Partially Ionized Solar Atmosphere: Two-fluid Waves and Their Cutoffs

2019 ◽  
Vol 882 (1) ◽  
pp. 32 ◽  
Author(s):  
D. Wójcik ◽  
K. Murawski ◽  
Z. E. Musielak
Keyword(s):  
Solar Atmosphere ◽  
Partially Ionized ◽  
Two Fluid

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 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.

scholarly journals Collisional and viscous damping of MHD waves in partially ionized plasmas of the solar atmosphere

2004 ◽  
Vol 422 (3) ◽  
pp. 1073-1084 ◽  
Author(s):  
M. L. Khodachenko ◽  
T. D. Arber ◽  
H. O. Rucker ◽  
A. Hanslmeier
Keyword(s):  
Solar Atmosphere ◽  
Mhd Waves ◽  
Viscous Damping ◽  
Ionized Plasmas ◽  
Partially Ionized Plasmas ◽  
Partially Ionized

Alfvén-like mode in partially ionized solar atmosphere

New Astronomy ◽  
2010 ◽  
Vol 15 (1) ◽  
pp. 119-125 ◽  
Author(s):  
K.A.P. Singh ◽  
V. Krishan
Keyword(s):  
Solar Atmosphere ◽  
Partially Ionized

Chromospheric anemone jets and magnetic reconnection in partially ionized solar atmosphere

2011 ◽  
Vol 18 (11) ◽  
pp. 111210 ◽  
Author(s):  
K. A. P. Singh ◽  
K. Shibata ◽  
N. Nishizuka ◽  
H. Isobe
Keyword(s):  
Magnetic Reconnection ◽  
Solar Atmosphere ◽  
Partially Ionized

scholarly journals Nonlinear coupling of Alfvén and slow magnetoacoustic waves in partially ionized solar plasmas

2020 ◽  
Vol 641 ◽  
pp. A48
Author(s):  
J. L. Ballester ◽  
R. Soler ◽  
J. Terradas ◽  
M. Carbonell
Keyword(s):  
Solar Atmosphere ◽  
Alfven Waves ◽  
Ambipolar Diffusion ◽  
Second Order ◽  
Slow Waves ◽  
The Other ◽  
Alfvén Waves ◽  
Temporal Behavior ◽  
Other Hand ◽  
Partially Ionized

Context. Partially ionized plasmas constitute an essential ingredient of the solar atmosphere since layers such as the chromosphere and the photosphere and structures such as prominences and spicules are made of this plasma. On the other hand, ground- and space-based observations have indicated the presence of oscillations in partially ionized layers and structures of the solar atmosphere, which have been interpreted in terms of magnetohydrodynamic (MHD) waves. Aims. Our aim is to study the temporal behavior of nonlinear Alfvén waves, and the subsequent excitation of field-aligned motions and perturbations, in a partially ionized plasma when dissipative mechanisms such as ambipolar diffusion, radiative losses, and thermal conduction are taken into account. Methods. First, we applied the regular perturbations method for small-amplitude initial perturbations to obtain the temporal behavior of perturbations. Then we solved the full set of nonlinear MHD equations for larger values of the initial amplitude. Results. We obtain analytical and numerical solutions to first-, second-, and third-order systems of equations and study the effects produced by ambipolar diffusion and thermal mechanisms on the temporal behavior of Alfvén and slow waves. We also study how the majority of the energy is transferred from the Alfvén waves to plasma internal energy. After numerically solving the full nonlinear equations when a large amplitude is assumed, the profile of the perturbations displays the typical sawtooth profile characteristic of associated shocks. Conclusions. When ambipolar diffusion is taken into account, first-order Alfvén waves are damped in time, while second-order perturbations are undamped. However, due to the release of heat produced by ambipolar diffusion, other physical effects that modify the physical conditions in the spatial domain under consideration appear. On the other hand, the second-order perturbations are damped by thermal effects with a damping time that can be longer or shorter than that of Afvén waves. Therefore, after the initial excitation, Alfvén waves can be quickly damped, while slow waves remain in the plasma for a longer time, and vice versa.

scholarly journals Magnetohydrodynamic waves in solar partially ionized plasmas: two-fluid approach

2011 ◽  
Vol 529 ◽  
pp. A82 ◽  
Author(s):  
T. V. Zaqarashvili ◽  
M. L. Khodachenko ◽  
H. O. Rucker
Keyword(s):  
Magnetohydrodynamic Waves ◽  
Ionized Plasmas ◽  
Partially Ionized Plasmas ◽  
Partially Ionized ◽  
Two Fluid
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