On quiet-day maximum minimum and range inH

Summary

Using geomagnetic horizontal intensity hourly mean values of Alibag for international quiet days for the years 1934 to 1953, split into two 10-year segments, the dependence of diurnal range on the maximum and minimum values is examined after elimination of secular trend in the data. Identical results are obtained for the two 10-year periods. The maximum value occures on 85% of days near local noon while the minimum value has two preferences, one for 05 LT and the other for 19 to 24 LT. Though the correlation coefficient (CC) of+0.7 is much higher for range and maximum hourly value, the scatter observed is very large, which is attributed mosly to fluctuations is base-level from one quiet-day to another. On correcting for these the scatter is much reduced and the CC registers an improvement to+0.95. Some remanent scatter, however, persits. This as well as the very small but statistically significant negative CC observed for range and minimum hourly value stress the influence of the minimum value on range even on quiet days.