  Penumbral microjets (PJs) are transient narrow bright features in the
chromosphere of sunspot penumbrae, first characterized by Katsukawa et al
(2007) using the \CaII\ H-line filter on {\it Hinode}'s Solar Optical Telescope
(SOT). It was proposed that the PJs form as a result of reconnection between
two magnetic components of penumbra (spines and interspines), and that they
could contribute to the transition region (TR) and coronal heating above
sunspot penumbrae. We propose a modified picture of formation of PJs based on
recent results on internal structure of sunspot penumbral filaments. Using data
of a sunspot from {\it Hinode}/SOT, High Resolution Coronal Imager, and
different passbands of the Atmospheric Imaging Assembly (AIA) onboard the {\it
Solar Dynamics Observatory}, we examine whether PJs have signatures in the TR
and corona. We find hardly any discernible signature of normal PJs in any AIA
passbands, except a few of them showing up in the 1600 \AA\ images. However, we
discovered exceptionally stronger jets with similar lifetimes but bigger sizes
(up to 600 km wide) occurring repeatedly in a few locations in the penumbra,
where evidence of patches of opposite polarity fields at the tails of some
penumbral filaments is seen in Stokes-V images. These large tail PJs do display
signatures in the TR. Whether they have any coronal-temperature plasma is
ambiguous. We infer that none of the PJs, including the large tail PJs,
directly heat the corona in ARs significantly, but any penumbral jet might
drive some coronal heating indirectly via generation of Alfv\'en waves and/or
braiding of the coronal field.
