Efficiency scaling for ionospheric ELF/VLF generation, Presentation at the URSI-GA 2002 conference
Abstract: Using experimental measurements and theoretical analysis, it is shown that the HF/ELF conversion efficiency is controlled by the timescale for electron temperature saturation. This is a function of the heater ERP and frequency and the ionospheric electron density profile. For the current H...
| Main Authors: | , , , , , |
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| Other Authors: | |
| Format: | Text |
| Language: | English |
| Published: |
2002
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| Subjects: | |
| Online Access: | http://citeseerx.ist.psu.edu/viewdoc/summary?doi=10.1.1.620.7756 http://www.ursi.org/Proceedings/ProcGA02/papers/p0936.pdf |
| Summary: | Abstract: Using experimental measurements and theoretical analysis, it is shown that the HF/ELF conversion efficiency is controlled by the timescale for electron temperature saturation. This is a function of the heater ERP and frequency and the ionospheric electron density profile. For the current HAARP parameters this corresponds to frequencies between 2 and 4 kHz. Efficiency optimization techniques as applied to the projected upgrading of the HAARP heater to its design power of 3.6 MW are discussed. A most fascinating and important property of the active ionosphere is its potential to act as a frequency transformer that converts HF power injected from a high power HF transmitter into the ionosphere, into coherent lower frequency VLF/ELF/ULF waves. The conversion principle relies on modulating the electrojet currents in the ionospheric D and E regions by using amplitude modulated HF heating. The low frequency fields subsequently couple to the earth-ionosphere waveguide, while a fraction of their power upwards towards the magnetosphere. Despite several years of theoretical and experimental work, many scientific and technical issues remain unresolved. Understanding the physics underlying the low frequency wave generation is important in increasing the HF to ELF conversion efficiency and utilizing the technique for ionospheric diagnostics. A puzzling feature in the results of the experiments conducted using the EISCAT and the HAARP ionospheric heaters, has been the variation of the conversion efficiency with ELF/VLF frequency and the unusually large relative amplitude |
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