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

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.