write_eigenfunc Subroutine

  subroutine write_eigenfunc(gnostics)
    use mp, only: proc0
    use file_utils, only: open_output_file, close_output_file
    use fields_arrays, only: phi, apar, bpar
    use kt_grids, only: ntheta0, naky, theta0, aky
    use theta_grid, only: theta, nperiod, ntheta
    use diagnostics_config, only: diagnostics_type
    use gs2_io, only: nc_eigenfunc
    implicit none
    type(diagnostics_type), intent(in) :: gnostics
    complex, dimension (ntheta0, naky) :: phi0
    integer :: it, ik, ig, ntg_out
    
    if (.not. proc0) return

    phi0 = get_phi0()
    
    !Do ascii output
    if (proc0 .and. gnostics%ascii_files%write_to_eigenfunc .and. (.not. gnostics%create)) then
       ntg_out = ntheta/2 + (nperiod-1)*ntheta
       do ik = 1, naky
          do it = 1, ntheta0
             do ig = -ntg_out, ntg_out
                write (unit=gnostics%ascii_files%eigenfunc, fmt="(9(1x,e12.5))") &
                     theta(ig), theta0(it,ik), aky(ik), &
                     phi(ig,it,ik)/phi0(it,ik), &
                     apar(ig,it,ik)/phi0(it,ik), &
                     bpar(ig,it,ik)/phi0(it,ik)
             end do
             write (unit=gnostics%ascii_files%eigenfunc, fmt="()")
          end do
       end do
    end if
    
    call nc_eigenfunc(gnostics%file_id, phi0)
  end subroutine write_eigenfunc