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Extended lateral heating of the nighttime ionosphere by ground‒based VLF transmitters
Author(s) -
Graf K. L.,
Spasojevic M.,
Marshall R. A.,
Lehtinen N. G.,
Foust F. R.,
Inan U. S.
Publication year - 2013
Publication title -
journal of geophysical research: space physics
Language(s) - English
Resource type - Journals
eISSN - 2169-9402
pISSN - 2169-9380
DOI - 10.1002/2013ja019337
Subject(s) - ionosphere , transmitter , signal (programming language) , very low frequency , scattering , physics , radio signal , incoherent scatter , electron precipitation , radio wave , computational physics , geophysics , radio frequency , optics , telecommunications , plasma , channel (broadcasting) , magnetosphere , computer science , quantum mechanics , programming language , astronomy
The effects of ground‒based very low frequency (VLF) transmitters on the lower ionosphere are investigated. Controlled modulation experiments are performed with the 21.4 kHz, 424 kW VLF transmitter NPM in Lualualei, Hawaii, and physical effects of the NPM transmissions are studied with a subionospherically propagating VLF probe signal. Observed perturbations to the probe signal are consistent neither with expectations from transmitter‒induced electron precipitation nor to off‒path scattering from a concentrated heating region near the transmitter but rather appear to be the result of scattering from extended lateral heating of the ionosphere by the NPM transmitter. A large‒scale computational modeling framework confirms theoretically that this form of ionospheric heating can account for the observed probe signal modulations, establishing that the lateral extent of ionospheric heating due to VLF transmitters is several thousand kilometers, significantly greater than previously recognized.