PyREC scaffolding (from YREC development, 7be4133)/ mcowind.fGlossary

mcowind.f

172 lines · 1 definitions · on GitHub (7be4133)

Python version: mcowind.py, 86 lines, on the right (switch to Python above the code).

Variables on this page (20)

c4pil, c_2, cgl, cln, clsunl, cmsun, constfactor, crsun, csigl, excen, exw, fracstep, lbscale, lmwind, lrossby, pmmsoltau, pmmsolw, taucz, taucz0, wmax

Purpose

MCOWIND returns the change in the angular velocity of the surface convection zone caused by magnetized-wind angular-momentum loss over a (diffusion) time step. It implements the newer wind law (G. Somers 3/17, "PMM-style," by its comment after van Saders and Pinsonneault, probably) with saturation, an optional Rossby scaling and the centrifugal correction of Matt et al. (2012, ApJ 754, L26). When the new law is off (LMWIND false) it hands over to the older COWIND.

How it fits

  • Who calls it: only SECULR, in the angular-momentum transport, once per iteration IT of the diffusion solution.
  • Inputs: BL ($\log L/L_\odot$), DT (the diffusion step, s), HICZ (moment of inertia of the surface convection zone), IT, OMEGAS (surface $\Omega$ at the end of the previous iteration), WOLD (surface $\Omega$ at the start of the step), SMASS ($M/M_\odot$), TEFFL.
  • Outputs: WIND1 and WIND2, the changes in $\Omega$ over the step computed with $\Omega$ at the start and at the end of the step; the caller averages them (its comment).
  • Calls: COWIND (old law) or AMCALC, which returns STRUCTFACTOR (an output argument, formerly in CWIND) from $M$, $L$ and $T_\mathrm{eff}$.
  • Modules: NMLPAR_MOD (the run's parameters, from PARMIN: the wind law's WMAX, EXW, CONSTFACTOR, EXCEN, formerly in CWIND, and LMWIND, LROSSBY, LBSCALE, the solar values PMMSOLW, PMMSOLTAU, formerly in PMMWIND), OVRTRN_MOD (TAUCZ, TAUCZ0, FRACSTEP: the convective turnover time at the start and end of the step and the fraction of the step reached), and CONSTANTS_MOD (the constants, with C_2, set once in PARMIN).

The method

  1. Saturation. With Rossby scaling, the turnover time is interpolated in the step, $\tau = \tau_0 + f\,(\tau_1 - \tau_0)$, and the saturation rate is $\Omega_\mathrm{sat} = \Omega_\mathrm{max}\,\tau_\odot/\tau$. With the extra field scaling as well (LBSCALE, which acts only with Rossby scaling) the rates $\Omega$ and $\Omega_\mathrm{sat}$ are multiplied by $\tau/\tau_\odot$. Otherwise $\Omega_\mathrm{sat}$ = WMAX.

  2. Coefficient. $C = (\Delta t/I_\mathrm{cz})\,K_\mathrm{const}\,K_\mathrm{struct}$.

  3. Centrifugal term. With $f = \Omega^2R^3/(2GM)$, for the star (at the start and end values of $\Omega$) and for the Sun ($f_\odot$), $$F_\mathrm{cen} = \left(\frac{c_2^2 + f_\odot}{c_2^2 + f}\right)^{n},$$ $c_2$ = C_2, $n$ = EXCEN; $R$ from $L = 4\pi R^2\sigma T_\mathrm{eff}^4$. The literals 0.5 and 3.0 in these lines are single precision but exact in binary, so the results are those of double precision (lines 150–154↗; settled from the code, Nov 9, 2026).

  4. Torque. With $\Omega_p = \min(\Omega,\Omega_\mathrm{sat})$ and the exponent $a$ = EXW, $$\Delta\Omega_1 = C\,\Omega_{p,\mathrm{start}}^{\,a-1}\,\Omega_\mathrm{start}\,F_{\mathrm{cen},1},\qquad \Delta\Omega_2 = C\,\Omega_{p,\mathrm{now}}^{\,a-1}\,\Omega_\mathrm{now}\,F_{\mathrm{cen},2},$$ and WIND2 is the running mean of $\Delta\Omega_2$ over the iterations (set at IT = 1, then averaged with the previous value).

Definitions

subroutineMCOWIND

lines 2–172 · GitHub

The new wind law: saturated power law in $\Omega$, optional Rossby scaling, Matt et al. centrifugal factor (above); otherwise COWIND.

Uses modules CONSTANTS_MOD, NMLPAR_MOD, OVRTRN_MOD

Called by SECULR

Flowchart of its calls, in order (2)
if (.NOT.LMWIND), lines 94–98
COWIND95
AMCALC139

Change log

The changes since rp_1

Changed since rp_1. Declarations only: COMMON blocks to modules, IMPLICIT NONE; CWIND and PMMWIND retired (C_2 to CONSTANTS_MOD, the rest to NMLPAR_MOD), so STRUCTFACTOR is now returned by AMCALC as an argument; the unused DEUTER dropped. No question settled: GL is still a local that is never set.

Changed since a8a5950. The Sun's centrifugal term FSUN now divides by $G$ (CGL, as the star's terms do) instead of EXP(CLN*GL) with GL an unset local, and GL is no longer declared; the code's comment puts the old $f_\odot$ about $1.5\times10^7$ too small. This settles former question 1; former questions 2–4 are now 1–3.