Simulation particles are organized in “species”, meaning sets of charged particles that share the same charge over mass ratio. You can control the number of species in the simulation using the particles section, and the parameters for each species using species sections. Users may choose to use as many species as they like (including none).

For example, to set up a simulation using three particles species you would choose in your input file:

particles {
  num_species = 3,
}

Species parameters

For each of the species selected in the particles section, the user must add a species section defining the main parameters for the particle species, namely:

  • The number of particles per cell used when creating the species (num_par_x parameter). This parameter should be set for all simulation directions.
  • The mass over charge ratio for the particle species (rqm parameter) in simulation units (for electrons this would be -1)

The user may also define a name for the species that will be used for diagnostic output.

Following each of these species sections, the user may optionally define the initial thermal/fluid distribution (udist section), and initial density profile (profile section). Users must also include a spe_bound section defining the boundary conditions for the species.

For example, to set up a simulation using a single reduced mass ratio ion species ($m/q = 100$), with initial fluid velocity 0.2 c along the y direction and temperature $10^-4$ in all directions, filling only the box for positions $x > 0$, you would choose in your input file:

particles {
  num_species = 1,
}

species
{
  name = "ions-up" ,
  num_par_x(1:2) = 2, 2,
  rqm=100.0,
}

udist
{
  ufl(1:3) =  0.0 , 0.2 , 0.0 ,
  uth(1:3) =  0.0001 , 0.0001 , 0.0001 ,
}

profile {
  profile_type = "math func",
  math_func_expr = 'x1 > 0',
}

For more details please check the particles and species sections of the reference guide.