Cheltenham Magnetic Observatory October to December, 1947

(Latitude 38° 44′.0 N.; Longitude 76° 50′.5 or 5h 07m.4 W. of Gr.)October 9–16—A prolonged period of moderate magnetic disturbance was ushered in with long‐period oscillations, at 01h GMT, October 9. Short‐period oscillations began in all three elements at 11h, October 9, and continued until 19h, October 11, with the exception of a few hours. The remainder of the storm continued with irregular oscillations. Between 00h 09m and 0lh 15m, October 10, D rapidly decreased 32′, and reached its extreme easterly value at 01h 58m. Z decreased 185 γ from 00h 57m to 09h 00m, October 10, where it reached its minimum value. H reached its minimum value of 18,099 γ at 16h 09m, October 11. From 0lh 44m to 02h 26m, October 12, oscillations of large amplitude occurred in all three elements, and double peaks occurred in D and H. Minor disturbance continued until the end of the storm at 17h, October 16, The highest K‐sum of 35 occurred on October 10, with a 6 being recorded for the first three‐hour interval.