However, the moon Io's volcanically derived atmosphere is lost by sputtering to the magnetosphere. The trapped radiation belt particles collide with the atmospheric particles and knock them out of Io's gravitational sphere of influence and into orbit about Jupiter. The velocities associated with this process combined with the high mass loss rate from To are sufficient to distort the magnetic field of Jupiter into a disk, or magnetodisk as sketched in Figure 1 . The centrifugal force associated with this magnetodisk stretches the magnetosphere in all directions and increases the forward radius of the magnetosphere to close to 100 Jovian radii at times. Since a Jovian radius is more than ten Earth radii, the linear dimension of the Jovian magnetosphere is about 100 times that of the Earth and its volume a million times bigger.
Solid lines represent the direction of the magnetic field.
The sputtering process leads to an interesting feedback process because the particles sputtered, lost to Jupiter and then accelerated, are eventually energized to high energies and return to sputter again and hence maintain the level of the radiation belts. The energy for all this acceleration is derived from the rotational energy of the planet. However, this energy reservoir is so large that no significant change in rotation has occurred due to magnetospheric processes over the age of the planet. As with other magnetospheres, both intrinsic to the planet and induced by the solar wind interaction, Jupiter has a magnetic tail extending in the antisolar direction. The Jovian magnetosphere is very dynamic.