1. Laboratory for Atmospheric and Space Physics and Department of Physics; University of Colorado; Boulder Colorado USA
2. School of Physics and Astronomy; University of Leeds; Leeds UK
3. Department of Physics, The Auroral Observatory; University of Tromsø; Tromsø Norway
4. Department of Electrical Engineering and Computer Sciences; University of California at San Diego; La Jolla California USA
5. Centre for Interdisciplinary and Plasma Science; Max-Planck-Institut für extraterrestrische Physik; Garching Germany