Rotation of a Solar Jet Driven by Plasma Flow along Helical Magnetic Fields in an Active Region

Abstract: Solar jets, collimated plasma ejections driven by magnetic reconnection, play a vital role in energy transport and coronal heating. While rotational motions in jets are often attributed to magnetic field untwisting, alternative explanatory mechanisms remain possible. This study investigates a rotating jet in an active region observed on 2023 August 1 using multi-wavelength observations from Atmospheric Imaging Assembly (AIA), Chinese Ha Solar Explorer (CHASE), and Interface Region Imaging Spectrograph (IRIS), combined with a self-consistent time-dependent magnetofrictional (TMF) model and magnetohydrodynamic (MHD) simulation. Spectral diagnostics reveal coexisting red and blue shifts along the edges and central axis of the jet, indicating helical plasma motion within a twisted magnetic structure. Numerical simulations demonstrate that the jet's rotation arises from plasma propagating along helical open field lines, formed via reconnection between a pre-existing flux rope and overlying magnetic fields. Contrary to classical untwisting models, both linear and rotational velocities decrease with altitude during the jet propagation. These results highlight that the observed rotation results from plasma spiral motion along twisted fields rather than untwisting dynamics of the magnetic field itself, providing new insights into solar jet energetics and their connection to broader solar phenomena.