Results of an investigation to detect an inter‐solar cloud of charged particles during magnetic storms

Abstract

Although it is commonly assumed that terrestrial magnetic storms are caused by streams of charged particles ejected from sunspots passing across the lines of force of the Earth's magnetic field, actually no direct observational evidence for such phenomenon exists.The suggestion was first made by S. CHAPMAN [Mon. Not. R. Astron. Soc, v. 89, p. 456, 1929; see also Geomagnetism, v. 2, p. 804, 1940] 15 years ago and discussed again more recently that such a stream might be detected by comparing selected regions of the solar spectrum during magnetic disturbance with the same region during magnetic calm. For if the atoms composing the stream are of the same kind and in the same state of excitation as those that produce the FRAUNHOFER lines, after ejection they should continue to absorb but on the violet side of the normal lines. This absorption will depend upon the intensity of the stream, the velocities of the particles, the geometrical relationship among the Earth, Sun, and stream at the time, and would doubtless be different for different storms.