Polar Geophysical Institute

The relevance of studying the dynamics of ozone concentration in the troposphere is due to the fact that in high concentrations it is a strong poison and a powerful oxidant that extremely negatively impacts both biological structures and the environment. Therefore, the dynamics of ozone concentration require urgent study in different areas of the Earth. Based on monitoring data, the paper examines the distribution of tropospheric ozone in Russia in 2023 in the surface air layer, as well as its vertical distribution based on the results of aircraft sensing. It is shown that the maximum permissible daily average concentrations established by the national hygienic standard, including maximal one-time, daily average, and annual average, were exceeded at all measurement sites. The current situation necessitates widespread public awareness of the results of monitoring and the development of environmental protection measures to reduce the concentration of ozone and its precursors in the surface air layer. The results of the work can be useful to specialists in the fields of atmospheric physics, climatology, and environmental protection, as well as to administrative bodies of different responsibility levels.

Polar” substorms are identified as substorm‐like disturbances that are exclusively observed at high geomagnetic latitudes (>70° MLAT) and are absent at lower latitudes. Although “polar” substorms typically occur during periods of quiet geomagnetic activity, it is still unclear whether they can develop under extremely quiet conditions when geoeffective space weather parameters are exceptionally low. Utilizing data from the IMAGE network across the Svalbard archipelago within the longitudinal sector of (∼108–114 Mlong), we examined 92 “extremely quiet geomagnetic” intervals from 2010 to 2020, which were associated with intervals of extremely slow solar wind (ESSWs, V < 300 km/s). We discovered that “polar” substorms can occur during ESSWs, but only with the presence of a negative Bz component. A total of 32 such events were identified from 17 ESSW intervals (∼19% of all ESSW intervals). We found that “polar” substorms during ESSWs display the primary characteristics of ordinary substorms, including the accompaniment of Pi1B geomagnetic pulsations, positive subauroral or mid‐latitude magnetic bays, a poleward shift of the westward electrojet, and auroral activity during their expansion phase. Additionally, it was found that the majority of “polar” substorm events during ESSWs (∼82%) were isolated substorms, developing solely in the pre‐midnight sector without disturbances in other longitudinal sectors. Several “polar” substorm events have been examined in detail.

The geophysical processes in the dayside polar cusp on December 22, 2003 under the northern orientation of the interplanetary magnetic field (IMF), relatively high speed and low density of the solar wind by using the ground-based optical observations on Spitsbergen and DMSP F16 spacecraft observations were examined. A comparison of spacecraft and ground-based observations shows that soft electron precipitation in the cusp region determine the region of the auroral luminosity in the (OI) 630.0 nm emission. The peculiarity of the event under consideration is the observation of a bright rayed auroral arc bordering the dayside cusp from its polar edge. The results of observations of the low-altitude DMSP F16 spacecraft during its pass over the rayed arc were analyzed. Explanations of the observed phenomena are proposed based on the analysis of changes in the spectra of precipitating electrons and the formation of an electron beam by a field-aligned electric field.

During the expansion phase of a substorm, the poleward jump of auroras (breakup) and the expansion of the auroral bulge are observed. The expansion is accompanied by a negative magnetic bay under the aurora and a positive magnetic bay at mid-latitudes. The magnitude of the negative bay is characterized by the auroral AL-index. The Mid-Latitude Positive Bay index (MPB-index) was previously proposed in order to characterize the positive bay. In this article, the statistical relationship of the MPB-index with the geomag-netic activity at different latitudes and with the parameters of the solar wind and interplanetary magnetic field is investigated. It is shown that all extremely high values of the MPB-index (above 10000 nT 2) are observed during strong geomagnetic storms (when the Dst-index falls below-100 nT), all extremely strong geomag-netic storms (when the Dst-index falls below-250 nT) are accompanied by extremely high values of the MPB-index. Statistically, the MPB-index increases with increasing geomagnetic activity at any latitude. On average, the MPB-index increases with increasing interplanetary magnetic field magnitudes and any of its components. However, for the Bz-component, large values of the MPB-index are observed at its southward orientation. For the plasma parameters of the solar wind, the MPB-index increases most strongly with the increase of its speed. The dependence on the dynamic pressure and on the value of the E Y-component of the electric field of the solar wind is also strong. However, the MPB-index weakly depends on the density and temperature of the solar wind.

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.

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.

It is generally recognized that the formation of the fold-and-thrust tectonic structures of mobile belts on continents is associated with crushing and narrowing of the Earth’s crust as a result of collision of lithospheric plates. The deformation of the Caucasian lithosphere in the neotectonic time is generally consistent with these ideas. However, the block differentiation of the Caucasian lithosphere introduces specific features in the directivity of modern vertical and horizontal movements. In this paper, we analyze vertical movements of the Caucasus estimated by means of high-precision leveling over more than a century and consider their spatial correlation with tectonics, seismicity, stress-strain state, and geophysical fields. A clear relationship indicating the deep tectonic nature of the long-term uplifting of the Caucasus crust is revealed. Due to the differentiation of the Arabian plate movement, the territory of the Caucasus is divided into provinces that differ from each other in the pattern of modern movements, in the orientation of faults, and in the stress-strain state. The seismic regime in these provinces also has differences in the number of seismic events and focal mechanisms of the earthquakes. We propose a model of the deformation mechanism of the Greater Caucasus, which takes into account the long-term trend of the Caucasus uplifting in the conditions of general shortening of the Earth’s crust. The results of the analysis are used as a basis for discussion of a probable mechanism of tectonic evolution of the Greater Caucasus in the neotectonic time, which can be used in the assessment of seismic hazard in the North Caucasus.

We analyzed 214 events of ‘polar’ substorms on the Scandinavian meridian IMAGE, i.e., substorms recorded by magnetometers located at geomagnetic latitudes above ~70° MLAT at 1900−0200 MLT during a magnetically quiet time in the absence of negative magnetic bays at lower latitudes. The Harang discontinuity, which separates the westward and eastward electrojets by latitude, is a typical structure for the indicated MLT sector of the high-latitude ionosphere. The global distribution of ionospheric electrojets and the location of the Harang discontinuity during development of ‘polar’ substorms were studied using the maps compiled from the results of spherical harmonic analysis of magnetic measurements on 66 simultaneous ionospheric communications satellites of the AMPERE project. Based on analysis of these maps, it is shown that the instantaneous location of the equatorial boundary of the ionospheric current of a ‘polar’ substorm determines the instantaneous location of the polar boundary of the Harang discontinuity, and the polar boundary of the eastward electrojet determines its equatorial boundary. It has been established that the appearance of 90% of ‘polar’ substorms is observed simultaneously with increasing planetary substorm activity according to the AL-index and development of a magnetospheric substorm in the postmidnight sector. At the same time, the development of evening ‘polar’ substorms is associated with the formation of near-midnight magnetic vortices at geomagnetic latitudes of ~70° MLAT (near the “nose” of the Harang discontinuity), indicating a sharp local enhancement of the field-aligned currents. This leads to the formation of a new substorm in the evening sector of near-polar latitudes, called a ‘polar’ substorm with typical features of the onset of a substorm (Pi2 geomagnetic pulsation bursts, sudden onset of the substorm close to the equatorial boundary of the contracted oval (the development of a “substorm current wedge”, etc.

Electromagnetic ion cyclotron (EMIC) waves can very rapidly and effectively scatter relativistic electrons into the atmosphere. EMIC‐driven precipitation bursts can be detected by low‐altitude spacecraft, and analysis of the fine structure of such bursts may reveal unique information about the near‐equatorial EMIC source region. In this study, we report, for the first time, observations of EMIC‐driven electron precipitation exhibiting energy, E, dispersion as a function of latitude (and hence L‐shell): two predominant categories exhibit dE/dL > 0 and dE/dL < 0. We interpret precipitation with dE/dL < 0 as due to the typical inward radial gradient of cold plasma density and equatorial magnetic field (∼65% of the statistics). Precipitation with dE/dL > 0 is interpreted as due to an outward radial gradient of the equatorial magnetic field, likely produced by energetic ions freshly injected into the ring current (∼35% of the statistics). The observed energy dispersion of EMIC‐driven electron precipitation was reproduced in simulations.