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We analyze variations in geomagnetically induced currents (GIC) and pulsations of the geomagnetic field latitudinal By component in the frequency range 1–20 mHz. The analysis is based on the data from GIC registration at the Kola Peninsula and magnetic data from IMAGE network stations, obtained with 10 s sampling in 2017. This allows us to include pulsations of both Pc5/Pi3 and Pc4/Pi2 frequency range in the analysis and examine polyharmonic pulsations with spectral maxima in both ranges. It is shown that GICs are effectively generated at frequencies above 5 mHz. Polyharmonic pulsations are potentially more dangerous than monoharmonic ones because the ratio of GIC to magnetic field pulsations’ amplitude is higher and the lifetime of unipolar GIC is longer.

In this paper, we describe the TeslaSwarm online system [http://aleph.gcras.ru/teslaswarm] for visualizing field-aligned currents in the upper ionosphere, using data from Swarm low-orbit satellites. The system provides researchers with a simple and convenient tool for event selection and detailed analysis of currents and electromagnetic fields in the upper ionosphere. The system user can select satellite passages over a given region, visualize the geomagnetic field structure and field-aligned currents, compare the pattern of field-aligned currents with the auroral particle precipitation map, using the OVATION-Prime model, and save the selected parameters in a file in text format. We demonstrate advantages of the developed system over its foreign analogues. In practice, the collection and pre-processing of raw data for experiments make up about 80 % of all work with data. The proposed online system largely saves the user from the most time-consuming work of choosing the required satellite passage segments and calculating the characteristics of interest from raw measurements.

We examine magnetic field variations at 4–12 Hz frequencies in the upper ionosphere and on Earth. The ground response to the coherent oscillations at two SWARM satellites near and above the high frequency boundary of the nominal Pc1 range is studied. We use CARISMA data to analyze ground pulsations. Ionospheric oscillations are predominantly registered at geomagnetic latitudes above 65°, i. e. from the auroral zone to the polar cusp-cleft region. The oscillations at the same frequencies are recorded at auroral and subauroral ground stations at distances from 1500 to 3000 km from satellite footprint. Ratio RGI of the oscillation amplitude on Earth to that in the ionosphere retrieved from the observed data is compared to the values calculated for a finite radius Alfvén beam incident onto a quasi-real ionosphere. [Fedorov et al., 2018]. Radial distribution of RGI depends on the oscillation frequency and the altitude distribution of ionospheric parameters controlled mostly by season and local time. The most probable values of RGI range from 10–3 to 10–1. The RGI values obtained from the observed data agree with model ones at incident beam radius of about several hundred kilometers.

Despite the existing variety of approaches to monitoring space weather and geophysical parameters in the auroral oval region, the issue of effective prediction and diagnostics of auroras as a special state of the upper ionosphere at high latitudes remains virtually unresolved. In this paper, we explore the possibility of local diagnostics of auroras through mining of geomagnetic data from ground-based sources. We assess the significance of indicative variables and their statistical relationship. So, for example, the application of Bayesian inference to the data from the Lovozero geophysical station for 2012–2020 has shown that the dependence of a posteriori probability of observing auroras in the optical range on the state of geomagnetic parameters is logarithmic, and the degree of its significance is inversely proportional to the discrepancy between empirical data and approximating function. The accuracy of the approach to diagnostics of aurora presence based on the random forest method is at least 86 % when using several local predictors and ~80 % when using several global geomagnetic activity indices characterizing the geomagnetic field disturbance in the auroral zone. In conclusion, we discuss promising ways to improve the quality metrics of diagnostic models and their scope.

We have analyzed geomagnetic variations in the 2.5–12 Hz frequency range in the ionospheric F layer above the electron density maximum, using data from two SWARM satellites. The analysis is based on the data obtained under weak and moderate magnetic activity for 12 days in September and December 2016. To separate spatial inhomogeneities from time variations of the magnetic field, we analyzed signal waveforms and cross-spectra in a 2.56 s sliding window. A maximum in the occurrence and power spectral density of the variations was found at latitudes above the polar boundary of the auroral oval, which correspond to the magnetospheric input layers and dayside polar cusp/cleft. Typical waveforms of the high-latitude variations are the wave packets lasting for 5–10 periods, recorded with a short time delay by two satellites spaced by 40–100 km. These variations might be the ionospheric manifestation of the electromagnetic ion-cyclotron waves generated at the non-equatorial magnetosphere near the polar cusp. The waveforms and cross-spectra of the variations are examined in more details for two cases with different spatial distributions of the magnetic field in the ionosphere. For the ionospheric conditions corresponding to event 1 (September 17, 80° geomagnetic latitude, afternoon sector), spatial distributions of wave magnetic field in the ionosphere and on Earth are estimated using a model of Alfvén beam with a finite radius incident on the ionosphere [Fedorov et al., 2018].

An interactive computer model of a short-term (with a horizon 30–70 min) forecast of aurora intensity has been developed in the form of a web-based geoinformation system. The OVATION-Prime empirical model is used as the basic software, which establishes statistical relationships between parameters of the solar wind, the interplanetary magnetic field, and auroral particle fluxes. On the basis of this model, a system has been built which simulates the spatial planetary distribution of the probability of observing auroras and a number of accompanying quantities. Data visualization is carried out on the basis of the virtual globe technology and is provided to the end user via a specialized web service. The forecast has been verified by comparing the model predictions with the data from 16 cameras conducting continuous observations of the auroras in the visible spectrum. The proportion of coincidences between the predicted and observed auroras was 86 %. The developed service enables both forecasting and analysis of past events. The system allows us to compare the spatial distribution of probability of auroras with railway transport systems for the territory of the Russian Federation.

The eruption of the Tonga volcano on January 13 and 15, 2022 and related intense lightning activity led to the excitation of a number of specific electromagnetic oscillations in different frequency ranges. We examine properties of these oscillations, using data from magnetometers of various types located in Kamchatka and in the Pacific region. We confirmed that there might have been a geomagnetic response to the formation of an acoustic resonance between the Earth surface and the ionosphere: localized harmonic oscillations with a frequency 3.5–4.0 mHz, which lasted for ~1.5 hr, were detected ~15 min after the beginning of the eruption at distance of ~800 km. An increase was observed in the intensity of the Schumann resonance at stations in the Far East. Broadband emission stimulated by intense volcanic lightning was detected to occur in the Pc1 range (2–5 Hz). The emission presumably results from the excitation of the magnetosonic waveguide in the upper ionosphere by lightning activity.

A numerical model has been elaborated to calculate ULF electromagnetic fields in the ground-atmosphere–ionosphere system created by an underground horizontal current source of a finite length. The modeling has enabled us to examine in detail characteristic features of ULF response to an underground large-scale emitter that may be used for a search of electromagnetic earthquake precursors. The most promising features that might discriminate signals from an underground source and from a magnetosphere-ionosphere source are (a) the apparent impedance of the electromagnetic field derived from simultaneous observations of horizontal magnetic and electric fields, and (b) the ratio of vertical and horizontal magnetic component amplitudes. Besides that, the amplitude-phase gradients of signals from an underground source differ significantly from those of the magnetospheric source. For the same magnitude of horizontal magnetic disturbance on surface, an underground current source produces in a borehole a much larger vertical electric field Ez than a magnetospheric source does. At the same time, some properties, such as the ratio between the vertical and horizontal electric components, are shown to be ineffective. However, all these differences with ionosphere-magnetosphere source reveal themselves only in a vicinity of lithospheric source (< 30 km for depth 20 km). [ABSTRACT FROM AUTHOR]

The feasibility of the detection of electromagnetic response in the upper ionosphere to ground large‐scale ultra‐low‐frequency (ULF) and extremely‐low‐frequency (ELF) transmitters by low‐Earth‐orbit (LEO) satellites is considered. As an example of such transmitters, we consider the ZEVS 82 Hz transmitter, FENICS installation driven by 0.5–150 Hz generator, and industrial 50 Hz unbalanced power transmission lines. We numerically model the ULF/ELF wave energy leakage into the upper ionosphere from an oscillating grounded linear power line of a finite length suspended above a ground with a finite resistivity. The numerical scheme is based on the theoretical formalism developed to describe the excitation of an electromagnetic field by a horizontal grounded dipole. A realistic altitudinal profile of the plasma parameters has been reconstructed with the use of the IRI ionospheric model. For the ZEVS transmitter powered by 200 A current the modeled amplitudes of electromagnetic response can reach in the upper nightside ionosphere up to 60 µV/m and 6 pT. The assumption of an infinite source scale overestimates the ionospheric response by a factor of ∼7 as compared with realistic scale 60 km of the ZEVS transmitter. Unbalanced 50 Hz current of 10 A in large‐scale (>100 km) power transmission lines can produce the electric response in the upper ionosphere that is sufficient to be detected by electric sensors at LEO satellite. The stimulation of artificial Pc1 pulsations (0.5 Hz) with amplitudes ∼1 pT and ∼10 µV/m by large‐scale (>100 km) power lines is possible with driving current >100 A. The use of decommissioned power lines can be a cheap and efficient tool to stimulate Pc1 pulsations in the ionosphere. Plain Language Summary: Our planet was found to exist in an electromagnetic environment, at least in some frequency bands, created by rather industrial activity than by natural processes. The electromagnetic response in the ionosphere to thunderstorms and radio transmitters has been well studied in the very‐low‐frequency range (>1 kHz), but much less attention has been paid to the extremely‐low‐frequency (ELF) (≪1 kHz) and ultra‐low‐frequency (ULF) (<1 Hz) bands. Any noticeable ULF/ELF emission efficiency may be expected only for extremely large‐scale emitting systems. Such man‐made transmitters do exist. Powerful ELF aerials for communication with submarines with a length of about several tens of km were constructed. Special experiments with controlled sources of electromagnetic fields of ULF/ELF bands were carried out using decommissioned power lines as a horizontal radiating antenna. Transportation systems can also be extended ULF antenna. Finally, unbalanced networks of electric power transmission 50/60 Hz lines become large‐scale emitters. Our numerical modeling has proved that manmade ULF/ELF electromagnetic activity near the ground can be monitored by low‐Earth‐orbit satellites. The large‐scale decommissioned power lines can be used to stimulate artificial Pc1 pulsations with frequency ≤1 Hz in the ionosphere‐magnetosphere system. These experiments open the possibility to stimulate a loss of relativistic electrons from the radiation belt. Key Points: New numerical model of ultra‐low‐frequency/extremely‐low‐frequency emission generation in the ionosphere by a near‐ground linear current of a finite length has been elaboratedThe model gives the possibility to estimate electromagnetic response of the ionosphere to current sources of different lengthsArtificial Pc1 pulsations can be generated in the upper ionosphere by a large‐scale power line system [ABSTRACT FROM AUTHOR]