[mesa-users] Brunt frequency error near convective/radiation zone boundary (solar model)

[Momchil Molnar]

Dear all,

I am an undergrad using the Brunt frequency profiles for 
asteroseismologic purposes and I encountered the following problem - the 
Brunt profile was not continuous very close to the convective/radiative 
zone interface for a Solar model.

I am attaching plots of the Brunt frequency squared profiles for current 
age (4.57 Gyrs) solar models, along with the attached inlist file.

Do you have an idea how this inconsistency (bump) can be avoided in 
further calculations and what is the reason for this numerical error?

Best,
Momchil Molnar
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&star_job  ! HD49385   

      show_log_description_at_start = .false.

	
      load_saved_model = .true.
      saved_model_name = 'solar_calibration_input.mod'

	
      change_net = .true. ! switch nuclear reaction network
      new_net_name = 'pp_and_cno_extras.net'

      	   set_rate_n14pg = 'Imbriani'
	   set_rate_c12ag = 'Kunz'

      kappa_file_prefix = 'OP_gs98'
      kappa_lowT_prefix = 'lowT_fa05_gs98' ! for lower temperatures.
      
      change_lnPgas_flag = .true.
      new_lnPgas_flag = .true.


      astero_just_call_my_extras_check_model = .true.

      !pgstar_flag = .true.
      
  ! save a model at the end of the run
      save_model_when_terminate = .true.
      save_model_filename = 'sol_4.57gyrs.mod'



  ! write output
      save_pulsation_info_when_terminate = .true.
      save_pulsation_info_filename = 'sol4.57Gyrs.mesa'
      

/ ! end of star_job namelist


&controls

      !max_age = 10d9
      max_age = 4.57d9
      ! controls for output
      photostep = 100
      profile_interval = 100
      history_interval = 10
      terminal_cnt = 10
      write_header_frequency = 10
      ! atmosphere
      which_atm_option = 'photosphere_tables'
      
      ! atomic diffusion
      do_element_diffusion = .true. ! determines whether or not we do diffusion
      diffusion_dt_limit = 7d11 ! no element diffusion if dt < this limit (in seconds)
      diffusion_T_full_on = 1d3
      diffusion_T_full_off = 1d3
      
      diffusion_calculates_ionization = .true.

      diffusion_num_classes = 4 ! number of classes of species for diffusion calculations
      diffusion_class_representative(1) = 'h1'
      diffusion_class_representative(2) = 'he4'
      diffusion_class_representative(3) = 'o16'
      diffusion_class_representative(4) = 'fe56'
   
      ! in ascending order.  species goes into 1st class with A_max >= species A
      diffusion_class_A_max(1) = 2
      diffusion_class_A_max(2) = 4
      diffusion_class_A_max(3) = 16
      diffusion_class_A_max(4) = 10000
 
      ! timesteps
      max_years_for_timestep = 1d8          
      varcontrol_target = 1d-4

      ! mesh adjustment
      mesh_delta_coeff = 0.15
      max_allowed_nz = 40000
   	
   	P_function_weight = 25
   	T_function1_weight = 75
      
      xtra_coef_czb_full_on = 1
      xtra_coef_czb_full_off = 1

      xtra_coef_a_l_nb_czb = 0.45 ! above lower nonburn convective boundary
      xtra_dist_a_l_nb_czb = 20 ! above lower nonburn convective boundary

      xtra_coef_b_l_nb_czb = 0.45 ! below lower nonburn convective boundary
      xtra_dist_b_l_nb_czb = 20 ! below lower nonburn convective boundary

         
      xa_function_species(1) = 'he4'  ! name of nuclide as defined in chem_def
		xa_function_weight(1) = 130
		xa_function_param(1) = 1d-2
         
      xa_function_species(2) = 'he3'  ! name of nuclide as defined in chem_def
		xa_function_weight(2) = 60
		xa_function_param(2) = 1d-5

      ! opacity
      
      use_Type2_opacities = .false.

      cubic_interpolation_in_Z = .true.

      pulse_info_format = 'GYRE'


/ ! end of controls namelist


&pgstar
         
      ! top level controls

         !pause = .true. 
            ! if true, the code waits for user to enter a RETURN on the command line
      


/ ! end of pgstar namelist