The Relation between Solar Spicules and Magnetohydrodynamic Shocks

TL;DR

This study uses 2D radiative MHD simulations to investigate how magnetohydrodynamic shocks influence the formation, acceleration, and height of solar spicules, revealing their role as drivers and linking them to coronal disturbances.

Contribution

It provides the first direct identification of slow MHD shocks as key drivers of spicule dynamics in a realistic solar atmosphere simulation.

Findings

Slow MHD shocks are regions of strong plasma acceleration at spicule tips.

Shock strength influences the maximum height of spicules.

Simulated propagating coronal disturbances are linked to shock-driven spicules.

Abstract

Spicules are thin, elongated jet-like features seen in observations of the solar atmosphere, at the interface between the solar photosphere and the corona. These features exhibit highly complex dynamics and are a necessary connecting link between the cooler, denser solar chromosphere and the extremely hot, tenuous corona. In this work, we explore the spatial and temporal relation between solar spicules and magneto-hydrodynamic (MHD) shocks using data from a 2D radiative MHD (rMHD) simulation of the solar atmosphere driven by solar convection. Here, we demonstrate, through direct identification, that slow MHD shocks, which propagate along magnetic field lines, are regions of strong positive vertical acceleration of the plasma that forms the tip of the spicule material during its rise phase. We quantify the effect of pressure and Lorentz forces on the acceleration of the plasma inside the shocks during the rise of spicules. The causality between spicule and shock propagation in the atmosphere of the model is also investigated. It is further shown that the strength of these shocks may play a vital role in determining the height of the spicules, supporting the idea that shocks act as drivers of some spicules. In addition, we also find the presence of structures similar to propagating coronal disturbances (PCDs) in the simulation, linked with the spicules. Here, PCDs appear to be associated with the shock waves driving the spicules that subsequently propagate into the corona and have similar speeds to those reported in observations.