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AGU: Journal of Geophysical Research, Space Physics

 

Keywords

  • triggered emissions
  • HF heating
  • wave injection

Index Terms

  • Space Plasma Physics: Wave/particle interactions
  • Space Plasma Physics: Nonlinear phenomena
  • Space Plasma Physics: Active perturbation experiments
  • Ionosphere: Active experiments
  • Magnetospheric Physics: Radiation belts
Abstract
Cited By (10)
 

Abstract

JOURNAL OF GEOPHYSICAL RESEARCH, VOL. 113, A10201, 12 PP., 2008
doi:10.1029/2008JA013157

Magnetospheric amplification and emission triggering by ELF/VLF waves injected by the 3.6 MW HAARP ionospheric heater

M. Gołkowski

STAR Laboratory, Department of Electrical Engineering, Stanford University, Stanford, California, USA

U. S. Inan

STAR Laboratory, Department of Electrical Engineering, Stanford University, Stanford, California, USA

A. R. Gibby

STAR Laboratory, Department of Electrical Engineering, Stanford University, Stanford, California, USA

M. B. Cohen

STAR Laboratory, Department of Electrical Engineering, Stanford University, Stanford, California, USA

The HF dipole array of the High Frequency Active Auroral Research Program (HAARP) in Gakona, Alaska, was recently upgraded to 180 elements, facilitating operations at a total radiated power level of 3.6 MW and an effective radiated power of ∼575 MW. In the first experiments at the new power level, the HAARP array is used for magnetospheric wave injection. Modulated heating of auroral electrojet currents in the ionosphere yields radiation in the ELF/VLF frequency range. The HAARP-generated signals are injected into the magnetosphere, where they propagate in the whistler mode in field-aligned “ducts,” allowing them to be observed at the conjugate point on a ship-borne receiver and on autonomous buoy platforms. The observation of the 1-hop signals is accompanied by the observation of associated 2-hop components in the northern hemisphere, which have reflected from the ionospheric boundary in the southern hemisphere. The observed signals are accompanied by triggered emissions and exhibit temporal amplification of 15–25 dB/s and bandwidth broadening to ∼50 Hz. Amplification occurs at injected signal frequencies selected in near real time on the basis of observations of natural emission activity, and only certain components of the frequency-time formats transmitted are amplified. Observations at multiple sites and dispersion analysis show that the signals are injected into the magnetosphere directly above the HF heater. The duration of echo observation and the prevalence of 1-hop observations are consistent with statistics from 1986 Siple Station experiments. The particle-trapping wave amplitude near the magnetic equator is estimated in the range 0.1–0.4 pT and gyroresonance with 10 keV–100 keV electrons.

Received 10 March 2008; accepted 26 June 2008; published 1 October 2008.

Citation: Gołkowski, M., U. S. Inan, A. R. Gibby, and M. B. Cohen (2008), Magnetospheric amplification and emission triggering by ELF/VLF waves injected by the 3.6 MW HAARP ionospheric heater, J. Geophys. Res., 113, A10201, doi:10.1029/2008JA013157.

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