1. Space Physics Laboratory, Vikram Sarabhai Space Centre, Trivandrum 695022, India
2. Currently CSIR-ES at Physical Research Laboratory, Ahmedabad, India
3. Swedish Institute of Space Physics, Box 812, SE-98128 Kiruna, Sweden
4. Physikalisches Institut, University of Bern, Sidlerstrasse 5, CH-3012 Bern, Switzerland
5. Institute of Space and Astronautical Science, 3-1-1 Yoshinodai, Sagamihara, Japan