J. Pietarila Graham (1 and 2), Darryl Holm (3 and 4), Pablo Mininni (1
  and 5), and Annick Pouquet (1) ((1) National Center for Atmospheric Research,
  Boulder, USA, (2) Max Planck Institute for Solar System Research,
  Katlenburg-Lindau, Germany, (3) Department of Mathematics, Imperial College
  London, UK, (4) Computer and Computational Science Division, Los Alamos
  National Laboratory, Los Alamos, USA (5) Departamento de Fisica, Universidad
  de Buenos Aires, Buenos Aires, Argentina)