Non-thermal velocities in flare plasmas

Abstract

The analysis of the profile and intensity of the soft X-ray lines formed in the wavelength range from 1.8 Angstroms to 20 Angstroms, observed with the Soft X-ray Polychromator of the Solar Maximum Mission (SMM), shows that solar flare plasmas are characterized by non-thermal velocities. Flare plasmas in general consist of two components at different temperatures: 5-8 10^6 K and 16-25 10^6 K, respectively. The non-thermal mass motions observed in the hotter component are affected by higher velocities and they depend on temperature in a way which is varying with the flare phase. The results obtained for flare plasmas are consistent with the functional relationship between temperature and non-thermal velocity derived for the lower temperature regimes existing in the upper chromosphere, in the transition region and in the non-flaring corona.