|Jupiter Bow Shock|
All of the planets in the Solar System are embedded in the interplanetary medium known as the solar wind. The solar wind travels supersonically with respect to the slower planets at a speed of about one million miles per hour. And, just as a supersonic jet will create a sonic boom in the slower atmosphere of Earth, a bow shock is created in the solar wind in front of each planet.
Jupiter has a strong magnetic field that reaches out more than 3.5 million miles in front of the planet, providing a substantial obstacle to the flow of the solar wind. The bow shock forms at that surface in interplanetary space where the supersonic solar wind encounters the magnetic force of Jupiter and it acts to slow and deflect the solar wind. In the process, the energy of motion of the solar wind is converted to thermal energy at the bow shock, heating the particles behind the shock and creating rapid and turbulent particle motions that generate the plasma waves associated with the bow shock.
When the Voyager spacecraft encountered the Jovian bow shock, there was a very sudden burst of intense, low-frequency emissions extending over a wide range of frequencies. These emissions are directly associated with the Jovian bow shock and are similar to the loud sound associated with a sonic boom. The shock noise signature is a sudden, loud, rumbling roar lasting more than a minute.
The signals presented here were recorded by the Voyager 1 plasma wave instrument as it approached Jupiter on March 1, 1979.
For more information, see the article, Plasma Waves Associated with the Bow Shock of Jupiter, by W. S. Kurth.
You can also view an AVI version of the video.
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The Radio and Plasma Wave Group, Department of Physics & Astronomy, College of Liberal Arts & Sciences.