We study the propagation of acoustic-gravity waves in the solar atmosphere. The waves are
excited by a space- and time-dependent random driver, whose action mimics turbulence in the
upper part of the solar convection zone. Our main goal is to find vertical variations of wave
periods of these waves and compare the obtained results to the recent observations of Wiśniewska
et al. (2016). We solve numerically the hydrodynamic equations in the solar atmosphere whose
temperature is given by the semi-empirical model of Avrett & Loeser (2008). The obtained
numerical results show that wave periods vary along vertical direction in agreement with the
recent observational data. We discuss physical consequences of our theoretical results.
Authors: K. Murawski, Z. Musielak
Publication Status: accepted
Last Modified: 2016-09-17 07:04
Entropy mode at a magnetic null point as a possible tool for indirect observation of nanoflares in the solar corona
Aims. We aim to explore analytically and numerically small-amplitude Alfvén waves in the solar atmosphere.
Methods. We transform the wave equations to obtain the cutoff frequency and wave travel time for strictly linear
Alfvén waves. The wave equations are solved numerically to find out spatial and temporal signatures of the
Results. The analytical predictions are verified by solving the wave equations for linear Alfvén waves numerically.
The waves are impulsively generated and their characteristics and behavior in the solar atmosphere are
investigated by the numerical simulations. The derived cutoff frequency is used to determine regions in the solar
atmosphere where strong reflection occurs for Alfvén waves of different frequencies.
Conclusions. The numerical results reveal that impulsively generated small-amplitude waves exhibit characteristic
spatial and temporal signatures which agree with the predictions of the analytical theory.
Authors: K. Murawski, Z. E. Musielak
Publication Status: submitted
Last Modified: 2010-05-11 07:11
Numerical simulations of spicule formation in the solar atmosphere
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 rebound shock model.
Methods. We solve two-dimensional time-dependent magnetohydrodynamic equations numerically to find out
spatial and temporal dynamics of spicules.
Results. The numerical simulations show that the strong initial pulse may lead to the quasi periodic raising 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.
Conclusions. The two-dimensional rebound shock model may explain the observed speed, width and heights of
type I spicules as well as observed multi-structure and bi-directional flows. The model also predicts the appearance
of spicules with 3 - 5 min period due to the consecutive shocks.
Authors: K. Murawski, T.V. Zaqarashvili
Publication Status: submitted
Last Modified: 2010-05-02 13:50