Connections Between the Quiet Corona Magnetic Topology and the Velocity Field of Propagating Disturbances

Abstract

The magnetic field of the low corona above quiet Sun regions is extremely challenging to observe directly, and the topology is difficult to discern from extreme ultraviolet (EUV) image data due to the lack of distinct loops that are present in, for example, active regions. We aim to show that the velocity field of faint propagating disturbances (PD) observed on-disk in the quiet corona can be interpreted in terms of the underlying magnetic topology. The PD are observed in Atmospheric Imaging Assembly/Solar Dynamics Observatory (AIA/SDO) time series in three channels: 304, 171, and 193 Å corresponding to the high chromosphere, transition region/low corona, and the corona, respectively. An established Time-Normalised Optical Flow method enhances the PD and applies a Lucas–Kanade algorithm to gain their velocity field. From the velocity field, we identify the source and sink locations of the PDs, and compare these locations between channels and with the underlying photospheric network. Source regions tend to be located above the photospheric network, and sink regions with the internetwork. Sink regions in the internetwork suggest either that closed field can be concentrated rather than evenly distributed in the internetwork, or that fieldlines opening into the corona can sometimes be concentrated above internetwork regions. We find regions of almost exact alignment between channels, and other regions where similar-shaped structures are offset by a few pixels between channels. These are readily interpreted as vertical or non-vertical alignment of the magnetic field relative to the observer viewing from above. Regions of isolated source regions in the cold (304 Å) or hotter (171 and 193 Å) channels can be interpreted in terms of the magnetic topology, but support for this is weaker. These results offer support for the future use of PD velocity fields as a coronal constraint on magnetic extrapolation models.