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TitleTruncation of the Earth impulse responses relating geoelectric fields and geomagnetic field variations
AuthorPirjola, R JORCID logo; Boteler, D HORCID logo
SourceGeosciences Research vol. 2, no. 2, 2017 p. 72-92, Open Access logo Open Access
Alt SeriesEarth Sciences Sector, Contribution Series 20160135
PublisherIsaac Scientific Publishing
Mediapaper; on-line; digital
File formatpdf
SubjectsHealth and Safety
ProgramPublic Safety Geoscience Northern Canada Geohazards Project
Released2017 05 15
AbstractTo assess the geomagnetic hazard to power systems, it is necessary to model the Geomagnetically Induced Currents (GIC) produced during space weather storms. This requires knowledge of the geoelectric fields that drive GIC. In the time domain, the geoelectric fields can be calculated using a convolution integral including the geomagnetic field or its time derivative and an impulse response function for the Earth. In principle, the integral extends to infinity but for practical calculations the impulse responses must be truncated at a finite length. In this paper, we investigate the effects of the truncation on the calculation of the geoelectric fields. We consider how long the impulse responses need to be to obtain sufficiently accurate geoelectric field values. It is found that the high-pass impulse response used with geomagnetic data can be truncated very early, e.g. at 1 h, while the low-pass impulse response used with geomagnetic time derivative data must be extended much longer, e.g. until 24 h.
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, satellites, radio communications and GNSS positioning to help Canadian industry understand and mitigate the effects of space weather. This paper examines using the Earth impulse response to calculate geoelectric fields that affect critical infrastructure. In particular we consider how long the impulse responses need to be to obtain sufficiently accurate geoelectric field values.

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