A correlation between Balmer and soft X-ray emission from stellar andsolar flares.

Abstract

Simultaneous optical spectroscopy and X-ray monitoring of stellar and solar flares shows that a well-defined linear correlation exists between the integrated Hγ and soft X-ray flux that extends over four orders of magnitude. The existence of this relationship implies a direct proportionality between the emission from the cooler and denser regions (T ≈ 10⁴K) responsible for Balmer lines and the emission from the hot plasma (T ≈ 10⁷K) responsible for soft X-rays. The consequences are considered for (a) several models which have been proposed for solar flares, and (b) the suggestion that the Balmer emission results from irradiation by soft X-rays.