Characteristics of the tail of comet Giacobini-Zinner

On September 11, 1985 the International Cometary Explorer (ICE) traversed the tail of Comet Giacobini-Zinner to provide the only in situ information on the physical structure and characteristics of a comet tail. ICE passed 7800 km behind the nucleus, where it clearly detected a draped two-lobe magnetic field configuration and a narrow central plasma sheet. Throughout the tail and inner sheath region, the ICE instruments gave complete information on variations in the vector B-field configuration, the electron distribution function, the energetic ion population, and the electromagnetic and electrostatic plasma wave spectrum. These direct observations supply a framework to test theoretical models of comet tail formation.