scholarly journals Association of Alfvén waves and proton cyclotron waves with electrostatic bipolar pulses: magnetic hole events observed by Polar

2004 ◽  
Vol 11 (2) ◽  
pp. 205-213 ◽  
Author(s):  
G. S. Lakhina ◽  
B. T. Tsurutani ◽  
J. Pickett
Keyword(s):  
Boundary Layer ◽  
Free Energy ◽  
High Frequency ◽  
Low Frequency ◽  
Alfven Waves ◽  
Alfvén Waves ◽  
Polar Cap ◽  
Electron Holes ◽  
Proton Cyclotron ◽  
Low Frequency Waves

Abstract. Two magnetic hole events observed by Polar on 20 May 1996 when it was in the polar cap/polar cusp boundary layer are studied. Low-frequency waves, consisting of nonlinear Alfvén waves and large amplitude (±14nT peak-to-peak) obliquely propagating proton cyclotron waves (with frequency f~0.6 to 0.7 fcp), accompanied by electric bipolar pulses (electron holes) and electron heating have been observed located within magnetic holes. It is shown that low-frequency waves can provide free energy to drive some high frequency instabilities which saturate by trapping electrons, thus, leading to the generation of electron holes.

scholarly journals Alfvén waves in the foreshock propagating upstream in the plasma rest frame: statistics from Cluster observations

2004 ◽  
Vol 22 (7) ◽  
pp. 2315-2323 ◽  
Author(s):  
Y. Narita ◽  
K.-H. Glassmeier ◽  
S. Schäfer ◽  
U. Motschmann ◽  
M. Fränz ◽  
...  
Keyword(s):  
Rest Frame ◽  
Low Frequency ◽  
Alfven Waves ◽  
Alfvén Waves ◽  
Phase Velocities ◽  
Wave Numbers ◽  
The Magnetic Field ◽  
Proton Cyclotron ◽  
Low Frequency Waves ◽  
Alfven Velocity

Abstract. We statistically study various properties of low-frequency waves such as frequencies, wave numbers, phase velocities, and polarization in the plasma rest frame in the terrestrial foreshock. Using Cluster observations the wave telescope or k-filtering is applied to investigate wave numbers and rest frame frequencies. We find that most of the foreshock waves propagate upstream along the magnetic field at phase velocity close to the Alfvén velocity. We identify that frequencies are around 0.1xΩcp and wave numbers are around 0.1xΩcp/VA, where Ωcp is the proton cyclotron frequency and VA is the Alfvén velocity. Our results confirm the conclusions drawn from ISEE observations and strongly support the existence of Alfvén waves in the foreshock.

scholarly journals Nonlinear Alfvén waves, discontinuities, proton perpendicular acceleration, and magnetic holes/decreases in interplanetary space and the magnetosphere: intermediate shocks?

2005 ◽  
Vol 12 (3) ◽  
pp. 321-336 ◽  
Author(s):  
B. T. Tsurutani ◽  
G. S. Lakhina ◽  
J. S. Pickett ◽  
F. L. Guarnieri ◽  
N. Lin ◽  
...  
Keyword(s):  
Interplanetary Space ◽  
Alfven Waves ◽  
Alfven Wave ◽  
Alfvén Waves ◽  
Reverse Shock ◽  
Propagating Waves ◽  
Mirror Mode ◽  
Interaction Regions ◽  
Electron Holes ◽  
Proton Cyclotron

Abstract. Alfvén waves, discontinuities, proton perpendicular acceleration and magnetic decreases (MDs) in interplanetary space are shown to be interrelated. Discontinuities are the phase-steepened edges of Alfvén waves. Magnetic decreases are caused by a diamagnetic effect from perpendicularly accelerated (to the magnetic field) protons. The ion acceleration is associated with the dissipation of phase-steepened Alfvén waves, presumably through the Ponderomotive Force. Proton perpendicular heating, through instabilities, lead to the generation of both proton cyclotron waves and mirror mode structures. Electromagnetic and electrostatic electron waves are detected as well. The Alfvén waves are thus found to be both dispersive and dissipative, conditions indicting that they may be intermediate shocks. The resultant "turbulence" created by the Alfvén wave dissipation is quite complex. There are both propagating (waves) and nonpropagating (mirror mode structures and MDs) byproducts. Arguments are presented to indicate that similar processes associated with Alfvén waves are occurring in the magnetosphere. In the magnetosphere, the "turbulence" is even further complicated by the damping of obliquely propagating proton cyclotron waves and the formation of electron holes, a form of solitary waves. Interplanetary Alfvén waves are shown to rapidly phase-steepen at a distance of 1AU from the Sun. A steepening rate of ~35 times per wavelength is indicated by Cluster-ACE measurements. Interplanetary (reverse) shock compression of Alfvén waves is noted to cause the rapid formation of MDs on the sunward side of corotating interaction regions (CIRs). Although much has been learned about the Alfvén wave phase-steepening processfrom space plasma observations, many facets are still not understood. Several of these topics are discussed for the interested researcher. Computer simulations and theoretical developments will be particularly useful in making further progress in this exciting new area.

scholarly journals Controlling the type and intensity of low-frequency waves generated by laser plasma clots in a force tube of magnetized plasma

2021 ◽  
Vol 2067 (1) ◽  
pp. 012019
Author(s):  
A G Berezutsky ◽  
V N Tishchenko ◽  
A A Chibranov ◽  
I B Miroshnichenko ◽  
Yu P Zakharov ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Laser Plasma ◽  
Low Frequency ◽  
Alfven Waves ◽  
Magnetized Plasma ◽  
Background Plasma ◽  
Alfvén Waves ◽  
Whistler Waves ◽  
Low Frequency Waves

Abstract In this work, we study the influence of the parameters of a magnetized background plasma on the intensity of whistler waves generated by periodic laser plasma bunches in a magnetic field tube. It is shown that at 0.3 < Lpi > 0.4 Alfvén waves and whistlers are generated. In the region Lpi> 0.5, intense whistlers with an amplitude of δBmax / B0 ∼ 0.24 are generated.

The parametric excitation of kinetic Alfvén waves by a magnetic pump

1981 ◽  
Vol 26 (2) ◽  
pp. 253-266 ◽  
Author(s):  
N. F. Cramer ◽  
I. J. Donnelly
Keyword(s):  
Finite Temperature ◽  
Acoustic Waves ◽  
Temperature Effects ◽  
Mode Conversion ◽  
Low Frequency ◽  
Alfven Waves ◽  
Alfven Wave ◽  
Alfvén Waves ◽  
Ion Acoustic Wave ◽  
Low Frequency Waves

The parametric decay of a magneto-acoustic pump wave into low-frequency waves modified by finite temperature effects is considered. The excited waves are the kinetic Alfvén wave and the ion-acoustic wave. The former wave plays an important role in linear heating schemes employing the mode conversion of magneto-acoustic waves at the Alfvén resonance. Here we calculate the parametric growth rates and pump thresholds for excitation of these waves. The main result is that finite temperature effects tend to reduce the growth rate of Alfvén waves.

Preferential acceleration of heavy ions from thermal velocities

1968 ◽  
Vol 46 (10) ◽  
pp. S638-S641 ◽  
Author(s):  
D. B. Melrose
Keyword(s):  
Frequency Spectrum ◽  
High Frequency ◽  
Heavy Ions ◽  
Crab Nebula ◽  
Low Frequency ◽  
High Frequency Waves ◽  
Hydromagnetic Waves ◽  
The Crab Nebula ◽  
Low Frequency Waves

The acceleration of ions from thermal velocities is analyzed to determine conditions under which heavy ions can be preferentially accelerated. Two accelerating mechanisms involving high-and low-frequency hydromagnetic waves respectively are considered. Preferential acceleration of heavy ions occurs for high-frequency waves if the frequency spectrum falls off faster than (frequency)−1. For the low-frequency waves heavy ions are less effectively accelerated than lighter ions. However, very heavy ions can be preferentially accelerated, the abundances of the very heavy ions being enhanced by a factor Ai over the thermal abundances. Acceleration of ions in the envelope of the Crab nebula is considered as an example.

Ion flow driven by low frequency Alfvén waves in a low-beta plasma

2021 ◽  
Vol 28 (2) ◽  
pp. 022903
Author(s):  
X. Q. Lu ◽  
L. M. Yu ◽  
W. Guo ◽  
K. H. Li
Keyword(s):  
Low Frequency ◽  
Alfven Waves ◽  
Alfvén Waves ◽  
Ion Flow

scholarly journals Upward propagating high-frequency Alfvén waves as identified from dynamic wave-like spicules observed by SOT onHinode

2009 ◽  
Vol 497 (2) ◽  
pp. 525-535 ◽  
Author(s):  
J.-S. He ◽  
C.-Y. Tu ◽  
E. Marsch ◽  
L.-J. Guo ◽  
S. Yao ◽  
...  
Keyword(s):  
High Frequency ◽  
Alfven Waves ◽  
Alfvén Waves ◽  
Dynamic Wave

scholarly journals Some properties of Alfvén waves: Observations in the tail lobes and the plasma sheet boundary layer

2005 ◽  
Vol 110 (A10) ◽  
Author(s):  
A. Keiling ◽  
G. K. Parks ◽  
J. R. Wygant ◽  
J. Dombeck ◽  
F. S. Mozer ◽  
...  
Keyword(s):  
Boundary Layer ◽  
Plasma Sheet ◽  
Alfven Waves ◽  
Alfvén Waves ◽  
Plasma Sheet Boundary Layer

Computation of Unsteady Viscous Marine-Propulsor Blade Flows—Part 2: Parametric Study

1999 ◽  
Vol 121 (1) ◽  
pp. 139-147 ◽  
Author(s):  
Eric G. Paterson ◽  
Fred Stern
Keyword(s):  
Boundary Layer ◽  
Frequency Response ◽  
High Frequency ◽  
Stokes Equations ◽  
Low Frequency ◽  
Driving Mechanism ◽  
Massachusetts Institute Of Technology ◽  
Flapping Foil ◽  
Displacement Thickness ◽  
Institute Of Technology

In this two-part paper, time-accurate solutions of the Reynolds-averaged Navier-Stokes equations are presented, which address through model problems, the response of turbulent propeller-blade boundary layers and wakes to external-flow traveling waves. In Part 1, the Massachusetts Institute of Technology flapping-foil experiment was simulated and the results validated through comparisons with data. The response was shown to be significantly more complex than classical unsteady boundary layer and unsteady lifting flows thus motivating further study. In Part 2, the effects of frequency, waveform, and foil geometry are investigated. The results demonstrate that uniquely different response occurs for low and high frequency. High-frequency response agrees with behavior seen in the flapping-foil experiment, whereas low-frequency response displays a temporal behavior which more closely agrees with classical inviscid-flow theories. Study of waveform and geometry show that, for high frequency, the driving mechanism of the response is a viscous-inviscid interaction created by a near-wake peak in the displacement thickness which, in turn, is directly related to unsteady lift and the oscillatory wake sheet. Pressure waves radiate upstream and downstream of the displacement thickness peak for high frequency flows. Secondary effects, which are primarily due to geometry, include gust deformation due to steady-unsteady interaction and trailing-edge counter-rotating vortices which create a two-layered amplitude and phase-angle profile across the boundary layer.

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