Alfven wave generation by disturbance of ionospheric conductivity in the field-aligned current region

A fundamental problem of the Alfven wave generation from a region of disturbed ionospheric conductivity in the ambient field-aligned current area is investigated. It is shown that the field-aligned current of the outgoing Alfven wave appears not only at the boundary but also inside the region of enhanced (or diminished) conductivity. If the ionosphere conductivity increases, the additional field-aligned current of the outgoing Alfven wave inside the region of disturbed conductivity is directed in the same way the background field-aligned current. For a circular region of disturbed conductivity the electric field of the outgoing Alfven wave can be presented as the sum of electric fields of the two-dimensional dipole, quadrupole, and screened monopole sources. For a strip-like region of disturbed conductivity the electric field of the outgoing Alfven wave appears only inside the strip and can be presented as the sum of homogeneous and linearly varying electric fields.