An Overview

Jupiter is the fifth planet from our Sun and the largest. It is associated in most people's minds primarily with its Giant Red Spot, a large hurricane.


Interior of Jupiter

Most of the interior of Jupiter is liquid, primarily hydrogen with about 10% helium. The central temperatures are thought to lie in the range of 13,000-35,000 degrees Celsius, and the central pressure is about 100 million Earth atmospheres.The inner layers of highly compressed hydrogen are in a state that has never been produced on the Earth. Under the extreme pressure found deep inside Jupiter, the prevailing scientific theory suggests that the electron is released from each hydrogen atom and is free to move about the interior, allowing hydrogen to conduct heat and electricity in the manner of a metal. Electrical currents in this region of metallic hydrogen give rise to Jupiter's intense magnetic field due to their rapid rate of spin. An environment as alien to us as Jupiter provides an opportunity for us to test our understanding of the properties of matter under extreme conditions


The Internal Source of Energy

Jupiter radiates 1.6 times as much energy as falls on it from the Sun and therefore it can be concluded that Jupiter must have an internal heat source. It is thought that much of this heat is residual thermal energy from the original collapse of the primordial nebula which formed our Solar System, although some of it may derive from slow planetary contraction. This internal heat source is presumably responsible for driving the complex weather patterns in its atmosphere, unlike the Earth on which the primary energy source for the weather is the Sun.


Features of the Magnetic Field

Jupiter's magnetic field is large, complex, and intense. It is thought to arise from electrical currents in the rapidly spinning metallic hydrogen interior. The Earth has a strong magnetic field, but even at the top of the cloud layer, Jupiter's magnetic field is 10 times stronger than that of the Earth. Furthermore, the Jovian magnetic field has much higher complexity than that of the Earth, with some aspects of Jupiter's fields having no equivalent on Earth. These differences from our own magnetic field are probably related to the greater speed of rotation and larger metallic interior of Jupiter.

The field is toroidal (doughnut shaped) and contains much larger versions of the Earth's Van Allen Belts which trap high-energy charged particles (mostly electrons and protons). Because of the forces associated with the rapid rotation of Jupiter and its magnetic field, these belts are flattened into plasma sheets. The field rotates in synchrony with the approximately nine hour rotational period of the planet. The satellites Amalthea, Io, Europa, and Ganymede all orbit through this region; they are affected by it and in turn affect the magnetic field and charged-particle belts. Io, for instance, has many active volcanoes on its surface which throw up particles which become ionized as Io moves about its orbit and which eventually diffuse into Jupiter's upper atmosphere. This effect is one of the primary sources of the charged particles which are trapped in the Jovian magnetic field.