8 August, 2018

A new study using data from the Galileo space probe reveals extraordinary high levels of electromagnetic activity near the moons of Jupiter.

Publishing this week in the journal Nature Communications an international team of scientists report that the power of Jupiter’s electromagnetic ‘chorus waves’ is a million times more intense near the moon Ganymede, and 100 times more intense near the moon Europa than the average around Jupiter.  These are the new results from a systematic study on Jupiter’s wave environment taken from the Galileo Probe spacecraft.

The new study will enhance scientists’ understanding of how Jupiter’s magnetic field interacts with its moons and with intense particle radiation.

Chorus waves are special type of very low frequency plasma waves produced in space.  They travel along the magnetic field down to the surface of the planets.  When converted to audible sound waves, they sound remarkably like birdsong and for this reason they were named “Dawn Chorus” when they were first discovered at the Earth in the mid 20th century.

At the Earth, chorus waves play a major role in producing high-energy ‘killer’ electrons that can damage communications spacecraft. The new observations raise the question as to whether they can do the same at Jupiter.

Lead author Dr Yuri Shprits of GFZ and the University of Potsdam said,

“It’s a really surprising and puzzling observation showing that a moon with a magnetic field can create such a tremendous intensification in the power of waves.”

Professor Richard Horne leads the Space Weather research programme at British Antarctic Survey.  He said,

“Chorus waves have been detected in space around the Earth but they are nowhere near as strong as the waves at Jupiter.  Even if small portion of these waves escapes the immediate vicinity of Ganymede, they will be capable of accelerating particles to very high energies and ultimately producing very fast electrons inside Jupiter’s magnetic field”.

Unlike the Earth, Ganymede and Europa orbit inside the giant magnetic field of Jupiter and the authors believe this is one of the key factors powering the waves. Jupiter’s magnetic field is the largest in the solar system, and some 20,000 times stronger than the Earth’s.

Jupiter’s moon Ganymede was first found to have a magnetic field by Professor Margaret Kivelson and her team at the University of California, Los Angeles, and strong plasma waves were first observed near Ganymede by Professor Don Gurnett and his team at the University of Iowa.  However, until now it remained unclear if this were just accidental or whether such increases are systematic and significant.

Professor Horne continued,

“Observations of Jupiter’s waves provides us unique opportunity to understand the fundamental processes that are relevant to laboratory plasmas and the quest for new energy sources, and processes of acceleration and loss around the planets in the solar system and in the distant corners of the Universe. Similar processes may occur in exoplanets orbiting other stars and the understanding obtained in this study may help us detect whether exoplanets have magnetic fields. This study will provide very important observational constraints for theoretical studies that will try to quantify the tremendous increase in wave power.

This research, supported by NASA, is a result of collaboration between GFZ German Research Center for Geosciences, University of Potsdam, UCLA, University of Iowa, British Antarctic Survey, Jet Propulsion Laboratory, and Applied Physics Lab.