Hasil untuk "Geomagnetism"

Ogawa Yasuo, Oda Hirokuni

V.S.P. Pranjali, Chinmaya Nayak, Erdal Yiğit et al.

The Martian northern hemisphere (NH) is relatively devoid of ambient magnetic fields compared to the southern hemisphere (SH), which houses the strong crustal field regions. On 2024 May 17, when Mars was hit by a coronal mass ejection (CME), the periapsis of NASA’s Mars Atmosphere and Volatile EvolutioN (MAVEN) spacecraft was entirely in the NH. The dynamic pressure in the ionosphere was enhanced by almost 2 orders of magnitude during the Mars–CME interaction, allowing penetration of solar origin magnetic fields into the Martian ionosphere. Even at altitudes below 500 km, the ratio of magnetic pressure ( P _b ) to ionospheric thermal pressure ( P _th ) was amplified more than 100 times, creating an overpressure (OP) regime. This OP condition exposed the topside ionosphere to the CME. The topside ionosphere was severely depleted, with the electron ( n _e ) and ${{\rm{O}}}_{2}^{+}$ ( ${n}_{{{\rm{O}}}_{2}^{+}}$ ) densities being reduced by nearly 50%–100%. The effects were particularly severe at altitudes above 350 km. The dayside ionosphere showed relatively stronger depletion compared to the terminator regions.

E. D. López, H. Barbier, W. Carvajal et al.

This study investigates the impact of the G5 geomagnetic storm on Total Electron Content (TEC) derived from the Global Positioning System (GPS) in Galápagos, Ecuador (geographic latitude 0.1807° S, longitude 78.4678° W) during May 10-13, 2024. Using vertical TEC (VTEC) data from a single pseudorandom noise (PRN) code, along with the average VTEC from the same PRN collected over the ten days before the storm, referred to as background TEC, to analyze the variations in TEC. Our findings indicate that during the main phase of the storm on May 10-11, 2024, TEC experienced a notable decrease, which contrasts with the typical responses observed in previous storms. This decrease can be attributed to rapid recombination processes and potential plasma instabilities triggered by the storm. In the recovery phase following the main storm, a gradual increase in TEC was observed, illustrating the complex dynamics of the ionosphere in response to geomagnetic disturbances. This study underscores the variability in TEC responses during geomagnetic storms. It highlights the importance of real-time monitoring to improve our understanding of the implications for satellite communication and navigation systems.

Stefano Markidis, Jonah Ekelund, Luca Pennati et al.

Geomagnetic storms are large-scale disturbances of the Earth's magnetosphere driven by solar wind interactions, posing significant risks to space-based and ground-based infrastructure. The Disturbance Storm Time (Dst) index quantifies geomagnetic storm intensity by measuring global magnetic field variations. This study applies symbolic regression to derive data-driven equations describing the temporal evolution of the Dst index. We use historical data from the NASA OMNIweb database, including solar wind density, bulk velocity, convective electric field, dynamic pressure, and magnetic pressure. The PySR framework, an evolutionary algorithm-based symbolic regression library, is used to identify mathematical expressions linking dDst/dt to key solar wind. The resulting models include a hierarchy of complexity levels and enable a comparison with well-established empirical models such as the Burton-McPherron-Russell and O'Brien-McPherron models. The best-performing symbolic regression models demonstrate superior accuracy in most cases, particularly during moderate geomagnetic storms, while maintaining physical interpretability. Performance evaluation on historical storm events includes the 2003 Halloween Storm, the 2015 St. Patrick's Day Storm, and a 2017 moderate storm. The results provide interpretable, closed-form expressions that capture nonlinear dependencies and thresholding effects in Dst evolution.

امیرحسین ضیاء, رضا قناتی, مهدی فلاح صفری

اندازه‌گیری‌های پلاریزاسیون القایی در حوزه زمان، اطلاعات ارزشمندی درباره میزان قطبش لایه‌های زیرسطحی فراهم می‌کنند. هدف اصلی این اندازه‌گیری‌ها، تعیین توزیع ویژگی‌های الکتریکی درون زمین است. این ویژگی‌ها را می‌توان با بهره‌گیری از مدل‌سازی ریاضی، به‌ویژه با استفاده از معادله پواسون و در نظر گرفتن شرایط مرزی مناسب، توصیف کرد. در فرایند مدل‌سازی پیشرو برای محیطی با هندسه دوبعدی و توزیع دلخواهی از رسانندگی الکتریکی، نخست معادله دیفرانسیل جزئی با استفاده از روش تفاضل محدود حل می‌شود. سپس با بهره‌گیری از روابط بین رسانندگی و شارژپذیری، پاسخ‌های پلاریزاسیون القایی ظاهری محاسبه می‌شود. مسائل وارون‌سازی در پلاریزاسیون القایی و مقاومت‌ویژه ظاهری الکتریکی معمولاً غیرخطی هستند و حل آنها نیازمند پیاده‌سازی یک فرایند دو مرحله‌ای است. در مرحله نخست، با استفاده از توزیع پتانسیل‌های الکتریکی اندازه­گیری شده، رسانندگی ذاتی تخمین زده می‌شود. در مرحله دوم، با استفاده از توزیع رسانندگی مرحله قبل و با بهره‌گیری از پاسخ‌های پلاریزاسیون القایی و روش‌های عددی مناسب، توزیع شارژپذیری در محیط زیرسطحی استخراج شود؛ به‌گونه‌ای که مدل نهایی تطابق قابل‌قبولی با داده‌های مشاهده‌شده داشته باشد. در این مطالعه، وارون‌سازی غیرخطی با استفاده از چارچوب الگوریتم اُکام و با به‌کارگیری ماتریس حساسیت مبتنی‌بر مشتقات جزئی پاسخ‌های شبیه‌سازی‌شده نسبت به پارامترهای مدل، پیاده‌سازی شده است. به‌منظور ارزیابی الگوریتم وارون‌سازی، دو مجموعه داده مصنوعی و یک مجموعه اندازه‌گیری‌های صحرایی مربوط به محدوده بورزمین مورد استفاده قرار گرفتند. نتایج عددی نشان می‌دهد که الگوریتم ارائه‌شده امکان برآورد مناسبی از مدل‌های مصنوعی دارد، هرچند که با افزایش پیچیدگی مدل پلاریزاسیون القایی، عدم‌قطعیت در تعیین دقیق توزیع کمیت شارژپذیری افزایش می‌یابد. همچنین مدل‌سازی داده‌های صحرایی نشان‌دهنده وجود ناهنجاری‌های شارژپذیری در پروفیل‌های مختلف منطقه است که با توجه به لیتولوژی منطقه، امکان وجود زون کانی‌زایی در محدوده موردمطالعه وجود دارد.

Gautam Gupta, G. Shailaja, K. Tahama et al.

Abstract Groundwater is a vital resource, particularly in arid and semi-arid regions where surface water availability is limited. This study focuses on mapping groundwater potential zones (GWPZs) in the Dhule district of Maharashtra, India, an area characterized by complex hydrogeological conditions within the Deccan Volcanic Province (DVP). Utilizing a multi-criteria decision analysis (MCDA) approach, the study integrates geospatial techniques with geoelectric data to accurately delineate areas with high groundwater potential. The analytical hierarchy process (AHP) combined with Geographic Information System (GIS) methodologies enables a detailed assessment of various influencing factors, including geological structures, soil texture, slope, drainage density, and land use patterns. Key findings highlight that regions with specific geological formations, such as weathered and fractured basalts and areas with dykes, show higher groundwater potential due to their enhanced porosity and permeability. The study identifies the central Shindkheda, southern Sakri, and Dhule subdivisions as critical areas for implementing groundwater recharge techniques to mitigate surface runoff and erosion. Recommendations for these regions include the construction of trenches, bunds, recharge pits, and percolation tanks. Additionally, the adoption of water-saving technologies such as drip irrigation and rainwater harvesting is emphasized to improve groundwater recharge and management. The validated approach establishes a strong foundation for future research and interventions aimed at enhancing water security in similar hydrogeological settings. The integration of AHP and GIS provides a robust framework for groundwater resource management, offering valuable insights for decision-makers focused on sustainable water resource utilization.

Yuki Harada, Robert J. Lillis, Matthew O. Fillingim et al.

Abstract Magnetic fields around Mars shape the pathways of energy input into, and ion escape from, the Martian atmosphere, thereby potentially affecting the atmospheric evolution of Mars. The Martian magnetic field environment is primarily determined by the global electric current system resulting from the solar wind interaction with the upper atmosphere and crustal magnetic fields of Mars. Recently, it has been recognized that neutral wind-driven ionospheric dynamo currents generate magnetic field perturbations observable in orbits and on the surface of Mars. However, the entire system of near-Mars currents is not fully understood. Here we present a newly identified current system in the Martian magnetosphere directly coupled to the wind-driven ionospheric currents, based on the spherical harmonic analysis of magnetic field data obtained by the Mars Atmosphere and Volatile Evolution spacecraft. This magnetospheric current system can be explained by diamagnetic currents associated with magnetic fields generated by the wind-driven ionospheric dynamo currents. Our results demonstrate a close coupling between the neutral atmospheric dynamics and the high-altitude magnetospheric current system at Mars mediated by wind-driven ionospheric dynamo currents. This reveals a previously unrecognized role of the neutral atmosphere in controlling magnetic field environments of unmagnetized planets.

Denny M. Oliveira, Eftyhia Zesta, Dibyendu Nandy

In this short communication, we qualitatively analyze possible effects of the 10 October 2024 geomagnetic storm on accelerating the reentry of a Starlink satellite from very low-Earth orbit (VLEO). The storm took place near the maximum of solar cycle (SC) 25, which has shown to be more intense than SC24. Based on preliminary geomagnetic indices, the 10 October 2024, along with the 10 May 2024, were the most intense events since the well-known Halloween storms of October/November 2003. By looking at a preliminary version of the Dst index and altitudes along with velocities extracted from two-line element (TLE) data of the Starlink-1089 (SL-1089) satellite, we observe a possible connection between storm main phase onset and a sharp decay of SL-1089. The satellite was predicted to reenter on 22 October, but it reentered on 12 October, 10 days before schedule. The sharp altitude decay of SL-1089 revealed by TLE data coincides with the storm main phase onset. We compare the de-orbiting altitudes of another three satellites during different geomagnetic conditions and observe that the day difference between actual and predicted reentries increases for periods with higher geomagnetic activity. Therefore, we call for future research to establish the eventual causal relationship between storm occurrence and satellite orbital decay. As predicted by previous works, SC25 is already producing extreme geomagnetic storms with unprecedented satellite orbital drag effects and consequences for current megaconstellations in VLEO.

Alok Kumar Ranjan, Dayakrishna Nailwal, MV Sunil Krishna et al.

During intense geomagnetic storms, the rapid and significant production of NO followed by its associated infrared radiative emission in lower thermosphere contributes crucially to the energetics of the upper atmosphere. This makes NO infrared radiative cooling a very important phenomenon which needs to be considered for accurate density forecasting in thermosphere. This study reports the investigation of variations in thermospheric density, and NO radiative cooling during the recent geomagnetic superstorm of May 2024. A very rare post-storm thermospheric density depletion of about -23% on May 12 was observed by Swarm-C in northern hemisphere in comparison to the prestorm condition on May 9. This overcooling was observed despite the continuous enhancement in solar EUV (24-36 nm) flux throughout the event. The thermospheric NO infrared radiative emission in the recovery phase of the storm seems to be the plausible cause for this observed post-storm density depletion. The TIMED/SABER observed thermospheric density between 105 and 110 km altitude shows an enhancement during this thermospheric overcooling. Our analysis also suggests an all time high thermospheric NO radiative cooling flux up to 11.84 ergs/cm2/sec during May 2024 geomagnetic superstorm, which has also been compared with famous Halloween storms of October 2003.

Marina Puente-Borque, F. Javier Pavón-Carrasco, Alberto Núñez et al.

Abstract The Earth’s magnetic field originated in the fluid core, the so-called core field, is the dominant contribution to the geomagnetic field. Since ancient times, the core geomagnetic field has been used primarily for geographical orientation and navigation by means of compasses. Nowadays, thanks to the large amount of geomagnetic data available, core field models can be developed on a global or regional scale. Global models resolve large-scale geomagnetic field features, while regional models can resolve greater detail over a particular region. The spherical harmonic cap analysis is a widely used technique for regional-scale modelling of the geomagnetic field. In this work we have developed a regional model of the core field and its secular variation between 2014.5 and 2020.5 over the Iberian Peninsula, based on data from Swarm satellites, geomagnetic observatories and repeat stations. Its performance has been validated by comparing the fit to the available geomagnetic data using the regional model and the global models IGRF and CHAOS over the whole spatio-temporal range studied. In order to optimise the model, a detailed study of its input parameters has been carried out, showing that not all parameters have an equal influence on the modelling. This new model reproduces the input data with a root mean square error of 2.9 nT, improving the outcome of global models on this region. The results of this work will allow the Spanish Instituto Geográfico Nacional to produce the magnetic cartography of Iberia and the Balearic Islands in 2020.0, which for the first time will be based on a regional core field model, replacing the polynomial variation method used in the past. Graphical abstract

K. C. Barik, S. V. Singh, G. S. Lakhina

The generation of kinetic Alfvén waves (KAWs) is investigated through a three-component theoretical model incorporating ion beam and velocity shear as the sources of free energy in a non-Maxwellian κ -distributed plasmas. The model considers Maxwellian distributed background ions, drifting-Maxwellian beam ions, and κ -electrons as its constituent species. It is found that the combination of either positive velocity shear with counter-streaming beam ions or parallel streaming beam ions with negative velocity shear favors the excitation of KAWs. The effect of the κ -parameter on the excitation of KAWs under the combined energy sources is explored. The effect of plasma parameters such as number density, propagation angle, and temperature of plasma species on the real frequency and the growth rate of KAWs are examined. For the plasma parameters pertinent to the magnetotail region of Earth’s magnetosphere, the model is able to produce KAWs in the frequency range of ≈(5–67) mHz, which matches well with the recent ‘Time History of Events and Macroscale Interactions during Substorms (THEMIS)’ observations in the near-Earth magnetotail region.

Rajat K. Dey

The distribution of the muon content of highly inclined Monte Carlo cosmic ray showers is affected by the influence of Earth's geomagnetic field. It is found that the shapes of the positive and negative muon distributions get affected/modified by the influence of the Earth's geomagnetic field. Such a correlation between the earth's geomagnetic activity and the cosmic ray (CR) air shower muons is found sensitive to the primary cosmic ray mass composition.

M. M. Katsova, B. A. Nizamov, A. A. Shlyapnikov

We analyze various tracers of magnetic activity for 23 solar twins which are characterized by significant scatter of lithium abundance in their atmospheres. A level of coronal and chromospheric activity has been studied from available X-ray and UV-archival data. It gives us a chance to compare coronae of solar twins of various ages with the solar case. We found a scatter in the X-ray to bolometric luminosity ratio $L_X/L_{bol}$ by several orders of magnitude, which exists in these stars along with a significant spread in Li abundance. This may link the surface activity of stars with phenomena at the base of their convective zones. The TESS data allowed us to reveal rotation modulation of stellar brightness associated with starspots. For some twins of our samples, periods of axial rotation are detected around 6 days, i.e. these stars rotate almost 4 times faster than the contemporary Sun. This indicates their relative youth. Flare activity of solar twins is discovered in the TESS data; we showed existence of various kinds of flares, and present temporal profiles for some of them. We obtained the energy about of $8 \times 10^{33}$ erg for the largest flare of our samples, lasting longer than 4 h. In addition, we discuss also magnetic fields and exoplanets, orbiting these stars.

GUO Qianqian, CUI Lizhen, YANG Yong et al.

The traditional pedestrian dead reckoning (PDR) algorithm has low positioning precision due to the accumulated errors of step size and heading, which can not meet the requirements of precise positioning of underground personnel. In order to solve the problem, a PDR algorithm for precise positioning of underground personnel based on long short-term memory (LSTM) personalized step size estimation is proposed. Firstly, the acceleration and gyroscope inertia information in the movement of underground personnel is collected, and the movement distance of each step is calculated to construct step size data. The LSTM model of personalized step size estimation of the underground personnel is obtained through off-line training. Secondly, in the online prediction stage, the underground personnel movement data such as acceleration, gyroscope and geomagnetism are collected in real-time through the mine intrinsically safe smart phone. The underground personnel movement step and step size of each step are obtained by using the step detection algorithm and personalized step size estimation model respectively. The heading angle is obtained by using the Kalman filtering and heading estimation algorithm. Finally, the current position of underground personnel is predicted according to step size estimation and heading angle. In Inner Mongolia Ordos Gaotouyao Coal Mine, the underground personnel movement data is collected for testing, and the results show as follows. The PDR algorithm for precise positioning of underground personnel based on LSTM personalized step size estimation has a step detection precision of 96.5% and a step size prediction precision of 90%. The algorithm has a relative positioning error of 2.33% in the real underground environment, which improves the personnel positioning precision in coal mine.

I. Michaelis, K. Styp-Rekowski, J. Rauberg et al.

Abstract The Gravity field and steady-state Ocean Circulation Explorer (GOCE) is part of ESA’s Earth Explorer Program. The satellite carries magnetometers that control the activity of magnetorquers for navigation of the satellite, but are not dedicated as science instruments. However, intrinsic steady states of the instruments can be corrected by alignment and calibration, and artificial perturbations, e.g. from currents, can be removed by their characterisation correlated to housekeeping data. The leftover field then shows the natural evolution and variability of the Earth’s magnetic field. This article describes the pre-processing of input data as well as calibration and characterisation steps performed on GOCE magnetic data, using a high-precision magnetic field model as reference. For geomagnetic quiet times, the standard deviation of the residual is below 13 nT with a median residual of (11.7, 9.6, 10.4) nT for the three magnetic field components (x, y, z). For validation of the calibration and characterisation performance, we selected a geomagnetic storm event in March 2013. GOCE magnetic field data show good agreement with results from a ground magnetic observation network. The GOCE mission overlaps with the dedicated magnetic field satellite mission CHAMP for a short time at the beginning of 2010, but does not overlap with the Swarm mission or any other mission flying at low altitude and carrying high-precision magnetometers. We expect calibrated GOCE magnetic field data to be useful for lithospheric modelling and filling the gap between the dedicated geomagnetic missions CHAMP and Swarm. Graphic Abstract

Nariaki V. Nitta, Tamitha Mulligan, Emilia K. J. Kilpua et al.

Geomagnetic storms are an important aspect of space weather and can result in significant impacts on space- and ground-based assets. The majority of strong storms are associated with the passage of interplanetary coronal mass ejections (ICMEs) in the near-Earth environment. In many cases, these ICMEs can be traced back unambiguously to a specific coronal mass ejection (CME) and solar activity on the frontside of the Sun. Hence, predicting the arrival of ICMEs at Earth from routine observations of CMEs and solar activity currently makes a major contribution to the forecasting of geomagnetic storms. However, it is clear that some ICMEs, which may also cause enhanced geomagnetic activity, cannot be traced back to an observed CME, or, if the CME is identified, its origin may be elusive or ambiguous in coronal images. Such CMEs have been termed "stealth CMEs." In this review, we focus on these "problem" geomagnetic storms in the sense that the solar/CME precursors are enigmatic and stealthy. We start by reviewing evidence for stealth CMEs discussed in past studies. We then identify several moderate to strong geomagnetic storms (minimum Dst < -50 nT) in solar cycle 24 for which the related solar sources and/or CMEs are unclear and apparently stealthy. We discuss the solar and in situ circumstances of these events and identify several scenarios that may account for their elusive solar signatures. These range from observational limitations (e.g., a coronagraph near Earth may not detect an incoming CME if it is diffuse and not wide enough) to the possibility that there is a class of mass ejections from the Sun that have only weak or hard-to-observe coronal signatures. In particular, some of these sources are only clearly revealed by considering the evolution of coronal structures over longer time intervals than is usually considered. We also review a variety of numerical modelling approaches...

Amalia Meza, Guillermo Bosch, Maria Paula Natali et al.

Solar eclipses provide an excellent opportunity to study the effects of a sudden localized change in photoionization flux in the Earth's ionosphere and its consequent repercussion in the Geomagnetic field. We have focused on a subset of the data available from the North American 2017 eclipse in order to study VTEC measurements from GNSS data and geomagnetic field estimations from INTERMAGNET observatories near the eclipse path. Our simultaneous analysis of both datasets allowed us to quantify the ionosphere and magnetic field reaction to the eclipse event with which allowed us to compare how differently these take place in time. We found that studying the behaviour of VTEC differences with respect to reference values provides better insight of the actual eclipse effect and were able to characterize the dependence of parameters such as time delay of maximum depletion and recovery phase. We were also able to test models that link the ionospheric variations in a quantitative manner. Total electron content depletion measured from GNSS were fed into an approximation of Ashour-Chapman model at the locations of geomagnetic observatories and its predictions match the behaviour of magnetic field components in time and magnitude strikingly accurately.

Clemens Kloss, Christopher C. Finlay, Nils Olsen

Models of the geomagnetic field rely on magnetic data of high spatial and temporal resolution. The magnetic data from low-Earth orbit satellites of dedicated magnetic survey missions such as CHAMP and Swarm play a key role in the construction of such models. Unfortunately, there are no magnetic data from such satellites after the end of CHAMP in 2010 and before the launch of Swarm in late 2013. This limits our ability to recover signals on timescales of 3 years and less during this gap period. The magnetic data from platform magnetometers carried by satellites for navigational purposes may help address this data gap provided that they are carefully calibrated. Earlier studies have demonstrated that platform magnetometer data can be calibrated using a fixed reference field model. However, this approach can lead to biased calibration parameters. An alternative has been developed in the form of a co-estimation scheme which consists of simultaneously estimating both the calibration parameters and a model of the internal geomagnetic field. Here, we develop a scheme, based on the CHAOS framework, that involves the co-estimation of a geomagnetic field model along with calibration parameters of platform magnetometers. Using our implementation, we are able to derive a geomagnetic field model from 2008 to 2018 with satellite magnetic data from CHAMP, Swarm, secular variation data from ground observatories, and platform magnetometer data from CryoSat-2 and GRACE. Through experiments, we explore correlations between the estimates of the geomagnetic field and the calibration parameters, and suggest how these may be avoided. We find that platform magnetometer data provide additional information on the secular acceleration, especially in the Pacific during the gap period. This study adds to the evidence that it is beneficial to use platform magnetometer data in geomagnetic field modeling.

Ming-Xian Zhao, Gui-Ming Le, Qi Li et al.

We use $Δ$SYM-H to capture the variation in the SYM-H index during the main phase of a geomagnetic storm. We define great geomagnetic storms as those with $Δ$SYM-H $\le$ -200 nT. After analyzing the data that were not obscured by solar winds, we determined that 11 such storms occurred during solar cycle 23. We calculated time integrals for the southward interplanetary magnetic field component I(B$_s$), the solar wind electric field I(E$_y$), and a combination of E$_y$ and the solar wind dynamic pressure I(Q) during the main phase of a great geomagnetic storm. The strength of the correlation coefficient (CC) between $Δ$SYM-H and each of the three integrals I(B$_s$) (CC = 0.74), I(E$_y$) (CC = 0.85), and I(Q) (CC = 0.94) suggests that Q, which encompasses both the solar wind electric field and the solar wind dynamic pressure, is the main driving factor that determines the intensity of a great geomagnetic storm. The results also suggest that the impact of B$_s$ on the great geomagnetic storm intensity is much more significant than that of the solar wind speed and the dynamic pressure during the main phase of associated great geomagnetic storm. How to estimate the intensity of an extreme geomagnetic storm based on solar wind parameters is also discussed.

Michal Švanda, Didier Mourenas, Karla Žertová et al.

Eruptive events of solar activity often trigger abrupt variations of the geomagnetic field. Through the induction of electric currents, human infrastructures are also affected, namely the equipment of electric power transmission networks. It was shown in past studies that the rate of power-grid anomalies may increase after an exposure to strong geomagnetically induced currents. We search for a rapid response of devices in the Czech electric distribution grid to disturbed days of high geomagnetic activity. Such disturbed days are described either by the cumulative storm-time $Dst$ or $d(\textit{SYM-H})/dt$ low-latitude indices mainly influenced by ring current variations, by the cumulative $AE$ high-latitude index measuring substorm-related auroral current variations, or by the cumulative $ap$ mid-latitude index measuring both ring and auroral current variations. We use superposed epoch analysis to identify possible increases of anomaly rates during and after such disturbed days. We show that in the case of abundant series of anomalies on power lines, the anomaly rate increases significantly immediately (within 1 day) after the onset of geomagnetic storms. In the case of transformers, the increase of the anomaly rate is generally delayed by 2--3 days. We also find that transformers and some electric substations seem to be sensitive to a prolonged exposure to substorms, with a delayed increase of anomalies. Overall, we show that in the 5-day period following the commencement of geomagnetic activity there is an approximately 5--10\% increase in the recorded anomalies in the Czech power grid and thus this fraction of anomalies is probably related to an exposure to GICs.