Light walls around sunspots observed by the Interface Region Imaging Spectrograph

Context. The Interface Region Imaging Spectrograph (IRIS) mission provides high-resolution observations of the chromosphere and transition region. Using these data, some authors have reported the new finding of light walls above sunspot light bridges. Aims. We try to determine whether the light walls exist somewhere else in active regions in addition to the light bridges. We also examine how the material of these walls evolves. Methods. Employing six months of (from 2014 December to 2015 June) high tempo-spatial data from the IRIS, we find many light walls either around sunspots or above light bridges. Results. For the first time, we report one light wall near an umbral-penumbral boundary and another along a neutral line between two small sunspots. The former light wall has a multilayer structure and is associated with the emergence of positive magnetic flux in the ambient negative field. The latter light wall is associated with a filament activation, and the wall body consists of the filament material, which flowed to a remote plage region with a negative magnetic field after the light wall disappeared. Conclusions. These new observations reveal that these light walls are multilayer and multithermal structures that occur along magnetic neutral lines in active regions.