Evidence for short-term variability of Jupiter's decimetric emission from VLA observations

¹ Space Science Department, SwRI, Tx, USA e-mail: daniel.santoscosta@swri.edu
² University of Melbourne, Australia

Received: 18 March 2009
Accepted: 21 August 2009

Abstract

Aims. We present the first evidence of short-term variations of Jupiter's radiation-belt emission obtained with interferometric measurements. Over a two-month period of observational time in 2002, the Jovian synchrotron emission was observed with the Very Large Array (VLA).

Methods. The images constructed at the wavelength of 6 cm demonstrate significant changes in the spatial structure of the brightness distribution. The comparisons of the two-dimensional maps with another campaign of VLA observations made in May 1997 confirm our discovery of changes in Jupiter's synchrotron emission on a time-scale of days to weeks.

Results. For a series of central meridian longitudes (CMLs), the radiation peak near 1.4 was observed to shift back and forth from one side of the planet to the other between October and December 2002. The change in the location of the emission peak was found to be the result of fluctuations in the peak brightness distribution by 10% up to 40%. These fluctuations are too significant to be associated with the small variation of the geometric parameter (the declination of the Earth as seen from Jupiter) during the campaign of observations. We have demonstrated that the variability of the synchrotron emission peak was observed when the angular sectors covering the Jupiter SIII longitudes where the field strength along the equatorial magnetic surface is maximum or minimum were monitored.

Conclusions. Short-term variations of Jupiter's synchrotron emission are expected to be reported when specific CMLs are observed and changes in the distributions of the 30–40 MeV electron population occur simultaneously. Our discussions led to the conclusion that the short-term variations of Jupiter's Decimetric brightness distribution may be the result of submicrometre charged dust particles undergoing significant electromagnetic perturbations while interacting with the radiation-belt electrons in the Jovian ring's innermost component.