This is not a scientific journal article – rather it is an educational resource (relying on widely agreed upon sources) – for people who want to understand what I am suggesting.
Please read Part One if you haven’t done so.
As a 20-year teacher of physics, I was surprised I had never been taught about geomagnetic conjugates. If you put paper over a bar magnet and then sprinkle iron filings over it, you can see the magnetic lines of force. Each point on one pole of the magnet is connected to another point on the other pole of the magnet. This other point is called the “magnetic conjugate”. Well, the Earth is a big magnet, and the exact same thing applies: wherever you are in your hemisphere on the planet, you are magnetically connected to a specific place in the opposite hemisphere. A physical demonstration of this came when scientists used the HAARP facility in Alaska to make a focused blast on the ionosphere with a high frequency wave. This wave created a secondary VLF radio disturbance which ran at the speed of light up the magnetic force lines way up into space, and then landing a few seconds later at a buoy floating at the geomagnetic conjugate point in the Southern Ocean, located between New Zealand and Antarctica.
In other words, a large VLF signal anywhere on Earth creates a mirror signal at its geomagnetic conjugate point. This adds yet another layer of VLF energy at various locations on Earth, interacting with each other, and creating unpredictable interference patterns of varying intensity. My current working theory is that the world Hum is a biological reaction to interaction between tissue and pulsed radio frequencies between 3 kHz and 30 kHz; that is, the VLF radio band. A full statement of that theory can be found here.
The propagation of VLF radio signals is of course further complicated because of mountain ranges, ice pack, and possibly other geographical features. And of course don’t forget the ground wave, the sky wave, and the line of sight wave, as described in Part One. If you need a review of EM basics, look at this.
At some point I need a radio engineer to comment on whether basic VLF receivers can in fact detect if one is, for example, standing at a radio antinode or otherwise, and whether instruments can indicate if one is experiencing pulsed (or roughly modulated) VLF signals.