  We study the role of rotating sunspots in relation to the evolution of
various physical parameters characterizing the non-potentiality of the active
region NOAA 11158 and its eruptive events using the magnetic field data from
the Helioseismic and Magnetic Imager (HMI) and multi-wavelength observations
from the Atmospheric Imaging Assembly (AIA) on board Solar Dynamics Observatory
(SDO). From the evolutionary study of HMI intensity and AIA channels, it is
observed that the AR consists of two major rotating sunspots one connected to
flare-prone region and another with CME. The constructed space-time intensity
maps reveal that the sunspots exhibited peak rotation rates coinciding with the
occurrence of the major eruptive events. Further, temporal profiles of twist
parameters, viz., average shear angle, $\alpha_{\rm av}$, $\alpha_{\rm best}$,
derived from HMI vector magnetograms and the rate of helicity injection,
obtained from the horizontal flux motions of HMI line-of-sight magnetograms,
corresponded well with the rotational profile of the sunspot in CME-prone
region, giving predominant evidence of rotational motion to cause magnetic
non-potentiality. Moreover, mean value of free-energy from the Virial theorem
calculated at the photospheric level shows clear step down decrease at the on
set time of the flares revealing unambiguous evidence of energy release,
intermittently that is stored by flux emergence and/or motions in pre-flare
phases. Additionally, distribution of helicity injection is homogeneous in CME
prone region while it is not and often changes sign in flare-prone region. This
study provides clear picture that both proper and rotational motions of the
observed fluxes played significant role to enhance the magnetic
non-potentiality of the AR, leading to favorable conditions for the observed
transient activity.
