antenna_apar Subroutine

  subroutine antenna_apar (kperp2, j_ext)
!      GGH ERR? Is this correct? It uses apar_new rather than just the applied
!      current, so does this include the plasma response? 
!      BD: No error.  Here, apar and apar_new are local variables for the antenna only. 7.1.06
!
!      this routine returns space-centered (kperp**2 * A_ext) at the current time

    use kt_grids, only: naky, ntheta0
    use run_parameters, only: beta, has_apar
    use theta_grid, only: ntgrid

    complex, dimension (-ntgrid:,:,:), intent(out) :: j_ext
    real, dimension (-ntgrid:,:,:), intent(in) :: kperp2
    integer :: ik, it, ig

    if (has_apar) then

       if (.not. allocated(apar_new)) return
       
       do ik = 1, naky
          do it = 1, ntheta0
             do ig = -ntgrid, ntgrid-1
                j_ext(ig,it,ik) = 0.5* &
                     ( &
!                  kperp2(ig+1,it,ik)*apar_old(ig+1,it,ik) &
!                 +kperp2(ig,  it,ik)*apar_old(ig,  it,ik) &
                     +kperp2(ig+1,it,ik)*apar_new(ig+1,it,ik) &
                     +kperp2(ig,  it,ik)*apar_new(ig,  it,ik))
             end do
          end do
       end do
     
! GGH Is this some normalization?  Yes.
       if (beta > 0.) j_ext = j_ext * 0.5 / beta

    else ! if apar itself is not being advanced in time, there should be no j_ext
       j_ext = 0.
    end if

  end subroutine antenna_apar