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An investigation of helicity injection by photospheric shear motions iscarried out for two active regions(ARs), NOAA 11158 and 11166, usingline-of-sight magnetic field observations obtained from the Helioseismic andMagnetic Imager on-board Solar Dynamics Observatory. We derived the horizontalvelocities in the active regions from the Differential Affine VelocityEstimator(DAVE) technique. Persistent strong shear motions at the maximumvelocities in the range of 0.6--0.9km/s along the magnetic polarity inversionline and outward flows from the peripheral regions of the sunspots wereobserved in the two active regions. The helicities injected in NOAA 11158 and11166 during their six days' evolution period were estimated as$14.16\times10^{42}$Mx$^2$ and $9.5\times10^{42}$Mx$^2$, respectively. Theestimated injection rates decreased up to 13% by increasing the time intervalbetween the magnetograms from 12 min to 36 min, and increased up to 9% bydecreasing the DAVE window size from $21\times18$ to $9\times6$ pixel$^2$,resulting in 10% variation in the accumulated helicity. In both ARs, the flareprone regions (R2) had inhomogeneous helicity flux distribution with mixedhelicities of both signs and that of CME prone regions had almost homogeneousdistribution of helicity flux dominated by single sign. The temporal profilesof helicity injection showed impulsive variations during some flares/CMEs dueto negative helicity injection into the dominant region of positive helicityflux. A quantitative analysis reveals a marginally significant association ofhelicity flux with CMEs but not flares in AR 11158, while for the AR 11166, wefound marginally significant association of helicity flux with flares but notCMEs, providing evidences of the role of helicity injection at localized sitesof the events.

On the injection of helicity by shearing motion of fluxes in relation to Flares and CMEs