UCL Magnetodisc Model for Jupiter and Saturn. The data consists of the
magnetic field in JMAG spherical coordinates. For details and further
references, see: Achilleos N. A., Guio, P. and Arridge, C. S., 2010, A model
of force balance in Saturn's magnetodisc, MNRAS, 401, 2349-2371,
<a href="https://doi.org/10.1111/j.1365-2966.2009.15865.x">doi:10.1111/j.1365-2966.2009.15865.x</a>
