1. Instituto de Astronomía y Física del Espacio (CONICET/UBA); Ciudad Universitaria; Buenos Aires Argentina
2. Physics Department; University of Maryland; College Park Maryland USA
3. Department of Physics and Astronomy; University of Iowa; Iowa City Iowa USA
4. Applied Physics Laboratory; Johns Hopkins University; Baltimore Maryland USA
5. Office for Space Research; Academy of Athens; Athens Greece
6. Swedish Institute of Space Physics; Uppsala Sweden
7. Blackett Laboratory; Imperial College London; London UK