On calculating the electric and magnetic fields produced in technological systems at the Earth's surface by a “wide” electrojet
✍ Scribed by D.H. Boteler; R. Pirjola; L. Trichtchenko
- Publisher
- Elsevier Science
- Year
- 2000
- Tongue
- English
- Weight
- 123 KB
- Volume
- 62
- Category
- Article
- ISSN
- 1364-6826
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✦ Synopsis
Forecasting the geomagnetic e ects to technological systems on the ground requires rapid calculations of the electric and magnetic ÿelds produced by the auroral electrojet. The electrojet is often modelled as a line current at a height of 100 km, but in reality it has a ÿnite width and is typically spread over 5 • or 6 • of latitude. We show that the width of the electrojet can easily be included in electric and magnetic ÿeld calculations by assuming that the ionospheric current density has a Cauchy distribution with a half-width a; j(x)=(I= )a=(x 2 + a 2 ), at a height h. It is shown that the electric and magnetic ÿelds produced at the surface of a layered earth by such a current are equivalent to the ÿelds produced by a line current I at a height h + a. This equivalence, combined with the complex image method, leads to simple formulas that provide a method for fast calculation of the electric and magnetic ÿelds that can a ect ground-based systems.