[Mesa-users] Questions about convective mixing during a proton ingestion event (when the He-convective zone engulfs H material)

Wed Feb 12 01:19:02 UTC 2025

Dear EbF,

Thank you for your response!

Regarding your point about the sensitivity of the behavior to the adopted convection physics, I would like to clarify that I have set the same convection parameters in my model: 

1.the mixing length parameter α is set to 1.75.

2. I am using the Schwarzschild criterion to determine the convective boundaries. 

3. I have not included any extra convective boundary mixing (e.g., overshoot).

I have attached the inlist file for the second thermal pulse below for your reference.

Thank you for your assistance!

Best regards,
Guo Li

At 2025-02-12 05:18:48, "Farag, Ebraheem" <ebraheem.farag at yale.edu> wrote:

Hi Guo,

It is hard to make an apples to apples comparison, as the authors have conducted their study in an entirely different stellar evolution software instrument (STAREVOL). It is likely that this type of behavior is highly sensitive toward the adopted convection physics (especially the convective boundary mixing schemes), to note just one among many differences. 

I'm not sure if your MESA inlists are perfectly replicating the physics adopted in the Choplin paper, however it important to note that they have different convective boundary mixing schemes than the defaults offered in MESA. See all of section (2), and eqn (9) in https://ui.adsabs.harvard.edu/abs/2018A%26A...609A..29G/abstract. As one of the adopted approaches is a slight modification/extension of the herwig (1997) exponential overshooting scheme: In principle one could include a similar boundary mixing routine in MESA using the run_star_extras using the "other_overshooting_scheme". This is where MESA excels in its modularity.

-EbF

From: Mesa-users <mesa-users-bounces at lists.mesastar.org> on behalf of Guo Li via Mesa-users <mesa-users at lists.mesastar.org>
Sent: Tuesday, February 11, 2025 3:25 AM
To: mesa-users <mesa-users at lists.mesastar.org>
Subject: [Mesa-users] Questions about convective mixing during a proton ingestion event (when the He-convective zone engulfs H material)

Hi all,
I hope this message finds you well.

I am simulating a 1Msun，[Fe/H]=-2.5 stellar evolution model based on the literature https://doi.org/10.1051/0004-6361/202040170. During the second Thermal Pulse (TP), the He-convective zone approaches the H-shell and engulfs H material, resulting in a proton ingestion event. After H is mixed into the He-convective zone, the literature indicates that the location with the highest H-burning energy production is in the middle of the He-convective zone, where energy accumulation leads to the splitting of the He-convective zone. However, in my results, the highest energy production occurs at the bottom of the convective zone, preventing the He-convective zone from splitting.

What could be the reason for this discrepancy? I suspect that the H profile gradient within the He-convective zone in my results is too small. Is this due to overly rapid convective mixing, or are there other reasons? The following figures show the mass fraction and energy profiles after the proton ingestion event.

I appreciate your assistance and look forward to your response.

Thank you!

Best regards,
Guo Li
National Astronomical observatories,CAS
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! inlist_agb

&star_job

      set_rate_c12ag = 'Kunz'

      show_log_description_at_start = .false.
      !list_net_reactions = .true.

      show_net_reactions_info = .true.

      load_saved_model = .true.
      saved_model_name = 'TP2_ip_Bmesh_models.mod'

      save_model_when_terminate = .true.
      save_model_filename = 'TP3_Bmesh_Snet4777_models.mod'

      change_net = .true.      
      new_net_name = 'agb__mg25n__flow_extend_toMg.net' 

      !pgstar_flag = .true.

!same rates as c13pocket
      set_rates_preference = .true. ! for use by net + rates modules
      new_rates_preference = 1
         ! 1 = NACRE rates -- this is the default
         ! 2 = jina reaclib rates -- to match jina where possible

      set_initial_cumulative_energy_error = .true.
      new_cumulative_energy_error = 0d0

! opacities
      initial_zfracs = 8

      show_net_reactions_info = .true.
      show_net_species_info = .true.

/ ! end of star_job namelist

&controls

      mixing_length_alpha = 1.75

      varcontrol_target = 1d-3
      power_he_burn_lower_limit = 99
      mesh_delta_coeff = 1.3d0

      log_directory = 'LOGS_agb_TP3_Bmesh_Snet_4777'

      max_model_number =4777

      initial_mass = 1.0
      initial_y = 0.276088544d0
      initial_z = 4.4272e-05

      Zbase = 4.4272e-05

      use_Type2_opacities = .true.

     atm_option = 'T_tau'
     atm_T_tau_relation = 'Eddington'
     atm_T_tau_opacity = 'varying'

      photo_interval = 50
      !photostep = 50
      profile_interval = 50
      !history_interval = 1
      !terminal_interval = 10
      write_header_frequency = 10

! resolve the C13 pockets 
      xa_function_species(1) = 'h1'  ! name of nuclide as defined in chem_def
        xa_function_weight(1) = 5
        xa_function_param(1) = 3d-4
      xa_function_species(2) = 'he4'  ! name of nuclide as defined in chem_def
        xa_function_weight(2) = 5
        xa_function_param(2) = 1d-2
      xa_function_species(3) = 'c13'  ! name of nuclide as defined in chem_def
        xa_function_weight(3) = 4
        xa_function_param(3) = 1d-3
      xa_function_species(4) = 'n14'  ! name of nuclide as defined in chem_def
        xa_function_weight(4) = 3
        xa_function_param(4) = 1d-2

      mesh_dlog_pp_dlogP_extra = 0.25
      mesh_dlog_cno_dlogP_extra = 0.25

      mesh_dlog_3alf_dlogP_extra = 0.225
      mesh_dlog_burn_c_dlogP_extra = 0.225
      mesh_dlog_burn_n_dlogP_extra = 0.225
      mesh_dlog_burn_o_dlogP_extra = 0.225

      mesh_logX_species(1) = 'h1'
      mesh_logX_min_for_extra(1) = -6
      mesh_dlogX_dlogP_extra(1) = 0.25

      mesh_logX_species(1) = 'he4'
      mesh_logX_min_for_extra(1) = -6
      mesh_dlogX_dlogP_extra(1) = 0.25

      use_other_mesh_delta_coeff_factor = .true.

! atmosphere option same as c13pocket
      !which_atm_option = 'photosphere_tables'
      atm_table = 'photosphere'

! mass loss
      cool_wind_RGB_scheme = 'Reimers'
      cool_wind_AGB_scheme = 'Blocker'
      RGB_to_AGB_wind_switch = 1d-4
      Reimers_scaling_factor = 0.4d0
      Blocker_scaling_factor = 0.01d0
      !Blocker_scaling_factor = 0.04d0

      ! FOR DEBUGGING

      !fill_arrays_with_NaNs = .true.
      !stop_for_NaNs = .true.

      !report_hydro_solver_progress = .true. ! set true to see info about newton iterations
      !report_ierr = .true. ! if true, produce terminal output when have some internal error
      !hydro_show_correction_info = .true.

      !max_years_for_timestep = 3.67628942044319d-05

      !report_why_dt_limits = .true.
      !report_all_dt_limits = .true.

      !show_mesh_changes = .true.
      !mesh_dump_call_number = 5189
      !okay_to_remesh = .false.

      !trace_evolve = .true.

      ! hydro debugging
      !hydro_check_everything = .true.
      !hydro_inspectB_flag = .true.

      !hydro_numerical_jacobian = .true.
      !hydro_save_numjac_plot_data = .true.
      !small_mtx_decsol = 'lapack'
      !large_mtx_decsol = 'lapack'
      !hydro_dump_call_number = 195

      !trace_newton_bcyclic_solve_input = .true. ! input is "B" j k iter B(j,k)
      !trace_newton_bcyclic_solve_output = .true. ! output is "X" j k iter X(j,k)

      !trace_newton_bcyclic_steplo = 1 ! 1st model number to trace
      !trace_newton_bcyclic_stephi = 1 ! last model number to trace

      !trace_newton_bcyclic_iterlo = 2 ! 1st newton iter to trace
      !trace_newton_bcyclic_iterhi = 2 ! last newton iter to trace

      !trace_newton_bcyclic_nzlo = 1 ! 1st cell to trace
      !trace_newton_bcyclic_nzhi = 10000 ! last cell to trace; if < 0, then use nz as nzhi

      !trace_newton_bcyclic_jlo = 1 ! 1st var to trace
      !trace_newton_bcyclic_jhi = 100 ! last var to trace; if < 0, then use nvar as jhi

      !trace_k = 0

/ ! end of controls namelist

&pgstar

      Grid4_win_flag = .true.
      Grid4_win_width = 11
      Kipp_mass_min = 0.510 ! (Msun units) negative means use default
      Kipp_mass_max = 0.590 ! (Msun units) negative means use default
      Grid4_plot_name(2) = 'Power'
      Power_xmin = 0.510 ! only used if /= -101d0
      Power_xmax = 0.590 ! only used if /= -101d0

      Grid4_file_flag = .true.
      Grid4_file_dir = 'png'
      Grid4_file_prefix = 'agb_'
      Grid4_file_interval = 5 ! output when mod(model_number,Grid4_file_interval)==0
      Grid4_file_width = -1 ! (inches) negative means use same value as for window
      Grid4_file_aspect_ratio = -1 ! negative means use same value as for window

/ ! end of pgstar namelist