Voyager observations of Jupiter's distant magnetotail

Abstract

Observations of nonthermal continuum radiation by Voyager 1 and 2 at large distances from Jupiter have led to the identification of brief encounters with the Jovian magnetosphere at distances greater than 700 R J and in directions substantially far from the Jupiter‐sun line. In addition, a number of examples of continuum radiation apparently trapped in local density depressions in the solar wind are observed. Simultaneous measurements by the Voyager plasma instrument have verified the distant magnetotail crossings and are used to correlate the occurrence of trapped continuum radiation events within solar wind density rarefactions. The Voyager observations of the distant Jovian magnetotail are compared with observations in the distant terrestrial magnetosphere and also with observations of the plasma tails of comets. Viable explanations of the observations are that the Jovian tail consists of filamentary structures, some of which extend to large distances in the predawn direction, or that the Jovian tail may be offset in the dawn direction by a combination of corotation angular momentum and forces associated with high‐speed streams in the solar wind. The observations of continuum radiation trapped in low‐density regions of the solar wind suggest that Voyager may at times be connected to the distant tail by a low‐density trough which acts as a wave guide and allows radiation from the tail to reach the spacecraft. This may provide an indirect method of detecting the tail extending more than 2 AU downstream from Jupiter.