In this study, we investigate analytically the generation of mass flux due to a torsional Alfvén pulse. We derive that the presence of torsional Alfvén waves, which have been observed in, e.g., photospheric magnetic bright points (MBPs), can result in vertical plasma motions. The formation of this mass flux may even be a viable contribution to the generation of chromospheric mass transport, playing potential roles in the form of localized lower solar atmospheric jets. This relationship is studied using a flux tube model, with the waves introduced at the lower boundary of the tube as a magnetic shear perturbation. Due to the nature of MBPs we simplify the model by using the zero-beta approximation for the plasma inside the tube. The analytical results are demonstrated by an example of the type of Alfvén wave perturbation that one might expect to observe, and comparison is made with properties of spicules known from observations. We find that field-aligned plasma flux is formed nonlinearly as a result of the Lorentz force generated by the perturbations, and could be consistent with jet formation, although the current model is not intended to determine the entire evolution of a jet. Critical discussion of the model follows, including suggestions for improvements and for high-resolution proposed observations in order to constrain the driving magnetic and velocity shear.

We model the behavior of a torsional Alfvén pulse, assumed to propagate through the chromosphere. Building on our existing model, we utilize the zero-beta approximation appropriate for plasma in an intense magnetic flux tube, e.g., a magnetic bright point. The model is adapted to investigate the connection between these features and chromospheric spicules. A pulse is introduced at the lower, photospheric boundary of the tube as a magnetic shear perturbation, and the resulting propagating Alfvén waves are reflected from an upper boundary, representing the change in density found at the transition region. The induced upward mass flux is followed by the reversal of the flux that may be identified with the rising and falling behavior of certain lower solar atmospheric jets. The ratio of the transmitted and reflected mass flux is estimated and compared with the relative total mass of spicules and the solar wind. An example is used to study the properties of the pulse. We also find that the interaction between the initial and reflected waves may create a localized flow that persists independently from the pulse itself.

We aim to provide insight into chromospheric spicules by suggesting a new formation mechanism. A magnetic field boundary condition is imposed, generating an Alfvén wave that shears a magnetic slab and propagates up the slab. The resulting Lorentz force accelerates material vertically, potentially nonlinearly driving a jet-like feature. This formation mechanism is applied to take place in a magnetic bright point embedded in the photosphere, providing motivation to use the simplifying assumption of a zero-β plasma. After deriving an analytical expression describing the vertical mass flux that constitutes the spicular jet, further understanding is gained by examining a model example of a magnetic field boundary condition in terms of standard functions. By visualizing the vertical mass flux through 3D plots, we demonstrate that the jet properties capture the observed properties of chromospheric spicules during their formation. This vindicates the model and simplifying assumptions used. Although we do not provide insight into the full evolution of a spicule, we show that the role of Alfvén waves triggered by shear in fact could be a viable formation mechanism for at least some chromospheric spicules. Consequently, we provide a starting point for further studies of this formation mechanism, which will lead to a greater understanding of the vast variety of chromospheric jets.

Spicule activity in the chromosphere is modeled via the perturbation resulting from the propagation of an Alfvén wave pulse in a magnetic flux tube. Building on previous work, the model is augmented by the inclusion of a finite transitional layer in which the atmospheric density decreases exponentially. This additional complexity of the density stratification provides a more physical representation of the solar atmosphere and improves on the existing model. The wave pulse is introduced at the lower boundary of the flux tube and interacts with the transitional layer, also being partially reflected. The total mass flux induced by the pulse, and the proportion of this pulse that is transmitted through the layer, is calculated and examined in the context of spicules and the solar wind using an example solution. We find that the inclusion of the transitional layer results in more plasma flux being transferred into the upper solar atmosphere when compared with the case of a discontinuity. We examine how varying the parameters of this transitional layer affects the ratio of the flux above and below the layer.