Affiliation: | a Institute of Australasian Geodynamics, Flinders University, Bedford Park, S.A. 5042, Australia b National Geophysical Research Institute, Uppal Road, Hyderabad 500007, India c Research School for Earth Sciences, Australian National University, Canberra, A.C.T. 2600, Australia d Indian Institute of Geomagnetism, Colaba, Bombay 400005, India |