Modelling the connection between propagating disturbances and solar spicules

Aims. Propagating (intensity) disturbances (PDs) have been extensively reported in observations of coronal loops and polar plumes, along with more recent links to co-temporal spicule activity in the solar atmosphere. However, despite their appearance in observations, PDs have yet to be studied or modelled in depth.

Methods. In this work, we present results from a three-dimensional magnetohydrodynamic (3D MHD) numerical model. It features a stratified solar atmosphere perturbed by a p-mode wave driver at the photosphere, subsequently forming spicules described by the rebound shock model.

Results. We find the features of the detected PDs to be consistent with the co-temporal transition region dynamics and spicular activity resulting from non-linear wave steepening and shock formation. Furthermore, the PDs could be interpreted as slow magnetoacoustic pulses propagating along the magnetic field, rather than high-speed plasma upflows carrying sufficient energy flux to (at least partially) heat the lower coronal plasma. Using forward modelling, we demonstrate the similarities between the PDs in the simulations and those reported from observations with IRIS and SDO/AIA.

Conclusions. Our results suggest that in the model presented here, the dynamical movement of the transition region is a result of wave dynamics and shock formation in the lower solar atmosphere. We find that PDs are launched co-temporally with the rising of the transition region, regardless of the wave-generating physical mechanisms occurring in the underlying lower solar atmosphere. However, it is clear that signatures of PDs appear much clearer when a photospheric wave driver is included. Finally, we present the importance of PDs in the context of providing a source for powering the (fast) solar wind.