An induced magnetosphere of a comet rotates around the Sun--comet line along with the interplanetary magnetic field (IMF) vector. During the Giotto flyby near comet Halley the direction of the IMF changed several times. For this reason, the trajectory of the Giotto spacecraft, being represented in the IMF-related coordinate system, covered rather well the transverse cross section of the comet Halley magnetosphere. As a result, two-dimensional distributions of both the magnetic field and electric current density have been calculated in the transverse cross section of the induced magnetosphere of comet Halley. The distributions reveal the following facts. The magnetic barrier is axially symmetric (within the accuracy of the grid ~103 km). Such a behavior is associated with the fact that the magnetic field strength in the barrier is governed by the dynamic pressure of the solar wind and does not depend on the ion-neutral friction (which affects only the location of the magnetic field maximum). Along with draping about the dayside of a comet, magnetic field lines also drape about its flanks (where the magnetic field turns out to be enhanced). As a result, the Lorentz electric field inside the cometary ionosphere decreases. Lines of the electric current drape about the cometary ionosphere in a manner resembling the magnetic lines. The region of the magnetic barrier in front of the contact surface is shown to be an electric load for the MHD generator arising as a result of the solar wind interaction with a comet. ¿ American Geophysical Union 1994 |