MINIMUF-85: An Improved HF MUF Prediction Algorithm

摘要

An improved version of MINIMUF-3.5, called MINIMUF-85, was developed to predict accurate maximum usable frequencies (MUFs) under conditions of anomalously high sunspot numbers; also, to predict values of fOF2 suitable for raytracing applications, to predict m3000 factor values usable for determining the mirror height of reflection for oblique incidence propagation, and to predict accurate MUFs for paths having a portion of the path in the polar region. This version includes sunspot number curve, reducing the error in predicted MUF values under very high sunspot number dependence in both FOF2 and the M-factor calculations and provides a natural saturation in the MUF versus sunspot number conditions. The polar and nonpolar FOF2 models are welded together by means of a folding function. MINIMUF-85 predicts 0.14 MHz low on average and has an error of 4.08 MHz; whereas; MINIMUF-3.5 had a bias of 0.51 MHz low and an 4.33 rms error when compared on the same 39 paths. The subjects of the choice of solar index for forecasting purposes, of sounder updating, of the effects of the underlying layers on both M-factor estimation and determination of the mirror height of reflection, and of future improvements in MINIMUF are discussed.