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Communication Dans Un Congrès Année : 2010

Spatial Power Distribution of ELF Radiation Induced by HF Heating of the Ionosphere

D. Piddyachiy
  • Fonction : Auteur
T. F. Bell
  • Fonction : Auteur
U. S. Inan
  • Fonction : Auteur
M. Cohen
N. G. Lehtinen
  • Fonction : Auteur

Résumé

The High Frequency Active Auroral Research Program (HAARP) transmitter array (3.6 MW, 2.8 - 10 MHz) is used to generate Extremely Low Frequency (ELF, 300 - 3000 Hz) waves through periodic heating of the ionospheric D-layer and subsequent modulation of the conductivity of the auroral electrojet. The generated ELF waves can be used in various manners depending on whether the part of energy which penetrates into the space, or the other part which propagates into the Earth-ionosphere waveguide, is considered. One application of ELF waves in space is the study of wave-particle interactions which occur in the Earth’s magnetosphere between waves of this frequency range and energetic electrons in the range of about 10 - 500 keV. One of the most important applications of ELF waves in the Earth-ionosphere waveguide is maritime communication over long distances. In all situations, the knowledge of ELF power distribution as a function of the distance from the source is required. The spatial power distribution depends on many factors. Some of them can be controlled: the ELF and HF frequencies, direction, and modulation techniques of an HF transmitter. Other parameters are natural and can not be directly affected: strength of the electrojet current, absorption of the waves in the ionosphere, and so on. The distribution of the ELF power can be effectively studied using a low-earth-orbit (LEO) satellite which passes through a large region of electromagnetic radiation in several minutes. This allows to keep most of the parameters constant during a single experiment. The waves propagating up into the space can be directly measured by such a satellite. As was shown in Piddyachiy et al., 2008, the waves observed in space at the horizontal distances of more than 300 km from the source are directly leaking from the Earth-ionosphere waveguide and therefore their power is a direct indication of the power in the waveguide at long distances. In this work we use the LEO DEMETER satellite (altitude of 670 km) in conjunction with HAARP to study the spatial power distribution of ELF waves radiated by HAARP. Initial studies were conducted on a case by case basis, but now they are complemented by a statistical study of many experiments conducted over 4 years. Case studies show that the signal distribution in space can be more variable in specific situations than predicted from theoretical modeling using a stratified ionosphere. Ionospheric density irregularities are deemed to be the main factor of an abrupt signal variation in space for specific examples. That is why the comparison of theoretical results with not only specific observations, but also with average power distributions over multiple passes, is need to increase the accuracy of modeling and adjust the techniques of ELF generation.
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Dates et versions

hal-03548975 , version 1 (31-01-2022)

Identifiants

Citer

D. Piddyachiy, T. F. Bell, U. S. Inan, M. Cohen, N. G. Lehtinen, et al.. Spatial Power Distribution of ELF Radiation Induced by HF Heating of the Ionosphere. American Geophysical Union, 2010, à renseigner, Unknown Region. pp. 1542-1550. ⟨hal-03548975⟩
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