Propagation velocity of Alfvén wave packets in a dissipative plasma

Amagishi, Yoshimitsu; Nakagawa, Hiroyuki; Tanaka, Masayoshi

doi:10.1103/physreve.50.2217

Cited by 12 publications

(6 citation statements)

References 12 publications

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“…A similar effect in the propagation of Alfvén wave packets in a dissipative plasma with an anomalous dispersion relation has been reported [16]. The velocity of Alfvén wave is much slower than that of light, so the superluminal to subluminal transition is usually hard to be observed.…”

supporting

confidence: 72%

Superluminal to Subluminal Transition in the Pulse Propagation in a Resonantly Absorbing Medium

2001

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We have examined the propagation of femtosecond laser pulses in an absorbing dye solution through a short to a long range of propagation distance. The transmitted pulses show strong spectral shift and a superluminal to subluminal transition in the propagation velocity keeping its initial shape almost intact. It is verified that the peak velocity is well described by a modified group velocity v(S) defined within the framework of the saddle-point method as well as by a recent prediction of the net group delay of surviving frequency.

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supporting

confidence: 72%

Superluminal to Subluminal Transition in the Pulse Propagation in a Resonantly Absorbing Medium

2001

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“…According to the literatures [2][3][4], a wave packet propagating in a dispersive medium is expressed as the following Fourier integral,…”

Section: Theory Of the New Group Velocitymentioning

confidence: 99%

“…Figure 5 shows that the wave packet propagates through an absorbing medium with a decrease in its central frequency, and that its packet profile looks self-similar but changes its amplitude. The dispersion relation of this mode has been identified as that of a SAW including ion-neutral collisons ( [4]).…”

Section: Evolution Of the Wave Packet In An Anomalous Mediummentioning

confidence: 99%

“…Here we should note that the derivative is taken at a saddle-point frequency ω 1 , which is a real number for the peak amplitude of the packet and is obtained from the following relation ( [2,4])…”

Section: Introductionmentioning

confidence: 99%

“…We have experimentally studied the behaviour of Alfvén wave packets in a dissipative plasma due to ion-neutral collisions ( [5]), and also found in [4] that the central frequency of the packet is observed to gradually decrease with a travelling distance in the absorption range of frequency because of different damping rates among the Fourier components. The measured average velocity is not accounted for by the conventional group velocity (1), but by the new velocity (2).…”

Section: Introductionmentioning

confidence: 99%

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Split of the Alfvén wave packet in a dissipative plasma

Amagishi

Tanaka

1997

Plasma Phys. Control. Fusion

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We have experimentally found that ion-neutral collisions in a magnetized plasma cause a drastic change in the dispersion relation of the Alfvén wave at frequencies below the ion-cyclotron frequency. In a consecutive experiment, we have also found that the measured average velocity of the wave packet does not obey the conventional group velocity that exceeds the velocity of light, but obeys a new defined group velocity that is much lower than the velocity of light. Furthermore, when the initial central frequency of the wave packet is just located on the anomalous dispersion range of frequency, the wave packet splits, when propagating along the magnetic field, into two new wave packets with central frequencies being higher and lower than the initial central frequency. One of the new packets with lower central frequency is confirmed to be the shear Alfvén wave and the other the compressional Alfvén wave; the behaviour of these new wave packets can also be explained by our new theory.

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Experimental observations of shear Alfvén waves generated by narrow current channels

Gekelman

Vincena

Leneman

1997

Plasma Phys. Control. Fusion

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AlfvŽn waves are ubiquitous in space plasmas and are the means by which information about changing currents and magnetic fields are communicated. Shear AlfvŽn waves radiated from sources with cross field scale size on the order of the electron inertial length, δ = c/ω pe , have properties which differ considerably from planar Magneto-hydrodynamic waves. Currents of cross field size δ are common in space plasmas. A series of experiments in the L L L La a a arge

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Propagation velocity of Alfvén wave packets in a dissipative plasma

Cited by 12 publications

References 12 publications

Superluminal to Subluminal Transition in the Pulse Propagation in a Resonantly Absorbing Medium

Superluminal to Subluminal Transition in the Pulse Propagation in a Resonantly Absorbing Medium

Split of the Alfvén wave packet in a dissipative plasma

Experimental observations of shear Alfvén waves generated by narrow current channels

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