vice.toolkit.J21_sf_law.index2
==============================

Type : float

Default : 3.6

The power-law index of the :math:`\dot{\Sigma}_\star - \Sigma_\text{gas}`
relation at gas surface densities :math:`\Sigma_\text{gas}` between
:math:`\Sigma_{\text{gas},1}` and :math:`\Sigma_{\text{gas},2}`, the
values of the attributes ``Sigma_g1`` and ``Sigma_g2``, respectively.
At :math:`\Sigma_\text{gas} \geq \Sigma_{\text{gas},2}`, the relation
is assumed to be linear.

Example Code
------------
>>> import vice
>>> mw = vice.milkyway(name = "example")
>>> mw.zones[0].tau_star.index2
3.6
>>> for i in range(mw.n_zones):
>>> 	mw.zones[i].tau_star.index2 = 3.4
>>> mw.zones[0].tau_star.index2
3.4