Balloon observations of auroral-zone X rays

A series of balloon flights launched from the vicinity of College, Alaska, during June and July 1960 show that auroral-zone X rays are detectable with Geiger counters approximately 10 per cent of the time at pressure altitudes in the range 10–15 mb. The results of these flights indicate that the daily flux of electrons with energies greater than 50 kev over the auroral zone is 6×1010 particles/cm2. Late in a magnetic storm that started with a sudden commencement at 1701 UT on July 14, 1960, the average electron influx exceeded the daily rate by more than a factor of 25.