User file
The user file, user_*.F90, such as user_shock.F90 or user_weibel.F90, is used for readily expanding the behavior of the code without having to alter any of the code-flow logic. The user defines routines for loading and injecting particles here, as well special boundary conditions on fields and particles (e.g. reflecting walls) and external fields.
subroutine get_external_fields
This subroutine compute external magnetic fields to be added to the particle mover. These fields do not evolve via Maxwell equations. Note that it uses local coordinates corresponding to different CPU, so one should convert that to global coordinates first.
Example: This example sets an external B_z field, that is an bz_ext0*sin(x)*sin(y) function of global coordinate x and y.
subroutine get_external_fields
real,intent(inout):: bx_ext,by_ext,bz_ext, ex_ext, ey_ext, ez_ext
real, intent(in):: x,y,z
ex_ext=0.
ey_ext=0.
ez_ext=0.
bx_ext=0.
by_ext=0.
bz_ext=bz_ext0*sin(x)*sin(y+modulo(rank,sizey)*(myall-5))
!bz_0 is defined in the input reading part above,
!note the coordinate transformation rule.
end subroutine get_external_fields
subroutine init_EMfields_user()
This subroutine sets the electromagnetic fields of any specific user purpose.
Example: This example sets an initial jump for in-plane magnetic field by. Also component perpendicular to interface surface bx is added.
subroutine init_EMfields_user()
integer :: i, j, k, jglob, kglob
!initialize B field to be set by Binit and the inclination angle
!-- used for shock problems
Binit=sqrt((gamma0)*ppc0*.5*c2*(mi+me)*sigma)
do k=1,mz
do j=1,my
do i=1,mx
jglob=j+modulo(rank,sizey)*(myall-5)
!global j,k coords are defined from local ones
kglob=k+(rank/sizey)*(mzall-5)
!magnetic fields components are initialized
bx(i,j,k)=0.5*Binit
bz(i,j,k)=0.*Binit*sin(btheta)*sin(bphi)
by(i,j,k)=2.*Binit*tanh((i-mx/2)/4.)
ex(i,j,k)=0. !electric field is initialized
ey(i,j,k)=0.
ez(i,j,k)=-0.
enddo
enddo
enddo
end subroutine init_EMfields_user