  This Letter reports two rarely observed three-ribbon flares (M1.9 and C9.2)
on 2012 July 6 in NOAA AR 11515, which we found with Halpha observations of
0.1" resolution from the New Solar Telescope and CaII H images from Hinode. The
flaring site is characterized with an intriguing "fish-bone-like" morphology
evidenced by both Halpha images and a nonlinear force-free field (NLFFF)
extrapolation, where two semi-parallel rows of low-lying, sheared loops connect
an elongated, parasitic negative field with the sandwiching positive fields.
The NLFFF model also shows that the two rows of loops are asymmetric in height
and have opposite twists, and are enveloped by large-scale field lines
including open fields. The two flares occurred in succession in half an hour
and are located at the two ends of the flaring region. The three ribbons of
each flare run parallel to the PIL, with the outer two lying in the positive
field and the central one in the negative field. Both flares show surge-like
flows in Halpha apparently toward the remote region, while the C9.2 flare is
also accompanied by EUV jets possibly along the open field lines.
Interestingly, the 12-25 keV hard X-ray sources of the C9.2 flare first line up
with the central ribbon then shift to concentrate on the top of the higher
branch of loops. These results are discussed in favor of reconnection along the
coronal null-line producing the three flare ribbons and the associated
ejections.
