[1] UCL Mullard Space Sci Lab, Holmbury St Mary, Dorking RH5 6NT, Surrey, England
[2] Naval Res Lab, Div Space Sci, Code 7681, Washington, DC 20375 USA
[3] Lockheed Martin Solar & Astrophys Lab, 3251 Hanover St B-252, Palo Alto, CA 94304 USA
[4] UBA CONICET, IAFE, CC 67,Suc 28, RA-1428 Buenos Aires, DF, Argentina
[5] CNRS, Observ Paris, LESIA, UMR 8109, F-92195 Meudon, France