Geomagnetically induced currents (GICs) are a consequence of space weather activity that can affect power grid operation and stability worldwide. GICs manifest as quasi-direct currents flowing between the power grids and the conductive earth, and are often measured with a Hall sensor placed at the transformer neutral. Globally, the number of power grid substations with GIC measurements has grown quickly in recent years, but Austria remains one of the few countries with a dataset of long-term GIC observations. GIC measurements in substations in the Austrian power grid have been carried out since 2016, with a maximum of seven concurrent substation measurements, providing a unique opportunity for GIC measurement analysis.

In this study, we present an analysis of the last six years of GIC measurements in Austria. Seven custom-built stand-alone GIC measurement systems have been installed in the 220 and 380 kV transmission levels, measuring currents up to 25 A. We identify recurrent geomagnetic activity in the measurements, and also find man-made sources of low frequency currents using frequency analysis. We focus on two geomagnetic storms from September 2017 and May 2021 to discuss the effects of GICs on a mid-latitude power transmission grid. In conclusion, we find that there is a daily level of noise in the data and that, even during the largest events when 14 A were measured, transformer heating remains unlikely.

How to cite: Bailey, R., Schachinger, P., Albert, D., Achleitner, G., and Leonhardt, R.: Analysis of six years of GIC measurements in the Austrian power grid, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-6199, https://doi.org/10.5194/egusphere-egu23-6199, 2023.

How to cite: Wild, J., Patterson, C., and Boteler, D.: Modeling the Impact of Geomagnetically Induced Currents on Electrified Railway Signalling Systems in the United Kingdom, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-9660, https://doi.org/10.5194/egusphere-egu23-9660, 2023.

Geomagnetically Induced Currents (GIC) constitute an integral part of space weather research and are a subject of ever-growing attention for countries located in the low and middle latitudes. A series of recent studies highlights the importance of considering GIC risks for the Mediterranean region. Here, we exploit data from the HellENIc GeoMagnetic Array (ENIGMA), which is deployed in Greece, complemented by magnetic observatories in the Mediterranean region (Italy, France, Spain, Algeria and Turkey), to calculate values of the GIC index, i.e., a proxy of the geoelectric field calculated entirely from geomagnetic field variations. We perform our analysis for the most intense magnetic storms (Dst < -150 nT) of solar cycle 24. Our results show that GIC index increases are well correlated with Storm Sudden Commencements (SSCs). However, the GIC indices do not exceed “low” activity levels despite the increases in their values, at all magnetic stations / observatories under study during the selected storm events.

How to cite: Boutsi, A. Z., Balasis, G., Dimitrakoudis, S., Daglis, I. A., Tsinganos, K., Papadimitriou, C., and Giannakis, O.: Investigation of the Geomagnetically Induced Current Index levels in the Mediterranean region during the strongest magnetic storms of solar cycle 24, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-3980, https://doi.org/10.5194/egusphere-egu23-3980, 2023.

Dedicated scientific measurements of the strength and direction of the Earth's field began at Greenwich and Kew observatories in London, UK, in the middle of the 19th century. Using advanced techniques for the time, light-sensitive photographic paper and light-levered reflections from magnetized needles allowed continuous analogue magnetograms to be recorded. By good fortune, both observatories were in full operation during the so-called Carrington storm in late August/early September 1859 providing as complete a record as possible. Based on digital images of the magnetograms and information from the observatory yearbooks and scientific papers scaling the measurements to SI units is possible at minute-mean cadence. However, due to the magnitude of the storm, periods of the greatest magnetic field variation are lost as the traces moved off-page. We present the most complete digitized magnetic records to date of the ten-day period from 25th August to 5th September 1859 encompassing the Carrington storm and its precursor on the 28^th August.

How to cite: Florczak, E., Beggan, C., and Clarke, E.: Digitizing the Carrington 1859 storm: magnetogram records from Greenwich and Kew observatories, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-6191, https://doi.org/10.5194/egusphere-egu23-6191, 2023.

In the marine environment, active and passive electromagnetic (EM) measurements are used to derive information about the conductivity structure beneath the seafloor. While the conductivity is mostly determined by the conductive seawater contained in the pore space or fractures, anomalies may occur in the presence of more resistive (e.g. hydrocarbons, free gas, gas hydrates, freshened water) or conductive materials (e.g. massive sulfides, brines). For the correct interpretation of EM data it is important to know the measurement geometry, including the orientations of receivers. From an experimental standpoint, this can be challenging because stations are often deployed free falling, thus, ending up in arbitrary orientations on the seafloor. The orientations are frequently derived from electronic compass measurements or magnetometers which record all components of the magnetic field. However, these measurements may be distorted by magnetic parts on stations (e.g. batteries), biased by local inhomogeneities in the local field or difficult to perform if no reliable reference data from a nearby observatory is available.

A possible remedy for such problems may come from space physics. Given a grid of stationary magnetometer stations, surrounding the area of interest but at relatively large distances, the method of spherical elementary current systems (SECS) (Amm & Viljanen, 1999, Earth, Plants and Space) can be used to reconstruct equivalent ionospheric currents and their resulting time variations of the magnetic field at any point within the grid. The method is especially suitable to be applied at northern latitudes, where fairly dense magnetometer networks such as IMAGE and CARISMA exist, and where the magnitude of geomagnetic disturbances from ionospheric currents is significant.

We have successfully applied the method to three marine EM data sets, one offshore Iceland, one in the arctic section of the North Atlantic (Loki's Castle) and one off the Canadian coast (Prince Edward Island). The SECS method qualitatively reproduces the magnetic variation as observed by the seafloor stations. Here we investigate the results from the above mentioned EM data sets, and discuss the applicability, accuracy and constraints of the SECS method for EM data calibrations. Furthermore, we illuminate the possibility for using SECS as an interpolation tool for other applications at remote offshore locations, such as measurement while drilling (MWD) operations.

How to cite: Hölz, S., Johnsen, M. G., Franz, G., Córdoba Ramírez, F., Cairns, G., Nedimovic, M., Jegen, M., Berndt, C., Elger, J., and Maselli, V.: Determination of orientation of marine magnetometers by means of modelled local field variations derived from spherical elementary current systems, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-1288, https://doi.org/10.5194/egusphere-egu23-1288, 2023.