Radio Noise

In 1955 Bernard Burke and Kenneth Franklin, scientists at the Carnegie Institute of Washington, reported bursts of radio noise at 22.2 MHz originating on Jupiter's surface.This is a type of radiation called nonthermal, because it does not originate from the energy that every object with a temperature above absolute zero is radiating at all times; it has some other source for its generation beyond heat. Soon, with additional observations, it was shown that Jupiter emits strong signals at two radio wavelengths, one at tens of centimeters ("deci-metric"), and the other at tens of meters ("decametric").Though since then about 10 radio emission components have been identified, the decimetric and decametric remain the main components. No other planet has so many types of radio emissions.

In 1959 Frank Drake and Hein Hvatum at the National Radio Astronomy Observatory pinpointed the origin of decimetric nonthermal radiation as a toroidal belt around Jupiter, inclined at about 10 degrees to Jupiter's equator.They theorized that the source of this radiation is electrons moving at relativistic speeds while trapped in Jupiter's magnetic field. The tipping of the toroidal region from Jupiter's equator matches the tip of Jupiter's magnetic field, supporting the magnetic field theory.The decimetric radio signals, which are more constant than the decametric, are thought to be caused by electrons orbiting along magnetic field lines and interacting with the motion of the large moon Io. Io has created a toroid of ions around Jupiter, in the shape of its orbit.When the gases that Io emits become ionized, they are attracted along Jupiter's magnetic field lines and rapidly accelerated to 34 miles per second (55 km/sec). When the ions collide or are cooled, they give off visible and radio emissions. The decametric emissions, on the other hand, come in strong, sporadic bursts, and are thought to be the results of magnetic storms, similar in some ways to those that occur on the Sun.

The strength and size of Jupiter's magnetic field create phenomena never seen on Earth: auroral displays caused by ions stripped off a moon orbiting far inside the magnetic field, and pink auroras at its poles as well as elsewhere around its globe where its non-dipolar magnetic field dives back into the planet.The planet's interior experiences such great pressures because of its mass that hydrogen and helium, almost invariably gaseous on Earth, are pressed into liquids, and finally into a solid metallic form. Under the great pressure of its mass and the heat from its sinking helium rain, along with primordial heat of formation, Jupiter's core is thought to be hotter than the surface of the Sun. In all these ways, except for internal nuclear fusion, Jupiter begins to resemble a tiny star with its own solar system of planets (its numerous moons).

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