Contribution of Characteristic X-rays to the Radiation of Solar Flares

Abstract

ATOMS bombarded by energetic electrons may experience ionization through the loss of a K-shell electron. Part of the subsequent rearrangement of the ion to its ground-state involves the movement of an outer (usually an L- or M-shell) electron to fill the K-shell vacancy. The energy released in this transition appears in one of two forms. Either a photon is emitted (characteristic radiation) or one or more outer electrons are expelled from the ion (the Auger process). The purpose of this communication is to point out thatcharacteristic X-rays emitted as a result of such inner-electron transitions may make an important contribution to the X-ray emission of solar flares. It is not yet known with certainty whether the radiation from flares in the λλ 1–3 Å region is predominantly of thermal^1,2 or non-thermal³ origin. The detection of the characteristic radiation of iron atoms in the X-radiation from flares would indicate that non-thermal processes are important in the production of X-rays in this wavelength range.