University of Colorado at Boulder
ENLIL is a time-dependent 3D MHD model of the heliosphere. It solves equations for plasma mass, momentum and energy density, and magnetic field, using a Flux-Corrected-Transport (FCT) algorithm. Its inner radial boundary is located beyond the sonic point, typically at 21.5 or 30 solar radii. It can accept boundary condition information from either the WSA or MAS models. The outer radial boundary can be adjusted to include planets or spacecraft of interest (eg 2 AU to include both Earth and Mars, 5 AU to include Ulysses, 10 AU to include Cassini). It covers 60 degrees north to 60 degrees south in latitude and 360 degrees in azimuth.
The Wang-Sheeley-Arge (WSA) model has two components: the WSA Potential Field + Current Sheet (WSA PF+CS) Model and the WSA Inner Heliosphere (WSA-IH) Model.
The WSA-PF+CS model is the inner coronal component of the complete WSA model. These combine a Potential Source Surface Model with the ‘Schatten’ current sheet model, to produce a model of the global coronal magnetic field between the solar surface and a bounding spherical surface, typically set at 5 solar radii. The magnetic field is assumed to be radial at this outer surface. At this outer surface the model computes the solar wind speed using an empirical relationship based on the divergence of the magnetic field and the proximity of the selected open field line to the nearest coronal hole boundary, to determine the local solar wind speed. The surface magnetic field is determined from synoptic magnetogram data. Currently we download magnetograms from both Kitt Peak and Mount Wilson.
The WSA-IH uses a simple kinematic model which propagates the solar wind and the magnetic polarity from the outer boundary of the Schatten current sheet model into the heliosphere.