Rocket Observation of X-Ray Emission in a Solar Flare

Abstract

FROM a dozen rocket flights scattered over the past seven years, we have obtained measurements of solar X-rays and far ultra-violet light that ionize the atmosphere above 70 km.¹. These experiments revealed the emissions of a ‘quiet’ sun, since none of the flights chanced to coincide with a solar flare. Briefly summarized, the results showed that the sun normally radiates sufficient X-ray energy between 10 A. and 100 A. to account for the E-region (100–140 km.). When coronal green- and red-line activity was high, X-ray intensities were observed to be correspondingly high and included wave-lengths shorter than 10 A. In the ultra-violet, the most prominent emission line observed in the solar spectrum was the Lyman α-line of hydrogen at 1216 A. This one emission line accounted for normal D-region ionization between 70 and 90 km. Within this narrow altitude-range of the ionosphere occur nearly all the effects that come under the heading of ‘sudden ionospheric disturbances’ (S.I.D.).