= Cold-limit degeneracy of a slow magnetosonic point
{title2=$c_{\rm slow}=0$}
In a strictly cold flow governed by <ideal magnetohydrodynamics> the <sound speed> vanishes, so the <slow magnetosonic wave> speed is zero. A nonzero-speed outflow therefore has no ordinary finite interior slow crossing. For the <cold radial magnetohydrodynamic wind integral>, $f_y=-\alpha(x-x^{-1})^2/(y-1)^3-\beta/(x^4y^3)<0$ on the sub-Alfvénic branch $y>1$, assuming $\beta>0$. A small retained <specific enthalpy> is needed to locate a finite slow point; the zero-temperature limit can move it to the launch boundary. The usual simultaneous numerator and denominator regularity conditions still apply to nondegenerate critical points.
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