Hi, My previous post stated that the frequency varied from about 150 Hz to 1 kHz. In fact due to the weakening of the Earth's field with altitude, the frequency actually remains fairly well constrained within a range of 300-350 Hz over the altitude interval where the effect would work.
Below 700 km there isn't much of the van Allen belts to speak of, and beyond about 1000 km one gets beyond 1 wavelength, but only slowly. By 2000 km the ratio is 1.4 and the frequency has dropped to about 200 Hz. Regards, Robin van Spaandonk The shrub is a plant.
