HR: 1340h
AN: GP43A-0887    [Abstracts]
TI: Magnetic Field Measurements As A Tool For Planetary Exploration
AU: * Langlais, B
EM: Benoit.Langlais@univ-nantes.fr
AF: Laboratoire de Planetologie et Geodynamique, CNRS-UMR 6112, Universite de Nantes, 2 rue de la Houssiniere, Nantes, 44000 France
AU: Mandea, M
EM: mioara@ipgp.jussieu.fr
AF: Laboratoire de Geomagnetisme et Paleomagnetisme, CNRS-UMR 7577, Institut de Physique de Globe de Paris, 4 Place Jussieu, Paris, 75005 France
AU: Menvielle, M
EM: michel.menvielle@cetp.ipsl.fr
AF: Centre d'Etude des Environnements Terrestre et Planétaires, CNRS UMR-8639, 4 Avenue de Neptune, Saint Maur des Fosse, 94107 France
AU: Tarits, P
EM: tarits@univ-brest.fr
AF: Laboratoire Domaines Oceaniques, CNRS-UMR 6538, Universite de Bretagne Occidentale, Institut Universitaire Europeen de la Mer, Place Nicolas Copernic, Plouzane, 29280 France
AU: Sotin, C
EM: Christophe.Sotin@univ-nantes.fr
AF: Laboratoire de Planetologie et Geodynamique, CNRS-UMR 6112, Universite de Nantes, 2 rue de la Houssiniere, Nantes, 44000 France
AB: In the absence of surface observations, magnetic measurements on-board orbiting satellites provide a unique tool for investigating planetary properties, such as interaction with the solar wind, internal structure, or nature of the magnetic sources. Modelling and interpreting the magnetic fields and and their sources are essential to determine and understand the dynamical properties of planets, as illustrated by the example of the Earth. The core and lithospheric sources of the geomagnetic field can be quite easily separated, considering the knee of the magnetic spectra around degree 13. Assuming that the magnetic sources lie below the core-mantle boundary, a rough estimate of the radius of the outer, liquid core can be computed. Using IGRF-10 model, we find a core radius within 1% of the commonly adopted seismological value. This method is applied to Ganymede and to Mercury. Ganymede's magnetic environment was explored by the Galileo spacecraft. The Jovian satellite was found to possess an internal magnetic field, which origin is still controversial. The origin of the Hermean magnetic field is still not fully confirmed. The Messenger (launch: 2004) and the BepiColombo (launch: 2012) probe measurements are thus eagerly awaited for. The first measurements by these satellites will undoubtedly reveal the nature of the magnetic field. If the internal origin is confirmed, direct conclusion will be the presence of a liquid, conductive, convecting layer inside Mercury. Additional measurements will allow the structure and the temporal variations of the Hermean magnetic field to be modelled. In practice, the measured field by the spacecraft is the sum of the planetary field (of internal and external sources) and on-board generated magnetic fields. Here, we first synthesize different on-board generated magnetic fields as a function of the distance to the satellite body. We then predict what would be the Hermean magnetic field, assuming a fixed value for the liquid core radius. We then add the planetary and satellite contributions, considering different lengths for the magnetometer boom. We finally compute magnetic models, and compare the output to the initial hypothesis.
DE: 1595 Planetary magnetism: all frequencies and wavelengths
DE: 5430 Interiors (8147)
DE: 5440 Magnetic fields and magnetism
DE: 6222 Ganymede
DE: 6235 Mercury
SC: Geomagnetism and Paleomagnetism [GP]
MN: Fall Meeting 2005