We construct a magnetic reconnection model for magnetar giant flare in the framework of solar flare/coronal mass ejection theory.
As is the case with the solar flare, the explosive magnetic reconnection plays a crucial role in the energetics of the magnetar flare. A key physics controlling the energy transport in the system, on the other hand, is the radiative process unlike that in the solar flare. After the release of the magnetic energy through the magnetic reconnection, the radiative heat flux drives the baryonic evaporation from the crustal surface of the magnetar. The evaporated baryonic mass $M_{\rm ev}$ is given by a simple scaling relation, $M_{\rm ev} \propto T_{\rm flare}^3$ in the range $T_{\rm flare } \lesssim 10^9\ {\rm K}$, where $T_{\rm flare}$ is the flare temperature. Finally, we propose a possible scenario for the flaring activity of the magnetar based on the magnetic reconnection model.
Our scenario predicts that the bayonic matter evaporated in the preflare stage would be the origin of the radio emitting ejecta observed
in association with the giant flare on 2004 December 27 from SGR1806-20.