Setting Initial Conditions for Regions

For each region, a set of initial conditions must be specified. This includes the following for each region:

• Thickness
• Number of spatial zones
• Mean atomic weight
• Mass density
• Temperature
• Fluid velocity
• Magnetic field (This feature is a beta version and not available to all users.)

These are entered in the Init. Conditions tab of the Spatial Grid parameters widget.

The initial mass density, temperature, fluid velocity, and magnetic field for each Spatial Region can be specified using one of the following approaches:

• Constant: Enter the (spatially uniform) value for the region.
• Analytic Expression: An analytic expression representing the variation of the quantity value with position (either "x" or "r" may be used as the independent variable). Select the Analytic Function Options button to show a list of available mathematical functions. Click on the button to show the table of values calculated using the analytic expression and plot them.
• Tabular: The dependence of the quantity value on position is determined from interpolation of values entered into a table. In this case, the minimum position should be 0 (which corresponds to the inner boundary of the region), and the maximum distance should be equal to the Region Thickness. The tabular values can also be plotted.

For initializing the mass density, an additional option is available:

• Gas Pressure @ 298K: Enter the pressure in atmospheres. In this case, the number of atoms per molecule must also be specified:

For initializing the magnetic field, an additional option is available:

• Default: It starts with Biot-Savart value for magnetic field at the boundary, diffuses it into the plasma, and from that computes current density using differential form of Ampere's law.

For several parameters, a choice of units is provided. Magnetic field distribution defines the shape, not the absolute values. The values are scaled to conserve the current.

For the Constant mass density option and the mean atomic weight, a list of values for common materials and states is provided (e.g., solid aluminum with density = 2.7 g/cm³ and mass = 27 amu). For these parameters, the user can directly enter the appropriate value, or select an item from the list provided.

Note that number of zones for each spatial region should be greater than or equal to 3.

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