Radio Science

The relative daily variability of f0F2 and hmF2 and their implications for HF radio propagation


  • C. M. Rush,

  • D. Miller,

  • J. Gibbs


The effect of the daily variability of f0F2 and hmF2 on the propagation conditions of an HF communication circuit has been studied in an empirical manner. The daily variability of f0F2 and hmF2 was determined by a detailed statistical analysis and the results were incorporated into a three-dimensional ionospheric model and ray-tracing program. During hours surrounding local noon, the relative day-to-day changes seen in both f0F2 and hmF2 are comparable while at all other times the daily variability of f0F2 substantially exceeds that of hmF2. In terms of HF propagation changes resulting from these changes in f0F2 and hmF2, it can be concluded that a knowledge of the critical frequency of the F2 region is much more important than that of hmF2 if account must be taken of the propagation changes resulting from the normal daily variability of the F2 region.