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.

An airborne tensor VLF system. From concept to realization

Abstract: Radio signals from very low frequency (VLF) transmitters distributed world-wide have been used for several decades to study the lateral variations of the electrical conductivity in the upper few hundred metres of the earth's crust. Traditionally, in airborne applications, the total magnetic fields from one or two transmitters are measured to form the basis for construction of maps that primarily show those conductive structures that are parallel or subparallel to the direction to the transmitters. The tensor VLF technique described in this paper makes use of all signals available in a predefined frequency band to construct transfer functions relating the vertical magnetic field and the two horizontal magnetic field components

Broadband VLF measurements of lightning-induced ionospheric perturbations

Abstract: [1] Very low frequency (VLF) electromagnetic pulses radiated by lightning are an effective tool for probing the D region ionosphere. We detect and measure the D region ionospheric disturbances caused by the strong lightning flash by analyzing the broadband VLF spectrum from lightning that occurred just before and after a nearby intense lightning discharge. Comparing the measured electron density changes to those from previous measurements and the theoretical expectations, we find the detected perturbations are consistent with the theoretically predicted ionization changes produced directly by the lightning electromagnetic pulse.

VLF transmission induced slot electron precipitation

Abstract: : Analysis of electron observations in the drift and bounce loss cones of the slot region of the magnetosphere indicates that the predominant mode in which electrons in the 100 to 400 keV energy range arrive in the drift loss cone is via discrete events. These events are usually traceable back to the vicinity of a high-power-level VLF transmitter. No gradual buildup of electron flux, proceeding eastward from the South Atlantic Anomaly, is observed. Estimates of the loss rate due to the discrete events show that this process can result in a depletion of 50% per day of the electron flux in the slot region. The wave-particle interaction must occur relatively low on the field line (lambda approximately 30 deg to 50 deg) because of the relationship of particle energies and wave frequencies involved. Additional scattering of the particles near the equator, either by power-line harmonic emissions or naturally occurring ELF hiss, is required to transport the particles to the lower interaction region. (Author)

Ion depletion in the high-latitude exosphere; simultaneous OGO 2 observations of the light ion trough and the VLF cutoff

Abstract: Ion depletion in high latitude exosphere, considering OGO 2 simultaneous observations of positive ion concentration, VLF signal propagation and whistlers