Open AccessElectric field at the seafloor due to a two‐dimensional ionospheric current
Author(s) -
Pirjola Risto J.,
Viljanen Ari T.,
Boteler David H.
Publication year - 2000
Publication title -
geophysical journal international
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.302
H-Index - 168
eISSN - 1365-246X
pISSN - 0956-540X
DOI - 10.1046/j.1365-246x.2000.00029.x
Subject(s) - geophysics , geology , electric field , seafloor spreading , magnetic field , magnetometer , geodesy , physics , quantum mechanics
The relation between the seafloor electric field and the surface magnetic field is studied. It is assumed that the fields are created by a 2‐D ionospheric current distribution resulting in the E‐polarization. The layered earth below the sea water is characterized by a surface impedance. The electric field at the seafloor can be expressed either as an inverse Fourier transform integral over the wavenumber or as a spatial convolution integral. In both integrals the surface magnetic field is multiplied by a function that depends on the depth and conductivity of the sea water and on the properties of the basement. The fact that surface magnetic data are usually available on land, not at the sea surface, is also considered. Test computations demonstrate that the numerical inaccuracies involved in the convolution method are negligible. The theoretical equations are applied to calculate the seafloor electric fields due to an ionospheric line current or associated with real magnetic data collected by the IMAGE magnetometer array in northern Europe. Two different sea depths are considered: 100 m (the continental shelf) and 5 km (the deep ocean). It is seen that the dependence of the electric field on the oscillation period is weaker in the 5 km case than for 100 m.