On the localization, size and structure of the regions of the X-ray flares on the Sun

Abstract

With the use of X-ray heliographs carried by the satellites 'Cosmos-166' and 'Cosmos-230' the height of an X-ray flare was found to be about 20-25 000 kin. The regions of the X-ray flares possess a filamentary structure which, during the development of the flares, shows spatial changings with speeds up to 107 cm/sec.

Spectra of solar flares from 8.5 � to 16 �

“…This result, which holds for all of the large flares we have examined, contradicts expectations of densities in flares based on the high electron densities determined from the heliumlike ions (Freeman et al, 1971 ;Neupert, 1971), and is consistent with the lower densities inferred by others, e.g., Beigman et al (1969), Vaiana (1972).…”

Solar Flare X-Ray Measurements and Their Relation to Microwave Bursts

“…Neither of the two last-mentioned reports refer to the bright points found by Beigman et al (1969). However, comparison of hard X-ray time profiles with series of Ha filtergrams has led De Jager (1967) and Zirin and coworkers (Vorpahl and Zirin, 1970;Zirin et al, 1971;Vorpahl, 1972) to conclude that the Ha features that occur simultaneously with the hard X-ray burst are bright knots, often referred to as 'flare kernels', with a diameter of 5" to 10" located near, to within 10", the magnetic neutral line (Vorpahl, 1972).…”

“…1'. For the wavelength region between 1 and 10 A observations have been made with two crossed Soller-type collimators on board the cosmos 166 and 230, flown in 1967 (June 16-September 11) and 1968 (February 5-November 1) respectively (Beigman et al, 1969(Beigman et al, , 1971. The resolution of these collimators was about 15".…”

On the behaviour of the hydrogen Lyman series in flares

“…Limb observations, which always correspond to heights above 5000 km, and often greater than 10000 kin, lead to T e values up to 15000K. Above this height a very steep rise in temperature must occur, since a temperature of the order of 10 v corresponds to the thermal X-ray flare emission which seems to concentrate on heights of 20000 to 25 000 km (Beigman et al, 1969;Friedman, 1969). There are indications that the lowest Te values are found for flare regions, which, when located close to the solar limb, show a facula-like continuous emission in the optical spectral region, and one can suppose that these regions are situated very low in the chromosphere (Svestka, 1966).…”