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TitleGeoelectric field modelling for canadian space weather services
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AuthorTrichtchenko, L; Fernberg, P A; Danskin, D W
SourceGeological Survey of Canada, Open File 8115, 2016, 140 pages, https://doi.org/10.4095/299116
Year2016
PublisherNatural Resources Canada
Documentopen file
Lang.English
Mediaon-line; digital
File formatpdf
Subjectsgeophysics; geoelectric variations; geomagnetism; geomagnetic fields; geomagnetic variations; electric power; remote sensing; modelling; resistivity
Illustrationsplots; graphs; tables; location maps; plots
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Location
 
Natural Resources Canada Library - Ottawa (Earth Sciences)
 
ProgramNorthern Canada Geohazards Project, Public Safety Geoscience
Released2016 09 29
Abstract(Summary)
Evaluation of the impacts of space weather on ground infrastructure requires information on the size of geomagnetically induced currents produced by the space weather events. The estimation of these currents in places where they are/were not recorded, the numerical modelling is allpied. The most common approach in the modelling of the geomagnetically induced currents is based on the knowledge of the geoelectric field driving these currents while the most common way to estimate the geoelectric field is to use the geomagnetic data recorded in the area. The NRCan on-line service allows calculations of the geoelectric field in the vicinity of each NRCan Geomagnetic Observatory (http://www.geomag.nrcan.gc.ca/index-en.php or http://www.geomag.nrcan.gc.ca/index-fr.php). This report explains the details on the modelling used in electric field calculations and gives all the needed information on all components of the used models. One of the most important components used to obtain electric field from measured magnetic field is the surface impedance. The report provides the details of the surface impedance models currently used for each observatory. Because there are currently more information on earth structure and also because some observatories have been moved to different locations, the updated surface impedance models are also presented. A comparison of the new and old surface impedance models shows for the most of them the differences are not significant (BRD, VIC, FCC, IQA, SNK, BLC), or occurred only in the high frequency part (i.e. OTT, MEA). The exception is the models for STJ observatory, which give significant differences between old and new ones and, therefore, the new STJ model should be checked before use in the on-line service. Comparison of the geoelectric field variations were calculated for 29 October 2003 (Halloween storm) with application of “new” and “old” models were done at several locations with the more dense the impacted infrastructure, such as power grids and pipelines. The results confirm that at the time of large high frequency fluctuations (i.e. during geomagnetic storm) the geoelectric field can be 30% different at many stations due to different earth models used. For the abovementioned STJ magnetic observatory the difference is up to 300%. The recommendation is, therefore, to validate the layered earth models by conducting MT surveys in the vicinity of observatories, specifically for the STJ observatory.
Summary(Plain Language Summary, not published)
Space weather refers to the dynamic conditions on the Sun and in the space environment, in particular, in the near-Earth environment, that can affect critical infrastructure. NRCan operates the Canadian Space Weather Forecast Centre and conducts research into space weather effects on power systems, pipelines, radio communications and GNSS positioning to help Canadian industry understand and mitigate the effects of space weather. The report presents the set of models used for development of the on-line service, such as geoelectric field model and Earth conductivity models for Canadian geomagnetic observatories. Several of Earth conductivity models were updated since the start of operational on-line service. These new models were presented and compared with old ones. The results show that for low-latitude observatories new models give smaller amplitudes of the geoelectric fields, which is important for assessment of the space weather hazards on the power grids and pipelines.
GEOSCAN ID299116