  We investigate the horizon structure and ergosphere in a rotating Bardeen
regular black hole, which has an additional parameter ($g$) due to magnetic
charge, apart from mass ($M$) and rotation parameter ($a$). Interestingly, for
each value of parameter $g$, there exist a critical rotation parameter
($a=a_{E}$), which corresponds to an extremal black hole with degenerate
horizons, while for $a<a_{E}$ describes a non-extremal black hole with two
horizons, and no black hole for $a>a_{E}$. We find that the extremal value
$a_E$ is also influenced by the parameter $g$ and so is the ergosphere. While
the value of $a_E$ remarkably decreases when compared with the Kerr black hole,
the ergosphere becomes more thick with increase in $g$. We also study collision
of two equal mass particle near the horizon of this black hole, and explicitly
bring out the effect of parameter $g$. The center-of-mass energy ($E_{CM}$) not
only depends on rotation parameter $a$, but also on parameter $g$. It is
demonstrated that the $E_{CM}$ could be arbitrary high in the extremal cases
when one of the colliding particle has critical angular momentum, thereby
suggesting that the rotating Bardeen regular black hole can act as a particle
accelerator.
