Stimulated wave‐particle interactions during high‐latitude ELF wave injection experiments

Garnier, Mickaël; Girolami, G.; Koons, H. C.; Dazey, M. H.

doi:10.1029/ja087ia04p02347

Cited by 6 publications

(2 citation statements)

References 3 publications

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“…This low value for the radiated power was s•fficient to occasionally stimulate plasma wave emissions in the outer magnetosphere. Plasma wave measurements from the high-altitude GEOS 2 and SCATHA satellites near the Kafjord, Norway, magnetic meridian during VLF wave injection experiments are reported by Garnier et al [1982].…”

Section: The Values Inmentioning

confidence: 99%

Characteristics of a Power Line Used as a VLF Antenna.

Dazey¹,

Koons²

1982

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The 100-kW transportable very low frequency transmitter system was used at Kafjord, Norway, for transmissions to the SCATHA and GEOS spacecraft. A 22-kV, 10.6-km long transmission line was used as an antenna. Modifications were made in the line to reduce telephone interference. Components were designed and installed to reduce the resonant frequency and increase the antenna current. The final practical operating current was 45 A at 1280 Hz. This resulted in power dissipation of 72 kW and an estimated radiated power of 0.17 to 0.79 W. BACKGROUND Attention in the Space Science community has recently been directed toward possible effects of powerline harmonic radiation on the earth's radiation belts [Helliwell et al., 1975; Park and Helliwell, 1978; Thorne and Tsurutani, 1979]. The members of the GEOS S-300 experiment scientific board proposed using power transmission lines for antennas in a program to transmit ELF signals to the GEOS satellite. Since The Aerospace Corporation also provided a VLF receiver for the P78-2 (SCATHA) satellite, this provided a unique opportunity to study power line radiation, wave-particle interactions and whistler-mode propagation in the outer magnetosphere. The measurements reported here were undertaken to understand the technical aspects of ELF/VLF radiation from an actual power line over a ground whose effective conductivity is a function of frequency. A 60-kV line was made available for tests at Andoya, Norway. Impedance measurements indicated that the line would be satisfactory as an antenna, however, local residents experienced troubles with appliances, which were being serviced temporarily with a 22-kV backup line. A 60-kV line, which did not require customers to receive service from an inferior line, was located in Konstadbotn, Norway, and preliminary transmissions were made by using the 100-kW TVLF transmitter [Koons and Dazey, 1974] running at currents as high as 50 amperes. Severe telephone interference was experienced. This was attributed to the fact that the line ran within a few hundred meters of a fjord, and most of the telephone Copyright ¸ 1982 by the American Geophysical Union. subscribers had residences between the line and the fjord. A third line was located in a remote part of Norway about 300 km from Tromso near the town of Kafjord. The line was approximately 15 km long. There were a few telephone subscribers near the Kafjord end of the line. Low-level tests indicated serious telephone interference in the nearby residences. Since the residences were all close to the transmitter end of the line, a test was made with the first 3.6 km of the line DAZEY AND KOONS

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Section: The Values Inmentioning

confidence: 99%

Characteristics of a Power Line Used as a VLF Antenna.

Dazey¹,

Koons²

1982

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“…For a horizontal antenna strung a few metres above a high conductivity ground, upwards radiation consists of the direct signal and the almost equal but almost opposite phase signal reflected from the ground. If the ground has relatively low conductivity then the effective reflection depth, which is related to the skin depth, can be a few kilometres (DAZEY and KOONS, 1982). This means that the reflected wave will not only be appreciably phase shifted from anti-phase but also, as in the case of ice, though to a far lesser extent, be reduced in amplitude and so will leave a significantly non-canceled upgoing wave.…”

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confidence: 98%

Generation of VLF and ELF waves for active probing.

Dowden

1988

J. geomagn. geoelec

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Generation of electrical power at any frequency in this range is quite simple. Significant generation of waves at frequencies below, say, 5kHz requires antennas some kilometres in length and height above the ground plane. Antenna methods used with some success to probe the magnetosphere and ionosphere are reviewed: balloon lofted vertical monopoles (Alaska and N.Z.), a dipole over ice (Siple), borrowed power lines (arctic Norway and N.Z.), electrojet modulation (U.S.S.R. and Norway).Any such generator consists of a transmitter and an antenna. At VLF, generator design is a simpler task than at higher frequencies and for the powers required the transmitter is relatively inexpensive. The antenna required for VLF on the other hand is very large and expensive having vertical dimensions of the order of a kilometre even for non-resonant antennas and horizontal dimensions of some tens of kilometres for resonant antennas.Following the discovery (HELLIWELL, 1965) that man-made VLF transmissions could (unintentionally) trigger VLF emissions in the magnetosphere, American and Soviet groups used such existing VLF transmitter and antenna installations to do intentional active experiments. These antennas are non-resonant vertical monopoles with extensive top-loading. Their effective heights are very much less than a quarter wave length at the frequencies used and so at the feeding terminals the impedance is almost pure capacitance. A series inductor between the transmitter and antenna terminal is used to tune out this capacitance. With an effective Q of one thousand, the total resistance is reduced to perhaps only 30% above the radiation resistance and so the efficiency may be 75% or more (WATT, 1967). The disadvantage of such a high Q is that the modulation frequency can be only a few hertz. For active experiments this may not be a serious problem for amplitude modulation but it is one if frequency modulation is desired over a large range. As such VLF installations were built for military purposes the active experimenters had very limited access and could only control the On-Off modulation and not the frequency (generally above 15kHz) or the location of the antenna. None-the-less, interesting active sounding ("artificial whistlers") were done by the Stanford group and the Soviet group studied non-linear amplification effects such as modulation instability (LIKHTER et al.,

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Discrete Electromagnetic Emissions in Planetary Magnetospheres

Anderson

Kŭrth

2013

Plasma Waves and Instabilities at Comets and in Magnetospheres

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Stimulated wave‐particle interactions during high‐latitude ELF wave injection experiments

Cited by 6 publications

References 3 publications

Characteristics of a Power Line Used as a VLF Antenna.

Characteristics of a Power Line Used as a VLF Antenna.

Generation of VLF and ELF waves for active probing.

Discrete Electromagnetic Emissions in Planetary Magnetospheres

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