The magnetosphere of Saturn is the cavity created in the flow of the solar wind by the planet's internally generated magnetic field.

The main source is the small moon Enceladus, which ejects as much as 1,000 kg/s of water vapor from the geysers on its south pole, a portion of which is ionized and forced to co-rotate with the Saturn's magnetic field.

The interaction between Saturn's magnetosphere and the solar wind generates bright oval aurorae around the planet's poles observed in visible, infrared and ultraviolet light.

[9] The first evidence that Saturn might have an internally generated magnetic field came in 1974, with the detection of weak radio emissions from the planet at the frequency of about 1 MHz.

[10] Nevertheless, the evidence available in the 1970s was too inconclusive and some scientists thought that Saturn might lack a magnetic field altogether, while others even speculated that the planet could lie beyond the heliopause.

[2] Like Jupiter's magnetic field, Saturn's is created by a fluid dynamo within a layer of circulating liquid metallic hydrogen in its outer core.

[2] The magnetopause distance from the planet's center at the subsolar point[note 1] varies widely from 16 to 27 Rs (Rs=60,330 km is the equatorial radius of Saturn).

[6] In front of the magnetopause (at the distance of about 27 Rs from the planet)[6] lies the bow shock, a wake-like disturbance in the solar wind caused by its collision with the magnetosphere.

[18] The innermost region co-located with Saturn's planetary rings, inside approximately 3 Rs, has a strictly dipolar magnetic field.

It is characterized by a low plasma density and a variable, non-dipolar magnetic field strongly influenced by the Solar wind.

[18] In the outer parts of Saturn's magnetosphere beyond approximately 15–20 Rs[20] the magnetic field near the equatorial plane is highly stretched and forms a disk-like structure called magnetodisk.

As revealed by ultraviolet observation of Cassini, the planet is enshrouded in a large cloud of hydrogen, water vapor and their dissociative products like hydroxyl, extending as far as 45 Rs from Saturn.

[29][30] The relatively cold plasma in the innermost region of Saturn's magnetosphere, inside 3 Rs (near the rings) consists mainly of O+ and O2+ ions.

[25][32] In the case of Saturn, charge exchange facilitates the transfer of energy from the previously hot ions to the neutral gases in the inner magnetosphere.

[32] The reconnection or substorm process is thought to be under the control of the solar wind and Saturn's largest moon Titan, which orbits near the outer boundary of the magnetosphere.

[30] In the magnetodisk region, beyond 6 Rs, the plasma within the co–rotating sheet exerts a significant centrifugal force on the magnetic field, causing it to stretch.

[38] Unlike Jupiter's, Saturn's main auroral ovals are not related to the breakdown of the co–rotation of the plasma in the outer parts of the planet's magnetosphere.

[38] The ovals themselves correspond to the boundaries between open and closed magnetic field lines—so called polar caps, which are thought to reside at the distance of 10–15° from the poles.

For instance, when Saturn was immersed into the giant magnetotail of Jupiter during Voyager 2 flyby in 1981, the SKR power decreased greatly or even ceased completely.

[7][44] The kilometric radiation is thought to be generated by the Cyclotron Maser Instability of the electrons moving along magnetic field lines related to the auroral regions of Saturn.

Scientists were surprised when Galileo and then Cassini returned a different value—10 h 45 min 45 ± 36 s.[45] Further observation indicated that the modulation period changes by as much as 1% on the characteristic timescale of 20–30 days with an additional long-term trend.

[45] One reason may be that the Saturnian perfectly axially symmetric magnetic field fails to impose a strict corotation on the magnetospheric plasma making it slip relative to the planet.

[46] Saturn has relatively weak radiation belts, because energetic particles are absorbed by the moons and particulate material orbiting the planet.

It contains protons and relativistic electrons with energies from hundreds of kiloelectronvolts (keV) to as high as tens of megaelectronvolts (MeV) and possibly other ions.

[note 3][48] The electrons in the main belt probably originate in the outer magnetosphere or Solar wind, from which they are transported by the diffusion and then adiabatically heated.

By far the strongest source is Enceladus, which ejects a fountain of water vapor, carbon dioxide and nitrogen through cracks in its south pole region.

[56] The first one has been detected in the surfaces of Rhea and Dione, while the second is thought to be responsible for the steep spectral slopes of moons' reflectivities in the ultraviolet region.

In the case of Saturn, the radiation levels are much lower and the plasma is composed mainly of water products, which, when implanted, are indistinguishable from the ice already present.

The spacecraft continued to provide information about the magnetic field and plasma parameters of the saturnian magnetosphere until its intentional destruction on September 15, 2017.

In the 1990s, the Ulysses spacecraft conducted extensive measurements of the Saturnian kilometric radiation (SKR),[7] which is unobservable from Earth due to the absorption in the ionosphere.