Auroral-E mode oblique HF propagation and its dependence on auroral oval position

Abstract

The characteristics of 25.5 MHz one-hop mode propagation on a 950 km Alaskan path, over a one-year period shortly after sunspot maximum are presented as a function of the "planetary geomagnetic index-Kp". The location of the E-region reflection point lies within the auroral oval for 3<Kp<5, and the specific behavior of the signal is related to auroral oval phenomena such as substorms, geomagnetic storms, and the "harang discontinuity". The auroral electrojet location, with respect to the path midpoint, is also of considerable importance. The 75 watt CW beacon has been in continuous operation since mid-August 1991 on a frequency of 25.545 MHz. The signal is characterized by "bursty" behavior lasting from about one minute to over three hours, with an average duration of eleven minutes. The authors believe that this is the first quantitative demonstration of the "forward propagation characteristics" of a one- or two-hop E-propagation path inside and parallel to the auroral oval on a frequency at the high end of the HF band.