  We analyse the multiwavelength observations of an M2.9/1N flare that occurred
in the active region (AR) NOAA 11112 in the vicinity of a huge filament system
on 16 October 2010. SDO/HMI magnetograms reveal the emergence of a bipole
(within the existing AR) 50 hours prior to the flare event. During the
emergence, both the positive and negative sunspots in the bipole show
translational as well as rotational motion. The positive polarity sunspot shows
the significant motion/rotation in the south-westward/clockwise direction and
continuously pushing/sliding the surrounding opposite polarity field region. On
the other hand, the negative polarity sunspot moves/rotates in the
westward/anticlockwise direction. The positive polarity sunspot rotates ~70
deg. within 30 hours, whereas negative polarity ~20 deg. within 10 hours.
SDO/AIA 94 {\AA} EUV images show the emergence of a flux tube in the corona
consistent with the emergence of the bipole in HMI. A high speed plasmoid
ejection (speed~1197 km/s) was observed during the flare impulsive phase, which
suggests the magnetic reconnection of the emerged positive polarity sunspot
with the surrounding opposite polarity field region. The entire AR shows the
positive helicity injection before the flare event. Moreover, the newly
emerging bipole reveal the signature of negative (left-handed) helicity. These
observations provide the unique evidences of the emergence of twisted flux tube
from below the photosphere to coronal heights triggering a flare mainly due to
the interaction between the emerged positive polarity sunspot and a nearby
negative polarity sunspot by the shearing motion of the emerging positive
sunspot towards the negative one. Our observations also strongly support the
idea that the rotation is most likely attributed to the emergence of twisted
magnetic fields, as proposed by recent models.
