Effects of the Solar Flares of 7 July 1958 Observed at Kiruna Geophysical Observatory, Sweden

Abstract

The very strong effects in the auroral zone of the solar flares of 7 July 1958 as observed at Kiruna Geophysical Observatory by means of magnetometers, an ionospheric sounder, a cosmic noise absorption receiver (riometer), oblique auroral reflection receivers, transpolar communications receivers, and cosmic ray telescopes are reported and discussed. Several remarkable features of the terrestrial disturbances were observed: 1 Extremely strong absorption became apparent a few hours after the solar flare. In spite of a linearly increasing absorption during the first seven hours after the flare no change in height or critical frequency of the F2 layer was noted during this period. 2 The SIDs reported by Pacific Observatories at the time of the flares were not observed at Kiruna although Kiruna was on the sunlit side of the earth. 3 A magnetic storm and a large decrease in the counting rate of the meson component of cosmic radiation appeared simultaneously 31 hours after the flare. 4 The maximum absorption at 27.6 Mc recorded during this period surmounted 20 decibels. DOI: 10.1111/j.2153-3490.1959.tb00037.x