  We make a comparative analysis for two filaments that showed quite different
activation in response to the flux emergence within the filament channels. The
observations from the Solar Dynamics Observatory (SDO) and Global Oscillation
Network Group (GONG) are carried out to analyze the two filaments on 2013
August 17-20 and September 29. The first event showed that the main body of the
filament was separated into two parts when an active region (AR) emerged with a
maximum magnetic flux of about 6.4*10^21 Mx underlying the filament. The close
neighborhood and common direction of the bright threads in the filament and the
open AR fan loops suggest similar magnetic connectivity of these two flux
systems. The equilibrium of the filament was not destroyed within 3 days after
the start of the emergence of the AR. To our knowledge, similar observations
have never been reported before. In the second event, the emerging flux
occurred nearby a barb of the filament with a maximum magnetic flux of
4.2*10^20 Mx, about one order of magnitude less than that of the first event.
The emerging flux drove the convergence of two patches of parasitic polarity in
the vicinity of the barb, and resulted in cancellation between the parasitic
polarity and nearby network fields. About 20 hours after the onset of the
emergence, the filament was entirely erupted. Our findings imply that the
location of emerging flux within the filament channel is probably crucial to
filament evolution. If the flux emergence appears nearby the barbs, flux
cancellation of emerging flux with the filament magnetic fields is prone to
occur, which probably causes the filament eruption. The comparison of the two
events shows that the emergence of an entire AR may still not be enough to
disrupt the stability of a filament system and the actual eruption does occur
only after the flux cancellation sets in.
