1. Department of Atmospheric, Oceanic and Space Sciences; University of Michigan; Ann Arbor Michigan USA
2. Geospace Physics Laboratory; NASA Goddard Space Flight Center; Greenbelt Maryland USA
3. The Johns Hopkins University Applied Physics Laboratory; Laurel Maryland USA
4. Lamont-Doherty Earth Observatory; Columbia University; Palisades New York USA
5. Department of Terrestrial Magnetism; Carnegie Institution of Washington; Washington District of Columbia USA