Papers on Magnetospheric Physics
Periodicities in the Io plasma torus
Article first published online: 20 SEP 2012
Copyright 1995 by the American Geophysical Union.
Journal of Geophysical Research: Space Physics (1978–2012)
Volume 100, Issue A11, pages 21683–21695, 1 November 1995
How to Cite
1995), Periodicities in the Io plasma torus, J. Geophys. Res., 100(A11), 21683–21695, doi:10.1029/95JA01988.(
- Issue published online: 20 SEP 2012
- Article first published online: 20 SEP 2012
- Manuscript Accepted: 23 JUN 1995
- Manuscript Received: 31 JAN 1995
We present a 6-month baseline of spatially resolved measurements of the Io plasma torus intensity and perpendicular ion temperature which we use to determine the periodicities of the torus during this time. We find large anticorrelated variations in the intensity and ion temperature which are periodic with the Jovian rotation rate (System III). The intensity variations are found to be a simple manifestation of the temperature variations, though no explanation for the temperature variations is apparent. Periodogram analysis shows an additional intensity periodicity which rotates 2.91±0.06% more slowly than System III. This period is found only in the intensity and not in the ion temperature. We conclude from these observations that the torus has a sinusoidal ion temperature variation locked into the rotation of Jupiter and that superimposed on this is a long-lived density pattern which rotates 2.91% more slowly than Jupiter. Based on the spatial structure and physical properties, we rule out all currently proposed mechanisms for the creation of these periodicities within the torus.