ENLIL: 3-D MHD heliospheric code

The ENLIL (Sumerian god of wind) code is a numerical model for simulations of the ambient corotating solar wind as well as transient disturbances throughout the inner and mid heliosphere. The model is based on ideal magnetohydrodynamic (MHD) equations with the ratio of specific heats, usually chosen to be 1.5. Two additional continuity equations may be used for tracing the injected material and the interplanetary magnetic field polarity. The inner heliospheric boundary is at the super-critical flow region (usually 18-30 Rs), thereby simplifying the numerical solution. The inner boundary conditions are prescribed values of all MHD variables as functions of time and all structures rotate along the inner boundary with an azimuthal velocity corresponding to the solar rotation. After an ambient state has been reached, transient disturbances can be specified as time dependent values on the inner boundary. These transient boundary values can be specified from:

  1. analytic formulae;
  2. empirical models;
  3. results from numerical coronal models; or
  4. derived from observations in certain applications (e.g., radial spacecraft alignment or geospace applications).

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