Magnetosphere

Given its predominance in size and physical characteristics, it should come as no surprise that Jupiter has the strongest magnetic field among the planets in our solar system, with a reach extending far beyond its orbiting moons. This strong magnetic field also strongly influences the motion of the electrically charged particles that travel through it. The Sun is one of the major sources of these charged particles which are ejected at enormous speeds from its corona into space, occasionally in spectacular bursts called Coronal Mass Ejection (CME) events. This traveling stream of particles is called the solar wind.

Jupiter's Magnetosphere

Animation of the variation of the synchrotron emission at 1400 MHz from Jupiter with a computer model (Levin et al., Geophys. Res. Lett., (28), No. 5, p. 903-906, 2001) using an assumed electron distribution and magnetic field. The model simulates ground based radio observations well. The thermal emission from Jupiter has been subtracted, and representative magnetic field lines are shown. The animation covers one rotation of Jupiter, frames are 20 degrees apart in central longitude. The animation shows the East West asymmetry of the emitted radiation in the equatorial plane. The "wobble" of the emitted radiation is due to the misalignment of the rotation pole of Jupiter and the magnetic pole.

Most planetary magnetic fields can be thought of as a bar magnet with its long axis tilted at some angle from the rotation axis of the planet. For Jupiter this angle is about ten degrees. (On Earth the magnetic axis has flipped often in its history, and at present the magnetic axis is close to the rotation axis). When this stream of particles reaches a planet's magnetic field, the charged particles are deflected around that magnetic field. The space within which the particles are influenced by the magnetic field, is the magnetosphere of the planet which is typically shortened on the sun ward side and extends far beyond the planet in the direction away from the Sun.

The volcanic activity on Io, also injects large amounts of ionized particles into Jupiter's magnetic field, causing a torus to form around the planet. The Io torus wobbles with Jupiter's magnetic field. The Juno spacecraft's highly elliptical orbit around Jupiter will enable it to sample different portions of the magnetosphere over the course of the mission. Here is an animation of the magnetosphere of Jupiter.