Jupiter's huge, intense magnetic field behaves as though there were a giant bar magnet inside
the planet. The magnetic field acts as a deflector shield against the stream of particles in the
solar wind coming from our Sun. Instead of striking Jupiter, some of these charged particles get
caught inside the magnetosphere, where they are accelerated to enormous speeds and zip along
the planet's magnetic field lines.
Galileo measures Jupiter's magnetic field while passing through it. To avoid picking up
interference, certain instruments are held away from the spacecraft. The
measures the strength and direction of the field. The Energetic Particle Detector and the Plasma
Instrument determine the number, energy, and direction of the particles inside the magnetosphere
and in the solar wind. A Plasma Wave detector senses waves in the streams of particles.
Galileo's camera records a bright aurora, as fast-moving particles from the Sun follow
magnetic field lines into Jupiter's atmosphere. The beautiful glow results as the charged particles
strike the upper atmosphere. The aurora also glows in ultraviolet light, which is measured by
Galileo's Ultraviolet Spectrometer
and Extreme Ultraviolet Spectrometer.
Next: Observing Interiors