calculate_initial_magnetic_field Subroutine

subroutine calculate_initial_magnetic_field(F)

  TYPE(FIELDS), INTENT(INOUT)                               :: F
  REAL(rp),dimension(F%dims(1),F%dims(3),2)                  :: gradA
  INTEGER                                                :: ii
  INTEGER                                                :: jj
  REAL(rp) :: psip_conv

  psip_conv=F%psip_conv

  call EZspline_interp(bfield_2d%A,F%dims(1),F%dims(3),F%X%R, F%X%Z, &
       F%PSIp, ezerr)
  call EZspline_error(ezerr)
 
  ! FR = (dA/dZ)/R
  call EZspline_gradient(bfield_2d%A,F%dims(1),F%dims(3),F%X%R, F%X%Z, &
       gradA, ezerr)
  call EZspline_error(ezerr)

  do ii=1,F%dims(1)
     F%B_2D%R(ii,:) = psip_conv*gradA(ii,:,2)/F%X%R(ii)
     F%B_2D%PHI(ii,:) = -F%Bo*F%Ro/F%X%R(ii)
     F%B_2D%Z(ii,:) = -psip_conv*gradA(ii,:,1)/F%X%R(ii)
  end do

  !        write(output_unit_write,'("AR",E17.10)') gradA(1)
  !        write(output_unit_write,'("AZ",E17.10)') gradA(2)        
       
end subroutine calculate_initial_magnetic_field