Low-frequency (ELF–VLF) radio atmospherics study at the Ukrainian Antarctic Akademik Vernadsky station

This paper describes the results of the atmospherics measurements in the extremely low-frequency (ELF) and very low-frequency (VLF) frequency ranges performed at the Akademik Vernadsky station (64.26W; 65.25S) during February–April 2019. The main objective of the study was the implementation of a single-site technique for monitoring the lower ionosphere parameters and locating globally distributed powerful lightning discharges.У даній статті описано результати вимірювань атмосфериків в діапазонах наднизькочастотних (ННЧ) і дуже низькочастотних (ДНЧ), виконаних на Українській антарктичній станції (УАС) «Академік Вернадський» (64.26 W; 65.25 S) протягом лютого—квітня 2019 року. Основною метою дослідження була реалізація однопозиційного методу для моніторингу параметрів нижньої іоносфери та локації потужних грозових розрядів, розподілених по всій планеті

Localized ionospheric disturbance over the earthquake epicentre and modifications of Schumann resonance electromagnetic fields

The impact of seismogenic ionosphere non-uniformity is considered on the Schumann resonance (SR) signals observed both in the vertical electric and two orthogonal horizontal magnetic field components. The model is able to interpret the anomalous signals observed in Japan in possible association with the earthquakes (EQs) in Taiwan. Changes in the SR intensity arise from a localized reduction of the ionosphere over the EQ epicentre. Signals in the regular Earth–ionosphere cavity are described by using the knee model of vertical conductivity profile. It is suggested that pre-seismic and seismic activity lowers the knee altitude by 20 km at the centre of disturbance, and the perturbation has the Gaussian radial dependence in the 1 Mm zone. The diffraction problem in the cavity with a localized disturbance is resolved by using the Stratton–Chu integral equation. The data of Optical Transient Detector are used to model the source distribution. A pronounced modification is obtained in the intensity around the fourth mode frequency in a form of abrupt spectral changes. The model data are found to be similar to observations, and properties of the model seismic anomalies are discussed

Observational and Model Impact of Tonga Volcano Eruption on Schumann Resonance

Tonga volcano eruption on 15 January 2022 was accompanied by an unprecedentedly high lightning activity in the volcano plume which significantly exceeded the lightning activity level of the whole globe. We compare model computations with the observed effect of the Tonga volcano eruption on the global electromagnetic Schumann resonance (SR). This SR disturbance was detected at many observatories covering the whole globe. SR power spectral density was computed using the updated model of the Earth-ionosphere cavity, with the global lightning detections recorded by the World Wide Lightning Location Network, as a source. The modeled dynamics of the SR disturbances during Tonga eruption agrees qualitatively and quantitatively with SR recordings from six globally separated observatories. Unprecedentedly high lightning activity during the active phase of eruption caused significant suppression of the global lightning detection rate without noticeable effect on real global thunderstorm activity.publishedVersio