Radio Storms on Jupiter
Radio storms from Jupiter were first noted in 1955. These radio beams are sent toward Earth from radio laser located near the magnetic poles of Jupiter. Unlike ordinary lasers, which are made of crystals and wires and chips, Jupiter's radio laser is naturally occurring - made of plasma and magnetic fields. Streams of magnetized plasma (ionized gases, etc.) streaming at high speed toward Jupiter's magnetic pole(s) emit intense radiation in the radio portion of the spectrum. When this is occurring, Jupiter outshines even the sun in the radio frequencies.
The laser is (partially) powered by one of Jupiter's moons, Io. Io's volcanoes spew plasma into Jupiter's magnetosphere, resulting in a torus of plasma which surrounds Jupiter - the Io plasma torus.
Hubble photo showing Io above Jupiter
Volcanic plume on Io (just below center left)
and Io's shadow on the cloudtops
Io plasma torus surrounding Jupiter
As Io plows through this plasma torus in its orbit, it produces waves (known as Alfven waves) which supply a power of about 40 trillion watts to Jupiter's magnetic polar regions. The radio energy is beamed out in a wide, hollow conical shell. When the Earth is inside this cone no radio bursts are received. If Earth is outside this cone no radio bursts are received. Only when the Earth passes through the "conical shell" itself are radio bursts received on Earth.
Because Jupiter rotates every 10 hours, with the conical beam sweeping with it like a lighthouse beam, the conical shell will periodically sweep across the Earth. In addition, Io must be in the correct position to be pouring energy into the radio laser. When these criteria are satisfied, radio bursts will be heard.
The sounds you hear will generally be of two types: (1) S-bursts which sound like woodpeckers, or whales when slowed down, and (2) L-bursts which sound like the gentle ebb and flow of waves at the beach.
Listen to RadioJupiter live.
Check SpaceWeather for good Jupiter radio listening times.