Nonlinear evolution of a large-amplitude circularly polarized Alfvén wave: High beta

1994 ◽  
Vol 99 (A10) ◽  
pp. 19289 ◽  
Author(s):  
S. Ghosh ◽  
A. F. Viñas ◽  
M. L. Goldstein
Keyword(s):  
Large Amplitude ◽  
Nonlinear Evolution ◽  
Alfven Wave ◽  
Circularly Polarized ◽  
High Beta

Parametric instabilities of circularly polarized large-amplitude dispersive Alfvén waves: excitation of parallel-propagating electromagnetic daughter waves

1991 ◽  
Vol 46 (1) ◽  
pp. 107-127 ◽  
Author(s):  
Adolfo F. Viñas ◽  
Melvyn L. Goldstein
Keyword(s):  
Magnetic Field ◽  
Growth Rate ◽  
Large Amplitude ◽  
Wave Amplitude ◽  
Pump Wave ◽  
Modulational Instability ◽  
Alfven Wave ◽  
Circularly Polarized ◽  
Background Magnetic Field ◽  
Electromagnetic Instability

We investigate the parametric decay and modulational instabilities of a large-amplitude circularly polarized dispersive Alfvén wave. Our treatment is more general than that of previous derivations based on the two-fluid equations in that we allow for propagation of the unstable daughter waves at arbitrary angles to the background magnetic field, although our main concern in this paper is the exploration of new aspects of propagation parallel to the DC magnetic field. In addition to the well-known coupling of pump waves to electrostatic daughter waves, we find a new parametric channel where the pump wave couples directly to electromagnetic daughter waves. Excitation of the electromagnetic instability occurs only for modulation (k/k0 ≤ 1) and not for decay (k/k0 < 1). In contrast with the modulational instability excited by the electrostatic coupling, the electromagnetic modulational instability exists for both left-hand (K > 0) and right-hand (K < 0) polarization. For large k/k0, the electromagnetic channel dominates, while at lower values the electrostatic channel has a larger growth rate for modest values of dispersion, pump-wave amplitude and plasma β. Unlike the electrostatic modulational instability, the growth rate of the electromagnetic instability increases monotonically with increasing pump wave amplitude. This analysis confirms that, for decay, the dominant process is coupling to electrostatic daughter waves, at least for parallel propagation. For modulation, the coupling to electromagnetic daughter waves usually dominates, suggesting that the parametric modulational instability is really an electromagnetic phenomenon.

Parametric instabilities of circularly polarized large-amplitude dispersive Alfvén waves: excitation of obliquely-propagating daughter and side-band waves

1991 ◽  
Vol 46 (1) ◽  
pp. 129-152 ◽  
Author(s):  
Adolfo F. Viñas ◽  
Melvyn L. Goldstein
Keyword(s):  
Large Amplitude ◽  
Broad Band ◽  
Alfven Wave ◽  
Band Width ◽  
Side Band ◽  
Circularly Polarized ◽  
Acoustic Instability ◽  
Parametric Instabilities ◽  
Filamentation Instability ◽  
Modulational Instabilities

We investigate the parametric instabilities of a large-amplitude circularly polarized dispersive parallel-propagating Alfvén wave. Our treatment is more general than that of previous derivations based on the two-fluid equations in that we allow for propagation of the unstable daughter and side-band waves at arbitrary angles to the background (DC) magnetic field. We present the characteristics of the decay and modulational instabilities as functions of propagation angle. We find, in addition to the well-known decay and modulational instabilities, that at oblique and perpendicular propagation there is another parametric instability, namely the filamentation instability, which is characterized by a broad band-width in wavenumber and which satisfies the condition Re (ω) ≪ γ. A second parametric process at oblique and perpendicular angles of propagation, which has not been reported before is also investigated, namely the parametric magneto-acoustic instability. This instability is distinct from the filamentation instability in that it is characterized by density perturbations with large real frequencies that satisfy the condition Re (ω) ≫ γ. Unlike the filamentation instability, the magneto-acoustic instability extends over a broad angular range, but has a very narrow band-width in wavenumber. We report the dispersive characteristics of the filamentation and magneto-acoustic instabilities as functions of plasma β dispersion η and pump amplitude η for arbitrary propagation angles.

Geomagnetic response to large-amplitude interplanetary Alfvén wave trains

1995 ◽  
Vol T60 ◽  
pp. 140-143 ◽  
Author(s):  
W D Gonzalez ◽  
A L Clúa de Gonzalez ◽  
B T Tsurutani
Keyword(s):  
Large Amplitude ◽  
Alfven Wave ◽  
Wave Trains

Chaotic dynamics of large-amplitude alfvén-wave trains in the solar wind.

2001 ◽  
Vol 28 (5) ◽  
pp. 771-774 ◽  
Author(s):  
F.A. Borotto ◽  
A.C.-L. Chian ◽  
A.L.C. Gonzalez ◽  
W.D. Gonzalez ◽  
B.T. Tsurutani
Keyword(s):  
Solar Wind ◽  
Large Amplitude ◽  
Chaotic Dynamics ◽  
Alfven Wave ◽  
Wave Trains
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