  Using the observations from the Atmospheric Imaging Assembly (AIA) and
Helioseismic and Magnetic Imager (HMI) aboard the Solar Dynamics Observatory
(SDO), we investigate six X-class and twenty-nine M-class flares occurring in
solar active region (AR) 12192 from October 18 to 29. Among them, thirty
(including six X- and twenty-four M-class) flares originated from the AR core
and the other five M-flares appeared at the AR periphery. Four of the X-flares
exhibited similar flaring structures, indicating they were homologous flares
with analogous triggering mechanism. The possible scenario is: photospheric
motions of emerged magnetic fluxes lead to shearing of the associated coronal
magnetic field, which then yields a tether-cutting favorable configuration.
Among the five periphery M-flares, four were associated with jet activities.
The HMI vertical magnetic field data show that the photospheric fluxes of
opposite magnetic polarities emerged, converged and canceled with each other at
the footpoints of the jets before the flares. Only one M-flare from the AR
periphery was followed by a coronal mass ejection (CME). From October 20 to 26,
the mean decay index of the horizontal background field within the height range
of 40-105 Mm is below the typical threshold for torus instability onset. This
suggests that a strong confinement from the overlying magnetic field might be
responsible for the poor CME production of AR 12192.
