1. C. T. Russell and M. G. Kivelson, Institute of Geophysics and Planetary Physics, and Department of Earth and Space Sciences, University of California, Los Angeles, CA 90095–1567, USA.
2. K. K. Khurana and D. E. Huddleston, Institute of Geophysics and Planetary Physics, University of California, Los Angeles, CA 90095–1567, USA.