Numerical simulations of spicule formation in the solar atmosphere

Abstract

Context. 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. Aims. We aim to explore the spicule formation scenario in the framework of the rebound shock model. Methods. We solve two-dimensional time-dependent magnetohydrodynamic equations numerically to find spatial and temporal dynamics of spicules.Results. 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 rising and falling off plasma portions resembles the time sequence of single and double (sometimes even triple) spicules, which is consistent with observational findings. Conclusions. 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.

Numerical simulations of solar macrospicules

“…Our more general model reveals that macrospicules are effectively excited by velocity pulses launched at the chromosphere. Additionally, our model confirms the findings of Murawski & Zaqarashvili (2010) who explained the observed properties of spicules (e.g., width, height, and bi-directional flows). We also present an observational case study using SDO/AIA 304 Å of a macrospicule in the north polar region, which approximately matches the simulated macrospicule in the oblique magnetic field.…”

“…However, these simulations could not mimic the double structures and bi-directional flows in spicules. On the other hand, Murawski & Zaqarashvili (2010) performed 2D numerical simulations of magnetohydrodynamic (MHD) equations and showed that the 2D rebound shock model (Hollweg 1982) may explain both the double structures and bidirectional flows. They used a single initial velocity pulse, which leads to the formation of consecutive shocks due to nonlinear wake in the stratified atmosphere.…”

Numerical simulations of magnetoacoustic oscillations in a gravitationally stratified solar corona

“…Bel & Leroy (1977) suggested that the cut-off frequency of the magnetic field-free atmosphere is lower when waves propagate with the angle to the vertical. McIntosh (2006) found the observational justification of the modification of the cut-off frequency along an inclined magnetic field (see Murawski & Zaqarashvili 2010 for recent numerical simulations of spicules). De Pontieu et al (2004) proposed that as a result of a fall-off in Movies attached to Figs.…”

“…De Pontieu et al (2004) argued that the observed quasi 5-min period in spicule appearance is associated with the periodicity of p-modes. Zaqarashvili et al (2010) proposed that 5-min oscillations in the solar corona originate in granules that they modeled by a vertical propagating wavefront in the vertical velocity component. However, Zaqarashvili et al (2010) considered a simple one-dimensional (1D) problem of 5-min oscillations.…”

“…Zaqarashvili et al (2010) proposed that 5-min oscillations in the solar corona originate in granules that they modeled by a vertical propagating wavefront in the vertical velocity component. However, Zaqarashvili et al (2010) considered a simple one-dimensional (1D) problem of 5-min oscillations. The 1D case treats the acoustic waves only while the internal gravity waves are removed from the system.…”