Grid-binned particle output is essentially the same as that for gas quantities. One example is given as below
<output1> out_fmt = ppm /* ppm image */ out = M1par /* particle x1-momentum */ id = M1par x2 = 1.0 dt = 1.0 /* time increment between outputs */
Here the variable
M1par denotes the particle x1-momentum. All built-in quantities for the particle output include dpar, M1par, M2par, M3par, V1par, V2par, V3par, which denote particle density, momentum and velocity respectively. The item
pargrid is automatically set to 1 for these built-in output variables. By default, particle property selection function is set to
all, but the user is free to define their own property selection functions.
The built-in variables can be retrieved in the grid from
pG is the pointer to the grid, and
Coup is of type
/athena/src/athena.h). It is mainly used for storing the intermediate step gas quantities for the particle integrators, but is also used in storing the grid-binned particle quantities for output purposes. Here its elements include
grid_d (particle density),
grid_v3 (particle momentum). The user can define their own particle-related output variables based on these grid-binned quantities in the same way as for gas variables (see User-defined Output Variables), but in such cases
pargrid in the output block must be set to 1 explicitly.