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, the authors present the results of study of weak turbulent coupling between VLF electrostatic waves by means of a novel 3D numerical code, which includes so-called vector nonlinearity.
Abstract: [1] Nonlinear interactions have been suggested to account for the missing mechanism of energy losses in the current models of propagation of very low frequency (VLF) waves from powerful transmitters into the magnetosphere. This paper presents the results of study of weak- turbulent coupling between VLF electrostatic waves by means of a novel 3D numerical code, which includes so-called vector nonlinearity. The results virtually reproduce the Demeter satellite observations of intense broadband lower hybrid (LH) electrostatic waves generated by whistler-mode waves from the VLF transmitter NWC.
10 citations
TL;DR: In this paper, the anisotropy of the electron distribution function is determined by the injection processes and by further modifications, e.g. convection and drift, which is large enough to allow the growth of VLF waves responsible for scattering of electrons into the loss cone.
10 citations
TL;DR: In this article, the amplitude and polarization properties of the Siple signals were predicted using a ray optics analysis, and an approximately 90° anomaly in the apparent arrival bearing of the signals from Siple was attributed to the essentially horizontal polarization of the received signal.
10 citations
10 citations
20 Jul 2018
TL;DR: In this article, a succession of earthquakes (EQs) occurred in the Kumamoto area in Kyusyu Island; two strong foreshocks with magnitude of 6.5 and 6.4 on 14 April and the main shock with magnitude 7.3 on 15 April (UT).
Abstract: There have been published many papers on VLF (very low frequency) characteristics to study seismo-ionospheric perturbations. Usually VLF records (amplitude and/or phase) are used to investigate mainly the temporal evolution of VLF propagation anomalies with special attention to one particular propagation path. The most important advantage of this paper is the simultaneous use of several propagation paths. A succession of earthquakes (EQs) happened in the Kumamoto area in Kyusyu Island; two strong foreshocks with magnitude of 6.5 and 6.4 on 14 April (UT) and the main shock with magnitude 7.3 on 15 April (UT). Because the EQ epicenters are not far from the VLF transmitter (with the call sign of JJI in Miyazaki prefecture), we can utilize simultaneously 8 observing stations of our network all over Japan. Together with the use of theoretical computations based on wave-hop theory, we try to trace both the temporal and spatial evolutions of the ionospheric perturbation associated with this succession of EQs. It is found that the ionospheric perturbation begins to appear about two weeks before the EQs, and this perturbation becomes most developed 5 - 3 days before the main shock. When the perturbation is most disturbed, the maximum change in vertical direction is depletion in the VLF effective ionospheric height of the order of 10 km, and its horizontal scale (or its radius) is about 1000 km. These spatio-temporal changes of the seismo-ionospheric perturbation will be investigated in details in the discus-sion, a comparison has made with the VLF characteristics of the 1995 Kobe with the same magnitude and of the same fault-type, and a brief discussion on the generation mechanism of seismo-ionospheric perturbation is finally made.
10 citations