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GEOPHYSICAL RESEARCH LETTERS, VOL. 34, L22201, doi:10.1029/2007GL031662, 2007

A feedback dynamo generating Mercury's magnetic field

Karl-Heinz Glassmeier

Institut für Geophysik und Extraterrestrische Physik, Technische Universität Braunschweig, Germany


Hans-Ulrich Auster

Institut für Geophysik und Extraterrestrische Physik, Technische Universität Braunschweig, Germany


Uwe Motschmann

Institut für Theoretische Physik, Technische Universität Braunschweig, Germany


Abstract

Planet Mercury has a global magnetic field of internal origin. Its low intensity, 340 nT at the equatorial surface, indicates that the Hermean dynamo is special as much stronger fields are to be expected. Here, we suggest a feedback dynamo model where Mercury is embedded in an external field which is generated by the Chapman-Ferraro current of the small magnetosphere of Mercury. This self-generated ambient field has a pronounced influence on the dynamo action. Based on a kinematic α-Ω-dynamo model we show that the feedback dynamo has two solutions, a Hermean-type solution with a weak magnetic field and an Earth-like one with a strong field. The Hermean solution is that one where the external field opposes dynamo action, while an Earth-like solution results as the Chapman-Ferraro field is negligible in the dynamo region.

Received 12 August 2007; accepted 24 October 2007; published 22 November 2007.

Keywords: Mercury; magnetic field; dynamo.

Index Terms: 6235 Planetary Sciences: Solar System Objects: Mercury; 1510 Geomagnetism and Paleomagnetism: Dynamo: theories and simulations; 1595 Geomagnetism and Paleomagnetism: Planetary magnetism: all frequencies and wavelengths; 2756 Magnetospheric Physics: Planetary magnetospheres (5443, 5737, 6033); 5440 Planetary Sciences: Solid Surface Planets: Magnetic fields and magnetism.

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Citation: Glassmeier, K.-H., H.-U. Auster, and U. Motschmann (2007), A feedback dynamo generating Mercury's magnetic field, Geophys. Res. Lett., 34, L22201, doi:10.1029/2007GL031662.