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Vertical acoustic resonance in the atmosphere as a source of Pc5 geomagnetic pulsationsстатья
- Автор: Surkov V.V.
- Журнал: Journal of Atmospheric and Solar-Terrestrial Physics
- Том: 271
- Год издания: 2025
- Издательство: Pergamon Press Ltd.
- Местоположение издательства: United Kingdom
- Первая страница: 1
- Последняя страница: 12
- Номер статьи: 106511
- Аннотация: Some strong earthquakes and volcano eruptions are accompanied by atmospheric pressure variations andgeomagnetic perturbations (GMPs), which contain spectral spikes in the Pc5 frequency range. GMPs are usuallyobserved in epicentral areas of several hundred kilometers in size and in a geomagnetically conjugated region.This effect can be explained by the impact on the ionosphere of an atmospheric acoustic wave caused by seismicvibration of the earth’s surface. A partial reflection of the acoustic wave from the region of a sharp change inatmospheric temperature near the bottom of the thermosphere can lead to a vertical acoustic resonance (VAR) inthe area between the earth’s surface and the thermosphere boundary. The acoustic wave partially penetrates intothe ionosphere, thereby exciting ionospheric currents and GMPs in the Pc5 frequency range. In this study wedevelop a plane-stratified model of the atmosphere and ionosphere in order to examine spectrum of the first VARharmonics. A set of 2D gas dynamics equations is treated to derive dispersion relations which determine the VARresonant frequencies. Ionospheric currents and GMP are found in the approximation of a thin ionospheric E-layerwith an inclined geomagnetic field. Analysis of the VAR dispersion relation shows that the resonant frequenciesof the first three harmonics lies within 3.7 5.9 mHz, that is, in the Pc5 frequency range, while their logarithmicdecrements range from zero to 0.6. The weak attenuation of VAR harmonics can explain the observed longduration of VAR and GMPs after a seismic event. Unlike previous studies, the effect of wind in the upper atmosphereis taken into account. It has been found that wind velocity weakly influences the resonant frequenciesbut it may greatly affect the attenuation coefficients of VAR harmonics. The model predicts a similar shape ofGMPs detected near the epicenter of strong seismic events and in the magnetically conjugated arears, which isconsistent with geomagnetic response to VAR detected by ground-based magnetometers.
- Добавил в систему: Сурков Вадим Вадимович