Magnetic Field Studies at Jupiter by Voyager 2: Preliminary Results

Data from the Goddard Space Flight Center magnetometers on Voyager 2 have yielded on inbound trajectory observations of multiple crossings of the bow shock and magnetosphere near the Jupiter-sun line at radial distances of 99 to 66 Jupiter radii (R$_{J}$) and 72 to 62 R$_{J}$, respectively. While outbound at a local hour angle of 0300, these distances increase appreciably so that at the time of writing only the magnetopause has been observed between 160 and 185 R$_{J}$. These results and the magnetic field geometry confirm the earlier conclusion from Voyager 1 studies that Jupiter has an enormous magnetic tail, approximately 300 to 400 R$_{J}$ in diameter, trailing behind the planet with respect to the supersonic flow of the solar wind. Additional observations of the distortion of the inner magnetosphere by a concentrated plasma show a spatial merging of the equatorial magnetodisk current with the current sheet in the magnetic tail. The spacecraft passed within 62,000 kilometers of Ganymede (radius = 2,635 kilometers) and observed characteristic fluctuations interpreted tentatively as being due to disturbances arising from the interaction of the Jovian magnetosphere with Ganymede.