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The results of practical use of a POS-4 vector magnetometer, developed by the Research Laboratory of Quantum Magnetometry, UrFU (Yekaterinburg) and based on POS Overhauser sensors, are presented. Continuous measurements by POS-4 have been carried out at the Paratunka observatory (IKIR FEB RAS, Kamchatka) since 2015, were done at the Saint Petersburg observatory (GC RAS / IZMIRAN SPb Branch, Leningrad Region) in 2017-2018 and have been performed at the Arti observatory (Institute of Geophysics, UB RAS, Sverdlovsk Region) since 2020. On the new high-latitude observatory White Sea (IAGA code WSE, GC RAS / MSU, Nikolai Pertsov White Sea Biological Station , Karelia), POS-4 is used as a main variometer for magnetic measurements. In April 2019, the magnetometer was successfully used for field measurements on ice during the TRANSARCTIC expedition in the Barents Sea (AARI, Roshydromet). At the beginning of 2021 IZMIRAN started testing two POS-4 magnetometers at the Moskow observatory. According to the results of field and observatory measurements it was possible to identify the advantages and disadvantages of the magnetometer and provide the information for its developers for further modernization in order to improve its efficiency and reliability. Many years of experience in POS-4 application determine the areas where its scientific and applied usage will provide important results, for example, for magnetic measurements in the Arctic regions or for monitoring of active zones around volcanoes.

A case is described of multiple current sheets crossed by the MAGION-2 satellite in the near-midnight quieting auroral oval. The data were obtained by the magnetometer experiment onboard. Results show during a quieting period after a preceding substorm, or during an early growth phase of the next substorm, two double-sheet current bands, POLB and EQUB, located at respectively the polar and equatorial borders of the auroral oval separated by about 500 km in latitude. This is consistent with the double-oval structure during recovery introduced by Elphinstone et al. (1995). Within the POLB, the magnetic field data show simultaneous existence of several narrow parallel bipolar current sheets within the upward current branch (at 69.5–70.3° invariant latitude) with an adjacent downward current branch at its polar side at (70.5–71.3°). The EQUB was similarly stratified and located at 61.2–63.5° invariant latitude. The narrow current sheets were separated on average by about 35 km and 15 km, respectively, within the POLB and EQUB. A similar case of double-oval current bands with small-scale structuring of their upward current branches during a quieting period is found in the data from the MAGION-3 satellite. These observations contribute to the double-oval structure of the late recovery phase, and add a small-scale structuring of the upward currents producing the auroral arcs in the double- oval pattern, at least for the cases presented here. Other observations of multiple auroral current sheets and theories of auroral arc multiplicity are briefly discussed. It is suggested that multiple X-lines in the distant tail, and/or leakage of energetic particles and FA currents from a series of plasmoids formed during preceding magnetic activity, could be one cause of highly stratified upward FA currents at the polar edge of the quieting double auroral oval.

Parameters of field-aligned currents reconstructed by ground-based measurements of magnetic field in the Scandinavian countries (IMAGE) and ionospheric conductivity for specific events of the 6 and 8 December 2004 are represented here. Ionospheric conductivity was calculated from precipitating electron flux measured at DMSP-13 satellite and electron density EISCAT incoherent scattering radar direct measurements. There is a high correlation between field-aligned currents, calculated from DMSP-13 satellite data and field-aligned currents calculated from radar measurements for the December 6, 2004 in the presence of developed ionospheric current system. The comparison of field-aligned currents, reconstructed by the proposed method, with the currents calculated by the variation of magnetic field on the DMSP satellites, confirms correctness of the offered algorithm.

The spatial dynamics of bursts of geomagnetic Pi2-type pulsations during a typical event of a magnetospheric substorm (April 13, 2010) drifting to the pole was investigated using the method of generalized variance characterizing the integral time increment of the total horizontal amplitude of the wave at a given point in the selected time interval. The digital data of Scandinavian profile observations from IMAGE magnetometers with 10-second sampling and data of the INTERMAGNET project observations at the equatorial, middle-latitude and subauroral latitudes with a 1-second sampling were used in the analysis. It was shown that Pi2 pulsation bursts in a frequency band of 8–20 mHz appear simultaneously on a global scale: from the polar to equatorial latitudes with maximum amplitudes at latitudes of the maximum intensity of the auroral electrojet and with a maximum amplitude of geomagnetic pulsations Pi3 within a band of 1.5–6 mHz. The first (left-polarized) intensive Pi2 burst appeared at auroral latitudes several minutes after breakup, while the second (right-polarized) burst occurred 15 min after breakup but at higher (polar) latitudes where the substorm had displaced by that time. The direction of wave-polarization vector rotation was opposite for auroral and subauroral latitudes, but it was identical at the equator and in the subauroral zone. The pulsation amplitude at the equator was maximal in the night sector.

The relationships between the average hourly values of the vertical ground-level electric field measured at the Vostok Antarctic station and the ionospheric potential above the station have been obtained. The ΔEz and Uext parts of both parameters controlled by the solar wind were considered. Convection models (Weimer, 1995; Lukianova and Christiansen, 2006) and a model based on the SuperDARN radar system were used to determine the ionospheric potential. An analysis has been performed for isolated days and the entire sample in 1998–2000 (including 170 days of “fine weather”). For an isolated day, the best correlation coefficients (R) between ΔEz and Uext obtained using the three models were 0.81, 0.80, and 0.88, respectively. The total correlation coefficient for the entire data set was R = 0.24−0.32. The R value was larger during daytime (R ≈ 0.4) and smaller at night (R ≈ 0.1) and slightly increased in the early morning hours. The specific features of daily variations in R apparently indicate that it is possible to adequately describe the structure of the ionospheric electric field equipotentials by using large-scale stationary convection models. The R value varies complexly, depending on the IMF orientation, but it generally tends to increase from IMF By 0, which is explained by the asymmetric convection patterns for opposite By signs.

Geomagnetic variations observed at the meridional chain of stations in Greenland during 1982–1992 are utilized for the study of relationships between occurrence of azimuthal currents in the dayside cusp/cleft region and changes in the interplanetary magnetic field (IMF) By and Bz components. Events were selected for analysis if (1) the Greenland West Coast stations were located near magnetic noon ∼ 1400 UT and (2) the absolute values of the IMF Bz were less than By. Sixteen events were selected under these conditions. The analysis shows that intensive azimuthal currents develop in the cusp/cleft region in association with the southward IMF despite the fact that the IMF By component had the same orientation during the few previous hours. The direction of these currents (westward or eastward) is specified by the sign of the By component (negative or positive, respectively). If the IMF By is not zero but Bz is mainly northward, no significant currents are observed in the cusp/cleft region at all. As a result, because magnetic substorms usually follow extended periods of southward Bz, the dayside cusp/cleft magnetic perturbations often precede substorm activity in the midnight sector of the auroral zone. This can simply be a connection between the dayside cusp/cleft and nighttime auroral electrojets and therefore could be used as the dayside substorm precursors.