Радиофизика и электроника (Dec 2019)
Polarisation of night-time ELF–VLF atmospherics as statistically approached
Abstract
Subject and Purpose. Tweek-atmospherics (night-time low-frequency atmospherics), along with radio transmission by VLF radio stations, are used to study the lower ionosphere. The predictions of the available analytical theory regarding the polarization of such atmospherics and the previously accumulated experimental material describe the left elliptical polarization as a characteristic feature of the tweek-atmospherics in their tail section. The horizontal geomagnetic field’s component in reflection layer of the lower ionosphere should lead, within the theory framework, to non-reciprocity of the “east–west” and “west – east” propagation of tweeks. The study aim was to determine the polarization of tweek-atmospherics using three-component records and to statistically evaluate the null hypothesis regarding to two polarization parameters of tweek-atmospherics. Methods and Methodology. By the ensemble of experimental tweek-atmospheric records of about 300 examples, that is large enough for statistical processing, the polarization was studied along the atmospherics’ waveforms. Results. For the first (fundamental) harmonic, two characteristics of the polarization of the tweek-atmospherics (the polarization ratio and the phase difference) were calculated and analyzed, depending on the parameter identical to an incidence angle. The difference in the polarization ratio values has found between tweek-atmospherics with near-equatorial paths and atmospherics outside the geomagnetic equator area, where the condition of quasi-longitudinal wave propagation along the geomagnetic field is satisfied. Conclusions. Study has shown that the non-reciprocity of the propagation of tweek-atmospherics in the “east–west” and “west–east” directions regarding the geomagnetic field is observed as statistically significant differences in the phase difference at an incidence angle about 40...60˚ that correspond to an ending of head area of atmospheric waveforms.
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