General Guidelines Concerning Correlation of Propagation Indices to Actual HF Propagation Conditions

These propagation indices “interpretations” are the intellectual property of NZ4O.
Copyright 1988-2012 by Thomas F. Giella, NZ4O, all rights reserved.

  1. Dropping geomagnetic field indices numbers are better, Kp of 0 best.
  2. A daily sunspot number of 150 or higher, 200 or higher best.
  3. A daily sunspot number of greater than 100 for routine stable formation of the E Valley/F Layer ducting mechanism.
  4. Previous 24 hour Ap index under 10, fewer than 7 for several days consecutively are best.
  5. Previous 3 hours Kp index fewer than 3 for mid latitude paths, fewer than 2 for high latitude paths, 0 for several days consecutively is best.
  6. Energetic protons no greater than 10 MeV (10+0).
  7. Background x-ray flux levels greater than B1 for several days consecutively, greater than C1 best.
  8. No current STRATWARM alert.
  9. Interplanetary magnetic field (IMF) Bz with a (positive number) sign, indicates a lesser chance of high latitude path aurora absorption/unpredictable refraction or scattering of medium frequency RF signals, when the Kp is above 3.
  10. A -20 or better towards a positive number Dst index during the recovery time after a geomagnetic storm, as related to the equatorial ring current. A positive number is best.
  11. Rising positive T index number. The T Index tracks with the F2 layer critical frequency (foF2) and sunspot number (SSN) and indicates the capability of the F2 layer to refract RF signals.