  The solar active region (AR) 12192 was one of the most flare productive
region of solar cycle 24, which produced many X-class flares; the most
energetic being an X3.1 flare on October 24, 2014 at 21:10 UT. Customarily,
such events are believed to be triggered by magnetic reconnection in coronal
magnetic fields. Here we use the vector magnetograms from solar photosphere,
obtained from Heliospheric Magnetic Imager (HMI) to investigate the magnetic
field topology prior to the X3.1 event, and ascertain the conditions that might
have caused the flare. To infer the coronal magnetic field, a novel
non-force-free field (NFFF) extrapolation technique of the photospheric field
is used, which suitably mimics the Lorentz forces present in the photospheric
plasma. We also highlight the presence of magnetic null points and
quasi-separatrix layers (QSLs) in the magnetic field topology, which are
preferred sites for magnetic reconnections and discuss the probable
reconnection scenarios.
