Some observed characteristics of daily minimum of an LF signal

摘要

The daily minimum (DM) of amplitude of a long distance 40 kHz radio signal propagated over a low latitude path shows seasonal variation in its time of occurrence and also in its magnitude. Later occurrence of minimum is observed in winter compared to other seasons. The level of the minimum is lowest in monsoon and highest in winter. The times of occurrence of DM are well correlated with meteorological parameters. During most of the geomagnetically active days DMs disappear.