Ionospheric very low frequency transmitter

Research output: Contribution to journalArticle

Abstract

The theme of this paper is to establish a reliable ionospheric very low frequency (VLF) transmitter, which is also broad band. Two approaches are studied that generate VLF waves in the ionosphere. The first, classic approach employs a ground-based HF heater to directly modulate the high latitude ionospheric, or auroral electrojet. In the classic approach, the intensity-modulated HF heater induces an alternating current in the electrojet, which serves as a virtual antenna to transmit VLF waves. The spatial and temporal variations of the electrojet impact the reliability of the classic approach. The second, beat-wave approach also employs a ground-based HF heater; however, in this approach, the heater operates in a continuous wave mode at two HF frequencies separated by the desired VLF frequency. Theories for both approaches are formulated, calculations performed with numerical model simulations, and the calculations are compared to experimental results. Theory for the classic approach shows that an HF heater wave, intensity-modulated at VLF, modulates the electron temperature dependent electrical conductivity of the ionospheric electrojet, which, in turn, induces an ac electrojet current. Thus, the electrojet becomes a virtual VLF antenna. The numerical results show that the radiation intensity of the modulated electrojet decreases with an increase in VLF radiation frequency. Theory for the beat wave approach shows that the VLF radiation intensity depends upon the HF heater intensity rather than the electrojet strength, and yet this approach can also modulate the electrojet when present. HF heater experiments were conducted for both the intensity modulated and beat wave approaches. VLF radiations were generated and the experimental results confirm the numerical simulations. Theory and experimental results both show that in the absence of the electrojet, VLF radiation from the F-region is generated via the beat wave approach. Additionally, the beat wave approach generates VLF radiations over a larger frequency band than by the modulated electrojet.

Original languageEnglish (US)
Article number022901
JournalPhysics of Plasmas
Volume22
Issue number2
DOIs
StatePublished - Feb 1 2015

Fingerprint

electrojets
very low frequencies
transmitters
ionospherics
heaters
synchronism
radiation
radiant flux density
antennas
auroral electrojets
F region
polar regions
ionospheres
continuous radiation
alternating current
simulation
electron energy
broadband

ASJC Scopus subject areas

  • Condensed Matter Physics

Cite this

Ionospheric very low frequency transmitter. / Kuo, Spencer P.

In: Physics of Plasmas, Vol. 22, No. 2, 022901, 01.02.2015.

Research output: Contribution to journalArticle

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