Aurorae

In March 2015, scientists reported that measurements with the Hubble Space Telescope of how the aurorae moved over Ganymede's surface suggest it has a subsurface ocean.

Such events led to the general conclusion that The effect of the aurorae on the electric telegraph is generally to increase or diminish the electric current generated in working the wires.

The solar X-ray and cosmic gamma-ray burst experiment (GRB) had 3 main objectives: study and monitor solar flares, detect and localize cosmic gamma-ray bursts, and in-situ detection of Jovian aurorae.

Unlike the aurorae of Earth and Jupiter, those of Uranus are not in line with its poles, due to its lopsided magnetic field.

Using Hubble to study the motion of its aurorae, the researchers determined that a large saltwater ocean was helping to suppress the interaction between Jupiter's magnetic field and that of Ganymede.