Spectrophotometry of the corona and a quiescent prominence based on observations of the total solar eclipse of 7 March, 1970 in Mexico

Abstract

Slit spectrograms of a quiescent prominence and the inner corona (h⩽2.5 arc min) in the range λλ3400–7000 A (dispersion 6–10 A/mm) were obtained. From an analysis of the Stark effect on the Balmer lines (up to number 36) the electron density in the prominence n e = (7 ± 3) × 1010 cm−3 was deduced. The kinetic temperature T k and the non-thermal velocities υ t, found from a simultaneous consideration of the Balmer and metal lines, are T k ≈ 10 000 K and v t≈6 km/s. Also the emission measure of the prominence along the line-of-sight was found: ME = 1031 cm−5. In the coronal spectrum 24 coronal lines were found. Thirteen of these lines were identified and measured photometrically to get their absolute intensities, profiles and halfwidths. For nine lines the intensities as a function of the height were studied and on this basis the coronal lines were divided into a few groups. The line-of-sight and non-thermal velocities are υ r ⩽ 10 km/s and υ t≈ 25 km/s. The coronal lines originate in at least three types of regions with different temperatures. The emission measure as a function of the ionization temperature was determined. The abundances of four elements of the iron group (V, Cr, Mn, Co) were estimated. The abundances of the other elements of the same group (A, Ca, Fe, Ni), found from EUV-data, are in a good agreement with our observations. The degree of inhomogeneity in the corona was estimated: $$\overline {n_e^2 } /(\overline n _e )^2 \approx 3 - 10$$ .