[1] Univ Calif Santa Barbara, Dept Phys, Santa Barbara, CA 93106 USA
[2] JAMSTEC, Earth Simulator Ctr, Kanazawa Ku, Yokohama, Kanagawa 2360001, Japan
[3] Johns Hopkins Univ, Dept Phys & Astron, Baltimore, MD 21218 USA
[4] Princeton Univ, Dept Astrophys Sci, Princeton, NJ 08544 USA