Acoustic Shock Waves Research Articles

The nonadiabatic dust charge variation on dust acoustic solitary and shock waves in strongly coupled dusty plasmas

The combined effects of nonadiabatic dust charge fluctuation and strongly coupled dust particles on the nonlinear propagation of dust acoustic (DA) waves in dusty plasma consisting of nonthermal electrons and trapped ions with vortex-like distribution are presented here. We use generalized viscoelastic hydrodynamic model for dust particles. In the weak nonlinearity limit, a modified Korteweg–de Vries (KdV) equation with a damping term and a KdV–Burger equation have been derived in the kinetic regime and hydrodynamic regime, respectively. The approximate analytical solitary solution of modified KdV equation is derived in the weak nonadiabatic dust charge variation limit, which shows that the amplitude of DA solitary waves decreases with time. The presence of viscosity due to strong coupling stands for the formation of DA shock waves in the hydrodynamic regime. The results show that the DA shock waves will be oscillating one for weak viscosity and will become monotonic ones for large viscosity.

Early warning of tsunami from seismo-ionospheric fluctuation after Japan’s March 11, 2011, M=9.0 Tohoku earthquake using two-dimensional principal component analysis

<p>Two-dimensional principal component analysis (2DPCA) is implemented to analyze the total electron content (TEC) anomalies after Japan’s Tohoku earthquake that occurred at 05:46 on March 11, 2011 (UTC) (M<sub>w</sub>=9). 2DPCA and TEC data processing were conducted just after this devastating earthquake. Analysis results show an earthquake-associated TEC anomaly near the epicenter that began at 05:47. This may represent an extension of the precursor of the earthquake, to the precursor of China’s Wenchuan earthquake on May 12, 2008, detected by the study of Lin [2012], for which the data were obtained at a height of 150-200 km by the FORMOSAT-3 satellite system. It is impossible that such precursor caused by the acoustic shock waves. Another TEC anomaly near the epicenter occurred at 05:53, and this initiated the propagation of the tsunami effect related to the ionosphere through the acoustic shock waves from the epicenter. However, the TEC anomalies did not appear to be affected by a contemporaneous geomagnetic storm and other non-earthquake effects. The propagation of anomalous fluctuation could be an early warning of the tsunami for the regions far from the epicenter as it began to propagate with the higher speed of 3960-4950 km/h than the tsunami speed (720-800 km/h).</p><div> </div>

Generator and Setup for Emulating Exposures of Biological Samples to Lightning Strokes.

We aimed to develop a system for controlled exposure of biological samples to conditions they experience when lightning strikes their habitats. We based the generator on a capacitor charged via a bridge rectifier and a dc-dc converter, and discharged via a relay, delivering arcs similar to natural lightning strokes in electric current waveform and similarly accompanied by acoustic shock waves. We coupled the generator to our exposure chamber described previously, measured electrical and acoustic properties of arc discharges delivered, and assessed their ability to inactivate bacterial spores. Submicrosecond discharges descended vertically from the conical emitting electrode across the air gap, entering the sample centrally and dissipating radially toward the ring-shaped receiving electrode. In contrast, longer discharges tended to short-circuit the electrodes. Recording at 341 000 FPS with Vision Research Phantom v2010 camera revealed that initial arc descent was still vertical, but became accompanied by arcs leaning increasingly sideways; after 8-12 μs, as the first of these arcs formed direct contact with the receiving electrode, it evolved into a channel of plasmified air and short-circuited the electrodes. We eliminated this artefact by incorporating an insulating cylinder concentrically between the electrodes, precluding short-circuiting between them. While bacterial spores are highly resistant to electric pulses delivered through direct contact, we showed that with arc discharges accompanied by an acoustic shock wave, spore inactivation is readily obtained. The presented system allows scientific investigation of effects of arc discharges on biological samples. This system will allow realistic experimental studies of lightning-triggered horizontal gene transfer and assessment of its role in evolution.

Ion acoustic shock wave in collisional equal mass plasma

The effect of ion-ion collision on the dynamics of nonlinear ion acoustic wave in an unmagnetized pair-ion plasma has been investigated. The two-fluid model has been used to describe the dynamics of both positive and negative ions with equal masses. It is well known that in the dynamics of the weakly nonlinear wave, the viscosity mediates wave dissipation in presence of weak nonlinearity and dispersion. This dissipation is responsible for the shock structures in pair-ion plasma. Here, it has been shown that the ion-ion collision in presence of collective phenomena mediated by the plasma current is the source of dissipation that causes the Burgers' term which is responsible for the shock structures in equal mass pair-ion plasma. The dynamics of the weakly nonlinear wave is governed by the Korteweg-de Vries Burgers equation. The analytical and numerical investigations revealed that the ion acoustic wave exhibits both oscillatory and monotonic shock structures depending on the frequency of ion-ion collision parameter. The results have been discussed in the context of the fullerene pair-ion plasma experiments.

Dust acoustic shock waves in arbitrarily charged dusty plasma with low and high temperature non-thermal ions

Using the well-known reductive perturbation technique, the three-dimensional (3D) Burgers equation and modified 3D Burgers equation have been derived for a plasma system comprising of non-thermal ions, Maxwellian electrons, and negatively charged fluctuating dust particles. The salient features of nonlinear propagation of shock waves in such plasmas have been investigated in detail. The different temperature non-thermal ions and Maxwellian electrons are found to play an important role in the shock waves solution. The analytical solution of the 3D Burgers equation and modified 3D Burgers equation ratifying the propagation of dust acoustic shock waves are derived using the well-known tanh method. On increasing the population of non-thermal ions, an enhancement in the amplitude of shock waves is seen for negatively charged dust particles. A striking dependence of amplitude and width of shock waves on the ratio of ion temperatures and densities are also reported. Finally we introduced a new stretching coordinate and perturbation for the nth-order nonlinear 3D Burgers equation and its solution by the use of the tanh method. We found that, due to higher nonlinearity, the amplitude of shock waves decreases while width remains constant for all plasma parameters considered in the present investigation. The features accounted here could be relevant in the case of different space and astrophysical plasmas and laboratory dusty plasma for negatively charged dust fluctuation.

Higher-order corrections to broadband electrostatic shock noise in auroral zone

Nonlinear shock wave structures in collisionless unmagnetized viscous plasma comprised of fluid of cold electron and nonisothermal hot electrons obeying superthermal electron distribution and ions in stationary state are examined. For nonlinear electron acoustic shock waves, a reductive perturbation method was applied to deduce the Burger equation in terms of first order potential. When the shock wave amplitude was enlarged, the steepness and the velocity of the wave sidetrack from Burger equation. We have to resume our calculations to obtain the Burger-type equation with higher order dissipation. The collective solution for the resulting equations has been given by the renormalization method. The effects of spectral index κ, the ratio of the initial equilibrium density of cold electron to hot electrons β, and the kinematic viscosity coefficient η on the broadband electrostatic shock noise in aurora are also argued.

Two‐mode ionospheric response and Rayleigh wave group velocity distribution reckoned from GPS measurement following Mw 7.8 Nepal earthquake on 25 April 2015

AbstractThe coseismic‐induced ionospheric total electron content (TEC) perturbations were analyzed following the Mw 7.8 Nepal earthquake (28.147°N, 84.708°E; depth ~15 km) that occurred on 25 April 2015 at 06:11:26 UTC. The ionospheric response is due to both the modes, i.e., shock acoustic waves (slow mode) and Rayleigh wave induced (fast mode). The continuous Global Positioning System (GPS) data at about 60 sites from various GPS networks have been used in the present study. All the sites within epicentral distance of ~2400 km and 70°–170° azimuth recorded the Rayleigh wave‐induced TEC response, while the sites within ~400–2200 km in the same azimuth recorded the response from both the modes. The maximum coseismic‐induced peak‐to‐peak TEC amplitude is ~1.2 total electron content unit, 1 TECU = 1016 el m−2. From Hodochron plot, the apparent Rayleigh wave velocity has been determined as ~2400 m/s on the average and the acoustic wave velocity as 1180 m/s, both these waves being discernible beyond ~1200 km of epicentral distance as also evident from Hodochron plot and wavelet spectrographs. We reckoned the Rayleigh wave group velocities using ionospheric response at selected radial pairs of stations and validated. The ionospheric response distribution seen mainly depending on the epicentral distance, satellite geometry, directivity of radiation pattern, and the upper crustal heterogeneity. This study highlights the characteristics of ionospheric response consequent to the 2015 Nepal earthquake.

High-Speed Camera and Fibered Optical Wave Microphone Measurements on Surface-Dielectric-Barrier Discharges

Much focus has been placed on the aerodynamics of surface-dielectric-barrier discharges to control air flow. An important factor to consider to understand the mechanism is pressure waves, which include acoustic waves and shock waves that are emitted from the surface-dielectric-barrier discharges. In this paper, a fibered optical wave microphone, which improves upon a conventional optical wave microphone with regard to signal-to-noise ratio, was developed to detect these pressure waves with high precision. This paper explores the properties of the fibered optical wave microphone. A high-speed camera was used to capture time-resolved microdischarges. After simultaneous observation of the applied voltage, current, pressure waves, and microdischarge images for the surface-dielectric-barrier discharge, the relationships among these factors were analyzed and discussed.

Dynamics of vertical ionospheric inhomogeneities over Irkutsk during 06:00–06:20UT 11/03/2011 caused by Tohoku earthquake

We study dynamics of vertical ionospheric irregularities caused by Tohoku earthquake 11/03/2011 (38.3N, 142.4E) at a distance of 3400km from the epicenter. Equivalent horizontal velocities of propagation in the ionosphere and vertical quasi-wavelength of the wave-like ionospheric irregularities, generated by the earthquake, are calculated.Based on the data of quasi-vertical sounding at Usolie–Tory path (midpoint – 52.3N, 103E, 120km distance), dynamics of vertical mid-scale inhomogeneities of the plasma frequency profile was reconstructed with a fine temporal resolution (60s).As a result of numerical simulation involving the data from TALAYA seismic station (TLY, 51.7N, 103.7E) and comparison with the experiment it is shown that vertical ionospheric irregularities of 5–40km quasi-wavelength observed from 06:00 to 06:20 UT are qualitatively explained by traveling of the acoustic shock wave cone (Mach cone ) from a supersonic ground source – the seismic wave.It is demonstrated that the most likely sources of the shock wave were Z and E components of the seismic oscillations observed at TLY station. Irregularities observed after 06:20UT were apparently linked with other mechanisms. It is found that current temporal resolution of CHIRP ionosonde (60s) and accuracy of the ionogram inversion technique used are not enough for detailed diagnosis of dynamics of the fine spatial vertical structures generated by the earthquake.

Shock wave solution in a hot adiabatic dusty plasma having negative and positive non-thermal ions with trapped electrons

In this report an investigation of the properties of a dust acoustic (DA) shock wave propagating in an adiabatic dusty plasma, including the effect of the negative-ion-rich non-thermal ions and trapped electrons, is presented. The reductive perturbation method is employed to derive the modified Burgers equation and a new form of the lower-order nonlinear modified Burgers equation for DA shock waves in a homogeneous, unmagnetized and collisionless plasma whose constituents are electrons, singly-charged positive ions, singly-charged negative ions and massive, charged dust particles. The stationary analytical solution of the Burgers equation and the new analytical solution of the lower-order nonlinear modified Burgers equation are numerically analyzed, and the effects of various dusty plasma constituents on the DA shock wave’s propagation are taken into account. Both positive and negative ions in the dusty plasma are observed to play a key role in the formation of both positive, as well as negative, DA shock waves, and the ion concentration can be used to control the transformation from negative to positive potentials of the waves.

Mach-Zehnder interferometry method for acoustic shock wave measurements in air and broadband calibration of microphones.

A Mach-Zehnder interferometer is used to measure spherically diverging N-waves in homogeneous air. An electrical spark source is used to generate high-amplitude (1800 Pa at 15 cm from the source) and short duration (50 μs) N-waves. Pressure waveforms are reconstructed from optical phase signals using an Abel-type inversion. It is shown that the interferometric method allows one to reach 0.4 μs of time resolution, which is 6 times better than the time resolution of a 1/8-in. condenser microphone (2.5 μs). Numerical modeling is used to validate the waveform reconstruction method. The waveform reconstruction method provides an error of less than 2% with respect to amplitude in the given experimental conditions. Optical measurement is used as a reference to calibrate a 1/8-in. condenser microphone. The frequency response function of the microphone is obtained by comparing the spectra of the waveforms resulting from optical and acoustical measurements. The optically measured pressure waveforms filtered with the microphone frequency response are in good agreement with the microphone output voltage. Therefore, an optical measurement method based on the Mach-Zehnder interferometer is a reliable tool to accurately characterize evolution of weak shock waves in air and to calibrate broadband acoustical microphones.

Dichotomy in mode propagation of coseismic ionospheric disturbance: Observations from 11 April 2012 Indian Ocean earthquake

AbstractThe ionosphere response to the great intraplate Indian Ocean earthquake of 11 April 2012 (Mw 8.6) and its largest aftershock (Mw 8.2) is analyzed using GPS‐aided total electron content (TEC) measurements. Data from the dense GPS networks, SuGAr (Sumatran GPS Array) and the permanent Andaman‐Nicobar array, formed the near‐field observations at distances 250–1200 km from the epicenter. Stations such as IISC, DGAR, and few others provided measurements over 2000 km from the epicenter. The coseismic ionospheric disturbances (CIDs) with a propagation velocity of 930–1262 m/s, equals the speeds of the shock acoustic waves, arrive within 10–18 min after the earthquake occurrence. The observed phenomenon of CID splitting into two modes, north and south of the epicenter, is akin to the well‐documented effects of anisotropy on wave propagation. Closer to the epicenter, to its south, the propagation velocity of CID is ~1 km/s, and farther southeast of the network the velocity reduces to 500–600 m/s. In contrast, toward Andaman in the north, the CID propagation velocity increases to 2–3.5 km/s. The zenith angle of the line of sight between the GPS receiver and satellite appears to influence the amplitude of the TEC fluctuations. The anomalous azimuthal variation of the Rayleigh wave radiation pattern best explains the observed N‐S asymmetry of CID.

Generation of long-lived underdense channels using femtosecond filamentation in air

Using femtosecond laser pulses at 800 and 400 nm, we characterize the formation of underdense channels in air generated by laser filamentation at the millijoule energy level by means of transverse interferometry. We find that using tight focusing conditions, filamentation generates an acoustic shock wave and that the resulting low-density channel lasts for more than 90 ms. Comparison of these results with hydrodynamic simulations using an Eulerian code gives a good agreement and allows us to estimate the initial gas peak temperature at . The influence of experimental parameters such as the focusing conditions for the ultrashort laser pulse, its polarization or the wavelength is studied and linked to previous characterizations of filamentation-generated plasma columns.

Early warning from seismic ionospheric anomaly of the 24 May 2014, Mw = 6.4 Aegean-Sea earthquake: two-dimensional principal component analysis (2DPCA)

Two-dimensional principal component analysis (2DPCA) has been used to determine ionospheric two-dimensional total electron content (TEC) anomaly after Aegean-Sea earthquake at 09:25:03(UT) on 24 May, 2014 (Mw = 6.4). The TEC anomaly was more intense localized at 09:30 to 9:35 (UT) post the earthquake. Potential reason of the TEC anomaly, which might be a anomalous fluctuation e.g., electron density variation, is rising high speed acoustic shock wave with the speed of at least 1818.18 Km/h. m/s resulted by the mainshock of the earthquake. The duration time of the TEC anomaly was at least 5minutes. The anomalous fluctuation could be an early warning for the regions far from the epicenter when it began to propagate because the tsunami arrived at the far regions very slower than anomalous fluctuation if the tsunami was caused by earthquake with epicenter in the sea.

Dust Acoustic Shock Waves with Non-Thermal and Vortex-Like Ions in Dusty Plasma

A rigorous investigation is presented on the propagation characteristics of non-linear dust acoustic (DA) waves in an unmagnetized dusty plasma system containing non-thermal and vortex-like ions and Maxwellian electrons under the effect of a fluctuating charged dust fluid. The three-dimensional (3D) Burgers' equation and a new form of a lower degree modified 3D Burgers' equation with their analytical solutions are derived to study the features of shock waves in such plasmas. The effect of the population of non-thermal ions, the vortex-like ion parameter as well as the temperature ratios of ions and electrons on the evolution of shock waves in the presence of dust charge fluctuation is presented. This theoretical investigation might be effectively utilized to unveil the nature of many astrophysical plasma environments (Saturn's spokes etc.) where such plasmas are reported to have existed.

Two-dimensional dissipative structures in spatially nonuniform dusty plasmas in planetary magnetospheres with kappa distributed ions

Linear and nonlinear propagation of coupled dust drift acoustic waves are investigated in the presence of a kappa distributed ion population and Boltzmannian electrons. It is observed that the frequency of the dust drift acoustic wave decreases by increasing the kappa value. Using the drift approximation, a nonlinear equation is derived for the dust drift acoustic shock wave that reduces to a Kadomtsev–Petviashvili–Burgers (KPB)-like equation in the comoving frame of reference. It is found that the nonlinear structure of dust drift acoustic shock waves modifies in the presence of increasing values of kappa, dust number density, ambient magnetic field, and the dust neutral collision frequency. Interestingly, it is found that the non-Maxwellian ion population modifies the scale lengths over which the nonlinear structures are formed. The results obtained are applied in Saturnʼs magnetosphere, where the non-Maxwellian distribution of particles has been reported by several satellite missions.

Charge-and-energy conserving moment-based accelerator for a multi-species Vlasov–Fokker–Planck–Ampère system, part I: Collisionless aspects

In this study, we propose a charge, momentum, and energy conserving discretization for the 1D–1V Vlasov–Ampère system of equations on an Eulerian grid. The new conservative discretization is nonlinear in nature, but can be efficiently converged with a moment-based nonlinear accelerator algorithm. We demonstrate the conservation and convergence properties of the scheme with various numerical examples, including a multi-scale ion–acoustic shockwave problem.

2P1-1 Classification of cylindrical shell using acoustic shock wave in water

2P1-1 Classification of cylindrical shell using acoustic shock wave in water

Dust-ion acoustic shock waves for nonplanar geometry with nonthermal electrons and adiabatic dusty plasma

The nonplanar Burgers' equation for dust-ion-acousti shock waves was derived for unmagnetized adiabatic dusty plasmas, comprising static negatively charged dust uid, nonthermal distributed electrons, and Boltzmann dis- tributed positron and adiabatic ion uid, by employing the standard reductive perturbation method. The solution of the modied Burgers' equation for nonplanar geometry is numerically analyzed. The dependence of dust-ion-acousti shock waves on some plasma parameters is explored. It is observed that inclusion of the nonthermal electron distribution mod- ies the shock wave prole signicantly. Likewise, it is found that the nonplanar geometry effects have an important role on the establishment of shock waves. It is also found that an increasing positron concentration decreases the amplitude of the dust-ion-acousti shock waves.

Dust-ion acoustic shock waves in a dusty multi-ion plasma with negatively dust-charge fluctuation

The nonlinear propagation of dust-ion acoustic shock waves in a collisionless, unmagnetized multi-ion dusty plasma contains Botlzemann-distributed electrons, negative and positive ions with extremely massive and stationary negative charge dust grains with dust charge fluctuations is investigated. By employing the reductive perturbation method, we obtain a Burgers equation that describes the two-ion fluid dynamics. The dust charge variation is found to play an important role in the formation of such dust-ion acoustic shock structures. The viscosity only affects the thickness of the shock waves. The dependences of the shock wave’s velocity, height and thickness on the system parameters are investigated.