It was proposed to introduce new regional geomagnetic indices SME-R and VAR characterizing the values of the geomagnetic field perturbation and its variability (i.e., dB/dt) in the Russian sector at auroral latitudes into space weather studies. The indices are calculated from data of the Russian magnetic stations at geomagnetic latitudes from 40° to 70°. We compared the unofficial and regional indices with the standard planetary indices during some magnetic storms of 2015. In addition to the official IAGA indices Dst/ SYM-H, AE, PC, modified and regional indices SME, PC-n, ULF, EI, Wp (Pi2) were considered. The analysis of these events showed that some auroral activations confidently distinguished by the SME index can be missed by the standard AE index. The discrepancy between the standard PC and the refined PC-n indices reaches 1 mV/m to 2 mV/m during strong perturbations. The variability of the magnetic field characterized by the VAR index is not uniquely related to the level of geomagnetic perturbation characterized by the AE or SME-R indices. The events considered show that the use of planetary indices to estimate regional space weather perturbations can lead to false conclusions. The database of standard, modified, and new regional indices for 2015 is freely available at the FTP site ftp://indexguest:indexguest@imagftp.gcras.ru/ for testing.

Ultralow frequency (ULF) waves in the Pc5 band have been suggested as a possible intermediary transferring energy from high‑speed streams of the solar wind to magnetospheric electrons. Although ULF waves are not the only mechanism of accelerating electrons up to relativistic energies, nonetheless they are an essential element of the electron energization process, though their role has not been finally established yet. Among observational facts regarding the interrelationships between Pc5 wave activity and electron dynamics, we discuss the following pro and con factors related to the ULF‑associated energization mechanisms: The correlation of electron fluxes at the geosta‑tionary orbit and the Pc5 wave power; The correspondence between the azimuthal phase velocities of toroidal and poloidal Pc5 waves and the electron magnetic drift; The correspondence between the latitudinal structure of Pc5 waves and the outer radiation belt. Consideration of these facts does not allow one to unambiguously resolve the issues concerning the role of ULF waves in the magnetospheric electron energization. We suggest that the acceleration of electrons by ULF disturbances may occur not in a regime of “geoserfotron” with Pc5 waves (match of the azimuthal velocities of waves and drifting electrons), but rather in a regime of “geosynchrotron” with transit‑time acceleration by substorm‑related Pi3 pulsations.

This review considers several issues of space weather studies that are directly related to the problem of geomagnetically induced current (GIC) excitation in the power line transmission systems. Expectations to reduce the damage to technological systems from space weather were related with elaboration of models capable of real-time predictions of electromagnetic disturbances at the Earth's surface. However, the examination of the feasibility of the MHD simulation to predict the level of geomagnetic field variability, and consequently GICs, during the May 27–28, 2017 storm showed that the modeling reasonably well reproduced the global magnetospheric parameters, but the predicted magnetic field variability dB/dt has turned out to be more than order of magnitude less than that observed. The reason is the inability of current global MHD models to adequately predict the fine structure of the storm/substorm – Pi3 disturbances, and consequently GICs that they drive. Moreover, impulsive disturbances such as Pi3 pulsations demand a special tool for their analysis. Data processing technique for a 2D network of magnetic stations has to be elaborated to automatically recognize eddy current structures in the ionosphere and estimate their characteristics. The proposed technique applied to Pi3 pulsations on March 17, 2013 revealed that each vortex caused a disturbance of the vertical magnetic component Z and GIC burst up to ∼ 100A. The efficiency of GIC generation by different types of magnetic storms must be examined. For that it is necessary to compare GIC responses to storms caused by coronal mass ejection and by corotating interaction region, and to estimate the normalized GIC-effectiveness of each storm. The excitation rate of GIC during storms may be associated with the occurrence of mesoscale current vortices.

Practical steps taken by the international community to reduce the damage to technological systems from space weather include the development of numerical models capable of real-time predictions of electromagnetic disturbances at the Earth’s surface. Here we examine the feasibility of a version of the Space Weather Modeling Framework (SWMF) global MHD simulation code similar to that used by the NOAA Space Weather Prediction Center to predict the level of geomagnetic field variability, and consequently geomagnetically induced currents (GICs). We consider the contribution of geomagnetic disturbances to the bursts of GIC in the electric power line of the Kola Peninsula during the May 27–28, 2017 storm and compare the observations with results of the global MHD model. During the maximal disturbance magnetic field variations at East Scandinavian stations become more irregular, as intense Pi3 pulsations are superposed on the magnetic bay. These pulsations are not quasi-sinusoidal waves like typical Pc5 pulsations, but they are rather a quasi-periodic sequence of magnetic impulses with time scales ~5–15 min. During this period with elevated Pi3 activity very high values of GIC were recorded (variations >100 A) in the electric power transmission line. The SWMF modeling reasonably well reproduces the global magnetospheric parameters, such as SYM-H index or cross-polar potential. However, the magnetic field variability dB / dt in the East Scandinavia predicted by the modeling has turned out to be more than order of magnitude less than that observed. Thus, the version of SWMF with the grid used by NOAA SWPC still cannot adequately predict for the May 27–28 event the fine structure of the storm/substorm—Pi3 geomagnetic disturbances, and consequently the magnitude of the GIC that they drive.

ULF (Ultra-Low-Frequency) wave index, characterizing the level of geomagnetic field fluctuations in the frequency band of most intense Pc5 pulsations (1.7–6.0 MHz), was introduced earlier for the analysis of space weather. This global hourly index was produced from available 1-min magnetometer data, but from stations in the Northern hemisphere only. If ULF wave powers in conjugate hemispheres were strongly asymmetric, an index derived from one hemisphere data only may be misleading to characterize the global magnetospheric ULF activity. Therefore, it is important to examine how strong is the interhemispheric asymmetry of the ULF power. This issue is relevant to important problem: how strongly does the ionosphere control interhemispheric properties of Pc5 pulsations? To resolve this problem, we use data from the conjugate Antarctica–Greenland autonomous magnetometer arrays along the 40° magnetic meridian. Regional ULF wave power indices and latitudes with a maximal ULF power have been calculated from pairs of conjugate stations in both hemispheres. Examination of daytime ULF indices shows that even under contrasting ionospheric conductances during winter/summer seasons the ULF wave powers in both hemispheres are nearly the same and differ not more that 10

The review offered for the first time in the Russian scientific literature is devoted to various aspects of the problem of the impact of space weather on ground transport systems. An analysis of available information indicates that space weather disturbances can affect rail infrastructure through both direct and indirect effects on system components. One of the main hazards is geomagnetically induced currents (GICs) in grounded extended structures excited by the geomagnetic field disturbances. The telluric electric fields and currents associated with them can cause power outages and malfunctions in the railway automation track circuits. Indirect impact is possible through disturbances in the stable supply of electricity, disturbances in communication systems and in the appearance of positioning errors in global navigation satellite systems. The review provides information necessary for engineers of transport and energy systems about the main factors of space weather that could pose a threat to such systems. Examples of the influence of geomagnetic disturbances on the automatic signaling of the northern sections of Russian Railways are given. The prospects for monitoring space weather and the aurora oval for the needs of Russian Railways are discussed.

При организации систем катодной защиты трубопроводов необходимо иметь возможность рассчитывать вариации потенциала «труба – земля» при геомагнитных возмущениях. С этой целью авторами разработан программный код для расчета потенциала трубопровода при заданном возмущении электротеллурического поля в поверхностных слоях Земли. В качестве примера проведены оценки искажения потенциала «почва – труба» при суббуре, имевшей место 9 октября 2018 года и сопровождавшейся интенсивными геомагнитными Pi3-пульсациями. Использована база данных магнитных станций в Российской Арктике и глобальная модель проводимости поверхностных слоев Земли. Возмущение теллурического поля построено с помощью пересчета зарегистрированного магнитного возмущения в амплитуду теллурического поля по импедансному соотношению. Модельная трубопроводная сеть представлена в виде набора эквивалентных схем замещения, которые объединяются между собой для формирования узловой сети проводимости. С использованием метода узловой матрицы полной проводимости определены значения потенциала в узлах трубопроводной системы. Показано, что имеется как экспериментальная база, так и расчетная методика для количественной оценки вариаций потенциала трубопровода для любой заданной системы в Арктической зоне Российской Федерации. Результаты данной методики могут быть апробированы сопоставлением с вариациями защитного потенциала реальных трубопроводов. For the implementation of the cathodic protection of the grounded pipelines from electro-corrosion it is necessary to have a possibility to estimate the variations of the pipe-to-soil potential caused by the geomagnetic disturbances. For that we have elaborated a program code for calculating the pipeline potential for a given perturbation of the electro-telluric field in the Earth surface layers. As an example, estimates were made of the distortion of the ground-pipeline potential during the October 9, 2018 substorm, which was accompanied by intense geomagnetic Pi3 pulsations. A database of magnetic stations in the Russian Arctic and a global model of the conductivity of the Earth’s surface layers were used. The telluric field disturbance has been constructed by recalculating the registered magnetic disturbance into the telluric field amplitude using the impedance relation. The model pipeline network is presented as a set of equivalent circuits, which are combined to form a nodal conduction network. Using the method of the nodal matrix of total conductivity, the values of the potential at the nodes of the pipeline system are determined. Thus, there is both an experimental basis and a calculation method for quantifying pipeline potential variations for any given system in the Russian Arctic, the results of which should be tested by comparison with variations in the protective potential of real pipelines.

—The paper presents the results of analysis of the geoelectric (telluric) field variability during the Earth’s magnetic field disturbances, caused by extreme space weather events. The area of the study is the territory of the Yenisei-Khatanga Regional Trough (YKRT) situated in the auroral zone, where geomagnetic disturbances are characterized by a high level of intensity. The economic development of the YKRT as a large oil and gas-bearing area in the Russian Arctic increases the relevance of the study of possible negative impacts of space weather on future infrastructure facilities. The most serious threat to conductive industrial structures in the polar region will be posed by geomagnetically induced currents (GIC) driven by geoelectrical responses to rapid geomagnetic field changes. The analysis of the variability of telluric fields and calculations of their extreme values in the YKRT area were made using a unique magnetotelluric impedance tensor database collected by Nord West Ltd. as a result of the regional phase of the geophysical study of the trough and adjacent areas. The geoelectric field spatial-frequency distributions on the Earth’s surface were calculated on the basis of the impedance estimates and harmonic approximations of the external geomagnetic excitation. The obtained maps were correlated with geological data to find areas characterized by maximal distortions of the telluric field. Extreme amplitudes of geoelectrical responses at a series of representative locations in the YKRT were evaluated on the time series of telluric field variations, synthesized through the impedance dependences on frequency and magnetic field time series recorded during geomagnetic storms and substorms at the nearest stationary monitoring sites. The resulting estimates of amplitudes and directions of geoelectric fields during space weather disturbances can be used to account for possible destructive effects of GIC in design of pipelines, power transmission lines and railways.

The influence of space factors on technological systems in the Arctic (power transmission lines, oil/gas pipelines) has become critically important. To examine in depth these effects, an archive of digital 1 min data from Soviet/Russian magnetic stations deployed along the Arctic coast was created, starting from 1983 to the present. All data from various sources were converted to daily files in standard IAGA-2002 format and supplemented with quick-look magnetograms. Some of these data are included already in the existing world magnetic field databases, but not all. Examples of disturbances known to excite intense geomagnetically induced currents in power transmission lines were presented: irregular Pi3 pulsations and magnetic perturbation events. The database was augmented with the global 3D model of the Earth’s conductivity structure. The given example showed how the combined usage of the geomagnetic field database and the conductivity model enables one to synthesize the geoelectric field response to geomagnetic variations, and to assess the distortions of the pipeline-soil potential. To determine regions most susceptible to geomagnetic hazard, a map with normalized telluric fields was created for a uniform sinusoidally varying magnetic disturbance. This map showed that the largest electrotelluric potentials and field are induced in regions with a high resistivity (e.g., Kola Peninsula and Ural Mountains). This database can be also a useful support for space missions in the magnetosphere. The database is publicly available on the anonymous FTP site.

This study uses multi-instrument geomagnetic and ionospheric observations in Antarctica to examine the causative mechanisms of the ultra-low-frequency (ULF) variations of the electrodynamics of the polar cap—the least explored part of the coupled solar wind-magnetosphere-ionosphere system. The ionospheric oscillations corresponding to Pc5–6 pulsation band (quasi-periods about 3–15 min) were detected by SuperDARN Mac-Murdo radar. The ground geomagnetic response B was examined using magnetometers at polar latitudes in Antarctica. We have selected events with quasi-periodic variations of the ionospheric Doppler velocity V and simultaneously observed by ground magnetometers. Supposedly, this class of events is produced by magnetospheric MHD waves. We have determined the effective wave impedance, that is V/B ratio, which enabled us to identify the physical nature of specific polar cap pulsations. This type of polar Pc5–6 pulsations has been associated with Alfven mode, though the occurrence of periodic disturbances in the region with open or strongly extended field lines seems puzzling.

In this paper, we study parameters of geomagnetic pulsations in the 1–4 mHz frequency range (Pc5/Pi3) in the magnetotail, utilizing data obtained by Cluster satellites at different levels of fluctuations in the interplanetary magnetic field (IMF) and the solar wind dynamic pressure in 2016. Particular attention is given to the conditions of “zero” disturbance when amplitudes of fluctuations in the interplanetary medium are smaller compared to their typical values. Both under quiet and disturbed conditions, waves of different spatial scales are recorded, with the occurrence rate of large-scale waves increasing under undisturbed conditions. Amplitudes of the large-scale waves occurring in the magnetotail under low intensity of fluctuations outside the magnetosphere are from few tenths to a few nanoteslas (nT), and their power is approximately equal in longitudinal and transverse components. Presumably, these waves are magnetotail eigen-modes.

An archive of digital 1-min data from Soviet/Russian Arctic magnetic stations has been created, starting from 1983 to the present. The archive includes data from stations deployed along the Arctic coast by various USSR/Russia institutes. All data are divided into daily files, converted into a standard IAGA2002 format, and provided with graphs for quick-look browsing. Some of the data are not included in the existing world data portals (SuperMAG, INTERMAGNET). We give examples of using the database for the Arctic: study of irregular disturbances and waves of the Pc5/Pi3 range exciting intense geomagnetically induced currents; distortion of the pipe-to-soil potential during magnetic storms; ground support for radar observations of the ionosphere. To assess the regions most susceptible to geomagnetic hazard, we calculated a map with normalized telluric fields for a uniform magnetic disturbance with a unit amplitude and periods 100–1000 s. This map shows that the geological structure significantly affects the magnitude of the geoelectric fields generated by magnetic disturbances. The database is made publicly available on the anonymous FTP site [ftp://door.gcras.ru/ftp_anonymous/ARCTICA_Rus].

The ionosonde at the Sodankylä Geophysical Observatory (SOD; 67∘ N, 27∘ E; Finland) routinely performs vertical sounding once per minute which enables the study of fast ionospheric variations at a frequency of the long-period geomagnetic pulsations Pc5–6/Pi3 (1–5 mHz). Using the ionosonde data from April 2014–December 2015 and colocated geomagnetic measurements, we have investigated a correspondence between the magnetic field pulsations and variations of the critical frequency of radio waves reflected from the ionospheric F2 layer (foF2). For this study, we have developed a technique for automated retrieval of the critical frequency of the F2 layer from ionograms. As a rule, the Pc5–6/Pi3 frequency band fluctuations in foF2 were observed at daytime during quiet or moderately disturbed space weather conditions. In most cases (about 80 %), the coherence between the foF2 variations and geomagnetic pulsations was low. However in some cases (specified as “coherent”) the coherence was as large as γ2≥0.5. The following conditions are favorable for the occurrence of coherent cases: enhanced auroral activity (6 h maximal auroral electrojet (AE) ≥800 nT), high solar wind speed (V>600 km/s), fluctuating solar wind pressure and northward interplanetary magnetic field. In the cases when the coherence was higher at shorter periods of oscillations, the magnetic pulsations demonstrated features typical for the Alfvén field line resonance.

This paper reviews individual cases of the relationships between variations of solar wind parameters and variations of the DC vertical atmospheric electric field, E-z, and current density, J(z), measured at ground level in the Arctic, at the S. Siedlecki Polish Polar Station Hornsund, Spitsbergen (Svalbard, Norway), and at the mid-latitude S. Kalinowski Geophysical Observatory in Swider (Poland). A considerable number of events from Hornsund confirmed previous observations of regularity of effects related to the station's position against the location of the potential bays of ionospheric convection and polar electrojets, observed in other polar locations, as well as effects of other polar cap current systems. This allowed us to conclude that the physical dependence of ground-level E-z and J(z) on solar wind changes produce measurable effects which do not require statistical analysis to be observed. We can also expect that the dependence does exist, especially in strongly disturbed circumstances, e.g., following solar flares and Earth-directed coronal mass ejections, at middle latitudes. However, further investigations of these physical relationships by this approach are practically almost impossible since a very large number of variable parameters simultaneously affect the recorded lower atmospheric variables. In addition, results of quantitative analysis of predicted and observed effects are not satisfactory. Future research studies require more efficient ways of investigation by theoretical treatment and modelling work using existing and novel observational data besides taking advantage of scientific progress in magnetospheric physics.

We compare the simultaneous magnetometer, SuperDARN radar, and GPS observations during Pc5 wave event on March 02, 2002. A possible correspondence between those instruments may help to determine the mechanism of the ionosphere modulation by magnetospheric disturbances. Transient Pc5 pulsations (2.6 mHz) in the morning sector, stimulated by the solar wind density jumps, have been detected simultaneously by ground magnetometers and the Kodiak and King Salmon SuperDARN radars. Besides that, pulsations with the same periodicity have been found in the rate of total electron content (TEC), dTEC/dt (ROT), variations in several GPS radio paths. The ratio between the spectral amplitudes of the Doppler velocities and magnetic pulsations (X component) on the ground are Vx/Bx~7-12 (m/s)/nT and Vy/Bx~27 (m/s)/nT. The ratio between the oscillation amplitudes of ROT and ionospheric Doppler meridional (Vx) and azimuthal (Vy) velocities are ROT/Vx~0.02-0.07 (dTECu/min)/(m/s) and ROT/Vy~0.004 (dTECu/min)/(m/s). The correspondence between simultaneous periodic variations of the ionospheric Doppler velocity and geomagnetic field can be reasonably well interpreted quantitively on the basis of theory of Alfven wave interaction with the thin ionospheric layer. However, order-of-magnitudes estimates of possible TEC modulation mechanisms show that a responsible mechanism which can interpret the observed ratios has not been found yet.

Abstract. Using data of the ionosonde in Sodankyla, (SOD, 67° N, 27° E, Finland), variations of the critical frequency of o-mode radiowave reflected from ionospheric F2 layer (foF2) in 1–5 mHz frequency range and their possible association with long period (Pc5/Pi3) geomagnetic pulsations are studied. For that, a technique of automatic detection of the foF2 critical frequency from an ionogram is developed and applied to daytime Pc5/Pi3 geomagnetic pulsations and foF2 fluctuations during several months of years 2014–2015 near the maximum of 24-th Solar cycle. The variations of foF2 are compared with the Pc5/Pi3 geomagnetic pulsations at SOD station, and the influence of pulsations' spatial scale is analyzed with the data of a station pair located at the same magnetic meridian but separated in latitude. The variations of foF2 are in the majority of cases decoupled from the geomagnetic pulsations on the ground. Meanwhile, the analysis of geomagnetic and foF2 variations show intervals with noticeable coherence for both horizontal components. These coherent pulsations are predominantly registered in the afternoon sector of the magnetic local time (MLT). Statistically, their spectral content, polarization and spatial distribution differ from averaged parameters of post-noon Pc5 pulsations. The pulsations, coherent to foF2 fluctuations, demonstrate features typical for Alfven field-line resonance. The analysis of space weather conditions favorable for the occurrence of coherent geomagnetic/foF2 pulsations show that these pulsations are registered mostly under moderately disturbed conditions. Comparison of space weather parameters for all the intervals analyzed and the intervals of high geomagnetic/foF2 coherence show that the latter correspond mostly to intermediate values of indexes of geomagnetic (Dst) and auroral (AE) activity, solar wind speed and dynamic pressure fluctuations.

We analyse temporal and spatial variability of geomagnetic and telluric electric fields in the Eastern Fennoscandia. These variations are compared with available geomagnetically induced current (GICs) measurements in electric power transmission lines at Kola Peninsula and Karelia. The information on impedance tensors is provided by the electromagnetic sounding array BEAR. We synthesize the telluric E-field from geomagnetic field variations, using the complex impedance tensor. We analyze geomagnetic and E-field variations at several sites for different space weather events: magnetic storm and Pi3 pulsations. We compare the spectral content of geomagnetic, telluric, and GIC variations. This comparison shows that the commonly used as a measure of GIC disturbances time derivative of geomagnetic field dB/dt does not totally control them. The suppression of high-frequency component in the GIC spectrum as compared with dB/dt variations is determined by the frequency-dependent character of the crustal geoelectric response.

Recent work has demonstrated that global Pc5 pulsations observed by ground-based magnetometers may be accompanied by periodic oscillations in the total electron content (TEC) of the ionosphere measured by GPS receivers. These TEC observations may provide new insights into magnetosphere-ionosphere coupling mechanisms, especially when combined with other ground-based observational techniques. Presented in this paper is a large-scale morning sector Pc5 event which was observed simultaneously by ground-based magnetometers, two high-frequency Super Dual Auroral Radar Network (SuperDARN) radars, and several Global Positioning System (GPS)/TEC receivers. The transient 2.6 mHz pulsations observed by the ground magnetometers and radars are accompanied by periodic fluctuations in the time rate-of-change of TEC (ROT) at the same frequency. To investigate possible mechanisms for the TEC modulation by ultralow frequency (ULF) waves, we determine the ratios between the spectral amplitudes of the magnetic, ionospheric Doppler velocity and ROT oscillations. The relationship between the simultaneous magnetic field and ionospheric Doppler velocity oscillations can be reasonably well interpreted using the theory of Alfven wave interaction with the thin ionospheric layer. Though the observed ratio between ROT and Doppler velocity amplitudes can be explained by the occurrence of local steep gradient of the topside ionosphere plasma at auroral latitudes, the responsible modulation mechanism cannot be considered as firmly established.

The study is based on the data of the rapid-run ionosonde at the Sodankyla Geophysical Observatory at auroral latitude (L = 5.25) which routinely performs one-minute sounding since 2007. This dataset allows a unique opportunity for investigating possible effects of ultra-low frequency (ULF, 1-7 mHz) waves in the auroral ionosphere. Suitable observations were made during moderately disturbed geomagnetic conditions typically at recovery of the geomagnetic storms caused by solar wind high-speed streams, in the daytime between 9 and 16 MLT. The ionospheric oscillations corresponding to Pc5 geomagnetic pulsations were found in variations of the virtual height of the F layer and the power of ionosonde reflections from E and F layers. The later are most probably caused by modulation of electron precipitation, which is also manifested in weak (about 0.01-0.06 dB) variations of cosmic noise absorption. The most important and novel result is that the pulsations of power of reflection from E and F layers typically has a spectral maximum at nearly half the periodicity of the Pc5 geomagnetic pulsations, whereas such spectral peak is negligible in the geomagnetic pulsations. (C) 2018 COSPAR. Published by Elsevier Ltd. All rights reserved.

Abstract. Using data of the ionosonde in Sodankyla, (SOD, 67° N, 27° E, Finland), parameters of variations of foF2 critical frequency in the Pc5/Pi3 (1–5 mHz) frequency range are studied. For that, a technique of automatic detection of critical frequency from an ionogram is developed. The variations of foF2 are compared with the Pc5/Pi3 geomagnetic pulsations on the ground and in the magnetosphere. The variations of foF2 are in the majority of cases decoupled from the Pc5/Pi3 on the ground. Meanwhile, the analysis of geomagnetic and foF2 variations at SOD show intervals with noticeable coherence for both horizontal components. These coherent pulsations are predominantly registered in the afternoon MLT sector. Statistically, their spectral content, polarization and spatial distribution differs from those of background variations. Coherent pulsation tend to occur under moderate geomagnetic and auroral activity, SW speed, and dynamic pressure fluctuations. The fraction of coherent geomagnetic and foF2 pulsations is higher for the geomagnetic pulsations registered in the magnetosphere, than on the ground.