Open AccessV‐shaped VLF streaks recorded on DEMETER above powerful thunderstorms
Author(s) -
Parrot M.,
Inan U. S.,
Lehtinen N. G.
Publication year - 2008
Publication title -
journal of geophysical research: space physics
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.67
H-Index - 298
eISSN - 2156-2202
pISSN - 0148-0227
DOI - 10.1029/2008ja013336
Subject(s) - whistler , thunderstorm , ionosphere , geology , lightning (connector) , very low frequency , geophysics , geomagnetic latitude , altitude (triangle) , earth's magnetic field , meteorology , physics , astronomy , magnetic field , power (physics) , geometry , mathematics , quantum mechanics
We report the observation of unusual V‐shaped streaks on VLF spectra observed on the low‐altitude satellite DEMETER during its overcrossing of highly active (i.e., high lightning flash rate) thunderstorms. At ∼700 km, wave activity observed on the E‐field spectrograms at mid‐to‐low latitudes during nighttime are mainly dominated by upgoing 0+ whistlers and occasional reflected (from the other hemisphere) whistler components. Over a 3 year period, 87 events with V‐shaped streaks associated with intense and numerous 0+ whistlers in VLF range have been observed. Using the National Lightning Detection Network for cases above the North American region indicates that these V‐shaped streaks exclusively occur when DEMETER passes above intense isolated thunderstorms, with relatively high (tens per second) lightning flash activity. Using a new model of VLF propagation in the Earth‐ionosphere waveguide, and transionospheric leakage to the satellite altitude, it is shown that the funnel‐like “V” shape of the streaks is a simple consequence of the mapping to high altitude of frequency‐dependent position of mode interference nulls (and crests) within the Earth‐ionosphere waveguide.