Solar spicule rotation driven by plasma curtain-vortex interactions

Abstract

Rotational and transverse motions are frequently observed in solar spicules, yet the physical origin of these motions remains debated. We investigate how apparent spicule rotation arises in a stratified, magnetized solar atmosphere using three-dimensional radiative magnetohydrodynamic (rMHD) simulations. We show that the observed spinning signatures can arise without intrinsic rotation of individual jets. Instead, spicules organize into fluted, curtain-like plasma structures. The evolving emission from these three-dimensional curtains, when projected onto the plane of the sky through line-of-sight integration, produces clustered spicule-like features with lifetimes, heights, and apparent speeds comparable to observed ranges. The synthetic spicules develop strong density gradients at their periphery that generate (i) baroclinic vorticity and also interact with (ii) vortical flows driven by magnetic tension in the surrounding plasma. The associated vortical flows in our simulation are organized as vertically extended rotating plasma columns that reach coronal heights---in some cases, the spicules directly feeding the swirling columns. As a result, recurrent spinning signatures emerge in projected jet clusters, consistent with commonly observed solar limb dynamics, including high-cadence observations from Hinode and IRIS as also shown here for comparison. These results link spicule rotation to jet--vortex coupling and show that rotating spicule clusters may trace vortical plasma structures that transport energy and momentum into the solar corona.