two_stream_ee_em
{

This is the classic electron/electron two-stream instability, with counter-propagating electron beams
having velocities much larger than their thermal velocity.


We work in pseudo-1D geometry.  It's 2D Cartesian geometry, but the y-direction is only
2 cells across with periodic BC's.  The x-direction is long.

The field solve is electromagnetic.  If the electrons are non-relativistic (as is the case here), then 
it is faster to use the electrostatic approximation.  See input file  "two_stream_ee_es.inp".

For the theory, see Sections 5-6 and 5-7 of the classic reference
  C.K. Birdsall and A.B. Langdon
  Plasma Physics via Computer Simulation
  McGraw-Hill, 1985
}

Variables
{
// General numerical parameters
  PI = 3.14159

// **********************************************************************
// General physical parameters
// **********************************************************************
  electronMassMKS = 9.1094e-31 
  electronCharge  = -1.6022e-19
  positronCharge = -electronCharge
  speedLight      = 2.9979e8

  electronDensityMKS = 0.5e+24
  plasmaFrequency    = 2.*PI*9000.*sqrt(2.e-06*electronDensityMKS)
  ds                 =  speedLight / plasmaFrequency /10

// **********************************************************************
// Grid parameters
// **********************************************************************
  Nx = 256
  Ny = 128
  dx =  ds
  dy =  dx
  Lx =  Nx * dx
  Ly =  Ny * dy

  simulationVolume = Lx * Ly
  numCells         = Nx * Ny

//
// streaming electrons
//
  totalNumElectrons    = electronDensityMKS * simulationVolume
  numElectronsPerCell  = 10
  numElectronPtcls     = numElectronsPerCell * numCells
  electronNumRatio     = totalNumElectrons / numElectronPtcls
  rmsElectronSpeedMKS  = 1.e+06
  electronVelocityMKS  = 1.5e+08  
//injector will produce strange velocities at higher values of the drift speed.

  d = 1. / sqrt( 1./(dx*dx) + 1./(dy*dy) )
  timeStep = 0.9 * d / speedLight
}

Region
{

Grid
{
  J = Nx 
  x1s = 0.0
  x1f = Lx 
  n1 = 1.0 
  K = Ny 
  x2s = 0.0
  x2f = Ly 
  n2 = 1.0

  Geometry = 1         // 2D (x-y) slab geometry
//  PeriodicFlagX1 = 1   // periodic in x1 (x)
  PeriodicFlagX2 = 1   // periodic in x2 (y)
}

Control
{
  dt = timeStep

// Turn off the initial Poisson solve
  initPoissonSolve = 0
  emdamping = 0.05

 CurrentWeighting = 0

//B02analytic = 150 // 0*5000 * (1-step(x1-Lx/8))
//B2init = 150
//E3init = 150 * electronVelocityMKS
}

Species
{
  name = electrons
  m = electronMassMKS
  q = electronCharge 
}

Species
{
  name = positrons
  m = electronMassMKS
  q = -electronCharge 
}

// Load the right-going plasma positrons over the entire simulation region
Load
{
  speciesName = positrons
  density = electronDensityMKS/2
  x1MinMKS = 0.0
  x1MaxMKS = Lx-10*dx
  x2MinMKS = 0.0
  x2MaxMKS = Ly
  np2c = electronNumRatio

// specify MKS units for all velocities
  units = MKS
  v1drift   = -electronVelocityMKS
  temperature = rmsElectronSpeedMKS
//  v1thermal = rmsElectronSpeedMKS
//  v2thermal = 0.
//  v3thermal = 0.
}

// Load the left-going plasma positrons over the entire simulation region
Load
{
  speciesName = electrons
  density = electronDensityMKS/2
  x1MinMKS = 0.0
  x1MaxMKS = Lx-10*dx
  x2MinMKS = 0.0
  x2MaxMKS = Ly
  np2c = electronNumRatio

// specify MKS units for all velocities
  units = MKS
  v1drift   = -electronVelocityMKS
  temperature = rmsElectronSpeedMKS
//  v1thermal = rmsElectronSpeedMKS
//  v2thermal = 0.
//  v3thermal = 0.
}


//emitter parallel to x axis 
BeamEmitter 
{
 j1 = Nx-10 
 k1 = 0
 j2 = Nx-10
 k2 = Ny
normal = -1 
speciesName = electrons 
thetadot = 0.0
I = electronVelocityMKS * electronDensityMKS/2 * electronCharge * Lx /3
np2c = electronNumRatio
v2drift = 0
v1drift = -electronVelocityMKS
v3drift = 0 
//  temperature = rmsElectronSpeedMKS
//v1thermal = 0 
//v2thermal = 0 
//v3thermal = 0
}

//emitter parallel to x axis 
BeamEmitter 
{
 j1 = Nx-10 
 k1 = 0
 j2 = Nx-10
 k2 = Ny
 normal = -1 
 speciesName = positrons 
 thetadot = 0.0
 I = electronVelocityMKS * electronDensityMKS/2 * (positronCharge) * Lx /3
 np2c = electronNumRatio
 v2drift = 0
 v1drift = -electronVelocityMKS
 v3drift = 0 
//  temperature = rmsElectronSpeedMKS
// v1thermal = 0 
// v2thermal = 0 
// v3thermal = 0
}

//walls along y
Conductor
{
  j1 = 0
  k1 = 0 
  j2 = 0
  k2 = Ny 
  normal = 1
  reflection = 1.0
}

Conductor
{
  j1 = Nx
  k1 = 0
  j2 = Nx
  k2 = Ny
  normal = -1
  reflection = 0.0
}


}