1. Center for Space Plasma and Aeronomic Research (CSPAR), University of Alabama in Huntsville , Huntsville, AL 35805 , USA
2. Department of Space Science, University of Alabama in Huntsville , Huntsville, AL 35899 , USA
3. University of Applied Sciences and Arts Northwestern Switzerland , CH-5210 Windisch , Switzerland
4. Institute for Particle Physics and Astrophysics, ETH Zürich , CH-8093 Zürich , Switzerland