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A Magnetic Signature at Io: Initial Report from the Galileo Magnetometer
1M. G. Kivelson, K. K. Khurana, R. J. Walker, C. T. Russell, Institute of Geophysics and Planetary Physics, University of California, Los Angeles, Los Angeles, CA 90095-1567, USA. J. A. Linker, Science Applications International Corporation, San Diego, CA 92171, USA. D. J. Southwood, Department of Physics, Imperial College of Science, Technology, and Medicine, London, SW7 2BZ, UK. C. Polanskey, Jet Propulsion Laboratory, Pasadena, CA 91109, USA.
Galileo spacecraft data suggest Jupiter's moon Io possesses its own intrinsic magnetic field. This intrinsic field, generated by dynamo action, is the most plausible explanation for observed magnetic field perturbations near Io.
Area of Science:
- Planetary Science
- Magnetohydrodynamics
- Space Physics
Background:
- Jupiter's moon Io is known for its intense volcanic activity and interaction with Jupiter's magnetosphere.
- Previous studies have debated the source of magnetic field anomalies observed near Io.
- Understanding Io's internal structure and magnetic properties is crucial for planetary formation theories.
Purpose of the Study:
- To investigate the source of observed magnetic field perturbations during the Galileo spacecraft's flyby of Io.
- To determine whether plasma interactions or an intrinsic magnetic field best explains the data.
- To assess the plausibility of Io possessing a global intrinsic magnetic field.
Main Methods:
- Analysis of 1-minute averaged magnetic field measurements acquired by the Galileo spacecraft magnetometer.
- Comparison of observed field data with models based on plasma sources and induced magnetic fields.
- Evaluation of an intrinsic magnetic field hypothesis consistent with dynamo theory.
Main Results:
- A significant decrease (nearly 40%) in the Jovian magnetic field was recorded near Io.
- Plasma sources alone could not account for the magnitude of the observed magnetic perturbations.
- An induced magnetic field required unrealistically high concentrations of iron in Io's mantle.
Conclusions:
- The observed magnetic field data strongly support the hypothesis of an intrinsic magnetic field generated by Io.
- Dynamo action within Io is proposed as the mechanism for generating this intrinsic field.
- Io is likely a magnetized solid planet, similar to Earth and Mercury.