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Movement of off-path ionospheric irregularities deduced from short-path VLF measurements

1968; Elsevier BV; Volume: 30; Issue: 10 Linguagem: Inglês

10.1016/0021-9169(68)90099-8

1878-593X

Earl E. Gossard, M. R. Paulson,

Earthquake Detection and Analysis

A short radio path is used to measure the spatial and temporal characteristics of fluctuations of VLF signals reflected from the ionosphere. The experiment uses multiple frequency transmissions from a horizontal VLF antenna received at a triangle of spaced receivers. Power spectrum and cross spectrum analyses of the phase and amplitude records are used to demonstrate that much of the fluctuation in the records results from Doppler beating of the principal signal and signal components reflected from off-path irregularities. A new technique for determining the position and movement of irregularities in the ionosphere is described for use when Doppler lines are an important part of the records. Some typical records are shown and some implications concerning previous published analyses of fading records are discussed. The risk of interpreting periodic features in radio records to result necessarily from a wave structure in the ionosphere is made evident.