1. Centre for Fusion, Space and Astrophysics, Department of Physics, University of Warwick, Coventry CV4 7AL, United Kingdom
2. Center for Space Physics, Department of Astronomy, Boston University, Boston, Massachusetts 02215, USA
3. Max-Planck-Institut für Plasmaphysik, Tokamak Scenario Development Division (E1), Boltzmannstrasse 2, 85748 Garching, Germany
4. CCFE, Culham Science Centre, Abingdon, Oxfordshire OX14 3DB, United Kingdom
5. Centre for the Analysis of Time Series, London School of Economics and Political Science, London WC2A 2AE, United Kingdom
6. School of Science, Technology, Engineering and Mathematics, Open University, Milton Keynes MK7 6AA, United Kingdom