Every giant planet has a strong magnetic field, generated by the rapidly rotating current inside. The magnetospheres of the planets are connected to magnetic fields, these are regions around the planet in which the planet’s own magnetic field dominates the general interplanetary magnetic field. The magnetospheres of these planets are their greatest features, extend millions of kilometers into space.
In late 1950s, astronomers discovered that Jupiter was a source of radio waves that became more intense at wavelengths longer than short, exactly the opposite of what was expected from thermal radiation. However, this behavior is typical of radiation that is emitted when high-speed electrons are accelerated by a magnetic field. We call this synchrotron radiation because it was first observed on Earth in particle accelerators, so-called synchrotrons. This was our first indication that Jupiter must have a strong magnetic field. .
Later observations showed that the radio waves come from a region around Jupiter, the diameter of which is a multiple of the planet’s diameter. The evidence suggested that a large number of charged atomic-particles must orbit Jupiter and spiral around the lines of force of a magnetic field associated with the planet. This is exactly what we observe in the Van Allen Belt around the earth, but on a smaller scale. The magnetic fields of Saturn, Uranus, and Neptune, detected by the spacecraft that passed close to these planets, work similarly, but they’re not as strong.
In every magnetosphere, the charged particles rotate in a magnetic field; This allows them to be accelerated to high energies. These charged particles can come from the sun or from the vicinity of the planet itself. In the case of Jupiter, Io, one of its moons, has volcanic eruptions that hurl charged particles into space and directly into Jovian magnetosphere.
The axis of Jupiter’s magnetic field (the line connecting the north magnetic pole to the south magnetic pole) is not precisely aligned with the planet’s axis of rotation; rather, it has an inclination of about 10 °, Uranus and Neptune have even greater magnetic inclinations of 60 ° and 55 °, respectively. The Saturn field, on the other hand, is perfectly aligned with its axis of rotation. It is not well understood why different planets have such different magnetic inclinations.
It turns out that the physical processes around jovian-planets are a smoother version of what astronomers have found in many distant objects, from the remains of the dead star to the mysterious distant power-forces we call quasars. One of the reasons for studying giant planets and the Earth’s magnetosphere is that they provide accessible analogues of more powerful and complex cosmic processes.
