[1
]Department of Physics and Astronomy; George Mason University; Fairfax Virginia USA
[2
]Max Planck Institute for Solar System Research; Göttingen Germany
[3
]Space Sciences Laboratory; University of California; Berkeley California USA
[4
]Institute of Astrophysics; Georg-August University; Göttingen Germany
[5
]NASA Goddard Space Flight Center; Greenbelt Maryland USA
[6
]Department of Geophysics; Tohoku University; Sendai Japan
[7
]Laboratory for Atmospheric and Space Physics; University of Colorado Boulder; Boulder
Colorado USA