Theory of magnetospheric standing hydromagnetic waves with large azimuthal wave number: 3. Particle resonance and instability

1994 ◽  
Vol 99 (A6) ◽  
pp. 11105 ◽  
Author(s):  
A. D. M. Walker
Keyword(s):  
Wave Number ◽  
Azimuthal Wave ◽  
Azimuthal Wave Number ◽  
Particle Resonance ◽  
Hydromagnetic Waves

scholarly journals Intermediate-<I>m</I> ULF waves generated by substorm injection: a case study

2010 ◽  
Vol 28 (8) ◽  
pp. 1499-1509 ◽  
Author(s):  
T. K. Yeoman ◽  
D. Yu. Klimushkin ◽  
P. N. Mager
Keyword(s):  
Phase Variation ◽  
Wave Activity ◽  
Wave Number ◽  
Ulf Wave ◽  
Azimuthal Wave ◽  
Azimuthal Wave Number ◽  
Source Particle ◽  
Phase Propagation ◽  
Field Lines

Abstract. A case study of SuperDARN observations of Pc5 Alfvén ULF wave activity generated in the immediate aftermath of a modest-intensity substorm expansion phase onset is presented. Observations from the Hankasalmi radar reveal that the wave had a period of 580 s and was characterized by an intermediate azimuthal wave number (m=13), with an eastwards phase propagation. It had a significant poloidal component and a rapid equatorward phase propagation (~62° per degree of latitude). The total equatorward phase variation over the wave signatures visible in the radar field-of-view exceeded the 180° associated with field line resonances. The wave activity is interpreted as being stimulated by recently-injected energetic particles. Specifically the wave is thought to arise from an eastward drifting cloud of energetic electrons in a similar fashion to recent theoretical suggestions (Mager and Klimushkin, 2008; Zolotukhina et al., 2008; Mager et al., 2009). The azimuthal wave number m is determined by the wave eigenfrequency and the drift velocity of the source particle population. To create such an intermediate-m wave, the injected particles must have rather high energies for a given L-shell, in comparison to previous observations of wave events with equatorward polarization. The wave period is somewhat longer than previous observations of equatorward-propagating events. This may well be a consequence of the wave occurring very shortly after the substorm expansion, on stretched near-midnight field lines characterised by longer eigenfrequencies than those involved in previous observations.

scholarly journals Standing Alfvén waves with m ≫ 1 in an axisymmetric magnetosphere excited by a stochastic source

1998 ◽  
Vol 16 (8) ◽  
pp. 900-913 ◽  
Author(s):  
A. S. Leonovich ◽  
V. A. Mazur
Keyword(s):  
White Noise ◽  
Broad Band ◽  
Alfven Waves ◽  
Statistical Properties ◽  
Wave Number ◽  
Alfvén Waves ◽  
Azimuthal Wave ◽  
Azimuthal Wave Number ◽  
Magnetic Shell

Abstract. In the framework of an axisymmetric magnetospheric model, we have constructed a theory for broad-band standing Alfvén waves with large azimuthal wave number m » 1 excited by a stochastic source. External currents in the ionosphere are taken as the oscillation source. The source with statistical properties of "white noise" is considered at length. It is shown that such a source drives oscillations which also have the "white noise" properties. The spectrum of such oscillations for each harmonic of standing Alfvén waves has two maxima: near the poloidal and toroidal eigenfrequencies of the magnetic shell of the observation. In the case of a small attenuation in the ionosphere the maximum near the toroidal frequency is dominated, and the oscillations are nearly toroidally polarized. With a large attenuation, a maximum is dominant near the poloidal frequency, and the oscillations are nearly poloidally polarized.

scholarly journals Axisymmetric Alfvén resonances in a multi-component plasma at finite ion gyrofrequency

2006 ◽  
Vol 24 (3) ◽  
pp. 1077-1084 ◽  
Author(s):  
D. Yu. Klimushkin ◽  
P. N. Mager ◽  
K.-H. Glassmeier
Keyword(s):  
Radial Component ◽  
Wave Number ◽  
Azimuthal Component ◽  
Azimuthal Wave ◽  
Wave Resonance ◽  
Azimuthal Wave Number ◽  
Light Ions ◽  
Component Plasma ◽  
Pole Type ◽  
Resonance Surface

Abstract. This paper deals with the spatial structure of zero azimuthal wave number ULF oscillations in a 1-D inhomogeneous multi-component plasma when a finite ion gyrofrequency is taken into account. Such oscillations may occur in the terrestrial magnetosphere as Pc1-3 waves or in the magnetosphere of the planet Mercury. The wave field was found to have a sharp peak on some magnetic surfaces, an analogy of the Alfvén (field line) resonance in one-fluid MHD theory. The resonance can only take place for waves with frequencies in the intervals ω<ωch or Ω0<ω< ωcp, where ωch and ωcp are heavy and light ions gyrofrequencies, and Ω0 is a kind of hybrid frequency. Contrary to ordinary Alfvén resonance, the wave resonance under consideration takes place even at the zero azimuthal wave number. The radial component of the wave electric field has a pole-type singularity, while the azimuthal component is finite but has a branching point singularity on the resonance surface. The later singularity can disappear at some frequencies. In the region adjacent to the resonant surface the mode is standing across the magnetic shells.

Three-Dimensional Viscous Potential Electrohydrodynamic Kelvin–Helmholtz Instability Through Vertical Cylindrical Porous Inclusions With Permeable Boundaries

2013 ◽  
Vol 136 (2) ◽  
Author(s):  
Galal M. Moatimid ◽  
Mohamed A. Hassan
Keyword(s):  
Dispersion Relation ◽  
Three Dimensional ◽  
Wave Number ◽  
Helmholtz Instability ◽  
Large Wave ◽  
Porous Layers ◽  
Azimuthal Wave ◽  
Azimuthal Wave Number ◽  
Streaming Velocity ◽  
The Stability

In this paper, the electrohydrodynamic three-dimensional Kelvin–Helmholtz instability of a cylindrical interface with heat and mass transfer between liquid and vapor phases is studied. The liquid and the vapor are saturated, two coaxial cylindrical porous layers, and the suction/injection velocities for the fluids at the permeable boundaries are also taken into account. The dispersion relation is derived and the stability analysis is discussed for various parameters. It is found that the streaming velocity has a destabilizing effect, while the axial electric field has a stabilizing one. The suction for both the liquid and the steam has a destabilizing effect in contrast with the injection at both boundaries. The flow through porous structure is more stable than the pure flow. The case of the axisymmetric (for zero value of the azimuthal wave number m) and asymmetric (for nonzero value of the azimuthal wave number m) disturbances at large wavelength (at the wave number k→0) are always stable. Meanwhile, it is the same dispersion relation for the plane geometry at large wave number. Finally, our results are corroborated by comparing them with the previous published results.

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