Anomalous cross-field motions of solar coronal loops

¹ Max Planck Institute for Solar System Research, Justus-von-Liebig-Weg 3, 37077 Göttingen, Germany
² Institut für Sonnenphysik (KIS), Georges-Köhler-Allee 401a, 79110 Freiburg, Germany
³ NASA Goddard Space Flight Center, Greenbelt, Maryland, USA

^⋆ Corresponding author: smandal.solar@gmail.com

Received: 28 January 2025
Accepted: 2 April 2025

Abstract

We present several examples of unusual evolutionary patterns in solar coronal loops that resemble cross-field drift motions. These loops were simultaneously observed from two vantage points by two different spacecraft: the High-Resolution Imager of the Extreme Ultraviolet Imager aboard the Solar Orbiter and the Atmospheric Imaging Assembly aboard the Solar Dynamics Observatory. Across all these events, a recurring pattern is observed: Initially, a thin, strand-like structure detaches and shifts several megameters away from a main or parent loop. During this period, the parent loop remains intact in its original position. After a few minutes, the shifted strand reverses its direction and returns to the location of the parent loop. Key features of this “split-drift” type evolution are: (i) the presence of kink oscillations in the loops before and after the split events and (ii) a sudden split motion at about 30 km s⁻¹, with additional slow drifts, either away from or back to the parent loops, at around 5 km s⁻¹. Co-temporal photospheric magnetic field data obtained from the Helioseismic and Magnetic Imager reveal that during such split-drift evolution, one of the loop points in the photosphere moves back and forth between nearby magnetic polarities. While the exact cause of this split drift phenomenon is still unclear, the consistent patterns observed in its characteristics indicate that there may be a broader physical mechanism at play. This underscores the need for further investigation through both observational studies and numerical simulations.