1. Virginia Polytechnic Institute and State University; Blacksburg Virginia USA
2. Physics Department; Augsburg College; Minneapolis Minnesota USA
3. Tromsø Geophysical Observatory; University of Tromsø; Tromsø Norway
4. Danish Meteorological Institute; Copenhagen Denmark
5. Department of Physics; University of Alberta; Edmonton, Alberta Canada
6. Space Environment Research Center; Kyushu University; Fukuoka Japan