1. Centre for Mathematical Plasma Astrophysics, Mathematics Department, KU Leuven, Celestijnenlaan 200B bus 2400, B-3001 Leuven, Belgium
2. Jeremiah Horrocks Institute, University of Central Lancashire, PR1 2HE, UK
3. Department of Physics, University of Warwick, Coventry, CV4 7AL, UK
4. Centre for Exoplanets and Habitability, University of Warwick, Coventry CV4 7AL, UK