1. Department of Earth, Planetary and Space Sciences; University of California; Los Angeles California USA
2. Helmholtz Centre Potsdam; GFZ German Research Centre for Geosciences; Potsdam Germany
3. Institute for Physics and Astronomy; University of Potsdam; Potsdam Germany
4. Laboratory for Atmospheric and Space Physics; University of Colorado Boulder; Boulder Colorado USA
5. William B. Hanson Center for Space Sciences, Department of Physics; University of Texas at Dallas; Richardson Texas USA