Volume 89, Nº 5 (2025)

The occurrence of geomagnetically induced currents (GIC) in the Northwest part of Russia associated with jumps in the solar wind dynamic pressure is investigated. Based on the data from the IMAGE and SuperMAG magnetometer networks, as well as the OMNI database, a detailed analysis of the complex space weather event of November 3-4, 2021 was carried out: phenomena in the solar wind, geomagnetic activity, which are compared with the occurrence of intense GICs. Direct measurements of the GIC in the neutral line of the transformers located on the Karelian-Kola power transmission line (Vykhodnoy, Louhi, Kondopoga) and on the natural gas pipeline nearM¨аnts¨аl¨а (South of Finland) are used. The complex space weather event was divided into three cases observed in the midnight, morning and daytime sectors. Each case was associated with the jump in the solar wind dynamic pressure (∼ 20-30 nPa). It is shown that in the midnight and morning sectors the cause of the GIC excitation was the intensification and expansion of the substorm westward electrojet; in the daytime and early evening sectors - sharp intensifications of the eastward electrojet, which were associated with the development of supersubstorms and intense substorms on the night side. In the morning and daytimeMLT sectors, during the recovery phase of substorms and after them, Pi3 pulsations were observed, which also caused GIС, but their values did not exceed the threshold values.

The evolution of polar tongue of ionization (TOI) in electron content measurements during 7 November 2022 geomagnetic storm was analyzed. The tongue was formed during the daytime over Canada and then occurred in the nighttime ionosphere on the European region. The increase of ionospheric irregularities intensity in the polar region was revealed and their connection with TOI was shown.

The PAIPS experiment was created for studying UV luminescence in the auroral region. This experiment represents a system of two imaging photometers with high temporal resolution, located 153 km apart in space and directed into the same region of the atmosphere. This experiment configuration allows stereometric spatial and temporal structure measurements of luminosity. We presented some results from the pulsating auroras (PA) and UV microbursts analysis, as well as examples of the track event reconstruction using probabilistic models based on Bayesian inference. Operation of luminescence altitude calculation algorithm is shown using a single PA event. A database of UV microbursts (series of short UV flashes) for two seasons of the experiment (2021/2022 and 2022/2023) was obtained and analysed.

The registration times of extreme values of the main parameters of the interplanetary medium, cosmic ray variations and geomagnetic activity during the passage of coronal mass ejections with a magnetic cloud past the Earth have been studied. The following parts of interplanetary disturbances were considered: (I) from the interplanetary disturbance onset to the magnetic cloud onset, (II) inside the magnetic cloud, (III) from the magnetic cloud end to the interplanetary disturbance end, which was often the onset of the next interplanetary disturbance. It is shown in which part of the interplanetary disturbances the extremes of solar wind speed, interplanetary magnetic field, density and anisotropy of cosmic rays, as well as geomagnetic activity indices are most often recorded.

We presented the results of the auroral hiss illuminated region location based on measurements of the magnetic field polarization and azimuthal angles of arrival of these emissions according to observations at the Barentsburg Observatory (BAB). The results obtained are compared with the position of the longitudinal current amplification region supplied by the AMPERE project. An event is identified where two separate regions of field-aligned current amplification exist simultaneously. The arrival angles histograms at BAB have two maxima, indicating waves arriving from two distinct directions. We also discussed the event of moving the hiss illumination region along the longitude from east to west, simultaneously with the movement of the aurora and the region of field-aligned currents in the same direction, as well as the simultaneous displacement of the illumination region and the area of amplification of the resulting longitudinal currents towards the auroral latitudes. Based on the findings of our analysis, we have proposed a possible connection between the occurrence of hiss on the ground-based level and the activity of longitudinal currents in the ionosphere.

We studied spectral characteristics of VLF waves observed onboard the Van Allen Probe B satellite on November 30, 2015. The peculiarity of the observed spectrum is the presence of two spectral maxima below and above half the electron gyrofrequency. Such a feature, typical of the spectra of chorus emissions, was observed for noise-like emissions in the case under discussion. Simultaneously with the observation of VLF emissions, the satellite also measured differential fluxes of energetic electrons, the magnitude of the ambient magnetic field, and cold plasma concentration. Based on these data, the growth rates of waves in the whistler band were calculated. The calculations were performed in two different ways, which yielded similar results. Comparison of the observed spectra of noise emissions and the calculated wave growth rates shows their good agreement.

We provided a description of the structures of aurora by fractal dimension and its anisotropy. The variability of structures is characterized by the slope of the spectrum of anisotropy variation over time. Statistics of these characteristics are presented based on data from the ground camera of the Polar Geophysical Institute in Apatity for 2013-2015 and referenced by position inside the auroral oval and geomagnetic field values in the Lovozero observatory.

The effect of three factors on the dependence of the average energy of the auroral electron flux on the ratio of the intensities of the 630.0 and 427.8 nm emissions, namely: the shape of the energy spectrum of the auroral electron flux, the concentration of atomic oxygen in the neutral atmosphere and the concentration of nitrogen oxide, was studied using numerical modeling. It is shown that the influence of the considered factors on the average dependence does not exceed 20% for the ratios of emission intensities of 630.0 and 427.8 nm, which lie in the range from 0.1 to 10. An analytical approximation of the calculated dependence is presented.

Numerical experiments were carried out aimed at investigating the changes in atmospheric and ionospheric parameters caused by the propagation of atmospheric waves from the troposphere from a meteorological source. Numerical simulations were carried out using the high-resolution numerical model AtmoSym and the Global Self-Consistent Model of the Thermosphere, Ionosphere and Protonosphere (GSM TIP). Acoustic and internal gravity waves are included in the large-scale model without parameterization.

The operation of a spin-injection THz emitter based on an array of two-layer FeCo/FeNi nanowires grown in a track membrane is investigated. The general operating principle of a spin-injection emitter is presented. The non-thermal nature of spin-injection radiation in the frequency range of 15–20 THz was experimentally demonstrated. When the voltage reached 3 V, the effect of an abrupt increase in the resistance of the emitter, a decrease in its current, and at the same time an increase in the emitted power was observed. The effect of power increase with decreasing current is presumably associated with the presence of spin impedance in the magnetic transitions of nanowires.

Interplay between properties of hyperonic interactions and neutron star observables is studied with Skyrme NN, ΛN, and ΛΛ potentials. It is shown that the ΛN potentials with different density dependencies, which describe Λ hypernuclear spectra equally well, lead to substantially different dependence of neutron star mass on its radius. The role of the nucleon density dependence of ΛΛ potential is considered within the Skyrme formalism at the first time. It is shown that this dependence influences the calculated masses and radii weaker.