Effect of high-frequency magnetic fluctuations on MHD waves

1994 ◽  
Vol 52 (1) ◽  
pp. 43-53
Author(s):  
Tadas K. Nakamura ◽  
C. F. Kennel
Keyword(s):  
Magnetic Field ◽  
Energy Transfer ◽  
High Frequency ◽  
Cyclotron Resonance ◽  
Mode Coupling ◽  
Energy Exchange ◽  
Wave Dispersion ◽  
Mhd Waves ◽  
Magnetic Fluctuations ◽  
Resonant Effect

We have shown earlier that compressional magnetic fluctuations modify the properties of MHD waves. The modifications can be large even when the fluctuation level is much smaller than the ambient magnetic field. There are two kinds of effects: resonant and non-resonant. The former is a result of the so- called parametric cyclotron resonance, and enables energy transfer from the wave to particle Larmor motion. This transfer causes the damping of waves even when their frequency is so small that ordinary cyclotron damping is negligible. The non-resonant effect does not cause energy exchange, but it does modify wave dispersion and causes mode coupling between the shear Alfvén mode and magnetosonic modes.

scholarly journals Magnetic turbulence and particle dynamics in the Earth’s magnetotail

2003 ◽  
Vol 21 (9) ◽  
pp. 1947-1953 ◽  
Author(s):  
G. Zimbardo ◽  
A. Greco ◽  
A. L. Taktakishvili ◽  
P. Veltri ◽  
L. M. Zelenyi
Keyword(s):  
Magnetic Field ◽  
Current Sheet ◽  
Sheet Thickness ◽  
Particle Dynamics ◽  
Particle Simulation ◽  
Mhd Waves ◽  
Magnetic Fluctuations ◽  
Magnetic Turbulence ◽  
Magnetospheric Configuration And Dynamics ◽  
Interplanetary Physics

Abstract. The influence of magnetic turbulence in the near-Earth magnetotail on ion motion is investigated by numerical simulation. The magnetotail current sheet is modelled as a magnetic field reversal with a normal magnetic field com-ponent Bn , plus a three-dimensional spectrum of magnetic fluctuations dB which represents the observed magnetic turbulence. The dawn-dusk electric field Ey is also considered. A test particle simulation is performed using different values of Bn and of the fluctuation level dB/B0. We show that when the magnetic fluctuations are taken into account, the particle dynamics is deeply affected, giving rise to an increase in the cross tail transport, ion heating, and current sheet thickness. For strong enough turbulence, the current splits in two layers, in agreement with recent Cluster observations.Key words. Magnetospheric physics (magnetospheric configuration and dynamics) – Interplanetary physics (MHD waves and turbulence) – Electromagnetics (numerical methods)

A multi-spacecraft analysis of energy transfer associated with near-Earth magnetic reconnection

2020 ◽  
Author(s):  
Sid Fadanelli ◽  
Benoit Lavraud ◽  
Francesco Califano
Keyword(s):  
Energy Transfer ◽  
High Frequency ◽  
Energy Exchange ◽  
Evolution Equations ◽  
Effective Energy ◽  
Large Database ◽  
Statistical Validity ◽  
Effective Energy Transfer ◽  
Energy Transfers ◽  
Plasma Theory

<p>We present an analysis of energy transfers in a reconnecting near-Earth plasma, obtained by interpreting MMS data within the framework of multi-fluid plasma theory. In our analysis, energy transfers are calculated and examined locally. This way, correlations between different mechanisms of energy exchange can be retrieved in all spatial and temporal detail provided by the high-frequency, multi-point sampling capacity of the four MMS satellites. <br>In particular, compressional effects are separated from effective sources in the energy density evolution equations, allowing to distinguish whether some effective energy transfer is occurring locally. A large database of MMS encounters with reconnecting current sheets is exploited in order to assess the statistical validity of all results presented.</p>

scholarly journals Spectral energy transfer of atmospheric gravity waves through sum and difference nonlinear interactions

2012 ◽  
Vol 30 (2) ◽  
pp. 303-315 ◽  
Author(s):  
K. M. Huang ◽  
A. Z. Liu ◽  
S. D. Zhang ◽  
F. Yi ◽  
Z. Li
Keyword(s):  
Energy Transfer ◽  
Gravity Waves ◽  
High Frequency ◽  
Energy Exchange ◽  
Low Frequency ◽  
Resonant Interaction ◽  
Resonant Excitation ◽  
Spectral Energy ◽  
Nonlinear Interactions ◽  
Resonant Interactions

Abstract. Nonlinear interactions of gravity waves are studied with a two-dimensional, fully nonlinear model. The energy exchanges among resonant and near-resonant triads are examined in order to understand the spectral energy transfer through interactions. The results show that in both resonant and near-resonant interactions, the energy exchange between two high frequency waves is strong, but the energy transfer from large to small vertical scale waves is rather weak. This suggests that the energy cascade toward large vertical wavenumbers through nonlinear interaction is inefficient, which is different from the rapid turbulence cascade. Because of considerable energy exchange, nonlinear interactions can effectively spread high frequency spectrum, and play a significant role in limiting wave amplitude growth and transferring energy into higher altitudes. In resonant interaction, the interacting waves obey the resonant matching conditions, and resonant excitation is reversible, while near-resonant excitation is not so. Although near-resonant interaction shows the complexity of match relation, numerical experiments show an interesting result that when sum and difference near-resonant interactions occur between high and low frequency waves, the wave vectors tend to approximately match in horizontal direction, and the frequency of the excited waves is also close to the matching value.

The possible origin of high frequency quasi-periodic oscillations in low mass X-ray binaries

2018 ◽  
Vol 14 (S346) ◽  
pp. 277-280
Author(s):  
Chang Sheng Shi ◽  
Shuang Nan Zhang ◽  
Xiang Dong Li
Keyword(s):  
Magnetic Field ◽  
High Frequency ◽  
Mhd Waves ◽  
Effective Surface ◽  
Periodic Oscillations ◽  
X Ray ◽  
Surface Magnetic Field ◽  
Low Mass ◽  
Mhd Model ◽  
X Ray Binaries

AbstractWe summarize our model that high frequency quasi-periodic oscillations (QPOs) both in the neutron star low mass X-ray binaries (NS-LMXBs) and black hole LMXBs may originate from magnetohydrodynamic (MHD) waves. Based on the MHD model in NS-LMXBs, the explanation of the parallel tracks is presented. The slowly varying effective surface magnetic field of a NS leads to the shift of parallel tracks of QPOs in NS-LMXBs. In the study of kilohertz (kHz) QPOs in NS-LMXBs, we obtain a simple power-law relation between the kHz QPO frequencies and the combined parameter of accretion rate and the effective surface magnetic field. Based on the MHD model in BH-LMXBs, we suggest that two stable modes of the Alfv́en waves in the accretion disks with a toroidal magnetic field may lead to the double high frequency QPOs. This model, in which the effect of the general relativity in BH-LMXBs is considered, naturally accounts for the 3:2 relation for the upper and lower frequencies of the QPOs and the relation between the BH mass and QPO frequency.

Observed Energy Exchange between Low-Frequency Flows and Internal Waves in the Gulf of Mexico

2018 ◽  
Vol 48 (4) ◽  
pp. 995-1008 ◽  
Author(s):  
Zhao Jing ◽  
Ping Chang ◽  
S. F. DiMarco ◽  
Lixin Wu
Keyword(s):  
Energy Transfer ◽  
Gulf Of Mexico ◽  
Internal Waves ◽  
High Frequency ◽  
Energy Exchange ◽  
Low Frequency ◽  
Net Energy ◽  
Energy Transfer Rate ◽  
Capture Mechanism

AbstractA long-term mooring array deployed in the northern Gulf of Mexico is used to analyze energy exchange between internal waves and low-frequency flows. In the subthermocline (245–450 m), there is a noticeable net energy transfer from low-frequency flows, defined as having a period longer than six inertial periods, to internal waves. The magnitude of energy transfer rate depends on the Okubo–Weiss parameter of low-frequency flows. A permanent energy exchange occurs only when the Okubo–Weiss parameter is positive. The near-inertial internal waves (NIWs) make major contribution to the energy exchange owing to their energetic wave stress and relatively stronger interaction with low-frequency flows compared to the high-frequency internal waves. There is some evidence that the permanent energy exchange between low-frequency flows and NIWs is attributed to the partial realization of the wave capture mechanism. In the periods favoring the occurrence of the wave capture mechanism, the horizontal propagation direction of NIWs becomes anisotropic and exhibits evident tendency toward that predicted from the wave capture mechanism, leading to pronounced energy transfer from low-frequency flows to NIWs.

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