One of the most important results of the Giotto mission to comet Halley was the discovery of a magnetic cavity surrounding the nucleus in which the magnetic field strength was apparently zero1. The boundary of the cavity, the ionopause, occurred at 4,760 km (3,840 km) and the maximum magnetic field strength was ∼55 nT (65 nT), thousands of km outside the rather sharply defined transition to zero field on the inbound (outbound) part of the trajectory, respectively. We show here with the aid of a simple model that such a magnetic field structure can be explained as being largely the result of ion-neutral friction2rather than simple pressure-balance alone 3,4.
|Number of pages||2|
|State||Published - 1987|