[1] Lockheed Martin Adv Technol Ctr, Palo Alto, CA 94304 USA
[2] Univ Colorado, Atmospher & Space Phys Lab, Boulder, CO 80303 USA
[3] Univ Alabama, Ctr Space Plasma & Aeronom Res, Huntsville, AL 35899 USA
[4] Los Alamos Natl Lab, Los Alamos, NM 87545 USA
[5] MIT, Ctr Space Res, Cambridge, MA 02139 USA