1. Centre for Fusion, Space and Astrophysics, Department of Physics, University of Warwick, Coventry CV4 7AL, UK
2. Armagh Observatory and Planetarium, College Hill, Armagh BT61 9DG, Northern Ireland, UK
3. Department of Mathematics & Information Sciences, Northumbria University, Newcastle Upon Tyne NE1 8ST, UK
4. Astrophysics Research Centre, School of Mathematics and Physics, Queen’s University Belfast, Belfast BT7 1NN, UK