Hi!
I have a question regarding the initial data thorn of GRHydro. The documentation and ccl files didn't really help me.
The following was taken from paper [1] and now I am trying to add magnetic fields to the stars.
My questions are:
1) What are the units of (A) and (B) below? Is the following conversion factor correct? The star should have a field strength of 10^16 Gauss. Using the following conversion would give "0.00011973228161339154" for (A) and (B).
2) What are reasonable values for (C..F)? Can I just use the default ones given in param.ccl? Is there a reason not to use the default ones? My plan is to analyse the structure of the field after the collapse and the influence on the wave signal.
# constants, in SI G = 6.673e-11 # m^3/(kg s^2) c = 299792458 # m/s M_sun = 1.98892e30 # kg mu0 = 1.2566370614e-6 # Newton/Ampere^2 Kb = 1.3806488e-23 # Joule/K Mparsec = 3.08567758e19 # km CU_to_Tesla = c**4 / M_sun / G**(1.5)* mu0**(0.5) CU_to_Gauss = c**4 / M_sun / G**(1.5)* mu0**(0.5) * 10000 #------------------------------------------------- # Magentic Fields: #------------------------------------------------- (A) GRHydro_InitData::poloidal_A_b_1 = 0.00011973228161339154 (B) GRHydro_InitData::poloidal_A_b_2 = 0.00011973228161339154 (C) GRHydro_InitData::poloidal_P_cut_1 = 3.72e-6 #Non è in percentuale!! (D) GRHydro_InitData::poloidal_P_cut_2 = 3.72e-6 #Non è in percentuale!! (E) GRHydro_InitData::poloidal_n_p = 1 #Esponente di max((rho-rho_cut),0) (F) GRHydro_InitData::poloidal_P_p = 2 #Esponente di max((P-P_cut),0) GRHydro_InitData::Xc_1 = -13.5 GRHydro_InitData::Xc_2 = 13.5 GRHydro_InitData::Yc_1 = 0.0 GRHydro_InitData::Yc_2 = 0.0 GRHydro_InitData::Zc_1 = 0.0 GRHydro_InitData::Zc_2 = 0.0
3) These should be fine, right?
GRHydro::transport_constraints = "yes" GRHydro::track_divB = "yes" GRHydro::calculate_bcom = "yes" #GRHydro::clean_divergence = "no" GRHydro::Grhydro_MaxNumConstrainedVars = 33 GRHydro::GRHydro_MaxNumEvolvedVars = 10
HydroBase::initial_Bvec = "bin_ns_poloidalmagfield"
The field is evolved and everything seems okay, I am just not sure about the units and (C..F).
4) Is there a good method to visualize the B-field? Visit + Carpet hdf5 reader + Streamlines? (seems to be "buggy")
Thank you!
Best regards, Daniel
References: [1] "R. De Pietri, A. Feo, F. Maione, and F. Löffler, “Modeling Equal and Unequal Mass Binary Neutron Star Mergers Using Public Codes,” Phys. Rev., vol. D93, no. 6, p. 064047, 2016."