Geomagnetic pulsations associated with MHD-waveguide in magnetospheric ducts

A theory of waveguide propagation of MHD waves in magnetospheric ducts (detached plasma regions) is presented. It is shown that Alfvénic waveguide modes can be excited due to the resonance interaction with the waveguide FMS modes. The Alfvénic modes penetrate to the ground and lead to electromagnetic field variations, registered as local geomagnetic Pcl-2 pulsations. The problem of the Alfvénic waveguide modes propagation from the magnetosphere to the Earth's surface is considered and a comparison is made of theoretical results with experimental data.