  A possibility of time-delayed radio brightenings of Sgr A* triggered by the
pericenter passage of the G2 cloud is studied by carrying out global
three-dimensional magnetohydrodynamic simulations taking into account the
radiative cooling of the tidal debris of the G2 cloud. Magnetic fields in the
accretion flow are strongly perturbed and re-organized after the passage of G2.
We have found that the magnetic energy in the accretion flow increases by a
factor 3-4 in 5-10 years after the pericenter passage of G2 by a dynamo
mechanism driven by the magneto-rotational instability. Since this B-field
amplification enhances the synchrotron emission from the disk and the outflow,
the radio and the infrared luminosity of Sgr A* is expected to increase around
A.D. 2020. The time-delay of the radio brightening enables us to determine the
rotation axis of the preexisting disk.
