ELF and VLF Propagation for Models of a Perturbed Ionosphere

Galejs, Janis

doi:10.1029/rs005i007p01041

Cited by 7 publications

(2 citation statements)

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“…We have used nominal working models of the ionosphere that are well within the prevailing uncertainties, and our main conclusions would be substantially unchanged if other equally reasonable models were used. Some of the effects of varying the assumed ion masses and collision frequencies were recently examined parametrically by Galejs [1970].…”

Section: Ionosr•re and Grovnd Mo•elsmentioning

confidence: 99%

“…It should be noted that, although the data clearly indicated that increased attenuation was usually produced by the icecap during quiet periods as well as during PCA's, there were a few exceptional instances where this situation did not appear to be true. Galejs [1970] noted that heavy ions can contribute importantly to VLF and ELF absorption during periods of abnormal ionization, such as occurs during many PCA's. Field [1970] analyzed the effects of PCA events on polar VLF propagation by performing calculations using model ionospheres corresponding to quiet conditions and three PCA's of widely varying intensity.…”

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Transpolar propagation of long radio waves

Field¹,

Greifinger²,

Schwartz³

1972

J. Geophys. Res.

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This report presents the results of a theoretical analysis and a laboratory simulation of certain transpolar VLF/ELF propagation phenomena. The calculations are based on daytime ionospheric models representative of ambient conditions and of conditions that prevail during polar-cap absorption (PCA) events. The laboratory simulation utilized a wave guide that models VLF propagation in the earth-ionosphere cavity. The influence of the Greenland icecap is included in both the theoretical and experimental approaches. The calculations predict, in agreement with actual transpolar propagation data, that much larger signal losses will be suffered on paths that cross Greenland than on paths that do not. Furthermore. the calculations correctly predict that a given PCA will typically produce much larger amplitude degradations and phase advances on signals that cross Greenland than on ones that propagate only over sea water and/or relatively highly conducting ground. The data from the laboratory model is in good general agreement with actual transpolar propagation measurements and our theoretical results. In addition to causing sizable ground losses, the presence of thick ice at the lower boundary of the earth-ionosphere wave guide distorts the structure of the modes greatly from that which prevails for propagation over highly conducting ground. This distortion manifests itself in ambiguities in mode numbering and in an increase in the losses due to ionospheric heating. Ions contribute significantly to the propagation phenomena during moderate and intense PCA events. The propagation of long radio waves in polar regions can be quite different from that at midlatitudes and low latitudes for two reasons, the existence of polar icecaps and the occurrence of certain ionospheric disturbances at polar latitudes. Much recent data [see below] indicate that, under ordinary conditions, signals on transmission paths crossing the Greenland icecap exhibit extraordinarily large attenuation as well as unusual phase phenomena and diurnal behavior. In addition, phase and amplitude anomalies on transpolar VLF (3-30 kHz) paths occur during polar-cap absorption (PCA) events during which energetic protons impinge on the polar ionosphere, and thus produce anomalous ionization. When a combination of the two effects takes place, the PCA-induced anomaly is greatly Now at R&D Associates, Santa Monica, California 90406. enhanced. Thus, during a PCA, much larger signal losses and phase advances are usually noted on paths that cross Greenland than on transpolar paths that do not. This report presents the results of both a theoretical study of the phenomena just described and an experimental study using a laboratory model that simulates polar VLF propagation. Previous relevant experimental and theoretical work is reviewed briefly. The ionosphere and ground models used in the theoretical analysis and a VLF model experiment are described, and some data that give insight into transpolar VLF propagation phenomenology are presented. The results of the full-wave...

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Section: Ionosr•re and Grovnd Mo•elsmentioning

confidence: 99%

mentioning

confidence: 99%

Transpolar propagation of long radio waves

Field¹,

Greifinger²,

Schwartz³

1972

J. Geophys. Res.

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Excitation and Propagation of SLF/ELF Electromagnetic Waves in the Earth–Ionosphere Waveguide/Cavity

Pan¹,

2013

Advanced Topics in Science and Technology in China

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In this chapter, the region of interest is a waveguide or cavity between the Earth's surface and an isotropic homogeneous ionosphere. The dipole (vertical electric dipole (VED), the vertical magnetic dipole (VMD), or the horizontal electric dipole (HED)) and the observation point are assumed to be located on or near the spherical surface of the Earth. The approximate all formulas are obtained for the electromagnetic field radiated by a VED and a VMD in the Earth-ionosphere waveguide or cavity. Based on the above results, the approximate formulas are derived readily for the electromagnetic field of an HED in the Earth-ionosphere waveguide or cavity by using the reciprocity theorem. Analyses and computations in SLF/ELF ranges are carried out specifically.

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V.L.F. Propagation

Galejs

1972

Terrestrial Propagation of Long Electromagnetic Waves

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ELF and VLF Propagation for Models of a Perturbed Ionosphere

Cited by 7 publications

References 14 publications

Transpolar propagation of long radio waves

Transpolar propagation of long radio waves

Excitation and Propagation of SLF/ELF Electromagnetic Waves in the Earth–Ionosphere Waveguide/Cavity

V.L.F. Propagation

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