Low-frequency wave modulations in an electronegative dusty plasma in the presence of charge variations

2011 ◽  
Vol 84 (6) ◽  
Author(s):  
Samiran Ghosh ◽  
Subrata Sarkar ◽  
Manoranjan Khan ◽  
M. R. Gupta
Keyword(s):  
Dusty Plasma ◽  
Low Frequency ◽  
Frequency Wave

Nonlinear low frequency wave propagation in electronegative dusty plasma: Effects of adiabatic and nonadiabatic charge variations

2011 ◽  
Vol 18 (9) ◽  
pp. 093703 ◽  
Author(s):  
Subrata Sarkar ◽  
Samiran Ghosh ◽  
Manoranjan Khan ◽  
M. R. Gupta
Keyword(s):  
Wave Propagation ◽  
Dusty Plasma ◽  
Low Frequency ◽  
Frequency Wave ◽  
Plasma Effects

Low frequency wave propagation in a cold magnetized dusty plasma

1998 ◽  
Vol 47 (1-2) ◽  
pp. 273-280 ◽  
Author(s):  
Susmita Sarkar ◽  
Samiran Ghosh ◽  
Manoranjan Khan
Keyword(s):  
Wave Propagation ◽  
Dusty Plasma ◽  
Low Frequency ◽  
Frequency Wave ◽  
Magnetized Dusty Plasma

Influences of the dust size and the dust charge variations to the low-frequency wave modes in a dusty plasma

2006 ◽  
Vol 13 (8) ◽  
pp. 082107 ◽  
Author(s):  
Gui-xin Wan ◽  
Wen-shan Duan ◽  
Quan-hai Chen ◽  
Xiao-yun Wang
Keyword(s):  
Dusty Plasma ◽  
Low Frequency ◽  
Frequency Wave ◽  
Dust Charge ◽  
Wave Modes

Modulation of Whistler Mode Waves by Ultra‐Low Frequency Wave in a Macroscale Magnetic Hole: MMS Observations

2021 ◽  
Author(s):  
He Zhang ◽  
Zhihong Zhong ◽  
Rongxin Tang ◽  
Xiaohua Deng ◽  
Haimeng Li ◽  
...  
Keyword(s):  
Low Frequency ◽  
Frequency Wave ◽  
Whistler Mode ◽  
Whistler Mode Waves

scholarly journals Changes in the ultra-low frequency wave field during the precursor phase to the Sichuan earthquake: DEMETER observations

2013 ◽  
Vol 31 (9) ◽  
pp. 1597-1603 ◽  
Author(s):  
S. N. Walker ◽  
V. Kadirkamanathan ◽  
O. A. Pokhotelov
Keyword(s):  
Low Frequency ◽  
Large Earthquake ◽  
Short Term ◽  
Frequency Wave ◽  
Sichuan Earthquake ◽  
Ulf Wave ◽  
Precursor Phase ◽  
Demeter Satellite ◽  
Short Term Prediction ◽  
Atmospheric Gravity

Abstract. Electromagnetic phenomena observed in association with increases in seismic activity have been studied for several decades. These phenomena are generated during the precursory phases of an earthquake as well as during the main event. Their occurrence during the precursory phases may be used in short-term prediction of a large earthquake. In this paper, we examine ultra-low frequency (ULF) electric field data from the DEMETER satellite during the period leading up to the Sichuan earthquake. It is shown that there is an increase in ULF wave activity observed as DEMETER passes in the vicinity of the earthquake epicentre. This increase is most obvious at lower frequencies. Examination of the ULF spectra shows the possible occurrence of geomagnetic pearl pulsations, resulting from the passage of atmospheric gravity waves generated in the vicinity of the earthquake epicentre.

Multifrequency full-waveform sonic logging in the screened interval of a large-diameter production well

Geophysics ◽  
2013 ◽  
Vol 78 (5) ◽  
pp. B243-B257 ◽  
Author(s):  
Majed Almalki ◽  
Brett Harris ◽  
J. Christian Dupuis
Keyword(s):  
Phase Velocity ◽  
Velocity Dispersion ◽  
Large Diameter ◽  
Low Frequency ◽  
Production Well ◽  
Frequency Wave ◽  
Full Waveform ◽  
Phase Velocity Dispersion ◽  
Production Wells ◽  
Sonic Logging

A set of field experiments using multiple transmitter center frequencies was completed to test the application potential of low-frequency full-waveform sonic logging in large-diameter production wells. Wireline logs were acquired in a simple open drillhole and a high-yield large diameter production well completed with wire-wound sand screens at an aquifer storage and recovery site in Perth, Western Australia. Phase-shift transform methods were applied to obtain phase-velocity dispersion images for frequencies of up to 4 kHz. A 3D representation of phase-velocity dispersion was developed to assist in the analysis of possible connections between low-frequency wave propagation modes and the distribution of hydraulic properties. For sandstone intervals in the test well, the highest hydraulic conductivity intervals were typically correlated with the lowest phase velocities. The main characteristics of dispersion images obtained from the sand-screened well were highly comparable with those obtained at the same depth level in a nearby simple drillhole open to the formation. The sand-screened well and the open-hole displayed an expected and substantial difference between dispersion in sand- and clay-dominated intervals. It appears that for clay-dominated formations, the rate of change of phase velocity can be associated to clay content. We demonstrated that with appropriate acquisition and processing, multifrequency full-waveform sonic logging applied in existing large-diameter sand-screened wells can produce valuable results. There are few wireline logging technologies that can be applied in this setting. The techniques that we used would be highly suitable for time-lapse applications in high-volume production wells or for reassessing formation properties behind existing historical production wells.

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