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 article, the variations of average amplitude of the very-low-frequency (VLF) signal thunderstorm origin propagating over areas of strong (magnitude > 5) earthquakes are considered.
10 citations
TL;DR: In this article, a 1-day period at each of four widely separated sites in the North Atlantic Ocean with freely drifting, surface-suspended hydrophones was measured for 1−20 Hz.
Abstract: Ambient noise in the frequency range 1–20 Hz was measured for 1‐day periods at each of four widely separated sites in the North Atlantic Ocean with freely drifting, surface‐suspended hydrophones. The acoustic data were recorded aboard an attending research vessel following transmission over a radio link. Narrow‐band spectral analysis was performed at 1‐h intervals to form time series of noise spectral level for each site. Statistical analyses of the power‐spectral time series included the determination of cumulative probabilities, standard deviation, skew, kurtosis, decorrelation times, and the wind‐speed dependence of mean spectral level. Comparisons with data from bottom‐mounted hydrophones and studies of inter‐ and intra‐array coherence indicate that the data were, with few exceptions, uncontaminated by self‐noise down to 1 Hz. A significant dependence of noise spectrum level upon local wind speed was observed in the 1.5‐ to 3‐Hz frequency band at each site. At 4 Hz, the dependence upon wind speed was ...
10 citations
25 Sep 1994
TL;DR: The authors' data support the hypothesis that this rhythm is transmitted to the cardiovascular control system through substantially linear mechanical and neural couplings, generating the VLF oscillation of HP and SAP.
Abstract: The authors have analyzed the spectral content of the very low frequency band (VLF, 0.01-0.04 Hz) of contemporary short-term recordings of heart period (HP), systolic arterial pressure (SAP), instantaneous lung volume (ILV) and instantaneous tidal volume (ITV) from 16 moderate congestive heart failure (CHF) patients not showing Cheyne-Stokes (C-S) respiration. A well-defined peak around 0.02 Hz was detected in the considered signals in most of the patients analyzed. The majority of patients also showed moderate (>0.5) to high (>0.8) coherence in the region of the VLF peak between HP and SAP and between these signals and the respiratory ones. Since the VLF oscillation of the respiratory signals can be explained as a mild form of periodic breathing, due to the instability of the respiratory control system, the authors' data support the hypothesis that this rhythm is transmitted to the cardiovascular control system through substantially linear mechanical and neural couplings, generating the VLF oscillation of HP and SAP. >
10 citations
TL;DR: Using the sudden ionospheric disturbance (SID) monitor provided by the Stanford University, the very low frequency (VLF) signals were observed in Nanjing during the total solar eclipse on 22nd July 2009 as mentioned in this paper.
10 citations
TL;DR: In this article, the ground level enhancement event No 70 observed on December 13, 2006, by correlating the observations from two research topics: cosmic rays and very low frequency (VLF), was analyzed.
10 citations