1. Department of Physics, Surendranath College, 24/2 M. G. Road, Kolkata 700009, India
2. Division of Science Education and Institute of Fusion Science, Chonbuk National University, Jeonju 54896, South Korea
3. Department of Physics, Kansas State University, 116 Cardwell Hall, Manhattan, KS 66506, USA
4. National Centre for Radio Astrophysics, TIFR, Post Bag 3, Ganeshkhind, Pune 411007, India