Europa's Magnetic Signature: Report from Galileo's Pass on 19 December 1996
Abstract
On 19 December 1996 as Galileo passed close to Jupiter’s moon, Europa, the magnetometer measured substantial departures from the slowly varying background field of Jupiter’s magnetosphere. Currents coupling Europa to Jupiter’s magnetospheric plasma could produce perturbations of the observed size. However, the trend of the field perturbations is here modeled as the signature of a Europa-centered dipole moment whose maximum surface magnitude is ∼240 nanotesla, giving a rough upper limit to the internal field. The dipole orientation is oblique to Europa’s spin axis. This orientation may not be probable for a field generated by a core dynamo, but higher order multipoles may be important as they are at Uranus and Neptune. Although the data can be modeled as contributions of an internal field of Europa, they do not confirm its existence. The dipole orientation is also oblique to the imposed field of Jupiter and thus not directly produced as a response to that field. Close to Europa, plasma currents appear to produce perturbations with scale sizes that are small compared with a Europa radius.
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We thank G. Schubert for his helpful comments and his careful reading of a preliminary version of this paper. Work was supported by the Jet Propulsion Laboratory under contract No. 958694. UCLA Institute of Geophysics and Planetary Physics Publication 4864.
Information & Authors
Information
Published In
Science
Volume 276 • Issue 5316 • 23 May 1997
Pages: 1239 - 1241
History
Received: 18 March 1997
Accepted: 5 May 1997
