Abstract
Abstract. Rapid changes in the ionospheric current system give rise to induction currents in the conducting ground that can significantly contribute to magnetic and especially electric fields at the Earth's surface. Previous studies have concentrated on the surface fields, as they are important in, for example, interpreting magnetometer measurements or in the studies of the Earth's conductivity structure. In this paper we investigate the effects of induction fields at the ionospheric altitudes for several realistic ionospheric current models (Westward Travelling Surge, Ω-band, Giant Pulsation). Our main conclusions are: 1) The secondary electric field caused by the Earth's induction is relatively small at the ionospheric altitude, at most 0.4 mV/m or a few percent of the total electric field; 2) The primary induced field due to ionospheric self-induction is locally important, ~ a few mV/m, in some "hot spots", where the ionospheric conductivity is high and the total electric field is low. However, our approximate calculation only gives an upper estimate for the primary induced electric field; 3) The secondary magnetic field caused by the Earth's induction may significantly affect the magnetic measurements of low orbiting satellites. The secondary contribution from the Earth's currents is largest in the vertical component of the magnetic field, where it may be around 50% of the field caused by ionospheric currents. Keywords. Geomagnetism and paleomagnetism (geomagnetic induction) – Ionosphere (electric fields and currents)
Highlights
In this paper we investigate the effects of induction on ionospheric electric and magnetic fields
Concerning the horizontal electric field, the Earth behaves as a perfect conductor, so that the horizontal part of the primary and secondary electric fields produced by curl-free Cartesian Elementary Current Systems (CECS) exactly cancel at the Earth’s surface
We have estimated an upper limit of the electric field associated with ionospheric self-induction
Summary
In this paper we investigate the effects of induction on ionospheric electric and magnetic fields. We investigate the magnitude of the secondary magnetic field (Bs) produced by the Earth’s currents as compared to the primary field (Bp) produced by the ionospheric currents at different altitudes and discuss the implications to satellite measurements This is the first time that these effects are studied using realistic time-dependent three-dimensional models for high latitude ionospheric current systems. For a layered Earth model, the secondary fields produced by induced currents in the Earth can be calculated by using CIM In this case the secondary fields of a divergence-free elementary system above the ground (z≤0) are. Concerning the horizontal electric field, the Earth behaves as a perfect conductor, so that the horizontal part of the primary and secondary electric fields produced by curl-free CECS exactly cancel at the Earth’s surface. In this case the resulting field E0 is not a pure potential field, but this does not affect the calculations
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