Multipath Doppler Shifts in Man-Made VLF Signals

Koons, H. C.; Edgar, B. C.; Dowden, R. L.; Carrington, C. G.; Amon, L. E. S.

doi:10.1007/978-94-010-2265-1_31

Cited by 5 publications

(3 citation statements)

References 1 publication

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“…The spectral distortion of multipath signals from VLF transmitters due to the Doppler effect on satellites is a common phenomenon which has been reported by a number of workers [Walter and Angerami, 1969;Cerisier, 1973;Koons et al, 1974;Edgar, 1976;Bell et al, 1983b]. In this effect fixed frequency signals propagate to the satellite along a number of separate paths and arrive at the satellite with different values of refractive index and wave normal direction.…”

Section: Sideband Generationmentioning

confidence: 98%

“…Two types of spectral distortion have been reported. One type, involving interhemispheric propagation, is generally characterised by sidebands which are not symmetric in frequency about the carrier and by differential time delays between carrier and sidebands which can be as large as one second [Walter and Angerami, 1969;Cerisier, 19'73;Koons et al, 1974;Edgar, 1976. ] The second type, seen predominantly on short propagation paths (< 6000 km), apparently involves the scattering of signals from irregularities in the ionosphere, and is generally characterized by sidebands symmetric about the carrier, differential time delays of approximately 150 ms or less, and a unique "chevron" spectral form [Bell et al, 1983b].…”

Section: Sideband Generationmentioning

confidence: 99%

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High‐amplitude VLF transmitter signals and associated sidebands observed near the magnetic equatorial plane on the ISEE 1 satellite

Bell¹

1985

J. Geophys. Res.

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On February 16, 1983, during a period of strong magnetic disturbance (Kp ∼ 5), as the ISEE 1 satellite passed near the magnetic meridian of the Omega navigation transmitter (98°W, 46°N geographic, L ∼ 3.4), the Stanford University VLF wave receiver detected the presence of Omega transmitter signals over the range 2 ≤ L ≤ 3.7 at magnetic latitudes (λm) within 10° of the magnetic equator. Over a 500‐km orbital segment near L ∼ 3.4 and λm ∼ 5°S, the electric field amplitude of the Omega signals reached ∼ 0.6 mV/m, a value > 40dB higher than the signal amplitude both preceding (L ∼ 3.7–3.5) and following (L ≤ 3.2) the high‐amplitude period. Over the range 3.3 ≤ L ≤ 3.7 the transmitter pulses at 13.1 and 13.6 kHz were associated with sideband signals spaced in frequency roughly symmetrically about the carrier and generally reduced in amplitude ∼5 dB with respect to the carrier. The strongest sidebands were generally offset in frequency from the carrier by ∼ ±55 Hz. Simultaneous data from the University of Iowa Plasma Wave experiment indicated that the region of high wave amplitude was located just beyond the outer edge of the plasmapause where low values of cold plasma density (∼40 el/cm³) prevailed. High amplitudes were observed only during the time in which the signal frequency lay within the range of a natural noise band of rising center frequency in which bursts of VLF emissions were occasionally triggered by “knee‐trace” whistlers. On the basis of the group time delay and amplitude distribution of the Omega signals and the presence of knee‐trace whistlers, it is concluded that the high amplitude signals originally propagated along the base of the plasmapause surface into the southern hemisphere and subsequently reflected or scattered back up to the satellite. The high‐wave amplitude was presumably produced through the coherent whistler mode instability as the input waves interacted with gyroresonant energetic electrons near the magnetic equatorial plane, and the presence of sideband signals indicates that this interaction had reached a nonlinear stage. The wave magnetic field in the interaction region is estimated to be approximately 20 mγ. The high amplitudes reached by the signals indicates that particle trapping effects could be responsible for the sideband generation.

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Section: Sideband Generationmentioning

confidence: 98%

Section: Sideband Generationmentioning

confidence: 99%

High‐amplitude VLF transmitter signals and associated sidebands observed near the magnetic equatorial plane on the ISEE 1 satellite

Bell¹

1985

J. Geophys. Res.

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“…The satellite spectral broadening phenomena are classified into two categories. The first is Doppler shift of the nominal carrier frequency observed by the OGO 4, FR 1, and ISIS 2 satellites in which VLF transmitter signals undergo a spectral distortion as they travel through the magnetosphere and arrive at a low-altitude satellite in the conjugate hemisphere [Walter and Angerami, 1969;Cerisier, 1974;Koons et al, 1974]. The large Doppler shift, usually • 100 Hz, can be interpreted in terms of a series of constant frequency wave components of nonducted VLF transmitter signals with the wave normal vector k near the resonance cone, due to a large negative latitudinal gradient of electron density between the L shells of • 2 and • 3.…”

Section: Introductionmentioning

confidence: 99%

Spectral broadening of VLF transmitter signals and sideband structure observed on Aureol 3 satellite at middle latitudes

Tanaka¹,

Lagoutte²,

Hayakawa³

et al. 1987

J. Geophys. Res.

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Electric and magnetic field wave data acquired on Aureol 3 satellite demonstrate the existence of a spectral broadening effect in which VLF transmitter signals from Alpha station (geographic coordinates, 50.5°N, 137°E) in USSR undergo a significant spectral broadening on electric fields as they propagate through the ionosphere up to the spacecraft in the altitude range of 500–2000 km at middle latitudes (L ∼ 2). The spectral broadening phenomena may be divided into two types: (1) spectrally broadened components occurring without any association with ELF/VLF emissions under disturbed ionospheric conditions and (2) spectrally broadened components with predominant sideband structure in association with ELF emissions. Bicoherence computation results suggest a nonlinear mode coupling between the transmitter signal and ELF emission which produces sidebands that are quasi‐electrostatic in nature. However, faint spectral broadened components in both types 1 and 2 may be connected with Doppler shift of quasi‐electrostatic whistler mode waves with a broad spectrum of k near the resonance cone, due to scattering of the transmitter signals from ionospheric irregularities in the F region.

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Proton precipitation by a whistler‐mode wave from a VLF transmitter

Koons¹

1975

Geophysical Research Letters

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Protons with 50 keV < E < 530 keV were detected by sensors aboard satellite 1972‐76B at an altitude of 700 km in the region conjugate to the transportable very‐low‐frequency (TVLF) transmitter which was being operated near Anchorage, Alaska (L ∼ 4). Temporal maxima in the proton count rates can be identified on a one‐to‐one basis with short pulsed transmissions by the VLF transmitter. The observed time delay between the center of a transmitted pulse and the detection of the next maximum in the proton count rate at the sensor agrees well with the delay predicted from a simple plasmaspheric model.

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Multipath Doppler Shifts in Man-Made VLF Signals

Cited by 5 publications

References 1 publication

High‐amplitude VLF transmitter signals and associated sidebands observed near the magnetic equatorial plane on the ISEE 1 satellite

High‐amplitude VLF transmitter signals and associated sidebands observed near the magnetic equatorial plane on the ISEE 1 satellite

Spectral broadening of VLF transmitter signals and sideband structure observed on Aureol 3 satellite at middle latitudes

Proton precipitation by a whistler‐mode wave from a VLF transmitter

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