Radio Saturn Wobbles and Sirens
Cassini has been in orbit around Saturn for
more than six years. And new data tells scientists that the sixth planet from the sun is weirder
than we’ve even imagined. Ever since we arrived, Cassini has been measuring
radio waves called ‘Saturn kilometric radiation.’ Cassini’s radio and plasma wave instrument
recently determined that the variation in radio waves is different in the northern and
southern hemispheres of Saturn. And the northern and southern rotational variations
also appear to change with the Saturnian seasons. The radio wave patterns are controlled by
the rotation of the planet. So, to Cassini, Saturn’s radio waves sound a bit like bursts
of a spinning air raid siren. We can’t normally hear these radio wave patterns.
But Cassini scientists have translated the patterns into the human audio range.
In this video you actually hear the radio wave patterns coming from the two hemispheres
swap rates over the course of several years. The crossover happened a few months after
spring began in the northern hemisphere. Scientists don’t think the radio wave patterns
indicate hemispheres actually rotating at different rates.
It has more to do with variations in high-altitude winds.
A recently result from the Hubble Space Telescope also gives us clues.
Scientists found that the northern and southern auroras wobbled back and forth in a pattern
matching the radio wave variations. The Cassini magnetometer also found that Saturn’s
magnetic field over the north and south poles wobbled in a similar pattern.
These signals are connected because they’re all affected by the behavior of the magnetic
bubble around Saturn and the sun’s influence on the whole Saturnian system.
For those of us watching Saturn, these findings all help explain the complicated dance between
the sun and Saturn’s magnetic bubble, something normally invisible to the human eye and imperceptible
to the human ear.