  Sgr~A* often shows bright, episodic flares observationally, the mechanism of
the flares intermittent brightening is not very clear. Many people believe the
flares may formed by the non-thermal particles, which can be a consequence of
the magnetic reconnection and shock waves. In this work, we use the larger
magnetic loop in the presence of pseudo-Newtonian potential which mimics
general relativistic effects. The simulation results show that the reconnection
of magnetic field lines passes through a current sheet, which bifurcates into
two pairs of slow shocks. We also find the shock waves heat the plasma,
especially when the plasma density is low. The shock wave heating effect by the
magnetic reconnection is confirmed by the simulation results, and thus the
process of instantaneous brightening of the flares on the accretion disk can be
explained.
