Institution: | Universitéde Paris VI and CNRS Laboratoire de Géomagnétisme, 94100 St-Maur-des-Fossés, France, and Geophysics Laboratory, Department of Physics and Erindale College, University of Toronto, Toronto M5S 1A7, Canada;Universitéde Paris VI and CNRS Laboratoire de Géomagnétisme, 94100 St-Maur-des Fossés, France, and United States Geological Survey, Menlo Park, California 94025, USA |