Transition Region Response of Moving Magnetic Features: Hinode and IRIS observations

Small unipolar and/or bipolar concentrations of magnetic field surrounding sunspots in an otherwise field-free photosphere are known as “Moving Magnetic Features” (MMFs). Most MMFs are $<$ 2\arcsec\ in size and last for 10 minutes to 10 hours. They move laterally outward (with a speed of $<$ 2 \kms) across the sunspot's ``moat" until they reach the network field, and carry a significant amount of magnetic flux -- thus, MMFs are proposed to be responsible for sunspot decay. Although many researchers have explored the photospheric properties of MMFs, only a few have studied how the chromosphere and transition region respond to the evolution of MMFs. We compare SJ images (\MgII, \SiIV, and \CII) from the Interface Region Imaging Spectrograph (IRIS), and line-of-sight (LOS) magnetograms, inferred from a Milne-Eddington inversion of the spectral data obtained by Spectropolarimeter (SP) on the Hinode spacecraft, to study the structure and dynamics of MMFs in the photosphere and their response to the transition region. Each MMF, either unipolar or bipolar, identified in SP LOS magnetograms, shows enhanced dynamic brightenings in IRIS SJ images. These brightenings accompany multiple jet-like events, particularly when the underlying MMF is bipolar and an obvious magnetic flux cancellation is going on. We also use IRIS \MgII, \SiIV, and \CII\ spectra to characterize these brightenings/jets in the transition region. A majority of the MMFs show redshifted IRIS spectra but some that most clearly correspond to flux cancellation sites show both blueshift and redshift. A detailed investigation is underway.