Functions to calculate the diffusion coefficients for resistivity. More...
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Functions | |
| void | convert_diffusion (Real sigma_O, Real sigma_H, Real sigma_P, Real *eta_O, Real *eta_H, Real *eta_A) |
| Convert conductivities to diffusivities. | |
| void | get_eta (GridS *pG) |
| Get magnetic diffusivities. | |
| void | eta_single_const (GridS *pG, int i, int j, int k, Real *eta_O, Real *eta_H, Real *eta_A) |
| Single-ion prescription with constant diffusivities. | |
| void | eta_single_user (GridS *pG, int i, int j, int k, Real *eta_O, Real *eta_H, Real *eta_A) |
| Single-ion prescription with user defined diffusivities. | |
| void | eta_general_user (GridS *pG, int i, int j, int k, Real *eta_O, Real *eta_H, Real *eta_A) |
| Generalized prescription with user defined conductivities. | |
Detailed Description
Functions to calculate the diffusion coefficients for resistivity.
We provide two standard prescriptions, divided into 3 cases:
- A. Single ion prescription (eq. 21 of Balbus & Terquem 2001, ApJ): E = eta_Ohm*J + (JxB)/(4pi*n_e*e/c) - [(JxB)xB]/(4pi*gamma*rho_i*rho)
- CASE 1: eta_Ohm is constant and n_e and rho_i are proportional to gas density rho. The user needs to provide eta_Ohm and two proportional coefficients Q_Hall and Q_AD, which are defined in global.h.
- CASE 2: The user provides his/her own function to evaluate the etas, e.g., spatially variable diffussivity, or adopting some chemical model. The (blank) function is given in the problem generator.
- B. Generalized prescription (eq. 25-31 of Wardle 2007, ApSS): E = eta_Ohm*J + eta_Hall*(JxB)/B + eta_AD*J_perp where eta_Ohm, eta_Hall and eta_AD are determined by sigma_O, sigma_H and sigma_P.
- CASE 3: The user provides his/her own function to calculate the sigmas, e.g., from non-equilibrium chemistry to evaluate them self-consistently. The (blank) function is given in the problem generator.
CONTAINS PUBLIC FUNCTIONS:
- get_eta() - main function call to get magnetic diffusivities
- eta_single_const() - constant diffusivities for single ion prescription
- eta_single_user() - user defined diffusivities for single ion prescription
- eta_general_user() - user defined diffusivities for general prescription
Definition in file get_eta.c.
Function Documentation
| void convert_diffusion | ( | Real | sigma_O, | |
| Real | sigma_H, | |||
| Real | sigma_P, | |||
| Real * | eta_O, | |||
| Real * | eta_H, | |||
| Real * | eta_A | |||
| ) |
Convert conductivities to diffusivities.
NOTE: c^2/4pi factor is NOT included, so (eta x sigma) is dimensionless. The conductivity coefficients should have the right dimension.
Definition at line 177 of file get_eta.c.
Referenced by eta_general_user().
Generalized prescription with user defined conductivities.
This corresponds to CASE 3. Note the same get_eta_user() function is used to calculate conductivities rather than diffusivities here.
Definition at line 155 of file get_eta.c.
References convert_diffusion(), and get_eta_user().
Single-ion prescription with constant diffusivities.
NEED global parameters: eta_Ohm, Q_Hall and Q_AD. ONLY eta_Ohm has the dimension of diffusivity. This correspond to CASE 1.
Definition at line 108 of file get_eta.c.
References ConsS::B1c, ConsS::B2c, ConsS::B3c, ConsS::d, d_ind, eta_Ohm, Q_AD, Q_Hall, and GridS::U.
Single-ion prescription with user defined diffusivities.
This corresponds to CASE 2.
Definition at line 136 of file get_eta.c.
References get_eta_user().
| void get_eta | ( | GridS * | pG | ) |
Get magnetic diffusivities.
Definition at line 63 of file get_eta.c.
References GridS::eta_AD, GridS::eta_Hall, GridS::eta_Ohm, get_myeta, GridS::ie, il, GridS::is, iu, GridS::je, jl, GridS::js, ju, GridS::ke, kl, GridS::ks, ku, and GridS::Nx.
Referenced by integrate_diff().
