Geomagnetic modification of the mid-latitude ionosphere: Toward a strategy for the improved forecasting of ƒ0 F 2

The reduction of maximum usable frequency (MUF) during a geomagnetic storm represents a serious hindrance to the efficient operation of HF transmission links. This paper outlines a new approach to the modeling and forecasting of ƒ₀F₂ at quiet and disturbed times. Statistical analyses of ionosonde data from the Argentine Islands (65°S) have been used to define patterns for the main phase effects of mid-latitude ionospheric storms. Extended to a number of stations, these could be incorporated into algorithms to permit the forecasting of MUF for a few hours ahead and enhance the frequency management of shortwave radio communication. Data from a complete solar cycle, 1971-1981, are used to determine the errors in the forecasts and to demonstrate that a useful advantage can be attained by this method. The root-mean-square error in ƒ₀F₂ for 90,175 samples is 15.6%, which compares favorably with those obtained using forecasts based upon quiet time values (20.4%) or the previous day's measurements (18%). Studies of error distribution with respect to local time, season, and phase of the solar cycle highlight limitations in the technique but also indicate avenues to further improvement.