# semiconvection¶

This test case checks placement of the convective and semiconvective boundaries when using the Ledoux criterion and predictive mixing, see MESA V. The test vehicle is with a 1.5 Msun, Z=0.02 metallicity, model.

This test case has 1 part. Click to see a larger version of a plot.

• Part 1 (inlist_semiconvection) loads a pre-built 1.5 Msun, Z=0.02 metallicity, model from test case make_zams_high_mass. New initial model generation should use the supplied inlist_to_ZAMS. The model is then evolved until the central hydrogen mass fraction drops below 0.4. At this time the convective core has almost reached its maximum mass extension, and there is a semiconvective layer above the convective core. The run_star_extars.f90 then checks the mixing types at three points (0.12, 0.135, and 0.15 Msun), where the convective types should be convection, semiconvection, and no mixing. In addition, the run_star_extars.f90 checks the average temperature and density between two points in the star :
              runtime (minutes), retries, steps        3.84         0       293

mixing type at 0.125 Msun    1.0000000000000000D+00    1.0000000000000000D+00    1.0000000000000000D+00
mixing type at 0.135 Msun    3.0000000000000000D+00    3.0000000000000000D+00    3.0000000000000000D+00
mixing type at 0.145 Msun    0.0000000000000000D+00    0.0000000000000000D+00    0.0000000000000000D+00
logT    7.2064593252093898D+00    7.1500000000000004D+00    7.3099999999999996D+00
logRho    1.7885667307278197D+00    1.7500000000000000D+00    1.8000000000000000D+00

all values are within tolerances


Note that the choice made for the inital mixture (a09 in this test case) and for the nuclear reaction network (here: pp_and_cno_extras.net) influence the growth of the convective core. The values used in this test case for the predictive_superad_thresh parameters work well here but need to be adjusted when using other mixtures or nuclear reaction networks. See the two pdf plots in the docs directory. Also note that for speed purposes the values used here for the maximum allowed timestep and the mesh size do not produce completely converged models. A convergence study should be done when using this inlist for science purposes.

pgstar commands used for the plot above:

&pgstar

file_white_on_black_flag = .true. ! white_on_black flags -- true means white foreground color on black background
!file_device = 'png'            ! png
!file_extension = 'png'

file_device = 'vcps'          ! postscript
file_extension = 'ps'

pgstar_interval = 10

Kipp_win_flag = .true.
Kipp_win_width = 16
Kipp_win_aspect_ratio = 0.75
Kipp_txt_scale = 1.0
Kipp_title = 'inlist_semiconvection'

Kipp_mass_max = 0.2
Kipp_mass_min = 0
Kipp_xmax = -101d0
Kipp_xmin = 0

Kipp_show_mixing = .true.
Kipp_show_burn = .true.
Kipp_show_luminosities = .true.
Kipp_show_mass_boundaries = .false.

Kipp_file_flag = .true.
Kipp_file_dir = 'pgstar_out'
Kipp_file_prefix = 'kipp_'
Kipp_file_interval = 10000
Kipp_file_width = 16
Kipp_file_aspect_ratio = -1

/ ! end of pgstar namelist


Last-Updated: 01Jul2021 (MESA 094ff71) by fxt, based on documentation from Anne Thoul.