On the global behaviour of the day-to-day MUF variation Original Research Article

Using data from more than a hundred ionospheric stations spread worldwide, day-to-day variations with location and time of the conventional maximum usable frequency (MUF) decile values are investigated. New bounds of day-to-day MUF variability are calculated and compared with reference figures currently used by radio users. An hourly-daily validation process shows a clear improvement of spatial bias and model accuracy. A significant dependence on longitude is revealed that might be introduced into future specifications.