On cosmic‐ray effects associated with magnetic storms

Abstract

Evidence indicates that the storm‐time field of some magnetic storms causes world‐wide changes of several per cent in cosmic‐ray intensity. That other magnetic storms of equal intensity at the Earth's surface occur with no appreciable cosmic‐ray effects definitely indicates that the entire current‐system for the storm‐time field of both types of storms can not be located at the same distance above the Earth. In particular, the possibility that the current‐systems responsible for the two types of storms both lie within the Earth's atmosphere appears remote. Assuming the current‐system for the storm‐time field of both types of storms to consist of a ring concentric with the Earth in the geomagnetic equatorial plane, magnetic data are analyzed to determine whether the radius of the assumed ring is, as would be expected, greater for magnetic storms which affect cosmic‐ray intensity. Although the analysis is not conclusive on this point, the results satisfy a necessary condition for the existence of such a ring‐current. The occurrence of aurora in temperate latitudes during most of the magnetic storms which affected cosmic‐ray intensity is interpreted, after Störmer, to indicate the existence of such ring‐currents. The percentage‐changes in cosmic‐ray intensity during magnetic storms is within the observational uncertainty the same at geomagnetic latitudes 50°.1 north and 0°.6 south. The significant correlation between changes in daily means of cosmic‐ray intensity, for two stations separated 50° in latitude, probably results from the same mechanism responsible for the magnetic‐storm effect.