Latitudinal amplitude-phase structure of MHD waves: STARE radar and image magnetometer observations and modeling

We have developed a numerical model that yields a steady-state distribution of field components of MHD wave in an inhomogeneous plasma box simulating the realistic magnetosphere. The problem of adequate boundary condition at the ionosphere–magnetosphere interface for coupled MHD mode is considered. To justify the model’s assumptions, we have derived the explicit inequality showing when the ionospheric inductive Hall effect can be neglected upon the consideration of Alfven wave reflection from the ionospheric boundaries. The model predicts a feature of the ULF spatial amplitude/phase distribution that has not been noticed by the field line resonance theory: the existence of a region with opposite phase delays on the source side of the resonance. This theoretical prediction is supported by the amplitude-phase latitudinal structures of Pc5 waves observed by STARE radar and IMAGE magnetometers. A gradual decrease in azimuthal wave number m at smaller L-shells was observed at longitudinally separated radar beams.

Download Full-text

A case study of a radially polarized Pc4 event observed by the Equator-S satellite

Annales Geophysicae ◽

10.1007/s00585-000-0411-5 ◽

2000 ◽

Vol 18 (4) ◽

pp. 411-415 ◽

Cited By ~ 5

Author(s):

R. Cramm ◽

K. H. Glassmeier ◽

C. Othmer ◽

K. H. Fornacon ◽

H. U. Auster ◽

...

Keyword(s):

Analytical Signal ◽

Alfven Wave ◽

Wave Number ◽

Mhd Waves ◽

Magnetic Field Data ◽

Line Resonance ◽

Mhd Waves And Instabilities ◽

Radially Polarized ◽

The Magnetic Field

Abstract. A 16 mHz Pc4 pulsation was recorded on March 17, 1998, in the prenoon sector of the Earth's magnetosphere by the Equator-S satellite. The event is strongly localized in radial direction at approximately L = 5 and exhibits properties of a field line resonance such as an ellipticity change as seen by applying the method of the analytical signal to the magnetic field data. The azimuthal wave number was estimated as m \\approx 150. We discuss whether this event can be explained by the FLR mechanism and find out that the change in ellipticity is more a general feature of a localized Alfvén wave than indicative of a resonant process.Key words: Magnetospheric physics (MHD waves and instabilities)

Download Full-text

Evolution of FMS and Alfven waves produced by the initial disturbance in the FMS waveguide

Journal of Plasma Physics ◽

10.1017/s0022377812000608 ◽

2012 ◽

Vol 79 (1) ◽

pp. 7-17 ◽

Cited By ~ 14

Author(s):

I. S. DMITRIENKO

Keyword(s):

Longitudinal Wave ◽

Perturbation Technique ◽

Inhomogeneous Plasma ◽

Alfven Waves ◽

Initial Disturbance ◽

Alfven Wave ◽

Wave Number ◽

Collective Modes ◽

Alfvén Waves ◽

Longitudinal Structure

AbstractA description of the evolution of the initial disturbance in the fast magnetosonic (FMS) waveguide in transversely inhomogeneous plasma, given a weak coupling between FMS and Alfven modes, is made. It is shown that the Fourier transform of the FMS waveguide disturbance with respect to the coordinates along which plasma is homogeneous can be presented as a superposition of collective modes of the leading approximation with respect to the weak FMS–Alfven wave coupling from the initial instant of time. Frequencies of such collective modes and dependence of their structures on the coordinate along the inhomogeneity are found without taking the FMS–Alfven resonance into consideration, and the mode decrements are calculated using the perturbation technique. On the basis of such a representation of the FMS waveguide disturbance, the evolution of Alfven waves generating with waveguide mode packets produced by the initial disturbance of an arbitrary longitudinal structure is described. It is shown that the longitudinal structure of the Alfven disturbance generated by the collective mode packet is determined by the ratio between longitudinal scales of the initial disturbance and scales specified by resonance conditions (the resonance longitudinal wave number and the width of the range of the resonance longitudinal wave numbers). The structures of Alfven disturbances for the cases of such different ratios are described.

Download Full-text

Theory of azimuthally small-scale hydromagnetic waves in the axisymmetric magnetosphere with finite plasma pressure

Annales Geophysicae ◽

10.1007/s00585-998-0303-7 ◽

1998 ◽

Vol 16 (3) ◽

pp. 303-321 ◽

Cited By ~ 25

Author(s):

D. Y. Klimushkin

Keyword(s):

Magnetic Surface ◽

Plasma Pressure ◽

The Other ◽

Wave Number ◽

Mhd Waves ◽

Small Scale ◽

Azimuthal Wave Number ◽

Field Lines ◽

Resonance Surface ◽

Hydromagnetic Waves

Abstract. The structure of monochromatic MHD-waves with large azimuthal wave number m≫1 in a two-dimensional model of the magnetosphere has been investigated. A joint action of the field line curvature, finite plasma pressure, and transversal equilibrium current leads to the phenomenon that waves, standing along the field lines, are travelling across the magnetic shells. The wave propagation region, the transparency region, is bounded by the poloidal magnetic surface on one side and by the resonance surface on the other. In their meaning these surfaces correspond to the usual and singular turning points in the WKB-approximation, respectively. The wave is excited near the poloidal surface and propagates toward the resonance surface where it is totally absorbed due to the ionospheric dissipation. There are two transparency regions in a finite-beta magnetosphere, one of them corresponds to the Alfvén mode and the other to the slow magnetosound mode.Key words. Magnetosphere · Azimuthally small-scale waves · MHD waves

Download Full-text

Experimental Study on Coherent Structures by Particles Suspended in Half-Zone Thermocapillary Liquid Bridges: Review

Fluids ◽

10.3390/fluids6030105 ◽

2021 ◽

Vol 6 (3) ◽

pp. 105

Author(s):

Ichiro Ueno

Keyword(s):

Coherent Structures ◽

Three Dimensional ◽

Wave Number ◽

Flow Structures ◽

Liquid Bridges ◽

Thermocapillary Effect ◽

Particle Accumulation ◽

Azimuthal Wave Number ◽

Experimental Approaches ◽

Particle Behaviour

Coherent structures by the particles suspended in the half-zone thermocapillary liquid bridges via experimental approaches are introduced. General knowledge on the particle accumulation structures (PAS) is described, and then the spatial–temporal behaviours of the particles forming the PAS are illustrated with the results of the two- and three-dimensional particle tracking. Variations of the coherent structures as functions of the intensity of the thermocapillary effect and the particle size are introduced by focusing on the PAS of the azimuthal wave number m=3. Correlation between the particle behaviour and the ordered flow structures known as the Kolmogorov–Arnold—Moser tori is discussed. Recent works on the PAS of m=1 are briefly introduced.

Download Full-text

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

Annales Geophysicae ◽

10.5194/angeo-28-1499-2010 ◽

2010 ◽

Vol 28 (8) ◽

pp. 1499-1509 ◽

Cited By ~ 16

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.

Download Full-text

Study of gradient effects on kinetic Alfven wave with inhomogeneous plasma

Astrophysics and Space Science ◽

10.1007/s10509-013-1376-7 ◽

2013 ◽

Vol 345 (1) ◽

pp. 99-107 ◽

Cited By ~ 7

Author(s):

P. Agarwal ◽

P. Varma ◽

M. S. Tiwari

Keyword(s):

Inhomogeneous Plasma ◽

Alfven Wave ◽

Kinetic Alfvén Wave ◽

Kinetic Alfven Wave ◽

Gradient Effects

Download Full-text

Compressional wave events in the dawn plasma sheet observed by Interball-1

Annales Geophysicae ◽

10.1007/s00585-999-1145-7 ◽

1999 ◽

Vol 17 (9) ◽

pp. 1145-1154 ◽

Cited By ~ 11

Author(s):

O. Verkhoglyadova ◽

A. Agapitov ◽

A. Andrushchenko ◽

V. Ivchenko ◽

S. Romanov ◽

...

Keyword(s):

Magnetic Field ◽

Time Series ◽

Field Line ◽

Plasma Sheet ◽

Inhomogeneous Plasma ◽

Partial Solution ◽

Alfven Wave ◽

Data Set ◽

Background Magnetic Field ◽

Phase Variations

Abstract. Compressional waves with periods greater than 2 min (about 10-30 min) at low geomagnetic latitudes, namely compressional Pc5 waves, are studied. The data set obtained with magnetometer MIF-M and plasma analyzer instrument CORALL on board the Interball-1 are analyzed. Measurements performed in October 1995 and October 1996 in the dawn plasma sheet at -30 RE ≤ XGSM and |ZGSM| ≤ 10 RE are considered. Anti-phase variations of magnetic field and ion plasma pressures are analyzed by searching for morphological similarities in the two time series. It is found that longitudinal and transverse magnetic field variations with respect to the background magnetic field are of the same order of magnitude. Plasma velocities are processed for each time period of the local dissimilarity in the pressure time series. Velocity disturbances occur mainly transversely to the local field line. The data reveal the rotation of the velocity vector. Because of the field line curvature, there is no fixed position of the rotational plane in the space. These vortices are localized in the regions of anti-phase variations of the magnetic field and plasma pressures, and the vortical flows are associated with the compressional Pc5 wave process. A theoretical model is proposed to explain the main features of the nonlinear wave processes. Our main goal is to study coupling of drift Alfven wave and magnetosonic wave in a warm inhomogeneous plasma. A vortex is the partial solution of the set of the equations when the compression is neglected. A compression effect gives rise to a nonlinear soliton-like solution.Key words. Magnetosphere physics (magnetotail) · Space plasma physics (kinetic and MHD theory; non-linear phenomena)

Download Full-text