1. Department of Earth and Space Sciences, Indian Institute of Space Science & Technology, Thiruvananthapuram 695547, Kerala, INDIA
2. Leiden Observatory, Leiden University, PO Box 9513, 2300 RA, Leiden, The Netherlands
3. The Pennsylvania State University, 413 Davey Lab, University Park, State College, PA 16802, USA
4. Department of Physics, University of California, Santa Barbara 93106, California, USA
5. Aryabhatta Research Institute of Observational Sciences (ARIES), Manora Peak, Nainital 263002, INDIA