scholarly journals Propagation of high frequency waves in the quiet solar atmosphere

2008 ◽  
pp. 87-99 ◽  
Author(s):  
A. Andic
Keyword(s):  
Solar Atmosphere ◽  
High Frequency ◽  
Low Frequency ◽  
Magnetic Structures ◽  
Partial Heating ◽  
Fabry Perot ◽  
High Frequency Waves ◽  
Propagation Of Waves ◽  
The Waves ◽  
Low Frequency Waves

High-frequency waves (5 mHz to 20 mHz) have previously been suggested as a source of energy accounting for partial heating of the quiet solar atmosphere. The dynamics of previously detected high-frequency waves is analyzed here. Image sequences were taken by using the German Vacuum Tower Telescope (VTT), Observatorio del Teide, Izana, Tenerife, with a Fabry-Perot spectrometer. The data were speckle reduced and analyzed with wavelets. Wavelet phase-difference analysis was performed to determine whether the waves propagate. We observed the propagation of waves in the frequency range 10 mHz to 13 mHz. We also observed propagation of low-frequency waves in the ranges where they are thought to be evanescent in the regions where magnetic structures are present.

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.

Integrity Diagnosis Method of Bolted Joint Based on Time Fluctuation of Reflection Intensity Caused by Nonlinear Wave Modulation

2014 ◽  
Author(s):  
Takashi Tanaka ◽  
Arata Masuda ◽  
Akira Sone
Keyword(s):  
Nonlinear Wave ◽  
High Frequency ◽  
Low Frequency ◽  
Bolted Joint ◽  
Contact Interface ◽  
Wave Modulation ◽  
Diagnosis Method ◽  
Time Fluctuation ◽  
High Frequency Waves ◽  
Reflection Intensity

This study presents the integrity diagnosis method of the bolted joint based on nonlinear wave modulation. When the structure that has the contact interface is vibrating at low-frequency, the contact interface is tapping and clapping due to low-frequency vibration. In this condition, the scatter characteristics, such as wave transmissivity and reflectivity, of high-frequency waves in vicinity of the contact interface are fluctuated in synchronization with low-frequency excitation because of the contact acoustic nonlinearity. The time fluctuation of reflection intensity, which expresses the reflectivity in the specific location, of high-frequency waves at the contact interface is given as the reflection intensity map which plots time-spatial map. In this paper, experiment using the beam specimen which has single bolted joint is conducted to examine the performance of the evaluation index based on the fluctuation amplitude of reflection intensity.

scholarly journals Energy Transfer from High-Shear, Low-Frequency Internal Waves to High-Frequency Waves near Kaena Ridge, Hawaii

2012 ◽  
Vol 42 (9) ◽  
pp. 1524-1547 ◽  
Author(s):  
Oliver M. Sun ◽  
Robert Pinkel
Keyword(s):  
Internal Waves ◽  
High Frequency ◽  
Low Frequency ◽  
Buoyancy Frequency ◽  
Reynolds Stresses ◽  
Turbulent Dissipation ◽  
Transfer Rates ◽  
Energy Transfers ◽  
High Frequency Waves ◽  
Parametric Subharmonic Instability

Abstract Evidence is presented for the transfer of energy from low-frequency inertial–diurnal internal waves to high-frequency waves in the band between 6 cpd and the buoyancy frequency. This transfer links the most energetic waves in the spectrum, those receiving energy directly from the winds, barotropic tides, and parametric subharmonic instability, with those most directly involved in the breaking process. Transfer estimates are based on month-long records of ocean velocity and temperature obtained continuously over 80–800 m from the research platform (R/P) Floating Instrument Platform (FLIP) in the Hawaii Ocean Mixing Experiment (HOME) Nearfield (2002) and Farfield (2001) experiments, in Hawaiian waters. Triple correlations between low-frequency vertical shears and high-frequency Reynolds stresses, 〈uiw∂Ui/∂z〉, are used to estimate energy transfers. These are supported by bispectral analysis, which show significant energy transfers to pairs of waves with nearly identical frequency. Wavenumber bispectra indicate that the vertical scales of the high-frequency waves are unequal, with one wave of comparable scale to that of the low-frequency parent and the other of much longer scale. The scales of the high-frequency waves contrast with the classical pictures of induced diffusion and elastic scattering interactions and violates the scale-separation assumption of eikonal models of interaction. The possibility that the observed waves are Doppler shifted from intrinsic frequencies near f or N is explored. Peak transfer rates in the Nearfield, an energetic tidal conversion site, are on the order of 2 × 10−7 W kg−1 and are of similar magnitude to estimates of turbulent dissipation that were made near the ridge during HOME. Transfer rates in the Farfield are found to be about half the Nearfield values.

Growth of low-frequency waves due to a photon beam in a magnetized electron–positron plasma

1997 ◽  
Vol 58 (2) ◽  
pp. 345-366 ◽  
Author(s):  
QINGHUAN LUO ◽  
D. B. MELROSE
Keyword(s):  
High Frequency ◽  
Random Phase ◽  
Low Frequency ◽  
Photon Beam ◽  
Radio Waves ◽  
Wave Interactions ◽  
Frequency Wave ◽  
Pair Plasma ◽  
Electron Positron ◽  
Low Frequency Waves

The effect of a beam of radio waves of very high brightness passing through a cold, magnetized, electron–positron plasma is discussed. The properties of the natural wave modes in such a plasma are summarized, and approximate forms for the nonlinear response tensor are written down. Photon-beam-induced instabilities of low-frequency waves in the pair plasma are analysed in the random-phase approximation. When three-wave interactions involve two high-frequency waves in the same mode and a low-frequency wave in a different mode, wave–wave interactions are similar to wave–particle interactions in that photons act like particles that emit and absorb low-frequency waves. The absorption coefficients for various low-frequency waves due to a photon beam are evaluated. In a pure electron–positron plasma, photon-beam-induced instabilities can be effective only when either the high-frequency or the low-frequency waves are strongly modified by the magnetic field. The growth of the low-frequency waves is most effective when the high-frequency photon beam has a frequency close to the cyclotron frequency.

Induced Three-wave Interactions in Eclipsing Pulsars

1995 ◽  
Vol 12 (1) ◽  
pp. 71-75
Author(s):  
Qinghuan Luo ◽  
D. B. Melrose
Keyword(s):  
Thermal Effects ◽  
Cold Plasma ◽  
Low Frequency ◽  
Wave Interaction ◽  
Wave Interactions ◽  
Frequency Wave ◽  
Frequency Branch ◽  
High Frequency Waves ◽  
The Magnetic Field ◽  
Low Frequency Waves

AbstractThree-wave interactions involving two high-frequency waves (in the same mode) and a low-frequency wave are discussed and applied to pulsar eclipses. When the magnetic field is taken into account, the low-frequency waves can be the ω-mode (the low-frequency branch of the ordinary mode) or the z-mode (the low-frequency branch of the extraordinary mode). It is shown that in the cold plasma approximation, effective growth of the low-frequency waves due to an anisotropic photon beam can occur only for z-mode waves near the resonance frequency. In the application to pulsar eclipses, the cold plasma approximation may not be adequate and we suggest that when thermal effects are included, three-wave interaction involving low-frequency cyclotron waves (e.g. Bernstein modes) is a plausible candidate for pulsar eclipses

scholarly journals Low-frequency Waves due to Newborn Interstellar Pickup He+ Observed by the Ulysses Spacecraft

2021 ◽  
Vol 923 (2) ◽  
pp. 185
Author(s):  
Anastasia V. Marchuk ◽  
Charles W. Smith ◽  
Abigale S. Watson ◽  
Matthew R. Argall ◽  
Colin J. Joyce ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Field Data ◽  
Low Frequency ◽  
Wave Excitation ◽  
Pickup Ions ◽  
Magnetic Field Data ◽  
Ion Production ◽  
Background Turbulence ◽  
The Waves ◽  
Low Frequency Waves

Abstract We have surveyed magnetic field data from the Ulysses spacecraft and found examples of magnetic waves with the expected characteristics that point to excitation by newborn pickup He+. With interstellar neutrals as the likely source for the pickup ions, we have modeled the ion production rates and used them to produce wave excitation rates that we compare to the background turbulence rates. The source ions are thought to be always present, but the waves are seen when growth rates are comparable to or exceed the turbulence rates. With the exception of the fast latitude scans, and unlike the waves excited by newborn interstellar pickup H+, the waves are seen throughout the Ulysses orbit.

Estimating the Areas of High-Frequency Wave Radiation on the Fault Plane of the 2008 Mw 7.9 Wenchuan, China, Earthquake by Envelope Inversion

2021 ◽  
Author(s):  
Deyu Yin ◽  
Yun Dong ◽  
Qifang Liu ◽  
Jingke Wu ◽  
Huasheng Sun ◽  
...  
Keyword(s):  
High Frequency ◽  
Fault Plane ◽  
Low Frequency ◽  
Rupture Process ◽  
Wave Radiation ◽  
Frequency Wave ◽  
High Frequency Wave ◽  
Initial Rupture ◽  
High Frequency Waves ◽  
Frequency Radiation

ABSTRACT We estimated the areas exhibiting high-frequency (1∼10  Hz) wave radiation on the fault plane of the 2008 Wenchuan earthquake, by applying envelope inversion to strong-motion acceleration records. The corrected records of two small earthquakes are adopted as the empirical Green’s functions. Considering the change in the rupture pattern of the Wenchuan earthquake from southwest to northeast, the records of small earthquakes dominated by thrust and strike-slip are utilized as the empirical Green’s function for the southwestern and northeastern fault sections, respectively. The results are as follows: (1) According to the high-frequency wave radiation, the rupture process is complex. High-frequency waves radiated strongly in six areas: around the initial rupture point, along the north and south edges of the fault plane, near the area of intersection with the cross-cutting Xiaoyudong fault, south of Nanba, and near the area of Qingchuan. In total, these areas can be divided into three cases. In the first situation, high-frequency waves radiated strongly around the initial rupture area, which may be associated with the initiation of rupture and a high stress drop. The second location is near the periphery of the fault, which is associated with the termination of rupture. The third condition comprises high-frequency waves near the intersection with the cross-cutting Xiaoyudong fault. This area as a geometric barrier, and the surface rupture is observed. (2) The distribution patterns of the high- and low-frequency radiation intensity differ on the fault plane. From the hypocenter to the point of intersection with the Xiaoyudong fault, the high-frequency wave is located around the area with large slip value. In other areas, the distribution of the high- and low-frequency radiation is no obvious relationship. This different characteristic indicates the complexity of the rupture process.

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