  High-resolution near infrared observations with GRAVITY instrument have
revealed rapid orbital motions of a hot spot around Sgr A*, the supermassive
black hole in our Galactic center, during its three bright flares. The
projected distances of the spot to the black hole are measured and seems to
increase with time. The values of distance, combined with the measured orbiting
time, imply that the spot is rotating with a super-Keplerian velocity. These
results are hard to understand if the spot stay within the accretion flow thus
provide strong constraints on theoretical models for flares. Previously we have
proposed a "ME" model for the flares by analogy with the coronal mass ejection
model in solar physics. In that model, magnetic reconnection occurred at the
surface of the accretion flow results in the formation of flux ropes, which are
then ejected out. Energetic electrons accelerated in the current sheet flow
into the flux rope region and their radiation is responsible for the flares. In
this paper, we apply the model to the interpretation of the GRAVITY results by
calculating the dynamics of the ejected flux rope, the evolution of the
magnetic field and the energy distribution of accelerated electrons, and the
radiation of the system. We find that the model can well explain the observed
light curve of the flares, the time-dependent distance and the super-Keplerian
motion of the hot spot. It also explains why the light curve of some flares
have double peaks.

High Energy Astrophysical Phenomena