Artykuły w czasopismach: „Alfevn Waves”

1

Rauf, S., i J. A. Tataronis. "Resonant four-wave mixing of finite-amplitude Alfvén waves". Journal of Plasma Physics 55, nr 2 (kwiecień 1996): 173–80. http://dx.doi.org/10.1017/s0022377800018766.

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Using the derivative nonlinear SchrÖdinger equation, resonant four-wave mixing of finite-amplitude Alfvén waves is explored in this paper. The evolution equations governing the amplitudes of the interacting waves and the conservation relations ale derived from the basic equation. These evolution equations are used to study parametric amplification and oscillation of two small-amplitude Alfvén waves due to two large-amplitude pump (Alfvén) waves. It is also shown that three pump waves can mix together to generate a low-frequency Alfven wave in a dissipative plasma.

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2

Kar, C., S. K. Majumdar i A. N. Sekar Iyengar. "Stabilization of collisional drift waves by kinetic Alfvén waves". Journal of Plasma Physics 47, nr 2 (kwiecień 1992): 249–60. http://dx.doi.org/10.1017/s002237780002420x.

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We have investigated a mode-coupling mechanism between kinetic Alfvén waves and a collisional drift wave in an inhomogeneous cylindrical plasma. Drift waves satisfying the condition k⊥D > 1/r0 (where r0 is the radius of the plasma cylinder) are stabilized by the low-frequency ponderomotive force generated by the kinetic Alfvén waves. For typical plasma parameters and a moderate level of Alfven-wave intensity the stabilization factor is comparable to the destabilization mechanism due to collisions.

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3

Леонович, Анатолий, Anatoliy Leonovich, Цюган Цзун, Qiugang Zong, Даниил Козлов, Daniil Kozlov, Юнфу Ван i Yongfu Wang. "Alfvén waves in the magnetosphere generated by shock wave / plasmapause interaction". Solar-Terrestrial Physics 5, nr 2 (28.06.2019): 9–14. http://dx.doi.org/10.12737/stp-52201902.

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We study Alfvén waves generated in the magnetosphere during the passage of an interplanetary shock wave. After shock wave passage, the oscillations with typical Alfvén wave dispersion have been detected in spacecraft observations inside the magnetosphere. The most frequently observed oscillations are those with toroidal polarization; their spatial structure is described well by the field line resonance (FLR) theory. The oscillations with poloidal polarization are observed after shock wave passage as well. They cannot be generated by FLR and cannot result from instability of high-energy particle fluxes because no such fluxes were detected at that time. We discuss an alternative hypothesis suggesting that resonant Alfvén waves are excited by a secondary source: a highly localized pulse of fast magnetosonic waves, which is generated in the shock wave/plasmapause contact region. The spectrum of such a source contains oscillation harmonics capable of exciting both the toroidal and poloidal resonant Alfvén waves.

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4

Suzuki, T. K. "Coronal heating and wind acceleration by nonlinear Alfvén waves – global simulations with gravity, radiation, and conduction". Nonlinear Processes in Geophysics 15, nr 2 (26.03.2008): 295–304. http://dx.doi.org/10.5194/npg-15-295-2008.

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Abstract. We review our recent results of global one-dimensional (1-D) MHD simulations for the acceleration of solar and stellar winds. We impose transverse photospheric motions corresponding to the granulations, which generate outgoing Alfvén waves. We treat the propagation and dissipation of the Alfvén waves and consequent heating from the photosphere by dynamical simulations in a self-consistent manner. Nonlinear dissipation of Alfven waves becomes quite effective owing to the stratification of the atmosphere (the outward decrease of the density). We show that the coronal heating and the solar wind acceleration in the open magnetic field regions are natural consequence of the footpoint fluctuations of the magnetic fields at the surface (photosphere). We find that the properties of the solar wind sensitively depend on the fluctuation amplitudes at the solar surface because of the nonlinearity of the Alfvén waves, and that the wind speed at 1 AU is mainly controlled by the field strength and geometry of flux tubes. Based on these results, we point out that both fast and slow solar winds can be explained by the dissipation of nonlinear Alfvén waves in a unified manner. We also discuss winds from red giant stars driven by Alfvén waves, focusing on different aspects from the solar wind.

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5

Mazur, V. A., i A. V. Stepanov. "Concerning the Dynamics of Energetic Protons in Coronal Magnetic Loops: Dispersion Effects of Alfven Waves". Symposium - International Astronomical Union 107 (1985): 559. http://dx.doi.org/10.1017/s0074180900076105.

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It is shown that the existence of plasma density inhomogeneities (ducts) elongated along the magnetic field in coronal loops, and of Alfven wave dispersion, associated with the taking into account of gyrotropy U ≡ ω/ωi ≪ 1 (Leonovich et al., 1983), leads to the possibility of a quasi-longitudinal k⊥ < √U k‖ propagation (wave guiding) of Alfven waves. Here ω is the frequency of Alfven waves, ωi is the proton gyrofrequency, and k is the wave number. It is found that with the parameter ξ = ω2 R/ωi A > 1, where R is the inhomogeneity scale of a loop across the magnetic field, and A is the Alfven wave velocity, refraction of Alfven waves does not lead, as contrasted to Wentzel's inference (1976), to the waves going out of the regime of quasi-longitudinal propagation. As the result, the amplification of Alfven waves in solar coronal loops can be important. A study is made of the cyclotron instability of Alfven waves under solar coronal conditions.

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6

Mazur, V. A., i A. V. Stepanov. "Concerning the Dynamics of Energetic Protons in Coronal Magnetic Loops: Dispersion Effects of Alfven Waves". Symposium - International Astronomical Union 107 (1985): 559. http://dx.doi.org/10.1017/s007418090007618x.

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It is shown that the existence of plasma density inhomogeneities (ducts) elongated along the magnetic field in coronal loops, and of Alfven wave dispersion, associated with the taking into account of gyrotropy U ≡ ω/ωi ≪ 1 (Leonovich et al., 1983), leads to the possibility of a quasi-longitudinal k⊥ < √U k‖ propagation (wave guiding) of Alfven waves. Here ω is the frequency of Alfven waves, ωi is the proton gyrofrequency, and k is the wave number. It is found that with the parameter ξ = ω2 R/ωi A > 1, where R is the inhomogeneity scale of a loop across the magnetic field, and A is the Alfven wave velocity, refraction of Alfven waves does not lead, as contrasted to Wentzel's inference (1976), to the waves going out of the regime of quasi-longitudinal propagation. As the result, the amplification of Alfven waves in solar coronal loops can be important. A study is made of the cyclotron instability of Alfven waves under solar coronal conditions.

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7

Nocera, Luigi, i Eric R. Priest. "Bistability of a forced hydromagnetic cavity". Journal of Plasma Physics 46, nr 1 (sierpień 1991): 153–77. http://dx.doi.org/10.1017/s0022377800016007.

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We study the nonlinear stability of a one-dimensional hydromagnetic cavity into which Alfvén waves are fed by harmonic shear motions of its boundaries and where they interact with slow magnetosonic waves. We use characteristic conditions for the outgoing and ingoing Alfven waves at the boundaries where the magnetosonic oscillations are required to vanish. Forcing of Alfven waves takes place at a frequency close to the eigenfrequency of the lowest-order mode of the cavity. We let the frequency detuning δω vary as a free parameter together with the amplitude of the forcing, the plasma β and the compressive Reynolds number Re0. Given these last three parameters and varying δω, we calculate the amplitude of the nonlinear equilibrium state of the cavity as the stationary solution of a simple forced, dissipative dynamical system that governs the evolution of the cavity over a slow time scale and to which we are led by multiple-scale and Galerkin analyses of the one-dimensional MHD equations. This amplitude is a multi-valued function of δω (bistability), and we discuss the possibility of nonlinear stabilization of the Alfven wave by locking it in one of the bistable states. This amplitude undergoes saddle-node bifurcations: we calculate the two values of δω at which this occurs and the lowest value of the Reynolds number (27/2) for this to happen. We show that the magnetic energy density released during a bistable transition scales as (Re0)2; it has a maximum at β = 1 - (⅔)½ and it may amount to a substantial part of the energy originally stored in the unperturbed cavity. The magnetic power density released scales as (Re0)3 and has a maximum at β = 1 ± (⅓)½5. We conclude that the cavity is a good site for plasma heating such as that of the solar corona.

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8

Sallago, P. A. "LARGE AMPLITUDE ALFVÉN WAVES IN PARTIALLY IONIZED PLASMAS". Anales AFA 33, nr 3 (15.10.2022): 85–89. http://dx.doi.org/10.31527/analesafa.2022.33.3.85.

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In this paper it is analyzed the propagation of large amplitude Alfvén waves in partially ionized plasmas (PIP) when electronic pressure, Hall and ambipolar terms of Ohm’s law are taken into account. Instead of linearizing and developing the perturbation in monochromatic waves, it is proposed that the perturbation satisfy the Alfvén wave’s conditions. As a result, a solution is found that in the fully ionized limit, it coincides with Sallago and Platzeck solution for Alfvénwaves in Hall magnetohydrodynamics (doi:10.1029/2003JA009920 ). Furthermore, if electronic pressure and Hall terms are null, in the linearized limit, the damping is equal to the one described by De Pontieu, B. Martens, P. C. H. and Hudson, H. S. (DOI = 10.1086/322408), if one imposes that the plasma is a perfect conductor.

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9

Леонович, Анатолий, Anatoliy Leonovich, Даниил Козлов i Daniil Kozlov. "On ballooning instability in current sheets". Solnechno-Zemnaya Fizika 1, nr 2 (17.06.2015): 49–69. http://dx.doi.org/10.12737/6425.

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The problem of instability of azimuthally small-scale Alfven and slow magnetosonic (SMS) waves in the geotail is solved. The solutions describe unstable oscillations in the presence of a current sheet and correspond to the region of stretched closed field lines of the magnetotail. The spectra of eigen-frequencies of several basic harmonics of standing Alfven and SMS waves are found in the local and WKB approximation, which are compared. It is shown that the oscillation properties obtained in these approximations differ radically. In the local approximation, the Alfven waves are stable in the entire range of magnetic shells. SMS waves go into the aperiodic instability regime (the regime of the ‘ballooning’ instability), on magnetic shells crossing the current sheet. In the WKB approximation, both the Alfven and SMS oscillations go into an unstable regime with a non-zero real part of their eigen-frequency, on magnetic shells crossing the current sheet. The structure of azimuthally small-scale Alfven waves across magnetic shells is determined.

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10

Guglielmi, Anatol, Boris Klain i Alexander Potapov. "Alfvén waves: To the 80th anniversary of discovery". Solar-Terrestrial Physics 8, nr 2 (30.06.2022): 69–70. http://dx.doi.org/10.12737/stp-82202210.

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The article is dedicated to the anniversary of the discovery of Alfvén waves. The concept of Alfvén waves has played an outstanding role in the formation and development of cosmic electrodynamics. A distinctive feature of Alfvén waves is that at each point in space the group velocity vector and the external magnetic field vector are collinear to each other. As a result, Alfvén waves can carry momentum, energy, and information over long distances. We briefly describe two Alfvén resonators, one of which is formed in the ionosphere, and the second presumably exists in Earth’s radiation belt. The existence of the ionospheric resonator is justified theoretically and confirmed by numerous observations. The second resonator is located between reflection points located high above Earth symmetrically with respect to the plane of the geomagnetic equator.

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11

Cuperman, S., C. Bruma i K. Komoshvili. "Non-inductive current drive via helicity injection by Alfvén waves in low-aspect-ratio tokamaks". Journal of Plasma Physics 56, nr 1 (sierpień 1996): 149–74. http://dx.doi.org/10.1017/s0022377800019152.

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A theoretical investigation of radio-frequency (RF) current drive via helicity injection in low aspect ratio tokamaks is carried out. A current-carrying cylindrical plasma surrounded by a helical sheet-current antenna and situated inside a perfectly conducting shell is considered. Toroidal features of low-aspect-ratio tokamaks are simulated by incorporating the following effects: (i) arbitrarily small aspect ratio, Ro/a ≡1/∈; (ii) strongly sheared equilibrium magnetic field; and (iii) relatively large poloidal component of the equilibrium magnetic field. This study concentrates on the Alfvén continuum, i.e. the case in which the wave frequency satisfies the condition , where is an eigenfrequency of the shear Alfven wave (SAW). Thus, using low-β magneto- hydrodynamics, the wave equation with correct boundary (matching) conditions is solved, the RF field components are found, and subsequently current drive, power deposition and efficiency are computed. The results of our investigation clearly demonstrate the possibility of generation of RF-driven currents via helicity injection by Alfvén waves in low-aspect-ratio tokamaks, in the SAW mode. A special algorithm is developed that enables one to select the antenna parameters providing optimal current drive efficiency.

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12

Dmitrienko, Irina. "Second-order perturbations in Alfvén waves in finite pressure plasma". Solar-Terrestrial Physics 8, nr 2 (30.06.2022): 31–36. http://dx.doi.org/10.12737/stp-82202205.

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It is shown first that in finite pressure plasma, just as in cold plasma, Alfvén waves created by an initial perturbation generate plasma flows and decreases in the magnetic field, which propagate along with these waves. Second, at the stage of their interaction, Alfvén waves generate slow magnetosonic (SMS) waves propagating along the magnetic field. These results suggest that at least some of the fast plasma flows observed in the magnetotail can be one of the manifestations of propagating Alfvén waves both in the magnetosphere regions with cold plasma and in the magnetosphere regions with finite pressure plasma. They also provide potential possibility for determining the position of a source of Alfvén disturbance from observations of Alfvén waves and their induced SMS waves.

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13

Jatenco-Pereira, V., A. C. L. Chian i N. Rubab. "Alfvén waves in space and astrophysical dusty plasmas". Nonlinear Processes in Geophysics 21, nr 2 (13.03.2014): 405–16. http://dx.doi.org/10.5194/npg-21-405-2014.

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Abstract. In this paper, we present some results of previous works on Alfvén waves in a dusty plasma in different astrophysical and space regions by taking into account the effect of superthermal particles on the dispersive characteristics. We show that the presence of dust and superthermal particles sensibly modify the dispersion of Alfvén waves. The competition between different damping processes of kinetic Alfvén waves and Alfvén cyclotron waves is analyzed. The nonlinear evolution of Alfvén waves to chaos is reviewed. Finally, we discuss some applications of Alfvén waves in the auroral region of space plasmas, as well as stellar winds and star-forming regions of astrophysical plasmas.

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14

Uberoi, C. "Resonant absorption of Alfven Waves and the Associated Phenomenon of Magnetic Reconnection". Symposium - International Astronomical Union 142 (1990): 245–49. http://dx.doi.org/10.1017/s007418090008801x.

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The mathematical analysis of the Alfven Wave equation in inhomogeneous magnetic fields which explain the resonance absorption of Alfven surface waves near a resonant layer can also be used to show that magnetic reconnection process can arise near the zero frequency resonant layer driven by very low frequency Alfven surface waves. The associated phenomena of resonant absorption and magnetic reconnection in inhomogeneous plasmas can explain the recent obsrevations of intense magnetic activity in the long period geomagnetic micropulsations range, at magnetospheric cusp latitudes, during the time of occurence of flux transfer events.

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15

Hamabata, Hiromitsu, i Tomikazu Namikawa. "The effect of random Alfvén waves on the propagation of hydromagnetic waves in a finite-beta plasma". Journal of Plasma Physics 43, nr 1 (luty 1990): 69–82. http://dx.doi.org/10.1017/s0022377800014628.

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Using first-order smoothing theory, Fourier analysis and perturbation methods, we obtain the evolution equation of the wave spectrum as well as the nonlinear forces generated by random Alfvén waves in a finite-β plasma with phenomenological Landau-damping effects. The effect of microscale random Alfvén waves on the propagation of large-scale hydromagnetic waves is also investigated by solving the mean-field equations. It is shown that parallel-propagating random Alfvén waves are modulationally stable and that obliquely propagating random Alfvén waves can be modulationally unstable when the energy of random waves is converted to slow magneto-acoustic waves that can be Landau-damped, providing a dissipation mechanism for the Alfvén waves.

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16

Kabin, K., R. Rankin, I. R. Mann, A. W. Degeling i R. Marchand. "Polarization properties of standing shear Alfvén waves in non-axisymmetric background magnetic fields". Annales Geophysicae 25, nr 3 (29.03.2007): 815–22. http://dx.doi.org/10.5194/angeo-25-815-2007.

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Abstract. In this paper we present results concerning periods and polarizations of cold plasma ultra-low frequency (ULF) guided Alfvén waves in a non-axisymmetric geomagnetic field. The background geomagnetic field is approximated by a compressed dipole for which we propose a simple description in terms of Euler potentials. This study is motivated by the problem of outer-radiation belt electron acceleration by ULF waves, for which the polarization of the wave is of paramount importance. We consider an approximation appropriate to decoupled Alfvénic waves and find that the polarization of the waves can change significantly with local time. Therefore, the ULF wave's contribution to the MeV electron energization process can be localized in space.

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17

McKee, Christopher F., i Ellen G. Zweibel. "Alfven Waves in Interstellar Gasdynamics". Astrophysical Journal 440 (luty 1995): 686. http://dx.doi.org/10.1086/175306.

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18

De Pontieu, B., P. C. H. Martens i H. S. Hudson. "Chromospheric Damping of Alfven Waves". Astrophysical Journal 558, nr 2 (10.09.2001): 859–71. http://dx.doi.org/10.1086/322408.

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19

Del Zanna, L., i M. Velli. "Coronal heating through Alfven waves". Advances in Space Research 30, nr 3 (styczeń 2002): 471–80. http://dx.doi.org/10.1016/s0273-1177(02)00320-4.

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20

Chakraborty, B., M. R. Khan, Susmita Sarkar, V. Krishan i B. Bhattacharyya. "Induced magnetization of Alfven waves". Annals of Physics 201, nr 1 (lipiec 1990): 1–12. http://dx.doi.org/10.1016/0003-4916(90)90351-n.

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21

Dmitrienko, Irina. "Second-order perturbations in Alfvén waves in finite pressure plasma". Solnechno-Zemnaya Fizika 8, nr 2 (30.06.2022): 34–40. http://dx.doi.org/10.12737/szf-82202205.

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It is shown first that in finite pressure plasma, just as in cold plasma, Alfvén waves created by an initial perturbation generate plasma flows and decreases in the magnetic field, which propagate along with these waves. Second, at the stage of their interaction, Alfvén waves generate slow magnetosonic (SMS) waves propagating along the magnetic field. These results suggest that at least some of the fast plasma flows observed in the magnetotail can be one of the manifestations of propagating Alfvén waves both in the magnetosphere regions with cold plasma and in the magnetosphere regions with finite pressure plasma. They also provide potential possibility for determining the position of a source of Alfvén disturbance from observations of Alfvén waves and their induced SMS waves.

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22

DMITRIENKO, I. S. "Spatio-temporal evolution of thin Alfven resonance layer". Journal of Plasma Physics 76, nr 5 (7.05.2010): 709–34. http://dx.doi.org/10.1017/s002237781000022x.

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AbstractWe describe the spatio-temporal evolution of one-dimensional Alfven resonance disturbance in the presence of various factors of resonance detuning: dispersion and absorption of Alfven disturbance, nonstationarity of large-scale wave generating resonant disturbance. Using analytical solutions to the resonance equation, we determine conditions for forming qualitatively different spatial and temporal structures of resonant Alfven disturbances. We also present analytical descriptions of quasi-stationary and non-stationary spatial structures formed in the resonant layer, and their evolution over time for cases of drivers of different types corresponding to large-scale waves localized in the direction of inhomogeneity and to nonlocalized large-scale waves.

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23

Tsurutani, B. T., G. S. Lakhina, J. S. Pickett, F. L. Guarnieri, N. Lin i B. E. Goldstein. "Nonlinear Alfvén waves, discontinuities, proton perpendicular acceleration, and magnetic holes/decreases in interplanetary space and the magnetosphere: intermediate shocks?" Nonlinear Processes in Geophysics 12, nr 3 (18.02.2005): 321–36. http://dx.doi.org/10.5194/npg-12-321-2005.

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Abstract. Alfvén waves, discontinuities, proton perpendicular acceleration and magnetic decreases (MDs) in interplanetary space are shown to be interrelated. Discontinuities are the phase-steepened edges of Alfvén waves. Magnetic decreases are caused by a diamagnetic effect from perpendicularly accelerated (to the magnetic field) protons. The ion acceleration is associated with the dissipation of phase-steepened Alfvén waves, presumably through the Ponderomotive Force. Proton perpendicular heating, through instabilities, lead to the generation of both proton cyclotron waves and mirror mode structures. Electromagnetic and electrostatic electron waves are detected as well. The Alfvén waves are thus found to be both dispersive and dissipative, conditions indicting that they may be intermediate shocks. The resultant "turbulence" created by the Alfvén wave dissipation is quite complex. There are both propagating (waves) and nonpropagating (mirror mode structures and MDs) byproducts. Arguments are presented to indicate that similar processes associated with Alfvén waves are occurring in the magnetosphere. In the magnetosphere, the "turbulence" is even further complicated by the damping of obliquely propagating proton cyclotron waves and the formation of electron holes, a form of solitary waves. Interplanetary Alfvén waves are shown to rapidly phase-steepen at a distance of 1AU from the Sun. A steepening rate of ~35 times per wavelength is indicated by Cluster-ACE measurements. Interplanetary (reverse) shock compression of Alfvén waves is noted to cause the rapid formation of MDs on the sunward side of corotating interaction regions (CIRs). Although much has been learned about the Alfvén wave phase-steepening processfrom space plasma observations, many facets are still not understood. Several of these topics are discussed for the interested researcher. Computer simulations and theoretical developments will be particularly useful in making further progress in this exciting new area.

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Дмитриенко, Ирина, i Irina Dmitrienko. "Second-order perturbations in Alfvén waves in cold plasma approximatio". Solar-Terrestrial Physics 5, nr 2 (28.06.2019): 81–87. http://dx.doi.org/10.12737/stp-52201912.

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The second-order amplitude perturbations driven by Alfvén waves are studied. Equations for such second-order perturbations are derived and their solutions are found. The second-order perturbations are shown to be generated by the magnetic pressure of the waves. They represent plasma flows and magnetic field perturbations in a plane perpendicular to the direction of the field perturbation and plasma displacement in the Alfvén wave. In connection with the interpretation of fast plasma flows observed in the magnetotail, of particular interest is the description of second-order flows, which relates their properties to properties of Alfvén waves and the disturbance that generates them. The results suggest that at least some of the fast plasma flows observed in the magnetotail can be one of the manifestations of propagating Alfvén waves. The environment model and cold plasma approximation in use are quite applicable for the plasma sheet boundary layers, where an essential part of the fast plasma flows occurs.

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Koide, Shinji, Sousuke Noda, Masaaki Takahashi i Yasusada Nambu. "One-dimensional Force-free Numerical Simulations of Alfvén Waves around a Spinning Black String". Astrophysical Journal 928, nr 1 (1.03.2022): 84. http://dx.doi.org/10.3847/1538-4357/ac47f8.

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Abstract We performed one-dimensional force-free magnetodynamic numerical simulations of the propagation of Alfvén waves along magnetic field lines around a spinning black-hole-like object, the Banados–Teitelboim–Zanelli black string, to investigate the dynamic process of wave propagation and energy transport with Alfvén waves. We considered an axisymmetric and stationary magnetosphere and perturbed the background magnetosphere to obtain the linear wave equation for the Alfvén wave mode. The numerical results show that the energy of Alfvén waves monotonically increases as the waves propagate outwardly along the rotating curved magnetic field line around the ergosphere, where energy seems not to be conserved, in the case of energy extraction from the black string by the Blandford–Znajek mechanism. The apparent breakdown of energy conservation suggests the existence of a wave induced by the Alfvén wave. Considering the additional fast magnetosonic wave induced by the Alfvén wave, the energy conservation is confirmed. Similar relativistic phenomena, such as the amplification of Alfvén waves and induction of fast magnetosonic waves, are expected around a spinning black hole.

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WEBB, G. M., G. P. ZANK, R. H. BURROWS i R. E. RATKIEWICZ. "Alfvén simple waves". Journal of Plasma Physics 77, nr 1 (4.02.2010): 51–93. http://dx.doi.org/10.1017/s0022377809990596.

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AbstractMulti-dimensional Alfvén simple waves in magnetohydrodynamics (MHD) are investigated using Boillat's formalism. For simple wave solutions, all physical variables (the gas density, pressure, fluid velocity, entropy, and magnetic field induction in the MHD case) depend on a single phase function ϕ, which is a function of the space and time variables. The simple wave ansatz requires that the wave normal and the normal speed of the wave front depend only on the phase function ϕ. This leads to an implicit equation for the phase function and a generalization of the concept of a plane wave. We obtain examples of Alfvén simple waves, based on the right eigenvector solutions for the Alfvén mode. The Alfvén mode solutions have six integrals, namely that the entropy, density, magnetic pressure, and the group velocity (the sum of the Alfvén and fluid velocity) are constant throughout the wave. The eigenequations require that the rate of change of the magnetic induction B with ϕ throughout the wave is perpendicular to both the wave normal n and B. Methods to construct simple wave solutions based on specifying either a solution ansatz for n(ϕ) or B(ϕ) are developed.

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Klimushkin, D. Yu, P. N. Mager i N. A. Zolotukhina. "Spatio-temporal structure of poloidal alfvén waves in the magnetosphere". Kosmìčna nauka ì tehnologìâ 16, nr 1 (30.01.2010): 46–54. http://dx.doi.org/10.15407/knit2010.01.046.

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Shukla, P. K., i L. Stenflo. "Nonlinear Alfvén waves". Physica Scripta T60 (1.01.1995): 32–35. http://dx.doi.org/10.1088/0031-8949/1995/t60/004.

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WEBB, G. M., Q. HU, B. DASGUPTA i G. P. ZANK. "Double Alfvén waves". Journal of Plasma Physics 78, nr 1 (17.10.2011): 71–85. http://dx.doi.org/10.1017/s0022377811000420.

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AbstractDouble Alfvén wave solutions of the magnetohydrodynamic equations in which the physical variables (the gas density ρ, fluid velocity u, gas pressure p, and magnetic field induction B) depend only on two independent wave phases ϕ1(x,t) and ϕ2(x,t) are obtained. The integrals for the double Alfvén wave are the same as for simple waves, namely, the gas pressure, magnetic pressure, and group velocity of the wave are constant. Compatibility conditions on the evolution of the magnetic field B due to changes in ϕ1 and ϕ2, as well as constraints due to Gauss's law ∇ · B = 0 are discussed. The magnetic field lines and hodographs of B in which the tip of the magnetic field B moves on the sphere |B| = B = const. are used to delineate the physical characteristics of the wave. Hamilton's equations for the simple Alfvén wave with wave normal n(ϕ), and with magnetic induction B(ϕ) in which ϕ is the wave phase, are obtained by using the Frenet–Serret equations for curves x=X(ϕ) in differential geometry. The use of differential geometry of 2D surfaces in a 3D Euclidean space to describe double Alfvén waves is briefly discussed.

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KLIMUSHKIN, DMITRI Yu, i PAVEL N. MAGER. "The structure of low-frequency standing Alfvén waves in the box model of the magnetosphere with magnetic field shear". Journal of Plasma Physics 70, nr 4 (27.07.2004): 379–95. http://dx.doi.org/10.1017/s0022377803002563.

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The paper is concerned with the influence of magnetic field shear on the structure of Alfvén waves standing along field lines in the one-dimensionally inhomogeneous box model of the magnetosphere, enclosed between two parallel, infinitely conducting planes (ionospheres). We consider the transverse small-scale Alfvén waves whose azimuthal component of the wave vector $k_y$ satisfies the condition $k_y l\,{\gg}\,1$, where $l$ is the distance between the ionospheres. For this model, the Alfvén resonance condition has been established. It is shown that resonance can also occur at a constant Alfvén velocity if the field-line inclination to the ionosphere is changed. On resonant magnetic shells there occurs a singularity of the wave field of the same kind as in the absence of shear. Moreover, there are found many resemblances between Alfvén-wave behavior in our one-dimensionally inhomogeneous model and in two-dimensional inhomogeneous models with plasma and magnetic field parallel inhomogeneity taken into account. Thus, the presence of shear leads to a difference of the frequencies of poloidal and toroidal oscillations of field lines, and to the dependence of the wave's frequency on the transversal components of wave vector. Then, in the sheared magnetic field with highly conductive boundaries the source excites multiple standing Alfvén harmonics at different locations. In general, the localization regions of different longitudinal harmonics overlap. However, in the small but finite shear limit, a total wave field represents a set of mutually isolated transparent regions corresponding to different harmonic numbers. In each of these regions the waves are found to be travelling across the magnetic shells, and the transparent region is limited in the coordinate $x$ by two turning points, at one of which the mode is poloidally polarized, and the other point it is toroidally polarized (it is at this latter point where Alfvén resonance occurs). Furthermore, the phase velocity of the wave is directed toward the poloidal point, and the group velocity is directed at the toroidal point.

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31

Sallago, P. A. "STABILITY OF ALFVEN WINGS IN HMHD". Anales AFA 32, nr 1 (15.04.2021): 1–6. http://dx.doi.org/10.31527/analesafa.2021.32.1.1.

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A conducting source moving uniformly through a magnetized plasma generates, among a variety of perturbations,Alfvén waves. Alfvén waves can build up structures in the plasma called Alfvén wings. The wings have been detec-ted and measured in many solar system bodies, and their existence have been theoretically proved also. Under certainconditions, Hall and electronic pressure must be taken into account in the Ohm’s law and so one gets Hall Magne-tohydrodynamics (HMHD). In spite of Sallago and Platzeck have shown the existence of Alfvén wings in HMHD, theirstability under such conditions remains to be studied. The aim of this paper is to analyze the stability of an Alfvén wing,in the presence of an incompressible perturbation that has the same symmetry than the structure and polarization, inHMHD. Palumbo has developed an analytical method for the study of the stability of static structures with a symmetryin magnetized plasmas, in the presence of incompressible perturbations with the same symmetry than the structure.Since Alfvén wings are stationary structures, Sallago and Platzeck have shown the stability of such Alfvén wings in MHD conditions by extending Palumbo’s method. In the present paper this method is extended for Alfvén wings in HMHD conditions, and one concludes that in the presence of this kind of perturbations they are stable.

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32

Chae, Jongchul, i Kyoung-Sun Lee. "Alfvén Wave Connection between the Chromosphere and the Corona of the Sun: An Analytical Study". Astrophysical Journal 954, nr 1 (22.08.2023): 45. http://dx.doi.org/10.3847/1538-4357/ace771.

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Abstract Alfvén waves are closely relevant to the three outstanding problems in the solar corona: coronal heating, solar wind acceleration, and the fractionization of low first ionization potential (FIP) elements. There has been increasing observational evidence for the Alfvén waves, not only in the corona, but also in the chromosphere. Here we investigate the Alfvén wave connection between the chromosphere and the corona based on the analytical solution of Alfvén waves in a layer where Alfvén speed varies along magnetic field lines with a constant gradient. The wave transmission of the layer is determined by two parameters: the Alfvénic cutoff frequency and the dimensionless thickness of the layer. It is shown that the ponderomotive acceleration originating from Alfvén waves is always directed upward in the solar atmosphere with the peak occurring in the chromosphere-corona transition region in association with downward low-frequency waves. We also find that some velocity amplitudes observed in the chromosphere of quiet regions and all the velocity amplitudes observed in active regions fall short of the theoretical estimates obtained with the assumption that the Alfvén waves generated below the chromosphere transport upward the energy required for the corona. We suggest considering the possibility that the Alfvén waves responsible for the coronal heating and the FIP fractionization originate from above the chromosphere.

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33

Han, Yimin, Lei Dai, Shuo Yao, Chi Wang, Walter Gonzalez, Suping Duan, Benoit Lavraud, Yong Ren i Zhenyuan Guo. "Geoeffectiveness of Interplanetary Alfvén Waves. II. Spectral Characteristics and Geomagnetic Responses". Astrophysical Journal 945, nr 1 (1.03.2023): 48. http://dx.doi.org/10.3847/1538-4357/acb266.

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Abstract Using multipoint observations over 10 yr near 1 au, we investigate the spectra (5 minutes to 2 hr) of interplanetary Alfvén waves and the responses in the geomagnetic activities. We compute the two-point correlations of the wave magnetic field between the ACE and the THEMIS spacecraft, which are separated by ∼200 Earth radius (R E) in the solar wind. Alfvén waves associated with high two-point correlations exhibit steep spectra (spectra index ∼−1.63). Such Alfvén waves occur mostly in slow-speed streams. By contrast, Alfvén waves with low two-point correlations exhibit flatter spectra (spectra index ∼−1.51) with a relative enhancement of power above 2 × 10−4 Hz. The occurrence of Alfvén waves with low two-point correlations is more equally distributed between high-speed and low-speed streams. In general, interplanetary Alfvén waves show correlations with moderate geomagnetic responses in symmetric ring-current intensity, SuperMAG electrojet (SME), and Kp indices. Statistical analyses indicate that the Alfvén waves with flat spectra correspond to stronger responses in the geomagnetic indices than those with steep spectra, suggesting the importance of the tens of minutes (30–90 minutes) Alfvénic power spectra in the generation of SME/Auroral Electrojets. These observations may shed light on the response of the magnetosphere to fluctuating interplanetary magnetic field B z .

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34

Belov, S. A., S. Vasheghani Farahani i N. E. Molevich. "Propagating torsional Alfvén waves in thermally active solar plasma". Monthly Notices of the Royal Astronomical Society 515, nr 4 (17.08.2022): 5151–58. http://dx.doi.org/10.1093/mnras/stac2066.

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ABSTRACT The aim of this study is to shed light on the effects connected with thermal misbalance due to non-equal cooling and heating rates induced by density and temperature perturbations in solar active regions hosting either propagating torsional or shear Alfvén waves. A description for the non-linear forces connected with Alfvén waves in non-ideal conditions is provided, based on the second-order thin flux tube approximation. This provides insight into the effects of Alfvén-induced motions on the boundary of thin magnetic structures in thermally active plasmas. The equations describing the process of generating longitudinal velocity perturbations, together with density perturbations by non-linear torsional Alfvén waves, are obtained and solved analytically. It is shown that the phase shift (compared with the ideal case) and the amplitude of the induced longitudinal plasma motions against the period of the mother Alfvén wave are greater for shear Alfvén waves compared with torsional Alfvén waves, although following the same pattern. The difference in the influence of thermal misbalance on the induced velocity perturbations is governed by the plasma-β although its effect is stronger for shear waves. It is deduced that for a harmonic Alfvén driver the induced density perturbations are left uninfluenced by the thermal misbalance.

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35

Mottez, F. "Non-propagating electric and density structures formed through non-linear interaction of Alfvén waves". Annales Geophysicae 30, nr 1 (9.01.2012): 81–95. http://dx.doi.org/10.5194/angeo-30-81-2012.

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Abstract. In the auroral zone of the Earth, the electron acceleration by Alfvén waves is sometimes seen as a precursor of the non-propagating acceleration structures. In order to investigate how Alfvén waves could generate non-propagating electric fields, a series of simulations of counter-propagating waves in a homogeneous medium is presented. The waves propagate along the ambient magnetic field direction. It is shown that non-propagating electric fields are generated at the locus of the Alfvén waves crossing. These electric fields have a component orientated along the direction of the ambient magnetic field, and they generate a significant perturbation of the plasma density. The non-linear interaction of down and up-going Alfvén waves might be a cause of plasma density fluctuations (with gradients along the magnetic field) on a scale comparable to those of the Alfvén wavelengths. The present paper is mainly focused on the creation process of the non-propagating parallel electric field.

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36

Cally, Paul S. "On the fragility of Alfvén waves in a stratified atmosphere". Monthly Notices of the Royal Astronomical Society 510, nr 1 (1.12.2021): 1093–105. http://dx.doi.org/10.1093/mnras/stab3466.

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ABSTRACT Complete asymptotic expansions are developed for slow, Alfvén, and fast magnetohydrodynamic waves at the base of an isothermal 3D plane stratified atmosphere. Together with existing convergent Frobenius series solutions about z = ∞, matchings are numerically calculated that illuminate the fates of slow and Alfvén waves injected from below. An Alfvén wave in a two-dimensional model is 2.5D in the sense that the wave propagates in the plane of the magnetic field but its polarization is normal to it in an ignorable horizontal direction, and the wave remains an Alfvén wave throughout. The rotation of the plane of wave propagation away from the vertical plane of the magnetic field pushes the plasma displacement vector away from horizontal, thereby coupling it to stratification. It is shown that potent slow–Alfvén coupling occurs in such 3D models. It is found that about 50 per cent of direction-averaged Alfvén wave flux generated in the low atmosphere at frequencies comparable to or greater than the acoustic cut-off can reach the top as Alfvén flux for small magnetic field inclinations θ, and this increases to 80 per cent or more with increasing θ. On the other hand, direction-averaged slow waves can be 40 per cent effective in converting to Alfvén waves at small inclination, but this reduces sharply with increasing θ and wave frequency. Together with previously explored fast–slow and fast–Alfvén couplings, this provides valuable insights into which injected transverse waves can reach the upper atmosphere as Alfvén waves, with implications for solar and stellar coronal heating and solar/stellar wind acceleration.

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37

Ratkiewicz, R., D. E. Innes i J. F. McKenzie. "Characteristics and Riemann invariants for multi-ion plasmas in the presence of Alfvén waves". Journal of Plasma Physics 52, nr 2 (październik 1994): 297–307. http://dx.doi.org/10.1017/s0022377800017918.

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In this paper the characteristics for a single- and a bi-ion plasma in the presence of Alfvén waves are given. In the single-ion case, the analysis is extended to the situation where Alfvén waves saturate and dissipatively heat the plasma. When there is no dissipation, there are three sound waves and one entropy wave in the single-ion plasma. Each sound wave is associated with two Riemann invariants relating the changes in density and wave pressure to changes in the flow. In the case when the Alfvén waves saturate and heat the plasma, there are two sound waves and one modified entropy sound wave. Each wave is associated with two Riemann invariants relating changes in density and entropy to changes in the flow. The analysis for the bi-ion plasma is simplified to very sub-Alfvénic flows. In this case the Alfvén waves behave like another plasma component, and both the electric and Alfvén wave forces have the same structure. The system possesses two entropy waves and four sound waves. Each sound wave is associated with two Riemann invariants relating changes in density and flow velocity along the characteristic curves.

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38

Goldreich, Peter. "Incompressible MHD Turbulence". International Astronomical Union Colloquium 182 (2001): 17–23. http://dx.doi.org/10.1017/s0252921100000622.

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AbstractThe inertial range of incompressible MHD turbulence is most conveniently described in terms of counter propagating waves. Shear Alfvén waves control the cascade dynamics. Slow waves play a passive role and adopt the spectrum set by the shear Alfvén waves. Cascades composed entirely of shear Alfvén waves do not generate a significant measure of slow waves. MHD turbulence is anisotropic with energy cascading more rapidly along k⊥ than along k‖. Anisotropy increases with k⊥ such that the excited modes are confined inside a cone bounded by . The opening angle of the cone, , defines the scale dependent anisotropy. MHD turbulence is generically strong in the sense that the waves which comprise it are critically damped. Nevertheless, deep inside the inertial range, turbulent fluctuations are small. Their energy density is less than that of the background field by a factor θ2(k⊥) « 1. MHD cascades are best understood geometrically. Wave packets suffer distortions as they move along magnetic field lines perturbed by counter propagating wave packets. Field lines perturbed by unidirectional waves map planes perpendicular to the local field into each other. Shear Alfvén waves are responsible for the mapping’s shear and slow waves for its dilatation. The former exceeds the latter by θ−1 (k⊥) » 1 which accounts for dominance of the shear Alfvén waves in controlling the cascade dynamics.

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39

Buti, B. "Nonlinear Alfven waves in inhomogeneous plasmas". Geophysical Research Letters 18, nr 5 (maj 1991): 809–12. http://dx.doi.org/10.1029/91gl00854.

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40

Liu, W. W. "Chaos driven by kinetic Alfven waves". Geophysical Research Letters 18, nr 8 (sierpień 1991): 1611–14. http://dx.doi.org/10.1029/91gl01779.

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Datars, W. R., i A. Weingartshofer. "Far-infrared Alfven waves in graphite". Journal of Physics: Condensed Matter 1, nr 38 (25.09.1989): 6829–34. http://dx.doi.org/10.1088/0953-8984/1/38/007.

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42

Tomczyk, S., S. W. McIntosh, S. L. Keil, P. G. Judge, T. Schad, D. H. Seeley i J. Edmondson. "Alfven Waves in the Solar Corona". Science 317, nr 5842 (31.08.2007): 1192–96. http://dx.doi.org/10.1126/science.1143304.

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43

Белов, С. А., Н. Е. Молевич i Д. И. Завершинский. "Усиление альфвеновских волн в результате нелинейного взаимодействия с быстрой магнитоакустической волной в акустически активной проводящей среде". Письма в журнал технической физики 44, nr 5 (2018): 41. http://dx.doi.org/10.21883/pjtf.2018.05.45706.16954.

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AbstractIt is shown that biexponential amplification of Alfvén waves is possible in isentropically unstable heat-releasing plasma. The amplification is due to parametric energy transfer to Alfvén waves from fast magnetoacoustic waves directed orthogonally to the former.

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44

Shi, Run, i Jun Liang. "Mode conversion from kinetic Alfvén waves to modified electron acoustic waves". Physics of Plasmas 29, nr 8 (sierpień 2022): 082104. http://dx.doi.org/10.1063/5.0093193.

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Possible mode conversion from kinetic Alfvén wave to modified electron acoustic wave is examined based on a multi-fluid model involving two electron populations. The mode conversion transpires when a kinetic Alfvén wave propagates through a transition between a hot-electron-dominant region and a cold-electron-dominant region. It is shown that the mode conversion and the kinetic Alfvén wave reflection depend strongly on the hot electron inertial length, the hot electron temperature, and the perpendicular wavelength. The results suggest that such conversion is ubiquitous whenever a steep gradient of electron temperature exists, for example, in the planetary auroral acceleration regions or at the boundary of the solar corona.

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45

Guglielmi, Anatol, Boris Klain i Alexander Potapov. "Alfvén waves: To the 80th anniversary of discovery". Solnechno-Zemnaya Fizika 8, nr 2 (30.06.2022): 75–77. http://dx.doi.org/10.12737/szf-82202210.

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The article is dedicated to the anniversary of the discovery of Alfvén waves. The concept of Alfvén waves has played an outstanding role in the formation and development of cosmic electrodynamics. A distinctive feature of Alfvén waves is that at each point in space the group velocity vector and the external magnetic field vector are collinear to each other. As a result, Alfvén waves can carry momentum, energy, and information over long distances. We briefly describe two Alfvén resonators, one of which is formed in the ionosphere, and the second presumably exists in Earth’s radiation belt. The existence of the ionospheric resonator is justified theoretically and confirmed by numerous observations. The second resonator is located between reflection points located high above Earth symmetrically with respect to the plane of the geomagnetic equator.

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46

Wu, Xianshu, Chao Shen, Jingchun Li, Jiaqi Dong i Kehua Li. "Nonlinear Interaction of Low-frequency Alfvén Waves and Ions". Astrophysical Journal 951, nr 2 (1.07.2023): 88. http://dx.doi.org/10.3847/1538-4357/acd642.

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Abstract The interaction between Alfvén waves and particles is a critical phenomenon in space and laboratory plasmas, and it has been observed that low-frequency Alfvén waves can accelerate and heat ions through subharmonic resonant interactions. In this study, we use test particle simulations to verify the nonlinear heating of parallelly propagating low-frequency Alfvén waves on ions and analyze the underlying process in terms of the Poincaré section. Our results demonstrate that low-frequency Alfvén waves can periodically pick up ions, leading to oscillations of average parallel velocity and temperature of the plasma by phase mixing, ultimately resulting in the stabilization of acceleration. Furthermore, we have developed an analysis that can estimate the time required for heating and accelerating. In the case of multiple waves, our findings indicate that the presence of more chaotic modes does not necessarily result in better wave heating. We have also discussed the effect of random phases on the heating process. Overall, this research sheds light on the crucial role played by the interaction between Alfvén waves and particles in astrophysics and provides new insights into the mechanisms underlying the heating and acceleration of ions through subharmonic resonant interactions with low-frequency Alfvén waves. These findings may have significant implications for the understanding of plasma dynamics in a range of astrophysical environments.

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47

Kumar, Nagendra, Vinod Kumar i Himanshu Sikka. "Alfvén Surface Waves in a Partially Ionized Resistive Medium". Applied Mechanics and Materials 110-116 (październik 2011): 867–73. http://dx.doi.org/10.4028/www.scientific.net/amm.110-116.867.

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We study the joint effects of viscosity, resistivity and ion-neutral collisions on Alfvén surface waves propagating along a partially ionized plasma - vacuum interface. Applying boundary conditions at plasma-vacuum interface, we obtain the dispersion relation for Alfvén surface waves and solve it numerically. For different values of resistivity and neutral gas friction parameters, the variation of real and imaginary parts of wave number with viscosity parameter are shown graphically. It is found that two-mode structure of Alfvén surface waves results due to the combined effects of resistivity, viscosity and ion-neutral collisions. These results might be useful for studying the behavior of Alfvén surface waves in laboratory and space plasmas.

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48

Ghosh, G., i K. P. Das. "Three-dimensional stability of solitary kinetic Alfvé waves and ion-acoustic waves". Journal of Plasma Physics 51, nr 1 (luty 1994): 95–111. http://dx.doi.org/10.1017/s0022377800017414.

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Starting from a set of equations that lead to a linear dispersion relation coupling kinetic Alfvén waves and ion-acoustic waves, three-dimensional KdV equations are derived for these waves. These equations are then used to investigate the three-dimensional stability of solitary kinetic Alfvén waves and ion-acoustic waves by the small-k perturbation expansion method of Rowlands and Infeld. For kinetic Alfvén waves it is found that there is instability if the direction of the plane-wave perturbation lies inside a cone, and the growth rate of the instability attains a maximum when the direction of the perturbation lies in the plane containing the external magnetic field and the direction of propagation of the solitary wave.

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Alpatov, V. V., M. G. Deminov, D. S. Faermark, I. A. Grebnev i M. J. Kosch. "Dynamics of Alfvén waves in the night-side ionospheric Alfvén resonator at mid-latitudes". Annales Geophysicae 23, nr 2 (28.02.2005): 499–507. http://dx.doi.org/10.5194/angeo-23-499-2005.

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Abstract. A numerical solution of the problem on dynamics of shear-mode Alfvén waves in the ionospheric Alfvén resonator (IAR) region at middle latitudes at nighttime is presented for a case when a source emits a single pulse of duration τ into the resonator region. It is obtained that a part of the pulse energy is trapped by the IAR. As a result, there occur Alfvén waves trapped by the resonator which are being damped. It is established that the amplitude of the trapped waves depends essentially on the emitted pulse duration τ and it is maximum at τ=(3/4)T, where T is the IAR fundamental period. The maximum amplitude of these waves does not exceed 30% of the initial pulse even under optimum conditions. Relatively low efficiency of trapping the shear-mode Alfvén waves is caused by a difference between the optimum duration of the pulse and the fundamental period of the resonator. The period of oscillations of the trapped waves is approximately equal to T, irrespective of the pulse duration τ. The characteristic time of damping of the trapped waves τdec is proportional to T, therefore the resonator Q-factor for such waves is independent of T. For a periodic source the amplitude-frequency characteristic of the IAR has a local minimum at the frequency π/ω=(3/4)T, and the waves of such frequency do not accumulate energy in the resonator region. At the fundamental frequency ω=2π/T the amplitude of the waves coming from the periodic source can be amplified in the resonator region by more than 50%. This alone is a basic difference between efficiencies of pulse and periodic sources of Alfvén waves. Explicit dependences of the IAR characteristics (T, τdec, Q-factor and eigenfrequencies) on the altitudinal distribution of Alfvén velocity are presented which are analytical approximations of numerical results.

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50

Ruderman, Michael S., i Nikolai S. Petrukhin. "Existence of Purely Alvén Waves in Magnetic Flux Tubes with Arbitrary Cross-Sections". Physics 4, nr 3 (29.07.2022): 865–72. http://dx.doi.org/10.3390/physics4030055.

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We study linear torsional Alfvén waves in a magnetic flux tube with an arbitrary cross-section. We assume that the equilibrium magnetic field is propagating in the z-direction in Cartesian coordinates x,y, and z. The tube cross-section is bounded by a smooth closed curve. Both plasma and magnetic field are homogeneous outside this curve. The magnetic field magnitude is a function of x and y, while the density is a product of two functions: one dependent on z and the other dependent on x and y. As a result, the Alfvén speed is also equal to V0(x,y) times a function of z. We define Alfvén waves as waves that do not disturb plasma density. We show that these waves can exist only when the magnetic field magnitude is a function of V0. When the condition of existence of Alfvén waves is satisfied, the waves are polarised in the directions tangent to the level lines of V0(x,y) and orthogonal to the equilibrium magnetic field. We found that the Alfvén wave amplitude has a specific form that depends on a particular coordinate system.

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