Topic
Very low frequency
About: Very low frequency is a research topic. Over the lifetime, 1540 publications have been published within this topic receiving 24233 citations. The topic is also known as: VLF.
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TL;DR: In this paper, standing Alfven waves of 1.1 mHz were observed by the Cluster satellites in the mid-tail during 06:00-07:00 UT on 8-August 2003.
Abstract: . Standing Alfven waves of 1.1 mHz (~15 min in period) were observed by the Cluster satellites in the mid-tail during 06:00-07:00 UT on 8 August 2003. Pulsations with the same frequency were also observed at several ground stations near Cluster's footpoint. The standing wave properties were determined from the electric and magnetic field measurements of Cluster. Data from the ground magnetometers indicated a latitudinal amplitude and phase structure consistent with the driven field line resonance (FLR) at 1.1 mHz. Simultaneously, quasi-periodic oscillations at different frequencies were observed in the post-midnight/early morning sector by GOES 12 (l0≈8.7), Polar (l0≈11-14) and Geotail (l0≈9.8). The 8 August 2003 event yields rare and interesting datasets. It provides, for the first time, coordinated in situ and ground-based observations of a very low frequency FLR in the mid-tail on stretched field lines.
16 citations
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TL;DR: In this article, the authors present the results of a theoretical analysis and a laboratory simulation of transpolar VLF/ELF propagation phenomena, based on daytime ionospheric models representative of ambient conditions and of conditions that prevail during polar-cap absorption (PCA) events.
Abstract: 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.
16 citations
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TL;DR: In this paper, the authors used ionization models for phase disturbances, HF absorption and solar protons in 1967 PCA events, using ionization model, and showed that VLF phase disturbances and HF absorption are correlated.
Abstract: VLF phase disturbances, HF absorption and solar protons in 1967 PCA events, using ionization model
16 citations
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TL;DR: The occurrence rate of bursts at 0.1, 0.73, 5.4, and 30 kHz in the night ionosphere of Venus and factors controlling these bursts are examined in this article.
16 citations
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21 Sep 1977
TL;DR: In this paper, the vlf/lf field strength measurements obtained between 9 and 60 kHz for several radio propagation paths are presented, including several radials outward from Hawaii, several transmission paths across the continental United States, and high latitude propagation over the Greenland Ice Cap.
Abstract: : This report presents vlf/lf field strength measurements obtained between 9 and 60 kHz for several radio propagation paths. These include several radials outward from Hawaii, several transmission paths across the continental United States, and high latitude propagation over the Greenland Ice Cap. Effective exponential electron density profiles are derived yielding predicted signal levels that simulate the experimental data.
16 citations