Theory of dispersive shear Alfvén wave focusing in Earth's magnetosphere

2005 ◽  
Vol 32 (5) ◽  
Author(s):  
R. Rankin
Keyword(s):  
Alfven Wave ◽  
Wave Focusing ◽  
Earth’S Magnetosphere ◽  
Earth's Magnetosphere

Numerical simulations to study whistler turbulence by kinetic Alfvén wave

2011 ◽  
Vol 77 (6) ◽  
pp. 715-724 ◽  
Author(s):  
R. P. SHARMA ◽  
K. BATRA ◽  
N. K. DWIVEDI
Keyword(s):  
Energy Exchange ◽  
Alfven Wave ◽  
Kinetic Alfvén Wave ◽  
Earth’S Magnetosphere ◽  
Localized Structures ◽  
Envelope Solitons ◽  
Kinetic Alfven Wave ◽  
Earth's Magnetosphere ◽  
Perturbation Energy ◽  
Model Equations

AbstractThis work presents the model equations governing the excitation of weak whistler by a stronger Kinetic Alfvén wave (KAW) in the plasma having β value (β ≫ me/mi, where beta is the ratio of the ion sound speed to the Alfvén speed), applicable to magnetotail in Earth's magnetosphere, when the ponderomotive nonlinearity is incorporated in the KAW dynamics. Numerical solution of the model equations has been obtained when the incident pump KAW is having a small perturbation. Energy exchange between main KAW and perturbation and the resulting localized structures of the KAW have been studied. A weak whistler signal propagating in these localized structures is amplified and leads to the development of envelope solitons. Our result reveals that the amplified (excited) whistler has an electric field power spectrum that is steeper than k−8/3. This result is consistent with recent observations by the Cluster spacecraft Eastwood et al. (Phys. Rev. Lett., vol. 102, 2009, 035001) in the magnetotail region of the Earth's magnetosphere.

scholarly journals Hydromagnetic waves in a compressed-dipole field via field-aligned Klein–Gordon equations

2016 ◽  
Vol 34 (4) ◽  
pp. 473-484 ◽  
Author(s):  
Jinlei Zheng ◽  
Qiang Hu ◽  
Gary M. Webb ◽  
James F. McKenzie
Keyword(s):  
Magnetic Field ◽  
Amplitude Ratio ◽  
Low Frequency ◽  
Alfven Wave ◽  
Earth’S Magnetosphere ◽  
Background Magnetic Field ◽  
Earth's Magnetosphere ◽  
Klein Gordon ◽  
Field Lines ◽  
Hydromagnetic Waves

Abstract. Hydromagnetic waves, especially those of frequencies in the range of a few millihertz to a few hertz observed in the Earth's magnetosphere, are categorized as ultra low-frequency (ULF) waves or pulsations. They have been extensively studied due to their importance in the interaction with radiation belt particles and in probing the structures of the magnetosphere. We developed an approach to examining the toroidal standing Aflvén waves in a background magnetic field by recasting the wave equation into a Klein–Gordon (KG) form along individual field lines. The eigenvalue solutions to the system are characteristic of a propagation type when the corresponding eigenfrequency is greater than a critical frequency and a decaying type otherwise. We apply the approach to a compressed-dipole magnetic field model of the inner magnetosphere and obtain the spatial profiles of relevant parameters and the spatial wave forms of harmonic oscillations. We further extend the approach to poloidal-mode standing Alfvén waves along field lines. In particular, we present a quantitative comparison with a recent spacecraft observation of a poloidal standing Alfvén wave in the Earth's magnetosphere. Our analysis based on the KG equation yields consistent results which agree with the spacecraft measurements of the wave period and the amplitude ratio between the magnetic field and electric field perturbations.

scholarly journals Current Systems in the Earth's Magnetosphere

2018 ◽  
Vol 56 (2) ◽  
pp. 309-332 ◽  
Author(s):  
N. Yu. Ganushkina ◽  
M. W. Liemohn ◽  
S. Dubyagin
Keyword(s):  
Earth’S Magnetosphere ◽  
Earth's Magnetosphere ◽  
Current Systems
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