Isaac Scientific Publishing

Geosciences Research

Truncation of the Earth Impulse Responses Relating Geoelectric Fields and Geomagnetic Field Variations

Download PDF (510.7 KB) PP. 72 - 92 Pub. Date: May 15, 2017

DOI: 10.22606/gr.2017.22002


  • Risto J. Pirjola*
    Geomagnetic Laboratory, Earth Science Sector, Natural Resources Canada, 2617 Anderson Road, Ottawa, Ontario, K1A 0E7, Canada
  • David H. Boteler

    Finnish Meteorological Institute, P. O. Box 503, FI-00101 Helsinki, Finland


To 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.


Geoelectromagnetics, geoelectric field, Geomagnetically Induced Currents (GIC), space weather


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