Propagation modes of whistlers received aboard satellites over Europe

The propagation modes of whistlers over Europe are investigated using polar orbiting satellite detectors. Two kinds of constant dispersion whistlers were received. In midlatitudes, they are characterized by diffuse multiple components with echoes and are propagated from L = 3.5 to L = 2.0. At low latitudes, they have a pure component followed by a discrete reflected component which occurs at latitudes lower than 1.8. Prolongitudinal and partly ducted propagation modes are considered to be the cause of quasi-permanent transfer of VLF (whistler) energy from one hemisphere to another. A better understanding of the morphology of the ducts is expected to provide an explanation for the trapping and leakage of waves as a function of VLF frequency.