Asymptotic behavior of global weak solutions for the micropolar dynamics in $L^{2}(\mathbb{R}^{3})$

In this paper the long time behavior of the micropolar fluid equations energy on three dimensional space are studied. We show that $\| (u,w)(\cdot,t) \|_{{L^{2}(\mathbb{R}^{3})}} \to 0$ as $t \to \infty$ for Leray-Hopf's global weak solutions in inviscid vortex case. Moreover, when the vortex viscosity are considered, i.e., $\chi >0$, we obtain a (faster) decay for micro-rotational field: $\| w (\cdot,t) \|_{{L^{2}(\mathbb{R}^{3})}} = o(t^{-1/2})$.