Earth's Magnetic Field Migration and Its Effects on HF Propagation

Propagation of radio waves in Earth's ionosphere and atmosphere critically depends on the strength and orientation of Earth's background magnetic field, due to the fact that electrons move much more readily along field lines than across them.  The background magnetic field evolves continuously, driven by currents and other processes inside the planet's molten core.  In particular, since 1990, the north magnetic pole has been migrating at an increased speed relative to its rate over most of the past century, and now moves more than 40 km/year.  However, the south magnetic pole migration is considerably slower.  The combination of these two effects has caused the global configuration of the geomagnetic field to change significantly.  We will describe the sustained drift of magnetic field line locations over the last 40 years, with an emphasis on mid-latitudes where a large number of amateur radio operations take place.  We will then provide estimates of induced changes in HF propagation over that time, using multiple models, and draw conclusions regarding the general climatology of propagation in various well used bands.