suydam_bfield.f90

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subroutine suydam_bfield
!-----------------------------------------------------------------------
! subroutine to calculate :
!      - the total magnetic field squared
!      - the radial and poloidal derivative of the total field squared
!    on the grid points of the straight field line coordinate system. 
!-----------------------------------------------------------------------

  use itm_types
  use mod_map
  use mod_mesh
  use mod_spline
  use mod_suydam

  implicit none

  type(spline_coefficients) :: s_spline
  integer(itm_i4) :: i, j, ij

  real(r8), dimension(npsi) :: sp

  allocate(b02(npsi * nchi))
  allocate(dt_b02(npsi * nchi))
  allocate(ds_b02(npsi * nchi))

!---------------------------------------- b0 on grid points -----------
  do i = 1, npsi
    do j = 1, nchi
       ij = (i - 1) * nchi + j
       b02(ij) = (g11_hel(i, j) + rbphi(i)**2) * g33_hel(i, j)
    end do
  end do
!---------------------------------------- d(b02)/d(theta) -------------
  do i = 1, npsi
    ij = (i - 1) * nchi + 1
    call theta_derivative(b02(ij), dt_b02(ij), nchi)     
  end do
!---------------------------------------- d(b02)/ds --------------------
  call allocate_spline_coefficients(s_spline, npsi)
  do j = 1, nchi
    do i = 1, npsi
      ij = (i - 1) * nchi + j
      sp(i) = b02(ij)
    end do
    call spline(npsi, cs, sp, 0.0_r8, 0.0_r8, 2, s_spline)
    do i = 1, npsi
      ij = (i - 1) * nchi + j
      ds_b02(ij) = s_spline%sp2(i)
    end do
  end do
  call deallocate_spline_coefficients(s_spline)  

  return

end subroutine suydam_bfield