Geophysical variations at Sodankyla during a geomagnetic storm, 17-18 December 1971

Extremely bright auroras could be seen at Sodankyla and throughout Scandinavia on the night of 17 - 18 December 1971. A detailed study was undertaken of the geophysical phenomena observed at Sodankyla during this storm. The all-sky camera records, magnetograms, riometer records, and ionograms obtained at Sodankyla were analyzed in detail and published data from neighboring stations were examined to elucidate the extent of the geomagnetic storm and its effects on the upper atmosphere. It was noted that the occurrence of active auroral forms overhead was invariably followed by an increase of riometer absorption, and by changes in sporadic E. The analysis of this storm indicates that at least three substorms occurred during the main phase of the storm.