scholarly journals Spatial variation of periods of ion and neutral waves in a solar magnetic arcade.

2021 ◽  
Author(s):  
Błażej Kuźma ◽  
Kris Murawski ◽  
Zdzisław Musielak ◽  
Stefaan Poedts ◽  
Dariusz Wójcik
Keyword(s):  
Magnetic Field ◽  
Solar Atmosphere ◽  
Gravity Waves ◽  
Solar Photosphere ◽  
Acoustic Gravity Waves ◽  
Partially Ionized ◽  
The Impact ◽  
Two Fluid ◽  
Lower Solar Atmosphere ◽  
Magnetic Arcade

<p>We present a new insight into the propagation of ion magnetoacoustic and neutral acoustic waves in a magnetic arcade in the lower solar atmosphere. By means of numerical simulations, we aim to: (a) study two-fluid waves propagating in a magnetic arcade embedded in the partially-ionized, lower solar atmosphere; and (b) investigate the impact of the background magneticfield configuration on the observed wave-periods. We consider a 2D approximation of the gravitationally stratified and partially-ionized lower solar atmosphere consisting of ion + electron and neutral fluids that are coupled by ion-neutral collisions. In this model, the convection below the photosphere is responsible for the excitation of ion magnetoacoustic-gravity and neutral acoustic-gravity waves. We find that in the solar photosphere, where ions and neutrals are strongly coupled by collisions, magnetoacoustic-gravity and acoustic-gravity waves have periods ranging from250s to350s. In the chromosphere, where the collisional coupling is weak, the wave characteristics strongly depend on the magnetic field configuration. Above the foot-points of the considered arcade, the plasma is dominated by vertical magnetic field along which ion slow magnetoacoustic-gravity waves are guided. These waves exhibit a broad range of periods with the most prominent periods of 180 s, 220 s, and 300 s. Above the main loop of the solar arcade, where mostly horizontal magnetic field lines guide ion magnetoacoustic waves, the main spectral power reduces to the period of about 180 s and longer wave-periods do not exist. The obtained results demonstrate unprecedented, never reported before level of agreement with the recently reported observational data of Wisniewska et al. (2016) and Kayshap et al. (2018). We demonstrate that the two-fluid approach is indeed crucial for a description of wave-related processes in the lower solar atmosphere, with energy transport and dissipation being of the highest interest among them.</p>

scholarly journals Photospheric magnetic vortex structures

2011 ◽  
Vol 29 (5) ◽  
pp. 883-887 ◽  
Author(s):  
S. Shelyag ◽  
V. Fedun ◽  
F. P. Keenan ◽  
R. Erdélyi ◽  
M. Mathioudakis
Keyword(s):  
Magnetic Field ◽  
Solar Atmosphere ◽  
Plasma Heating ◽  
Primary Source ◽  
Magnetic Vortex ◽  
Solar Photosphere ◽  
Mhd Simulations ◽  
Different Types ◽  
Vorticity Production ◽  
Lower Solar Atmosphere

Abstract. Using direct numerical magneto-hydrodynamic (MHD) simulations, we demonstrate the evidence of two physically different types of vortex motions in the solar photosphere. Baroclinic motions of plasma in non-magnetic granules are the primary source of vorticity in granular regions of the solar photosphere, however, there is a significantly more efficient mechanism of vorticity production in strongly magnetised intergranular lanes. These swirly motions of plasma in intergranular magnetic field concentrations could be responsible for the generation of different types of MHD wave modes, for example, kink, sausage and torsional Alfvén waves. These waves could transport a relevant amount of energy from the lower solar atmosphere and contribute to coronal plasma heating.

scholarly journals On the influence of magnetic topology on the propagation of internal gravity waves in the solar atmosphere

2020 ◽  
Vol 379 (2190) ◽  
pp. 20200177 ◽  
Author(s):  
G. Vigeesh ◽  
M. Roth ◽  
O. Steiner ◽  
B. Fleck
Keyword(s):  
Magnetic Field ◽  
Flux Density ◽  
Solar Atmosphere ◽  
Gravity Waves ◽  
Internal Gravity Waves ◽  
Magnetic Flux Density ◽  
Horizontal Field ◽  
Crucial Difference ◽  
Propagation Properties ◽  
Lower Solar Atmosphere

The solar surface is a continuous source of internal gravity waves (IGWs). IGWs are believed to supply the bulk of the wave energy for the lower solar atmosphere, but their existence and role for the energy balance of the upper layers is still unclear, largely due to the lack of knowledge about the influence of the Sun’s magnetic fields on their propagation. In this work, we look at naturally excited IGWs in realistic models of the solar atmosphere and study the effect of different magnetic field topographies on their propagation. We carry out radiation-magnetohydrodynamic simulations of a magnetic field free and two magnetic models—one with an initial, homogeneous, vertical field of 100 G magnetic flux density and one with an initial horizontal field of 100 G flux density. The propagation properties of IGWs are studied by examining the phase-difference and coherence spectra in the k h  −  ω diagnostic diagram. We find that IGWs in the upper solar atmosphere show upward propagation in the model with predominantly horizontal field similar to the model without magnetic field. In contrast to that the model with predominantly vertical fields show downward propagation. This crucial difference in the propagation direction is also revealed in the difference in energy transported by waves for heights below 0.8 Mm. Higher up, the propagation properties show a peculiar behaviour, which require further study. Our analysis suggests that IGWs may play a significant role in the heating of the chromospheric layers of the internetwork region where horizontal fields are thought to be prevalent. This article is part of the Theo Murphy meeting issue ‘High-resolution wave dynamics in the lower solar atmosphere’.

scholarly journals Numerical simulations of the lower solar atmosphere heating by two-fluid nonlinear Alfvén waves

2020 ◽  
Vol 639 ◽  
pp. A45
Author(s):  
B. Kuźma ◽  
D. Wójcik ◽  
K. Murawski ◽  
D. Yuan ◽  
S. Poedts
Keyword(s):  
Magnetic Flux ◽  
Numerical Simulations ◽  
Solar Atmosphere ◽  
Flux Tube ◽  
Alfven Waves ◽  
Alfven Wave ◽  
Magnetic Flux Tube ◽  
Alfvén Waves ◽  
Two Fluid ◽  
Lower Solar Atmosphere

Context. We present new insight into the long-standing problem of plasma heating in the lower solar atmosphere in terms of collisional dissipation caused by two-fluid Alfvén waves. Aims. Using numerical simulations, we study Alfvén wave propagation and dissipation in a magnetic flux tube and their heating effect. Methods. We set up 2.5-dimensional numerical simulations with a semi-empirical model of a stratified solar atmosphere and a force-free magnetic field mimicking a magnetic flux tube. We consider a partially ionized plasma consisting of ion + electron and neutral fluids, which are coupled by ion-neutral collisions. Results. We find that Alfvén waves, which are directly generated by a monochromatic driver at the bottom of the photosphere, experience strong damping. Low-amplitude waves do not thermalize sufficient wave energy to heat the solar atmospheric plasma. However, Alfvén waves with amplitudes greater than 0.1 km s−1 drive through ponderomotive force magneto-acoustic waves in higher atmospheric layers. These waves are damped by ion-neutral collisions, and the thermal energy released in this process leads to heating of the upper photosphere and the chromosphere. Conclusions. We infer that, as a result of ion-neutral collisions, the energy carried initially by Alfvén waves is thermalized in the upper photosphere and the chromosphere, and the corresponding heating rate is large enough to compensate radiative and thermal-conduction energy losses therein.

scholarly journals Mode conversion of two-fluid shocks in a partially-ionised, isothermal, stratified atmosphere

2020 ◽  
Vol 637 ◽  
pp. A97
Author(s):  
B. Snow ◽  
A. Hillier
Keyword(s):  
Solar Atmosphere ◽  
Mode Conversion ◽  
Frictional Heating ◽  
Fast Mode ◽  
Compressional Waves ◽  
Pressure Scale ◽  
Velocity Drift ◽  
Two Fluid ◽  
Lower Solar Atmosphere

Context. The plasma of the lower solar atmosphere consists of mostly neutral particles, whereas the upper solar atmosphere is mostly made up of ionised particles and electrons. A shock that propagates upwards in the solar atmosphere therefore undergoes a transition where the dominant fluid is either neutral or ionised. An upwards propagating shock also passes a point where the sound and Alfvén speed are equal. At this point the energy of the acoustic shock can separated into fast and slow components. The way the energy is distributed between the two modes depends on the angle of magnetic field. Aims. We aim to investigate the separation of neutral and ionised species in a gravitationally stratified atmosphere. The role of two-fluid effects on the structure of the shocks post-mode-conversion and the frictional heating is quantified for different levels of collisional coupling. Methods. Two-fluid numerical simulations were performed using the (PIP) code of a wave steepening into a shock in an isothermal, partially-ionised atmosphere. The collisional coefficient was varied to investigate the regimes where the plasma and neutral species are weakly, strongly, and finitely coupled. Results. The propagation speeds of the compressional waves hosted by neutral and ionised species vary and, therefore, velocity drift between the two species is produced as the plasma attempts to propagate faster than the neutrals. This is most extreme for a fast-mode shock. We find that the collisional coefficient drastically impacts the features present in the system, specifically the mode conversion height, type of shocks present, and the finite shock widths created by the two-fluid effects. In the finitely-coupled regime, fast-mode shock widths can exceed the pressure scale height, which may lead to a new potential observable of two-fluid effects in the lower solar atmosphere.

Magnetohydrostatic modelling of the solar atmosphere: Test and application

2020 ◽  
Author(s):  
Xiaoshuai Zhu ◽  
Thomas Wiegelmann
Keyword(s):  
Magnetic Field ◽  
High Resolution ◽  
Magnetic Fields ◽  
Solar Atmosphere ◽  
Solar Photosphere ◽  
Optimization Approach ◽  
Mhd Simulation ◽  
Vector Magnetograms ◽  
Magnetic Forces

<div><span><span lang="en-US">Both magnetic field and plasma play important roles in activities in the solar atmosphere. Unfortunately only the magnetic fields in the photosphere are routinely measured precisely. We aim to extrapolate these photospheric </span></span><span><span lang="en-US">vector magnetograms upwards into  the solar atmosphere. In this work </span><span lang="en-US">we are mainly interested in reconstructing the upper solar photosphere </span><span lang="en-US">and chromosphere. In these layers magnetic and non-magnetic forces are equally important. Consequently we have to compute an equilibrium of plasma </span></span><span><span lang="en-US">and magnetic forces with a magnetohydrostatic model. A optimization approach which minimize a functional defined by the magnetohydrostatic equations is used in the model. In this talk/poster, I will present a strict test of the new code with a radiative MHD simulation and its first application to a high resolution vector magnetogram measured by SUNRISE/IMaX.</span></span></div>

The Extreme Downflow in the Umbral Light Bridge of the sunspot

2014 ◽  
Vol 4 (2) ◽  
pp. 530-534
Author(s):  
Layali Yahya Salih AL-Mashhadani ◽  
Orooba Jameel Tarish
Keyword(s):  
Magnetic Field ◽  
Solar Atmosphere ◽  
Speed Of Sound ◽  
Solar Magnetic Field ◽  
Solar Photosphere ◽  
Horizontal Flows

Sunspots are the most readily visible manifestations of the interaction of the solar magnetic field with the solar atmosphere and the most prominent tracers of solar magnetic activity.Results of the recent studies based on observation from Hinoddetectedthe presence of extremedownflows in a sunspot light bridgeup to 7.2 kms-1 which is exceed the speed of sound in solar photosphere of about 6 kms-1.The convective downflows and upflows are associated with a strong horizontal outflow directed radially outwards from the sunspot centre. These horizontal flows constitute the famous and mysterious Evershed effect.In the present paperwe studied the asymmetries and wavelength shifts of the FeI lines at 630.25 nm to detect the exiting of the extreme downflows in the sunspot light bridge.Our analysis reveals the presence of extreme downflows in the umbra light bridge of the sunspot of more than 10 km s-1.

scholarly journals Identification of linear slow sausage waves in magnetic pores

2007 ◽  
Vol 3 (S247) ◽  
pp. 351-354 ◽  
Author(s):  
I. Dorotovič ◽  
R. Erdélyi ◽  
V. Karlovský
Keyword(s):  
Magnetic Field ◽  
Gravity Waves ◽  
Morphological Changes ◽  
Average Rate ◽  
Linear Trend ◽  
Solar Interior ◽  
Small Scale ◽  
Temporal Area ◽  
Acoustic Gravity Waves ◽  
The Magnetic Field

AbstractThe analysis of an 11-hour series of high resolution white light observations of a large pore in the sunspot group NOAA 7519, observed on 5 June 1993 with the Swedish Vacuum Solar Telescope at La Palma on Canary Islands, has been recently described by Dorotovičet al. (2002). Special attention was paid to the evolution of a filamentary region attached to the pore, to horizontal motions around the pore, and to small-scale morphological changes. One of the results, relevant to out work here, was the determination of temporal area evolution of the studied pore where the area itself showed a linear trend of decrease with time at an average rate of −0.23 Mm2h−1during the entire observing period. Analysing the time series of the are of the pore, there is strong evidence that coupling between the solar interior and magnetic atmosphere can occur at various scales and that the referred decrease of the area may be connected with a decrease of the magnetic field strength according to the magnetic field-to-size relation. Periods of global acoustic, e.g.p-mode, driven waves are usually in the range of 5–10 minutes, and are favourite candidates for the coupling of interior oscillations with atmospheric dynamics. However, by assuming that magneto-acoustic gravity waves may be there too, and may act as drivers, the observed periodicities (frequencies) are expected to be much longer (smaller), falling well within the mMHz domain. In this work we determine typical periods of such range in the area evolution of the pore using wavelet analysis. The resulted periods are in the range of 20–70 minutes, suggesting that periodic elements of the temporal evolution of the area of this studied pore could be linked to, and considered as, observational evidence of linear low-frequency slow sausage (magneto-acoustic gravity) waves in magnetic pores. This would give us further evidence on the coupling of global solar oscillations to the overlaying magnetic atmosphere.

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