TY - JOUR

T1 - Deriving the geomagnetically induced electric field at the Earth's surface from the time derivative of the vertical magnetic field

AU - Vanhamäki, Heikki

AU - Viljanen, Ari

AU - Pirjola, Risto

AU - Amm, Olaf

N1 - Funding Information:
Acknowledgments. The work of H. Vanhamäki was supported by the Academy of Finland (project number 126552). We thank all institutes maintaining the IMAGE magnetometer network (http://space.fmi.fi/image/). The BEAR project was partly supported by INTAS (no. 97-1162).

PY - 2013

Y1 - 2013

N2 - We present a new method for estimating the geomagnetically induced electric field at the Earth's surface directly from the time derivative of the vertical magnetic field, without any need for additional information about the Earth's electric conductivity. This is a simplification compared to the presently used calculation methods, which require both the magnetic variation field and ground conductivity model as input data. The surface electric field is needed e.g. in modeling Geomagnetically Induced Currents (GIC) that flow in man-made conductor systems, such as gas and oil pipelines or high-voltage power grids. We solve the induced electric field directly from Faraday's law, by representing the magnetic variation field in terms of external equivalent current and taking time derivative of the associated vector potential. This gives an approximative solution, where the divergence- free part of the electric field is reproduced accurately (at least in principle), but the curl-free part related to lateral variations in ground conductivity is completely neglected. We test the new calculation method with several realistic models of typical ionospheric current systems, as well as actual data from the Baltic Electromagnetic Array Research (BEAR) network. We conclude that the principle of calculating the (divergence-free part of the) surface electric field from time derivative of the vertical magnetic field is sound, and the method works reasonably well also in practice. However, practical applications may be rather limited as the method seems to require data from a quite dense and spatially extended magnetometer network.

AB - We present a new method for estimating the geomagnetically induced electric field at the Earth's surface directly from the time derivative of the vertical magnetic field, without any need for additional information about the Earth's electric conductivity. This is a simplification compared to the presently used calculation methods, which require both the magnetic variation field and ground conductivity model as input data. The surface electric field is needed e.g. in modeling Geomagnetically Induced Currents (GIC) that flow in man-made conductor systems, such as gas and oil pipelines or high-voltage power grids. We solve the induced electric field directly from Faraday's law, by representing the magnetic variation field in terms of external equivalent current and taking time derivative of the associated vector potential. This gives an approximative solution, where the divergence- free part of the electric field is reproduced accurately (at least in principle), but the curl-free part related to lateral variations in ground conductivity is completely neglected. We test the new calculation method with several realistic models of typical ionospheric current systems, as well as actual data from the Baltic Electromagnetic Array Research (BEAR) network. We conclude that the principle of calculating the (divergence-free part of the) surface electric field from time derivative of the vertical magnetic field is sound, and the method works reasonably well also in practice. However, practical applications may be rather limited as the method seems to require data from a quite dense and spatially extended magnetometer network.

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U2 - 10.5047/eps.2013.03.013

DO - 10.5047/eps.2013.03.013

M3 - Article

AN - SCOPUS:84892393938

SN - 1343-8832

VL - 65

SP - 997

EP - 1006

JO - Earth, Planets and Space

JF - Earth, Planets and Space

IS - 9

ER -