Numerical simulations of spicule formation in the solar atmosphere

TL;DR

This paper uses 2D magnetohydrodynamic simulations to model how localized velocity pulses can generate spicules in the solar atmosphere, reproducing observed features and periodicities.

Contribution

It introduces a 2D rebound shock model that explains spicule formation, dynamics, and periodicity consistent with observations.

Findings

Simulations reproduce observed spicule speeds, heights, and widths.

The model predicts spicule periodicity of 3-5 minutes due to shocks.

The superposition of plasma motions explains single and multiple spicule structures.

Abstract

We study the upward propagation of a localized velocity pulse that is initially launched below the transition region within the solar atmosphere. The pulse quickly steepens into a shock, which may lead to the formation of spicules. We solve two-dimensional time-dependent magnetohydrodynamic equations numerically to find spatial and temporal dynamics of spicules. The numerical simulations show that the strong initial pulse may lead to the quasi periodic rising of chromospheric material into the lower corona in the form of spicules. The periodicity results from the nonlinear wake that is formed behind the pulse in the stratified atmosphere. The superposition of raising and falling off plasma portions resembles the time sequence of single and double (sometimes even triple) spicules, which is consistent with observational findings. The two-dimensional rebound shock model may explain the observed speed, width, and heights of type I spicules, as well as observed multi-structural and bi-directional flows. The model also predicts the appearance of spicules with 3-5 min period due to the consecutive shocks.