
This window provides a two-dimensional simulation of the movement of a
pulse of photons created at the center of the Sun.  The photons travel
independently to the surface, where they escape as light or heat.  The
distribution of the number of photons escaping per time interval is
displayed to illustrate the diffusion of the pulse.  The following
features are provided to control and vary the simulation and record the
results:

Menu Selections

    Parameters - Two parameters may be set by the user:

        # of Layers - The size of the simulated Sun may be adjusted by
        setting the number of layers to any value from 5 to 80.  The
        average length of time for a photon to escape is proportional to
        the square of the number of layers.  Setting the number of
        layers to a high value will greatly increase the time required
        for all the photons to escape, but will not significantly affect
        the appearance of the # Escaping distribution.

        # of Pulse Photons - The number of photons in the pulse may be
        set to any value from 5 to 1000.  A larger pulse will produce a
        smoother and more characteristic distribution.

    Quit - Terminates the simulation and closes the window.

Control Buttons

    Run Simulation - Begins the simulation by clearing the counters and
    graph, and "launches" a pulse of photons at the center of the Sun.
    The Run Simulation button and the Parameters menu item are
    deactivated, the Stop Simulation button is activated.  The run
    continues until all the photons reach the surface or the Stop
    Simulation button is pressed.

    Stop Simulation - Use the Stop Simulation button to terminate the
    current run before all the photons have escaped.  Note that the
    simulation cannot be restarted at the stop point - pressing Run
    Simulation will reset the counters and graph and start over at the
    center.  Pressing the Stop Simulation button reactivates the
    Parameters menu item and the Run Simulation button.

Display

    # of Layers - The size of the current Sun model (set via menu).

    Pulse Photons - The number of photons in the simulated pulse (set
    via menu).

Counters

    Interactions - A running total of the number of interactions per
    photon experienced by the photons remaining in the Sun.  In this
    model the number of interactions is also a measure of the time since
    the pulse began at the center.

    # Escaped - The number of photons that have reached the surface.

    % Escaped - The percentage of photons in the original pulse that
    have reached the surface.

Display

    The number of escaping photons per time interval is shown plotted vs
    time.  The vertical line shows the time represented by the square of
    the number of layers in the model.

