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 Cut-off wavenumber of Alfvén waves in partially ionized plasmas of the solar atmosphere

2012 ◽  
Vol 544 ◽  
pp. A143 ◽  
Author(s):  
T. V. Zaqarashvili ◽  
M. Carbonell ◽  
J. L. Ballester ◽  
M. L. Khodachenko
Keyword(s):  
Solar Atmosphere ◽  
Alfven Waves ◽  
Alfvén Waves ◽  
Ionized Plasmas ◽  
Partially Ionized Plasmas ◽  
Partially Ionized

Estimation of the Energy Flux of Torsional Alfvén Waves in the Lower Solar Atmosphere Based on Measurements of the Doppler Velocities

2021 ◽  
Vol 61 (7) ◽  
pp. 1035-1037
Author(s):  
Yu. T. Tsap ◽  
A. V. Stepanov ◽  
Yu. G. Kopylova ◽  
O. V. Khaneychuk ◽  
T. B. Goldvarg
Keyword(s):  
Solar Atmosphere ◽  
Energy Flux ◽  
Alfven Waves ◽  
Alfvén Waves ◽  
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 Die konstruksie en evaluering van 'n werks tevredenheidvraelys vir predikante

1993 ◽  
Vol 19 (1) ◽  
Author(s):  
S. M. Van Vuuren ◽  
M. Schepers
Keyword(s):  
Job Satisfaction ◽  
Second Order ◽  
The Other ◽  
Self Concept ◽  
Factor Analyses ◽  
Multidimensional Construct ◽  
Other Hand ◽  
Order Factor ◽  
The One ◽  
Mate Waarin

The construction and evaluation of a job satisfaction inventory for ministers. Job satisfaction is a multidimensional construct indicating the degree of adjustment of a worker to his work. A questionnaire was constructed for measuring the various aspects of job satisfaction of ministers. It was administered to 307 ministers. First and second order factor analyses were performed on the items of the questionnaire. Three strong factors of the job satisfaction of ministers were identified, viz. satisfaction with the work as such, the minister's experience of the relationships between him and his wife on the one hand, and his church council and congregation on the other hand, and his vocational self concept. The implications of these findings are discussed. Opsomming Werkstevredenheid is 'n meerdimensionele konstruk wat 'n aanduiding gee van die mate waarin 'n werker in sy werk aanpas. 'n Vraelys om verskeie aspekte van die werkstevredenheid van predikante te meet, is gekonstrueer. Dit is op 'n steekproef van 307 predikante toegepas. Eerste- en tweedeorde-faktorontledings is op die items van die vraelys uitgevoer. Drie sterk faktore van die werkstevredenheid van predikante is geidentifiseer, te wete die belewing van sy werk as sodanig, die belewing van die verhouding tussen horn en sy vrou aan die een kant, en die kerkraad en gemeente aan die ander kant, en sy beroepselfkonsep. Die implikasies van die bevindinge word bespreek.

scholarly journals A Survey of Conceptualizations of Politeness

2015 ◽  
Vol 5 (6) ◽  
pp. 115
Author(s):  
Lei Qiu
Keyword(s):  
Second Order ◽  
The Other ◽  
Theoretical Construct ◽  
First Order ◽  
Relational Work ◽  
Other Hand ◽  
Uniform Definition

<p>Along with the general trends of research from traditional Gricean approach to postmodern approach, politeness has been conceptualized as facework, social indexing concept, relational work and interactional work. Based on examination of debates over East group-oriented and Western individual-oriented politeness, first-order and second-order politeness, as well as the universality and relativity of conceptualizations, this paper has roughly demonstrated that the tension between universality and relativity of politeness can help to explain the reason for lack of uniform definition and concept in this field. It is essential for researchers to seek a universal second-order culture-general theoretical construct on one hand, and to look at first-order culture-specific constructs on the other hand.</p>

Are There Alfven Waves in the Solar Atmosphere?

Science ◽  
2007 ◽  
Vol 318 (5856) ◽  
pp. 1572-1574 ◽  
Author(s):  
R. Erdelyi ◽  
V. Fedun
Keyword(s):  
Solar Atmosphere ◽  
Alfven Waves ◽  
Alfvén Waves

On the effects of viscosity and anisotropic resistivity on the damping of Alfvén waves

2000 ◽  
Vol 63 (3) ◽  
pp. 221-238 ◽  
Author(s):  
L. M. B. C. CAMPOS ◽  
P. M. V. M. MENDES
Keyword(s):  
Wave Equation ◽  
Fourth Order ◽  
Magnetic Energy ◽  
Propagation Speed ◽  
Alfven Waves ◽  
Second Order ◽  
Alfven Wave ◽  
Alfvén Waves ◽  
Total Energy Density ◽  
Polarized Waves

The equations of magnetohydrodynamics (MHD) are written for non-uniform viscosity and resistivity – the latter in the cases of Ohmic and anisotropic resistivity. In the case of Ohmic (anisotropic) diffusivity, there is (are) one (two) transverse components of the velocity and magnetic field perturbation(s), leading to a second-order (fourth-order) dissipative Alfvén- wave equation. In the more general case of dissipative Alfvén waves with isotropic viscosity and anisotropic resistivity, the fourth-order wave equation may be replaced by two decoupled second-order equations for right- and left-polarized waves, whose dispersion relations show that the first resistive diffusivity causes dissipation like the viscosity, whereas the second resistive diffusivity causes a change in propagation speed. The second resistive diffusivity invalidates the equipartition of kinetic and magnetic energy, modifies the energy flux through the propagation speed, and also changes the ratio of viscous to resistive dissipation. If the directions of propagation and polarization are equal (i.e. for right-polarized upward-propagating or left-polarized downward-propagating waves), the magnetic energy increases relative to the kinetic energy, the resistive dissipation increases relative to the viscous dissipation, and the total energy density and flux increase relative to the case of isotropic resistivity; the reverse is the case for opposite directions of propagation, i.e. upward-propagating left-polarized waves and downward-propagating right-polarized waves, which can lead to the existence of a critical layer. The role of the viscosity and first and second resistive diffusiveness on the dissipation of Alfvén waves is discussed with reference to the solar atmosphere.

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