Page 16 - Curriculum Visions Dynamic Book

 This is an ultraviolet hubble space telescope closeup view of an electric-blue aurora glowing around Jupiter. The image shows the main oval of the aurora, which is centreed on the magnetic north pole, plus more diffuse emissions inside the polar cap.
The Hubble image also shows emissions from the magnetic “footprints” of three of Jupiter’s largest moons. Io is on the left, Ganymede is near the centre,
and Europa is just below and to
the right of Ganymede. These emissions, produced by electric currents generated by the satellites, flow along Jupiter’s magnetic
field, bouncing in and out of the upper atmosphere. They are unlike anything seen on Earth.
It turns out that the magnetic field of Jupiter is 19,000 times as powerful as the Earth’s magnetic field. Jupiter’s magnetic field is exactly opposite that of the Earth, meaning that a compass taken from Earth would point to its south pole. But it is also worth remembering that the Earth’s magnetic field flips every few hundred thousand years, so there is no reason to suppose that the Jovian magnet remains the same either.
The result of Jupiter having a magnetic field is that it experiences auroras, a phenomenon also common to the polar regions on Earth.
Jupiter’s magnetic field stretches out to between the moons Europa and Ganymede. Io is in this range, and there is an invisible magnetic tube linking this moon with the planet. In this tube flows an electrical current of something like five million amps (a typical Earth lightning strike is just 20,000 amps for a fraction of a second).
Inside Jupiter
We have never seen beyond the outer regions of the Jovian atmosphere, and so we know nothing directly of the planet. But there are some things of which we can be sure: Jupiter’s core is not a dead, icy rock but a searingly hot body of about 25,000°C. We know this because Jupiter sends out twice as much heat as it receives from the Sun.
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