Attenuation of whistler waves through conversion to lower hybrid waves in the low-altitude ionosphere

Xi Shao, Bengt Eliasson, A. S. Sharma, Gennady Milikh, Dennis K. Papadopoulos

Research output: Contribution to journalArticle

16 Citations (Scopus)

Abstract

VLF waves excited by powerful ground-based transmitters propagate in the Earth-ionosphere waveguide and leak through the ionosphere to the magnetosphere, where they are often recorded by satellites. Simulations of the propagation of whistler waves using coupled transionospheric VLF propagation and three-dimensional ray-tracing models have shown systematic overestimates of the VLF wavefield strength near 20 kHz in the magnetosphere by about 20 dB in the night and 10 dB during the day. The paper presents numerical simulations of the conversion between whistler and lower hybrid waves interactions in the presence of short-scale field-aligned density irregularities (striations) in Earth's lower ionosphere. The simulations, which incorporate a realistic ionospheric density profile, show that the mode conversion of whistler waves to lower hybrid waves leads to significant attenuation of whistler waves at altitudes between 90 and 150 km. The striation width plays an important role in the conversion efficiency between whistler and lower hybrid wave. Uniformly distributed striations with 8 m transverse size result in 15 dB attenuation in the 90–150 km propagation range, while a spectrum from 2 to 10 m results in 9 dB attenuation. It is argued that the attenuation of whistler waves in the presence of short-scale density striations in Earth's ionosphere can account for most of the observed ∼20 dB loss in VLF intensity. Furthermore, it predicts that VLF/ELF waves with frequencies below 5 kHz will not suffer similar attenuation.
Original languageEnglish
Article numberA04311
JournalJournal of Geophysical Research
Volume117
Issue numberA4
DOIs
Publication statusPublished - 12 Apr 2012

Fingerprint

Ionosphere
low altitude
ionospheres
ionosphere
attenuation
striation
Magnetosphere
Earth (planet)
magnetospheres
propagation
magnetosphere
Earth-ionosphere waveguide
Earth ionosphere
lower ionosphere
simulation
wave interaction
Antenna grounds
irregularities
ray tracing
Ray tracing

Keywords

  • ionosphere
  • whistler waves
  • density irregularities
  • lower hybrid waves
  • mode conversion

Cite this

Shao, Xi ; Eliasson, Bengt ; Sharma, A. S. ; Milikh, Gennady ; Papadopoulos, Dennis K. / Attenuation of whistler waves through conversion to lower hybrid waves in the low-altitude ionosphere. In: Journal of Geophysical Research. 2012 ; Vol. 117, No. A4.
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abstract = "VLF waves excited by powerful ground-based transmitters propagate in the Earth-ionosphere waveguide and leak through the ionosphere to the magnetosphere, where they are often recorded by satellites. Simulations of the propagation of whistler waves using coupled transionospheric VLF propagation and three-dimensional ray-tracing models have shown systematic overestimates of the VLF wavefield strength near 20 kHz in the magnetosphere by about 20 dB in the night and 10 dB during the day. The paper presents numerical simulations of the conversion between whistler and lower hybrid waves interactions in the presence of short-scale field-aligned density irregularities (striations) in Earth's lower ionosphere. The simulations, which incorporate a realistic ionospheric density profile, show that the mode conversion of whistler waves to lower hybrid waves leads to significant attenuation of whistler waves at altitudes between 90 and 150 km. The striation width plays an important role in the conversion efficiency between whistler and lower hybrid wave. Uniformly distributed striations with 8 m transverse size result in 15 dB attenuation in the 90–150 km propagation range, while a spectrum from 2 to 10 m results in 9 dB attenuation. It is argued that the attenuation of whistler waves in the presence of short-scale density striations in Earth's ionosphere can account for most of the observed ∼20 dB loss in VLF intensity. Furthermore, it predicts that VLF/ELF waves with frequencies below 5 kHz will not suffer similar attenuation.",
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Attenuation of whistler waves through conversion to lower hybrid waves in the low-altitude ionosphere. / Shao, Xi; Eliasson, Bengt; Sharma, A. S.; Milikh, Gennady; Papadopoulos, Dennis K.

In: Journal of Geophysical Research, Vol. 117, No. A4, A04311, 12.04.2012.

Research output: Contribution to journalArticle

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AU - Eliasson, Bengt

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