Identification of a solar X-ray source using D layer ionization behavior during an eclipse

Abstract

Semi-quantitative reports of shortwave radio reception during the 12 November 1966 total solar eclipse have been used to determine the characteristics of a major source of D layer ionization. An effective electron depletion coefficient of 1.2 × 10−2 sec−1 was found empirically and used to reduce the data. Analysis of the radio absorption shows the source was located near heliographic coordinates, B = +7°, L = 340° and was probably less than 0′.5 of arc in diameter. At the time of the eclipse, the source accounted for 40% of the radio absorption on a single, vertical pass through the D layer. Preoccultation behavior of the signal strength is interpreted by assuming a portion of the source X-ray flux was reflected at grazing incidence from the limb of moon. For point sources, such reflections have specific chromatic characteristics which were used to derive a crude source spectrum in the 3–140 A range. X-ray absorption edges of N, O, Na, Be, and possible Mg, Ar, Ne, Ca, and K arising from the terrestrial atmosphere have been identified. A source temperature approximately twice that of the rest of the corona is indicated.