VLF wave generation by amplitude-modulated HF heater waves at Gakona, Alaska

Spencer Kuo, Yen Liang Wu, R. Pradipta, J. A. Cohen, M. C. Lee

Research output: Contribution to journalArticle

Abstract

Experiments conducted at Gakona, Alaska, using the intensity-modulated HF heating waves to interact with electrojet currents for the generation of VLF waves, are reported. An unexpected large increasing rate from 4 to 8 kHz in the frequency dependency of the VLF radiation intensity was observed. The peak value at 8 kHz was intense (about 7.5 dB above that of the 2 kHz signal used as a marker) and the wave intensity from 5 to 17 kHz appeared to be abnormally high (i.e., stronger than that at 2 kHz). In the experiments, we also observed the enhancement of spread-E irregularities at electrojet current altitudes due to the amplitude-modulated heater wave. These results and theoretical analyses suggest that temporally modulated electrojet currents mix with heater wave-excited density irregularities to form whistler mode currents, which generate VLF whistler waves directly with much larger intensities and better directivity than a Hertzian dipole can.

Original languageEnglish (US)
Article numberL13101
JournalGeophysical Research Letters
Volume35
Issue number13
DOIs
StatePublished - Jul 16 2008

Fingerprint

wave generation
heaters
electrojets
electrojet
irregularities
directivity
markers
heater
radiant flux density
experiment
dipoles
heating
augmentation

ASJC Scopus subject areas

  • Earth and Planetary Sciences(all)
  • Geophysics

Cite this

VLF wave generation by amplitude-modulated HF heater waves at Gakona, Alaska. / Kuo, Spencer; Wu, Yen Liang; Pradipta, R.; Cohen, J. A.; Lee, M. C.

In: Geophysical Research Letters, Vol. 35, No. 13, L13101, 16.07.2008.

Research output: Contribution to journalArticle

Kuo, Spencer ; Wu, Yen Liang ; Pradipta, R. ; Cohen, J. A. ; Lee, M. C. / VLF wave generation by amplitude-modulated HF heater waves at Gakona, Alaska. In: Geophysical Research Letters. 2008 ; Vol. 35, No. 13.
@article{560647f1d4494a919e0a3f1676aa57d5,
title = "VLF wave generation by amplitude-modulated HF heater waves at Gakona, Alaska",
abstract = "Experiments conducted at Gakona, Alaska, using the intensity-modulated HF heating waves to interact with electrojet currents for the generation of VLF waves, are reported. An unexpected large increasing rate from 4 to 8 kHz in the frequency dependency of the VLF radiation intensity was observed. The peak value at 8 kHz was intense (about 7.5 dB above that of the 2 kHz signal used as a marker) and the wave intensity from 5 to 17 kHz appeared to be abnormally high (i.e., stronger than that at 2 kHz). In the experiments, we also observed the enhancement of spread-E irregularities at electrojet current altitudes due to the amplitude-modulated heater wave. These results and theoretical analyses suggest that temporally modulated electrojet currents mix with heater wave-excited density irregularities to form whistler mode currents, which generate VLF whistler waves directly with much larger intensities and better directivity than a Hertzian dipole can.",
author = "Spencer Kuo and Wu, {Yen Liang} and R. Pradipta and Cohen, {J. A.} and Lee, {M. C.}",
year = "2008",
month = "7",
day = "16",
doi = "10.1029/2008GL034414",
language = "English (US)",
volume = "35",
journal = "Geophysical Research Letters",
issn = "0094-8276",
publisher = "American Geophysical Union",
number = "13",

}

TY - JOUR

T1 - VLF wave generation by amplitude-modulated HF heater waves at Gakona, Alaska

AU - Kuo, Spencer

AU - Wu, Yen Liang

AU - Pradipta, R.

AU - Cohen, J. A.

AU - Lee, M. C.

PY - 2008/7/16

Y1 - 2008/7/16

N2 - Experiments conducted at Gakona, Alaska, using the intensity-modulated HF heating waves to interact with electrojet currents for the generation of VLF waves, are reported. An unexpected large increasing rate from 4 to 8 kHz in the frequency dependency of the VLF radiation intensity was observed. The peak value at 8 kHz was intense (about 7.5 dB above that of the 2 kHz signal used as a marker) and the wave intensity from 5 to 17 kHz appeared to be abnormally high (i.e., stronger than that at 2 kHz). In the experiments, we also observed the enhancement of spread-E irregularities at electrojet current altitudes due to the amplitude-modulated heater wave. These results and theoretical analyses suggest that temporally modulated electrojet currents mix with heater wave-excited density irregularities to form whistler mode currents, which generate VLF whistler waves directly with much larger intensities and better directivity than a Hertzian dipole can.

AB - Experiments conducted at Gakona, Alaska, using the intensity-modulated HF heating waves to interact with electrojet currents for the generation of VLF waves, are reported. An unexpected large increasing rate from 4 to 8 kHz in the frequency dependency of the VLF radiation intensity was observed. The peak value at 8 kHz was intense (about 7.5 dB above that of the 2 kHz signal used as a marker) and the wave intensity from 5 to 17 kHz appeared to be abnormally high (i.e., stronger than that at 2 kHz). In the experiments, we also observed the enhancement of spread-E irregularities at electrojet current altitudes due to the amplitude-modulated heater wave. These results and theoretical analyses suggest that temporally modulated electrojet currents mix with heater wave-excited density irregularities to form whistler mode currents, which generate VLF whistler waves directly with much larger intensities and better directivity than a Hertzian dipole can.

UR - http://www.scopus.com/inward/record.url?scp=53749096493&partnerID=8YFLogxK

UR - http://www.scopus.com/inward/citedby.url?scp=53749096493&partnerID=8YFLogxK

U2 - 10.1029/2008GL034414

DO - 10.1029/2008GL034414

M3 - Article

AN - SCOPUS:53749096493

VL - 35

JO - Geophysical Research Letters

JF - Geophysical Research Letters

SN - 0094-8276

IS - 13

M1 - L13101

ER -