1. Department of Physics, Imperial College London 1 , London SW7 2AZ, United Kingdom
2. Department of Mathematics, Physics and Electrical Engineering, Northumbria University 2 , Newcastle upon Tyne NE1 8ST, United Kingdom
3. Lunar and Planetary Laboratory and Department of Planetary Sciences, University of Arizona 3 , Tucson, Arizona 85721, USA
4. Space Sciences Laboratory, University of California 4 , Berkeley, California 94720, USA
5. Southwest Research Institute 5 , San Antonio, Texas 78238, USA
6. Department of Astrophysical and Planetary Sciences, University of Colorado 6 , Boulder, Colorado 80305, USA
7. Laboratory for Atmospheric and Space Physics, University of Colorado 7 , Boulder, Colorado 80303, USA
8. NASA Goddard Space Flight Center 8 , Greenbelt, Maryland 20771, USA
9. Department of Earth, Planetary, and Space Sciences, University of California 9 , Los Angeles, California 90095, USA
10. School of Electrical Engineering, KTH Royal Institute of Technology 10 , 114 28 Stockholm, Sweden