  The difference between the spin alignments of $K^\ast$ and those of $\phi$ at
the low collision energies is a puzzle raised by the recent experiments. Unlike
$\phi$ meson, $K^\ast$, carrying a unit strange charge, should react to strange
chemical potential $\mu_S$. In this paper, we shall first convince you that
$\mu_S$ is not small in a brayon-rich medium for keeping strange neutrality,
and then derive the spin alignment induced by the gradient of $\mu_S$, and
hence of baryon chemical potential $\mu_B$, using linear response theory, with
the transport coefficients expressed, without any approximation, in terms of
the $K^\ast$'s in-medium spectral properties by employing Ward-Takahashi
identity. It turns out that such an effect applies mainly to the particles
whose longitudinal and transverse modes diverge, and induces only the local
spin alignment in a static medium. The magnitudes of these coefficients will be
further estimated under the quasi-particle approximation.
