Although it is only about one-third the size of Jupiter’s magnetosphere,
Saturn’s magnetosphere is still an enormous structure, extending nearly
two million kilometers from the planet toward the Sun. The size of the
magnetosphere fluctuates rhythmically as the flow of charged particles
in the solar wind increases or decreases in intensity. The magnetosphere
can be pushed inside Titan’s orbit, so that at times the satellite finds
itself outside of the magnetosphere altogether.
Charged particles in the planet’s magnetosphere are dragged along by the
magnetic field, circling the planet at Saturn’s rotation rate of 10
hours, 39 minutes. These charged particles whiz by Titan at a dizzying
rate of more than 200 kilometers (120 miles) per second. Titan leaves a
motorboat-like wake in its orbital path.
Extending from the orbit of Titan inward to the orbit of Rhea, an
enormous cloud of uncharged hydrogen atoms forms a doughnut-shaped torus
of ultraviolet-emitting particles. Because of their neutrality, these
atoms are not towed around by Saturn’s magnetic field.
Close to the planet, Saturn’s rings act as an effective shield or
absorber of charged particles. The rings themselves are apparently
substantially affected in this process, however, as evidenced by their
“spokes” of fine particles and the lightning-like electrical discharges
attributed to the rings.