scholarly journals Propagation of a nonlinear wave packet driven in a relaxed magnetohydrodynamic plasma

2018 ◽  
Vol 84 (6) ◽  
Author(s):  
M. Kaur ◽  
M. R. Brown
Keyword(s):  
Wave Packet ◽  
Group Velocity ◽  
Nonlinear Wave ◽  
High Current ◽  
Theta Pinch ◽  
Single Turn

We report the observation of a nonlinear wave packet propagating through a relaxed Taylor state in the Swarthmore Spheromak eXperiment (SSX) device. The wave packet is launched by a fast, pulsed, high current (${\approx}21~\text{kA}$) single-turn theta-pinch coil mounted outside the plasma vessel. The theta-pinch coil is energized by discharging a 40 kV, 2 kJ capacitor circuit. The wave packet velocity is super-thermal and super-Alfvénic; its group velocity is more consistent with a whistler pulse than other characteristic velocities. We also observe a fast density pulse which indicates that it is not Alfvénic in nature.

scholarly journals Optical wave-packet with nearly-programmable group velocities

2020 ◽  
Vol 3 (1) ◽  
Author(s):  
Zhaoyang Li ◽  
Junji Kawanaka
Keyword(s):  
Wave Packet ◽  
Group Velocity ◽  
Wave Packets ◽  
Bessel Beam ◽  
Propagation Path ◽  
Uniform Motion ◽  
Optical Wave ◽  
Straight Line ◽  
Line Trajectory ◽  
Group Velocities

AbstractDuring the process of Bessel beam generation in free space, spatiotemporal optical wave-packets with tunable group velocities and accelerations can be created by deforming pulse-fronts of injected pulsed beams. So far, only one determined motion form (superluminal or luminal or subluminal for the case of group velocity; and accelerating or uniform-motion or decelerating for the case of acceleration) could be achieved in a single propagation path. Here we show that deformed pulse-fronts with well-designed axisymmetric distributions (unlike conical and spherical pulse-fronts used in previous studies) allow us to obtain nearly-programmable group velocities with several different motion forms in a single propagation path. Our simulation shows that this unusual optical wave-packet can propagate at alternating superluminal and subluminal group velocities along a straight-line trajectory with corresponding instantaneous accelerations that vary periodically between positive (acceleration) and negative (deceleration) values, almost encompassing all motion forms of the group velocity in a single propagation path. Such unusual optical wave-packets with nearly-programmable group velocities may offer new opportunities for optical and physical applications.

scholarly journals Statistical characteristics of AGW wave packet propagation in the lower atmosphere observed by the MU radar

2009 ◽  
Vol 27 (10) ◽  
pp. 3737-3753 ◽  
Author(s):  
F. S. Kuo ◽  
H. Y. Lue ◽  
C. L. Fern ◽  
J. Röttger ◽  
S. Fukao ◽  
...  
Keyword(s):  
Wave Packet ◽  
Group Velocity ◽  
Wave Period ◽  
Lower Atmosphere ◽  
Statistical Characteristics ◽  
Data Set ◽  
Horizontal Structure ◽  
North West ◽  
Mu Radar ◽  
Upward Moving

Abstract. We study the horizontal structure of the atmospheric gravity waves (AGW) in the height ranges between 6 and 22 km observed using the MU radar at Shigaraki in Japan, during a 3 day period in January and a 4 day period in August 1988. The data were divided by double Fourier transformation into a data set of upward moving waves and a data set of downward moving waves for independent analysis. The phase and group velocity tracing technique was applied to measure the vertical group and phase velocity as well as the characteristic period of the gravity wave packet. Then the dispersion equation of the linear theory of AGW was solved to obtain its intrinsic wave period – horizontal wavelength and horizontal group velocity – and the vertical flux of horizontal momentum associated with each wave packet was estimated to help determine the direction of the characteristic horizontal wave vector. The results showed that the waves with periods in the range of 30 min~6 h had horizontal scales ranging from 20 km to 1500 km, vertical scales from 4 km to 15 km, and horizontal phase velocities from 15 m/s to 60 m/s. The upward moving wave packets of wave period of 2 h~6 h had horizontal group velocities mainly toward east-south-east and northeast in winter, and mainly in the section between the directions of west-north-west and north in summer.

Nonlinear wave-packet dynamics resonantly driven by AC and DC fields

2018 ◽  
Vol 64 ◽  
pp. 89-97 ◽  
Author(s):  
A.L.S. Pereira ◽  
M.L. Lyra ◽  
F.A.B.F. de Moura ◽  
A. Ranciaro Neto ◽  
W.S. Dias
Keyword(s):  
Wave Packet ◽  
Nonlinear Wave ◽  
Wave Packet Dynamics

Application-Oriented Ray Theory

1978 ◽  
Vol 15 (3) ◽  
pp. 215-223 ◽  
Author(s):  
Dan Censor
Keyword(s):  
Wave Packet ◽  
Group Velocity ◽  
Dispersion Equation ◽  
Electrical Engineering ◽  
Ray Theory ◽  
Velocity Wave ◽  
The Subject ◽  
Fermat’S Principle ◽  
Equation Group ◽  
Fermat's Principle

This is a tutorial presentation of the subject of ray theory as provided for third-year students of electrical engineering. The concepts of the eikonal and dispersion equation, group velocity, wave packet, Fermat's principle and the ray equations are introduced. This is essential for students majoring in electromagnetic engineering.

Intramode wave packet in a thin left-handed film with the spectrum near the frequency of the zero group velocity

2016 ◽  
Vol 46 (11) ◽  
pp. 1040-1046 ◽  
Author(s):  
D A Konkin ◽  
R V Litvinov ◽  
E S Parfenova ◽  
Rakhim R.A.A. ◽  
O V Stukach
Keyword(s):  
Wave Packet ◽  
Group Velocity ◽  
Left Handed ◽  
Zero Group

scholarly journals The effects of trapped and untrapped particles on an electrostatic wave packet

1974 ◽  
Vol 12 (3) ◽  
pp. 487-500 ◽  
Author(s):  
Magne S. Espedal
Keyword(s):  
Wave Equation ◽  
Wave Packet ◽  
Group Velocity ◽  
Wave Packets ◽  
Particle Interaction ◽  
Finite Amplitude ◽  
Amplitude Wave ◽  
Electrostatic Wave ◽  
Wave Particle Interaction ◽  
Poisson Equations

We present a procedure to solve the Vlasov–Poisson equations for electrostatic wave packets. We obtain a Schrödinger type of wave equation, taking the wave– particle interaction into account. We use this equation to study the propagation of one finite-amplitude wave packet. We find a change in amplitude caused by interaction between the packet and particles propagating near to the group velocity. Also, we find a modulation of the plasma in the front of the packet, caused by trapping effects.

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