The Expected behaviour of the Hydrogen Lyman Lines in Solar Flares

Extract

While the merging of the higher lines of the Balmer series emitted by solar flares is solely determined by the electron density, the merging of the high Lyman lines is determined both by the electron density, through Stark broadening of the line absorption coefficient, and by the total number of hydrogen atoms in the flare, through the effect of self-absorption. Preliminary results of model calculations indicate that two or more intensity measurements, each midway between two consecutive lines of the Lyman series (lines 3–4, 4–5, 5–6) allow the determination of the column density of hydrogen atoms in the ground state provided that the electron density is known. One can believe that in between the Lyman lines only the flare elements contribute to the measured intensity since excited interflare matter of much lower electron density produces line profiles of substantially smaller width. Thus the data in between the lines can be reasonably compared to the N_e values deduced from high members of the Balmer series.