[1] Univ Colorado, Lab Atmospher & Space Phys, 3665 Discovery Dr, Boulder, CO 80303 USA
[2] Univ Colorado, JILA, Box 440, Boulder, CO 80303 USA
[3] Univ Colorado, Dept Astrophys & Planetary Sci, Box 440, Boulder, CO 80303 USA
[4] KTH Royal Inst Technol, NORDITA, Roslagstullsbacken 23, SE-10691 Stockholm, Sweden
[5] Stockholm Univ, Roslagstullsbacken 23, SE-10691 Stockholm, Sweden
[6] Stockholm Univ, Dept Astron, AlbaNova Univ Ctr, SE-10691 Stockholm, Sweden
[7] Ben Gurion Univ Negev, Dept Mech Engn, POB 653, IL-84105 Beer Sheva, Israel
[8] Carnegie Mellon Univ, McWilliams Ctr Cosmol, 5000 Forbes Ave, Pittsburgh, PA 15213 USA
[9] Carnegie Mellon Univ, Dept Phys, 5000 Forbes Ave, Pittsburgh, PA 15213 USA
[10] Ilia State Univ, Abastumani Astrophys Observ, 3-5 Cholokashvili St, GE-0194 Tbilisi, Georgia
[11] Leiden Univ, Inst Lorentz Theoret Phys, Niels Bohrweg 2, NL-2333 CA Leiden, Netherlands
[12] ETH Honggerberg, Inst Theoret Phys, CH-8093 Zurich, Switzerland
[13] Niels Bohr Inst, Discovery Ctr, Blegdamsvej 17, DK-2100 Copenhagen, Denmark