2018-11-08, 07:00
Hi Mike and Cutty, During the night time there is no "D or E Layer," only "F" Layer.
During the Daytime it is possible, due to ionisation density variations, to have Sky wave signals at VLF and ELF from all three and possibly four ionised layers ("D, E, F, or F1 and/or F2,) simultaneously or at varying intervals.
Theoretically it is possible to have Sky wave propagation without contact with the ground for considerable distances, especially where there is a transition from day to night, night to day, Chordal Hop and Grey line effects.
Neither the Ionosphere nor the Earth are smooth flat surfaces, nor perfect curves, so there are various forms of Diffraction, Refraction, Absorption and Scattering etc., and other natural phenomenon, (Aurora? Non Great circle paths, due to ground wave becoming sky wave or vice-versa) that may account for fading or enhanced propagation at varying distances and for the different frequencies in the bandwidth of a stroke of lightning.
There possibly could also be considerable time differences for the same stroke, if there is long path and short path propagation, at the same time, or multiple around the world paths, as in near antipodal situations.
While this probably does not make things much clearer in regards to our case, there have been many studies done with ELF propagation for submarines.
Kindest regards,
Brian.
During the Daytime it is possible, due to ionisation density variations, to have Sky wave signals at VLF and ELF from all three and possibly four ionised layers ("D, E, F, or F1 and/or F2,) simultaneously or at varying intervals.
Theoretically it is possible to have Sky wave propagation without contact with the ground for considerable distances, especially where there is a transition from day to night, night to day, Chordal Hop and Grey line effects.
Neither the Ionosphere nor the Earth are smooth flat surfaces, nor perfect curves, so there are various forms of Diffraction, Refraction, Absorption and Scattering etc., and other natural phenomenon, (Aurora? Non Great circle paths, due to ground wave becoming sky wave or vice-versa) that may account for fading or enhanced propagation at varying distances and for the different frequencies in the bandwidth of a stroke of lightning.
There possibly could also be considerable time differences for the same stroke, if there is long path and short path propagation, at the same time, or multiple around the world paths, as in near antipodal situations.
While this probably does not make things much clearer in regards to our case, there have been many studies done with ELF propagation for submarines.
Kindest regards,
Brian.
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