## Introduction

The model described here represents the state of the art in solar model construction circa 1998. It includes the effects of helium and heavy element diffusion.

## Description

The Yale stellar evolution code (YREC, for Yale Rotating Evolution Code)
was used in its non-rotating configuration to construct this solar model
(Guenther et al. 1992; Guenther & Demarque 1997). YREC uses the nuclear energy generation routines
of Bahcall (Bahcall & Pinsonneault 1992a & b) and the cross-sections
listed in Bahcall's Neutrino Astrophysics (Bahcall 1989). We have updated
the cross-section of the pp reaction, the 7Be-proton capture reaction, and
the hep reaction (Pinsonneault, private communication). The equation of
state tables prepared by the OPAL group were used.

The OPAL95 opacity tables were used throughout most of the model,
except at lower temperatures where Alexander & Furgeson opacities were used. Both sets of opacity tables are provided with Z interpolation
routines so that we were able to use the tables at any Z value we chose.
Due to the time consuming nature of generating the tables at a given Z we
calculated a set of Z specific tables at startup.

The effects of helium diffusion and helium and heavy element diffusion are
included. The diffusion formulation is identical to that described in (Bahcall
and Pinsonneault 1995). We note that the heavy element diffusion coefficients
and equations are for iron alone. The other elements are assumed, for this
calculation, to diffuse at similar rates, that is we assume the iron diffusion
rate scaled to the total Z mass abundance is the total Z diffusion rate.
This is certainly not correct but at this time we cannot carry out more
sophisticated calculations.

The effects of rotation are not included in any of the model calculations
presented here. As discussed in detail in Chaboyer et al. (1995) rotation
tends to inhibit the effects of diffusion by approximately a factor two.

The model was evolved from a zero age main sequence (ZAMS) model to near
the age of the Sun, 4.5-Gyr (Guenther 1989) in 50 equally spaced time steps.
By adjusting the helium abundance and mixing length parameter of each model,
the models were tuned to have identical radii to one part in 1.0E7 (Rsun
= 6.9598E10 cm) and identical luminosities (Lsun=3.8515E33 erg/s) to one
part in 1.0E6. The atmosphere is modeled using the Krishna Swamy (1966)
T-tau relation. This relation is derived from a fit to the Sun's observed
T-tau dependence in the lower atmosphere.

## Table of Model Characteristics

Radius..........................................6.95980E+10 cm

Mass............................................1.98910E+33 g

Luminosity......................................3.85150E+33 erg/s

Age.............................................4.7 Gyr

Initial X.......................................0.7079

Initial Z.......................................0.0200

Surface X.......................................0.7403

Surface Z.......................................0.0180

Mass of convective envelope.....................0.0242 Msun

Radius fraction depth of convective envelope....0.7140 Rsun

Central pressure................................2.382E17 dyne/cm*cm

Central temperature.............................1.581E7 K

Central density.................................156.3 g/cm*cm*cm

Central X.......................................0.328

Central Z.......................................0.211

37 Cl SNU.......................................8.74

71 Ga SNU.......................................135

## Detailed Model Listing

The following file (linked to below) contains a complete listing of
all the physical variables of the solar model as a function of radius. Data
from every fifth shell is listed. The file lists: luminosity, temperature,
density, pressure, specific heat at constant volume, specific heat at constant
pressure, the adiabatic exponent Gamma_1, mean molecular weight, sound speed,
nuclear reaction rate, X, Z, opacity, derivative of opacity w.r.t. log density,
derivative of opacity w.r.t. log temperature, temperature gradient, adiabatic
temperature gradient, derivative of log pressure w.r.t. log density, derivative
of log pressure w.r.t. log temperature, derivative of log energy generation
rate w.r.t. log density, derivative of log energy generation rate w.r.t.
log temperature, Lamb frequency squared, Brunt Viäsälä frequency
squared, critical frequency plus squared, critical frequency minus squared,
(remaining parameters not defined in this model).

The file is an ASCII text file 240K in size. Click on the link below to
view the file with your WWW browser. Note that each line is 132 columns
wide.

Solar Model 1998 (240K)** **(c) 2010
David B. Guenther

If you use this model in your research please contact me to obtain the appropriate
citation.