this question later, but for now the variable of greatest interest for addressing equation 1 is not luminosity, but other aspects of the Sun’s radiation, specifically the solar wind (mainly hydrogen ionized to protons), X-rays and energetic UV radiation. Unlike Earth, where field strength relates to buoyancy forces, the Sun’s magnetic field is a strong function of its rotation rate. The solar dynamo has its origin in the interactions between rotation and its convective outer envelope [@Parker1970]. The Sun sheds angular momentum through the emission of magnetized winds and rotation slows in a process known as magnetic braking. The rotation period slows as $\sim t^{\frac{1}{2}}$ [e.g. @Ayres1997].

Stellar winds are not detected directly, but through interaction with the interstellar medium. The interaction forms an “astrosphere" surrounding a star created by hot, interstellar neutral hydrogen which is heated by the stellar wind. Hot hydrogen atoms can be detected spectroscopically because they produce an absorption feature (H [I]{} Lyman-$\alpha$) thereby proving an indirect means of gauging stellar winds.

Observational constraints on ancient mass are available from the study of solar analogs - stars that are approximately the same size as the Sun but have different ages [e.g. @Wood2006]. These data suggest that 