Energetics of magnetic transients in a solar active region plage
Densely packed coronal loops are rooted in plages in the vicinity of active regions on the Sun. The photospheric magnetic features underlying these plages are patches of mostly unidirectional magnetic field extending several arcsec on the solar surface. We aim to explore the transient nature of the magnetic field, its mixed-polarity characteristics, and the associated energetics in plages using high resolution observations and simulations. We used photospheric Fe I 6173 {\AA} spectropolarimetric observations of a decaying active region obtained from the SST. These data were inverted to retrieve the photospheric magnetic field underlying the plage as identified in the EUV emission maps obtained from the SDO/AIA. To obtain better insight into the evolution of plages, we performed 3D radiation magnetohydrodynamic simulations of magnetoconvection using the MURaM code. The observations show transient magnetic flux emergence and cancellation events within the plage on timescales of a few 100 s and on spatial scales comparable to granules. These transient events occur at the footpoints of active region plage loops. In one case the coronal response at the footpoints of these loops is clearly associated with the underlying transient. The simulations also reveal similar magnetic flux emergence and cancellation events that extend to even smaller spatial and temporal scales. Individual simulated transient events transfer an energy flux in excess of 1 MW m$^{-2}$ through the photosphere. We suggest that the magnetic transients could play an important role in the energetics of active region plage. Both in observations and simulations, the opposite-polarity magnetic field brought up by transient flux emergence cancels with the surrounding plage field. Magnetic reconnection associated with such transient events likely conduits magnetic energy to power the overlying chromosphere and coronal loops.