg/cm2/s/A

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