1. Laboratory for Atmospheric and Space Physics University of Colorado Boulder Boulder CO USA
2. Astrophysical and Planetary Sciences Department University of Colorado Boulder Boulder CO USA
3. Department of Physics and Astronomy West Virginia University Morgantown WV USA
4. Department of Earth Planetary and Space Sciences University of California, Los Angeles Los Angeles CA USA
5. Space Sciences Laboratory University of California, Berkeley Berkeley CA USA
6. Physics Department University of California, Berkeley Berkeley CA USA