The May 2024 Gannon storm, one of the most intense geomagnetic disturbances (GMDs) in two decades, provides a valuable opportunity to examine geomagnetically induced currents (GICs), their drivers, and impacts on bulk power system resilience. We analyzed GICs over the United States using direct measurements from three North American Electric Reliability Corporation (NERC) monitoring devices, magnetometer-derived proxy indices, and continuous wavelet transform (CWT). The storm featured multiple substorm onsets, supersubstorms (SSSs), and westward electrojet (WEJ). Results show that during the sudden storm commencement on 10 May, magnetic field variations, dH/dt reached 80 nT/min at ∼54° MLAT with GICs of up to 70 A recorded by device 10659 (∼54° MLAT) at about 17:08 UT. During the main phase on 10 May, GICs peaked at 128 A at device 10659 around 21:44 UT due to substorm activity in conjunction with Ps6 pulsations. Furthermore, the substorm onset at ∼02:00 UT on 11 May was associated with an enhanced dH/dt of 437 nT/min at ∼56° MLAT and the largest GIC response to this GMD with a peak of 176 A (device 10659) at 02:04 UT. CWT analysis further suggests that Ps6 magnetic pulsations contributed as secondary driving mechanisms. The recovery phase was characterized by significant GICs up to 120 A at the same device around 08:41 UT, related to coupled magnetospheric drivers, including Pc5 magnetic pulsations and a SSS under magnetic cloud conditions. This storm phase further featured a GIC of 91 A (at 04:32 UT) associated with substorm activity detected during the high-speed stream on 12 May. The study highlights the role of substorms, SSSs, and associated localized magnetic disturbances driven by distinct ICME features, in generating substantial GICs during the recovery phase of intense storms, emphasizing their critical impact on space-weather hazards.

Possible sources of intense Geomagnetically Induced Currents (GIC) registered at auroral zone latitudes from 62° to 69° GLAT° in the north-west of Russia were studied. Our analysis was carried out according to the data of the direct measurements from 3 stations (Vykhodnoy, Loukhi and Kondopoga) during strong storm on 10–11 October 2024. It was shown that main GIC sources were interplanetary shock (IS), substorms development and geomagnetic pulsations. Besides, the GIC peak of 30 A at VKH station recorded 15:15 UT at the onset of the magnetic storm and was associated with the interplanetary shock wave. Other GIC peaks during the development of the October storm were intense 7–18 A, but still half as strong as the initial GIC burst. It was also demonstrated that the sources of intense GICs 7–18 A in the evening and night sectors were the magnetic disturbances during substorms, while intense GICs 8–12 A in the morning sectors were caused by Pc5/Pi3 geomagnetic pulsations observed simultaneously with the substorm development at the morning sector.

The GICs in the power system in the northwest of Russia during one of the strongest storms of the space age on 10-12 May 2024 was studied. Several ICME on 8-10 May caused three-stage strong magnetic storm with long recovery phase. The analysis was performed for a long period-from 17 UT on 10 May to 06 UT on 12 May and based on GIC direct measurements at 3 substations (Vykhodnoy, Loukhi and Kondopoga) located at auroral zone latitudes from 62 degrees to 69 degrees GLAT degrees. It was confirmed that GIC sources are distributed over MLT sectors: sources of an intense GICs (similar to 15-30 A +/- 0.6 A) in the evening and night sectors were substorms and supersubstorm, while sources of GICs (similar to 15-30 A +/- 0.6 A) in the morning sector were Pc5/Pi3 geomagnetic pulsations. Besides, there were 3 strongest GIC peaks of similar to 50-62 A +/- 1.2 A-one in the night and two in the morning sectors. These peaks were probably caused by the superposition of these sources and another local magnetic disturbance caused by a large jump in the solar wind dynamic pressure. The feature of this storm was the presence of two supersubstorms (SSS) in night and day sectors. Sources of GICs in the night sector was the polar edge of first SSS. GICs in the day sector appeared to be linked to intensifications of the eastward electrojet during the development of the second SSS. Thus, first it was found that intense GIC can be produced on the dayside through the intensification of the eastward electrojet during night supersubstorm. (c) 2025 COSPAR. Published by Elsevier B.V. All rights are reserved, including those for text and data mining, AI training, and similar technologies.

We analyzed the solar origin and ground response during the severe geomagnetic storms (GSs) of 23–24 March (GS1) and 23–24 April 2023 (GS2) using Geomagnetically Induced Currents Indices (GIC indices) computed from geomagnetic field data. The GSs were initiated by erupting filaments and associated slow (fast) halo coronal mass ejections on 20 March (21 April) 2023. GS1 was also influenced by coronal hole high speed streams (CR HSSs) while substorm onsets drove the most intense GIC X (GIC Y ) of 86 (70) in Abisko, Sweden. GS2 was marked by strong negative Bz in a sheath and magnetic cloud with larger GIC indices of 84 (69) driven by magnetic pulsations, as evident at Abisko. This posed a moderate risk to power networks in Sweden. The threat however, reached only a low/moderate risk level in Boulder during the Sudden Impulse (SI)/main phase of GS1. For GS2, a low risk level was attained in Vernadsky and Eyrewell. As expected, at low latitude, GIC indices constituted a very low risk to ground infrastructures during both storms. The results also revealed longitudinal features with larger GIC indices in Boulder (Vernadsky) during the GS1 (GS2), and a North South Asymmetry characterized by a higher risk level in the northern (southern) hemisphere at the American longitude. Additionally, this study provides evidence that the equatorial electrojet can enhance GIC indices at the magnetic equator in the presence of sufficiently strong dH/dt. Finally, we relate GIC indices at high latitudes to the CR HSS on 23 March, and a magnetic cloud during the recovery phase on 24 April 2023.

Here we analyzed four very intense substorms with the AL-index reached ~ -1500 nT and recorded in the main phases of the strong magnetic storms on 27 February and on 23-24 March 2023. The global dynamics of the considered very intense substorms have been studied basing on the AMPERE satellite data provided the maps of the ionospheric and field aligned currents (FAC) distributions in the planetary scale. These maps are constructed by analyzing the magnetometer measurements from the Iridium constellation of 66 simultaneous low-altitude (780 km) communication satellites. The common features of the considered intense substorms have been established. It was found that in the substorm intensity maximum, there was the strong morning-side magnetic vortex with clockwise rotation, indicating an intensification of the downward FACs, probably associated with the enhanced magnetosphere-ionosphere convection. The strongest westward electrojet was observed in the early morning sector and it was accompanied by the significant increasing of the post-noon eastward electrojet as it was found by [Despirak et al., 2021, 2022] to be typical for the supersubstorms. The large-scale eastward electrojet with intensity comparable to the westward electrojet, occurred at lower latitudes in huge longitudinal area - from the afternoon to the late evening. The latitude area between westward and eastward electrojets can be referred to the conventional Harang region.

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 geomagnetic 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 10 000 nT2) are observed during strong geomagnetic storms (when the Dst-index falls below –100 nT), all extremely strong geomagnetic 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 EY-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 analyzed intense geomagnetically induced currents (GICs) recorded during a complex space weather event observed on 23-24 April 2023. Two geomagnetic storms characterized by SYM/H intensities of -179 nT and -233 nT were caused by southward interplanetary magnetic field (IMF) Bz component of -25 nT in the sheath fields, and -33 nT in the magnetic cloud (MC) fields, respectively. GIC observations were divided into two local time sectors: nighttime (1700-2400 UT on 23 April) GICs observed during the interplanetary sheath magnetic storm, and morning sector (0200-0700 UT on 24 April) GICs observed during the MC magnetic storm. By using the direct measurements of GICs on several substations of Karelian-Kola power line (located in the north-west portion of Russia) and gas pipeline station near Mantsala (south of Finland), we managed to trace the meridional profile of GIC increases at different latitudes. It was shown that the night sector GIC intensifications (similar to 18-42 A) occurred in accordance with poleward expansion of the westward electrojet during a substorm. On the other hand, the intense morning sector GICs (similar to 12-46 A) were caused by Ps 6 magnetic pulsations. In addition, a strong local morning GIC (similar to 44 A) was associated with a local substorm-like disturbance caused by a high-density solar wind structure, possibly a coronal loop portion of an interplanetary coronal mass ejection.

The substorms that we term as “polar” substorms, are recorded in the evening sector of the Earth at the geomagnetic latitudes above 70° MLAT under the absence of negative magnetic bays at the lower latitudes. Like the “classical” substorms, the “polar” substorms are accompanied by aurora arcs brightening, poleward expansion, substorm current wedge formation. The onsets of “polar” substorms are typically located near 70° MLAT at ~19-23 MLT. Other important structure, namely, the Harang discontinuity (the evening narrow latitude-zone between the westward and eastward electrojets), is often observed in the same area and at the same MLT interval. Our aim is to study a possible relationship between the location of the “polar” substorms and the Harang discontinuity (HD). Using the IMAGE geomagnetic data, we found that the “polar” substorm onsets exhibit a tendency to occur near the HD latitude. The longitudinal relationship between the “polar” substorms and the HD was studied basing on the ionospheric AMPERE measurements by the 66 simultaneous satellites. We revealed the ground-based magnetic vortex associated with FACs enhancement near the eastward edge of the Harang discontinuity region separated the evening “polar” substorm development and the after-midnight westward electrojet location. Two typical events of the “polar” substorms are discussed in detail.

Statistical studies allow probability statements about the frequency of certain events. The occurrence of magnetic substorms and their activity have been described with the help of extreme value distributions in the last few decades using the auroral electrojet indices AE, AL and AU. In this work we examined the distribution of the IL index, derived from observations at stations of the IMAGE magnetometer network. The distributions of magnetic disturbances, based on IL, were studied separately in the morning (3-9 MLT), day (9-15 MLT), evening (15-21 MLT), and night (21-3 MLT) sectors. In addition, we used the values of the IL index calculated from the meridional chains in the auroral zone (PPN-SOR) and from the chain of stations at high latitudes (BJN-NAL). By help of the histograms and the empirical cumulative distributions, the occurrence rates were computed. It was shown that the empirical distributions could be well approximated with exponential distributions. The distribution parameters were determined from the occurrence rates. Three classes were discovered, which differ significantly by the respective distribution parameters. Structure changes in the distributions were found in the morning sector at both auroral and high latitudes.

In this paper, we statistically analyzed substorm activity at auroral latitudes for 2007–2020 and its relationship with magnetic disturbances at middle latitudes using the INTERMAGNET, SuperMAG, and IMAGE magnetometer data. The appearance and development of magnetic disturbances at auroral latitudes was monitored by the IL index (similar to the AL index, but calculated according to IMAGE data). For the 2007–2020 period, events that were observed near the meridian of the IMAGE network, in the night sector (2103 MLT), were selected. Two samples of events were used: (1) IL < –200 nT for at least 10 min, with an additional criterion for the presence or absence of positive bays at the Panagyurishte station in Bulgaria, and (2) isolated substorms observed on the IMAGE meridian according to the list of Ohtani and Gjerloev (2020). The distributions of the IL index, as well as the empirical and theoretical cumulative distribution functions, are obtained, and the of the occurrence of extreme events are also estimated. It is shown that, in general, the IL distributions are described well by exponential functions, and out of all events, events accompanied by mid-latitude positive bays were observed in ~65% of cases while their fraction increased with increasing disturbance intensity. Events with positive bays at midlatitudes of MPB and isolated substorms were better described by the Weibull distribution for extreme events. From both distributions, annual and semi-annual variations were identified: annual variations have a summer minimum and a winter maximum, and semi-annual variations have maxima near the equinoxes, which is most likely due to the Russell-McPherron effect. The semi-annual variation is also shown to be more pronounced for events with accompanying mid-latitudinal positive bays.

We studied the geomagnetic effects of abrupt and large-amplitude changes in the solar wind dynamic pressure (Psw) on 3 November 2021. when there were observed three large-amplitude Psw pulses (up to 20 nPa) under the strong (up to −18 nT) southward IMF Bz and significantly varying IMF By (from +20 to −15 nT). Basing on IMAGE magnetometer data, we found three substorms associated with these Psw impulses. These substorms followed one after another with a short interval and each subsequent substorm began developing during the unfinished recovery phase of the previous one under disturbed space weather conditions. Under strong negative IMF Bz there was significant input of energy into the magnetosphere that indicated by the increasing PC-index values. It was shown that the spatial-temporal features of the substorm subsequence development was complicated, differed from a typical isolated “normal” substorm and changed from one substorm to another. According to the AMPERE 66 ionospheric satellite data, the global distribution of the ionospheric and field-aligned currents (FAC) was established during the considered substorms. We found that during all these substorms, there were strong FACs and corresponding ionospheric electrojets in the morning sector indicating an enhanced magnetospheric convection which formed the DP2 current system. In addition, in the night sector, the DP1 current system was observed, the clearest in the second event.

The project is directed to one of the topical tasks of the solar-terrestrial physics: study of the midlatitude effects of the magnetospheric substorms as a key element of the space weather. The goal of the project was to conduct a comprehensive analysis of the spatiotemporal characteristics of magnetospheric substorms and their effects at midlatitudes depending on space weather conditions. For this purpose, studies of various phenomena related to the development of substorm disturbances and their propagation to midlatitudes were carried out. For the first time, an original catalog of the variations of the magnetic field at the midlatitude Bulgarian station Panagjurishte (PAG) was created for the period 2007 - 2022. A methodology was developed and universal programs were created for processing data from European stations, for obtaining maps of the spatial distribution of magnetic variations, and for calculating the midlatitude positive bay (MPB) index. Analyses of events during quiet and disturbed geomagnetic conditions, during slow flows in the solar wind or high speed streams from coronal holes, were carried out. Some cases of supersubstorms have been studied in detail. The hypothesis of the development of an additional substorm current wedge during supersubstorms was confirmed. The morphological features of the polar substorms were also studied. Catalogs of supersubstorms and polar substorms for the past 20 years have been created. The relationships between the statistical distributions of the MPB index and widely used geomagnetic indices and solar wind parameters were established. Cases of occurrence of intense geomagnetically induced currents (GIC) during several strong magnetic storms were identified and analyzed.

It is known that very intense substorms, so-called "supersubstorms" (SSSs: SML < -2500 nT) usually occur in the main phase of the magnetic storms. At the same time, it was found that such intense events are observed not only during very strong storms (superstorm with Dst<-250 nT), but also during intense or moderate magnetic storms (-100 nT >Dst>-250 nT; -50 nT >Dst>-100 nT). The aim of this work is to study the supersubstorms observed during non-storm conditions by the OMNI data base and global magnetometer networks SuperMAG, INTERMAGNET and IMAGE. For this purpose, we selected the SSS events observed by SYM/H>-50 nT. We found 18 such SSS events in the period 1998-2017. Among them, several typical events can be distinguished: (1) - the events near the magnetic storm commencements SC, (2) - the events observed in the distant recovery phase of the storm, (3) - the events observed outside of a magnetic storm. Besides, we discussed some special conditions in the solar wind and interplanetary magnetic field (IMF) under which such events have been observed.

Geomagnetic activity and occurrence of large values of geoinduced currents (GICs) during a moderate magnetic storm (SYM/H - -65 nT) on September, 12-13 2017 have been studied. Two intense substorms (AL -600 nT and -1200 nT) were observed within the period of this magnetic storm. Amplification and motion of electrojets during substorms is known to be one of the important sources of GIC value increase in the auroral zone. The fine spatial temporal structure of westward electrojet has been analyzed using the latitudinal profiles of the IMAGE network and the equivalent currents of the MIRACLE system data. GICs activity were monitored by EURISGIC from Russian stations Vykhodnoy (VKH) and Revda (RVD) in the North-West of Russia (eurisgic.ru) and Ma center dot ntsa center dot la center dot station (MAN) in South Finland. The data from these stations are convenient to track GIC from -60 degrees to -69 degrees geographical latitudes. It has been shown that the increase in GIC amplitudes at different latitudes was associated with the poleward movement of the westward electrojet during the expansion phase of the substorm. Besides, it has been found that the source of the GICs at the recovery phase of the second substorm appeared to be a short pulse of Pc5 pulsations and the amplitudes of GICs were comparable with substorms one. It is also shown that the increase in GIC amplitude are in good agreement with the increase in the Wp- and IL-geomagnetic indices used for global and local control over the substorm appearance.

A study is performed on the increasing of geomagnetic induced currents (GICs) during supersubstorms (SSS) that occurred on September 7–8, 2017 against the background of magnetic storms. The analysis includes two periods: from 23 to 04 UT on September 7–8, 2017 (the first supersubstorm with SML ~ –3600 nT) and from 12 to 20 UT on September 8, 2017 (the second supersubstorm with SML ~ –2600 nT and two intense substorms (with SML ~ –1500 nT). GIC is analyzed using data from detecting stations in Vykhodnoy and Kondopoga (Russia), Mäntsälä (Finland), Halfway Bush (New Zealand), and Torness (Scotland). Results show the GICs developed in a manner similar to that of the substorm westward electrojet’s spatiotemporal dynamics, with maximum GIC values observed at stations in the midnight sector. It is found that there is a relationship between the increasing of the GICs and an increase in geomagnetic indices IL and Wp that characterize substorm activity.

The high-latitude magnetic substorms observed at geomagnetic latitudes higher 70 degrees MLAT under the substorm absence at the lower latitudes are known as "substorms on the contracted oval" or "polar" substorms. Such substorms appear during quiet or weakly disturbed space weather conditions. The study of 254 "polar" sub -storms, recorded at the Scandinavian IMAGE magnetometer chain during the winter seasons of 2010-2020, confirmed a tendency to occur in the late evening (-19-23 MLT), that is a bit earlier than the "normal" sub -storms (22-24 MLT). It was found that before the onset of "polar" substorms, like "normal" substorms, there is an increase in the PC-index indicating an energy input into the magnetosphere. We established that "polar" sub -storms, like "normal" substorms, are accompanied by positive mid-latitude magnetic bays, demonstrating a substorm current wedge (SCW) development.Several "polar" substorms are examined in detail. The ionospheric electrojets and field-aligned currents (FAC) distribution was studied basing on the AMPERE satellites measurements. We found that "polar" substorm onsets are associated with an enhancement of FACs in a localized evening area. Thus, "polar" substorms exhibited the properties, typical for "normal" substorms, so, they could be referred as a specific type of substorms developing under rather quiet space weather conditions.

The Harang discontinuity (HD) is a longitudinally extended ionospheric signature before the local magnetic midnight of a latitude flow reversal (from westward to eastward). The "polar" substorms are those substorms that recorded at the geomagnetic latitudes above 70 degrees MLAT under the absence of negative magnetic bays at the lower latitudes. Like the "classical" substorms, the "polar" substorms are accompanied by aurora brightening, poleward expansion, substorm current wedge formation. Onsets of "polar" substorms are typically located near 70 degrees MLAT at similar to 19-23 MLT. This MLT sector is common area of the HD development. The aim of our work is to study a possible relationship between the "polar" substorm onsets and the HD location. Our study of about 250 "polar" substorms, recorded at IMAGE magnetometer profile in 2010-2020, revealed the tendency of these substorms to occur near the HD location, detected by the AMPERE measurements at the 66 ionospheric satellites. It was found that in the case of the "polar substorm", the Harang reversal was observed at higher latitude then during the "classical" substorm. That explained why the strongest amplitudes of lower-latitude positive magnetic bays, accompanied "polar" substorms, are recorded not at middle, but at subauroral latitudes. Near the eastward edge of the HD, we found a magnetic vortex associated with FACs enhancement separated the evening "polar" substorms and after-midnight westward electrojet. Some individual events of the "polar" substorms are discussed.

Statistical studies allow probability statements about the frequency of certain events. The occurrence of magnetic substorms and their activity have been described with the help of extreme value distributions in the last few decades using the auroral electrojet indices AE, AL and AU. In this work we examined the distribution of the IL index, derived from observations at stations of the IMAGE magnetometer network. The distributions of magnetic disturbances, based on IL, were studied separately in the morning (3–9 MLT), day (9–15 MLT), evening (15–21 MLT), and night (21–3 MLT) sectors. In addition, we used the values of the IL index calculated from the meridional chains in the auroral zone (PPN-SOR) and from the chain of stations at high latitudes (BJN-NAL). The histograms, the empirical cumulative distributions and the occurrence rates were computed. It was shown that the empirical distributions could be well approximated with exponential distributions. The distribution parameters were determined from the occurrence rates. Three classes were discovered, which differ significantly by the respective distribution parameters. Structural changes in the distributions were found in the morning sector at both auroral and high latitudes. The relationship between the occurrence rate of magnetic disturbances with IL < −1000 nT and the frequency of occurrence of geomagnetic induced currents was highlighted.

В работе анализируется связь величины MPB-индекса, введенного для анализа проявлений суббуревой активности на средних широтах, с уровнем геомагнитной активности и с параметрами межпланетной среды. Показано, что величина MPB-индекса растет с ростом геомагнитной активности на разных широтах, экстремально большие значения MPB-индекса регистрируются во время развития сильных и очень сильных геомагнитных бурь. Величина MPB-индекса растет с увеличением как величины, так и модуля компонент межпланетного магнитного поля и скорости солнечного ветра.