Broadband high-frequency waves and intermittent energy conversion at dipolarization fronts

NASA Astrophysics Data System (ADS)

Yang, J.; Cao, J.; Fu, H.; Wang, T.; Liu, W.; Yao, Z., Sr.

2017-12-01

Dipolarization front (DF) is a sharp boundary most probably separating the reconnection jet from the background plasma sheet. So far at this boundary, the observed waves are mainly in low-frequency range (e.g., magnetosonic waves and lower hybrid waves). Few high-frequency waves are observed in this region. In this paper, we report the broadband high-frequency wave emissions at the DF. These waves, having frequencies extending from the electron cyclotron frequency fce, up to the electron plasma frequency fpe, could contribute 10% to the in situ measurement of intermittent energy conversion at the DF layer. Their generation may be attributed to electron beams, which are simultaneously observed at the DF as well. Furthermore, we find intermittent energy conversion is primarily to the broadband fluctuations in the lower hybrid frequency range although the net energy conversion is small.

Magneto-acoustic wave energy in sunspots: observations and numerical simulations

NASA Astrophysics Data System (ADS)

Felipe, T.; Khomenko, E.; Collados, M.; Beck, C.

2011-11-01

We have reproduced some sunspot wave signatures obtained from spectropolarimetric observations through 3D MHD numericalsimulations. The results of the simulations arecompared with the oscillations observed simultaneously at different heights from the SiI lambda10827Å line, HeI lambda10830Å line, the CaII H core and the FeI blends at the wings of the CaII H line. The simulations show a remarkable agreement with the observations, and we have used them to quantify the energy contribution of the magneto-acoustic waves to the chromospheric heating in sunspots. Our findings indicate that the energy supplied by these waves is 5-10 times lower than the amount needed to balance the chromospheric radiative losses.

Simultaneous Observations of p-mode Light Walls and Magnetic Reconnection Ejections above Sunspot Light Bridges

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hou, Yijun; Zhang, Jun; Li, Ting

Recent high-resolution observations from the Interface Region Imaging Spectrograph reveal bright wall-shaped structures in active regions (ARs), especially above sunspot light bridges. Their most prominent feature is the bright oscillating front in the 1400/1330 Å channel. These structures are named light walls and are often interpreted to be driven by p-mode waves. Above the light bridge of AR 12222 on 2014 December 06, we observed intermittent ejections superimposed on an oscillating light wall in the 1400 Å passband. At the base location of each ejection, the emission enhancement was detected in the Solar Dynamics Observatory 1600 Å channel. Thus, wemore » suggest that in wall bases (light bridges), in addition to the leaked p-mode waves consistently driving the oscillating light wall, magnetic reconnection could happen intermittently at some locations and eject the heated plasma upward. Similarly, in the second event occurring in AR 12371 on 2015 June 16, a jet was simultaneously detected in addition to the light wall with a wave-shaped bright front above the light bridge. At the footpoint of this jet, lasting brightening was observed, implying magnetic reconnection at the base. We propose that in these events, two mechanisms, p-mode waves and magnetic reconnection, simultaneously play roles in the light bridge, and lead to the distinct kinetic features of the light walls and the ejection-like activities, respectively. To illustrate the two mechanisms and their resulting activities above light bridges, in this study we present a cartoon model.« less

Electromagnetic Whistler Precursors at Supercritical Interplanetary Shocks

NASA Technical Reports Server (NTRS)

Wilson, L. B., III

2012-01-01

We present observations of electromagnetic precursor waves, identified as whistler mode waves, at supercritical interplanetary shocks using the Wind search coil magnetometer. The precursors propagate obliquely with respect to the local magnetic field, shock normal vector, solar wind velocity, and they are not phase standing structures. All are right-hand polarized with respect to the magnetic field (spacecraft frame), and all but one are right-hand polarized with respect to the shock normal vector in the normal incidence frame. Particle distributions show signatures of specularly reflected gyrating ions, which may be a source of free energy for the observed modes. In one event, we simultaneously observe perpendicular ion heating and parallel electron acceleration, consistent with wave heating/acceleration due to these waves.

Fast Magnetosonic Waves Observed by Van Allen Probes: Testing Local Wave Excitation Mechanism

NASA Astrophysics Data System (ADS)

Min, Kyungguk; Liu, Kaijun; Wang, Xueyi; Chen, Lunjin; Denton, Richard E.

2018-01-01

Linear Vlasov theory and particle-in-cell (PIC) simulations for electromagnetic fluctuations in a homogeneous, magnetized, and collisionless plasma are used to investigate a fast magnetosonic wave event observed by the Van Allen Probes. The fluctuating magnetic field observed exhibits a series of spectral peaks at harmonics of the proton cyclotron frequency Ωp and has a dominant compressional component, which can be classified as fast magnetosonic waves. Furthermore, the simultaneously observed proton phase space density exhibits positive slopes in the perpendicular velocity space, ∂fp/∂v⊥>0, which can be a source for these waves. Linear theory analyses and PIC simulations use plasma and field parameters measured in situ except that the modeled proton distribution is modified to have larger ∂fp/∂v⊥ under the assumption that the observed distribution corresponds to a marginally stable state when the distribution has already been scattered by the excited waves. The results show that the positive slope is the source of the proton cyclotron harmonic waves at propagation quasi-perpendicular to the background magnetic field, and as a result of interactions with the excited waves the evolving proton distribution progresses approximately toward the observed distribution.

Joint inversion of seismic and gravity data for imaging seismic velocity structure of the crust and upper mantle beneath Utah, United States

NASA Astrophysics Data System (ADS)

Syracuse, E. M.; Zhang, H.; Maceira, M.

2017-10-01

We present a method for using any combination of body wave arrival time measurements, surface wave dispersion observations, and gravity data to simultaneously invert for three-dimensional P- and S-wave velocity models. The simultaneous use of disparate data types takes advantage of the differing sensitivities of each data type, resulting in a comprehensive and higher resolution three-dimensional geophysical model. In a case study for Utah, we combine body wave first arrivals mainly from the USArray Transportable Array, Rayleigh wave group and phase velocity dispersion data, and Bouguer gravity anomalies to invert for crustal and upper mantle structure of the region. Results show clear delineations, visible in both P- and S-wave velocities, between the three main tectonic provinces in the region. Without the inclusion of the surface wave and gravity constraints, these delineations are less clear, particularly for S-wave velocities. Indeed, checkerboard tests confirm that the inclusion of the additional datasets dramatically improves S-wave velocity recovery, with more subtle improvements to P-wave velocity recovery, demonstrating the strength of the method in successfully recovering seismic velocity structure from multiple types of constraints.

ISEE 1 observations of electrostatic ion cyclotron waves in association with ion beams on auroral field lines from about 2.5 to 4.5 R(E)

NASA Technical Reports Server (NTRS)

Catell, C. A.; Mozer, F. S.; Roth, I.; Anderson, R. R.; Elphic, R. C.

1991-01-01

Quasi-monochromatic waves at about the hydrogen cyclotron frequency were observed as the ISEE 1 satellite traversed auroral field lines at radial distances of about 2.5-4.5 R(E) near midnight on June 19, 1981. Waves and both lower and higher frequencies were observed at higher altitudes, and possible electrostatic helium cyclotron and oxygen cyclotron waves occurred at lower altitudes. Upflowing hydrogen and oxygen beams and field-aligned currents occurred simultaneously. The features of the waves are most consistent with the current-driven mode. In addition, numerical studies of the linear dispersion relation, using parameters based on the observations, show that both the parallel and oblique two-stream modes and the ion-beam-driven modes were stable while oblique current-driven modes were unstable. The O(+) and H(+) distributions provide evidence for interactions with local electrostatic ion cyclotron waves and for the H(+)-O(+) two-stream instability at altitudes below the satellite.

Direct evidence for EMIC wave scattering of relativistic electrons in space

NASA Astrophysics Data System (ADS)

Zhang, X.-J.; Li, W.; Ma, Q.; Thorne, R. M.; Angelopoulos, V.; Bortnik, J.; Chen, L.; Kletzing, C. A.; Kurth, W. S.; Hospodarsky, G. B.; Baker, D. N.; Reeves, G. D.; Spence, H. E.; Blake, J. B.; Fennell, J. F.

2016-07-01

Electromagnetic ion cyclotron (EMIC) waves have been proposed to cause efficient losses of highly relativistic (>1 MeV) electrons via gyroresonant interactions. Simultaneous observations of EMIC waves and equatorial electron pitch angle distributions, which can be used to directly quantify the EMIC wave scattering effect, are still very limited, however. In the present study, we evaluate the effect of EMIC waves on pitch angle scattering of ultrarelativistic (>1 MeV) electrons during the main phase of a geomagnetic storm, when intense EMIC wave activity was observed in situ (in the plasma plume region with high plasma density) on both Van Allen Probes. EMIC waves captured by Time History of Events and Macroscale Interactions during Substorms (THEMIS) probes and on the ground across the Canadian Array for Real-time Investigations of Magnetic Activity (CARISMA) are also used to infer their magnetic local time (MLT) coverage. From the observed EMIC wave spectra and local plasma parameters, we compute wave diffusion rates and model the evolution of electron pitch angle distributions. By comparing model results with local observations of pitch angle distributions, we show direct, quantitative evidence of EMIC wave-driven relativistic electron losses in the Earth's outer radiation belt.

Steepened magnetosonic waves in the high beta plasma surrounding Comet Giacobini-Zinner

NASA Technical Reports Server (NTRS)

Tsurutani, B. T.; Smith, E. J.; Thorne, R. M.; Gosling, J. T.; Matsumoto, H.

1986-01-01

Studies of intense hydromagnetic waves at Giacobini-Zinner are extended to investigate the mode and direction of wave propagation. Simultaneous high-resolution measurements of electron density fluctuations demonstrate that long period waves propagate in the magnetosonic mode. Principal axis analyses of the long period waves and accompanying partial rotations show that the sum of the wave phase rotations is 360 deg, indicating that both are parts of the same wave oscillation. The time sequence of the steepened waveforms observed by ICE shows that the waves must propagate towards the Sun with Cph less than Vsw. Observations are consistent with wave generation by resonant ion ring or ion beam instability which predicts right-hand polarized waves propagating in the ion beam (solar) direction. The large amplitudes and small scale sizes of the cometary waves suggest that rapid pitch-angle scattering and energy transfer with energetic ions should occur. Since the waves are highly compressive, first-order Fermi acceleration is forecast.

Conjugate observations of electromagnetic ion cyclotron waves associated with traveling convection vortex events

NASA Astrophysics Data System (ADS)

Kim, Hyomin; Clauer, C. Robert; Gerrard, Andrew J.; Engebretson, Mark J.; Hartinger, Michael D.; Lessard, Marc R.; Matzka, Jürgen; Sibeck, David G.; Singer, Howard J.; Stolle, Claudia; Weimer, Daniel R.; Xu, Zhonghua

2017-07-01

We report on simultaneous observations of electromagnetic ion cyclotron (EMIC) waves associated with traveling convection vortex (TCV) events caused by transient solar wind dynamic pressure (Pd) impulse events. The Time History of Events and Macroscale Interactions during Substorms (THEMIS) spacecraft located near the magnetopause observed radial fluctuations of the magnetopause, and the GOES spacecraft measured sudden compressions of the magnetosphere in response to sudden increases in Pd. During the transient events, EMIC waves were observed by interhemispheric conjugate ground-based magnetometer arrays as well as the GOES spacecraft. The spectral structures of the waves appear to be well correlated with the fluctuating motion of the magnetopause, showing compression-associated wave generation. In addition, the wave features are remarkably similar in conjugate hemispheres in terms of bandwidth, quasiperiodic wave power modulation, and polarization. Proton precipitation was also observed by the DMSP spacecraft during the wave events, from which the wave source region is estimated to be 72°-74° in magnetic latitude, consistent with the TCV center. The confluence of space-borne and ground instruments including the interhemispheric, high-latitude, fluxgate/induction coil magnetometer array allows us to constrain the EMIC source region while also confirming the relationship between EMIC waves and the TCV current system.

Four-wave parametric oscillation in sodium vapor by electromagnetically induced diffraction.

PubMed

Harada, Ken-ichi; Ogata, Minoru; Mitsunaga, Masaharu

2007-05-01

We have observed a novel type of parametric oscillation in sodium atomic vapor where four off-axis signal waves simultaneously build up under resonant and counterpropagating pump beams with elliptical beam profiles. The four waves, two of them Stokes shifted and the other two anti-Stokes shifted, have similar output powers of up to 10 mW with a conversion efficiency of 30% and are parametrically coupled by electromagnetically induced diffraction.

Gastric dysrhythmias and the current status of electrogastrography

NASA Technical Reports Server (NTRS)

Koch, K. L.

1989-01-01

Myoelectrical activity recorded simultaneously from mucosal, serosal, and cutaneous electrodes has confirmed that the 3-cpm signal from such electrodes reflects gastric slow-wave activity. Now, the observation that patients with unexplained nausea and vomiting may have very rapid slow-wave frequencies (tachygastrias) and very slow, slow-wave frequencies (bradygastrias) suggests that electrogastrography, a reliable and noninvasive technique, may be useful in the diagnosis and management of patients with upper abdominal symptoms and gastroparesis.

On the use of volumetric strain meters to infer additional characteristics of short-period seismic radiation

USGS Publications Warehouse

Borcherdt, R.D.; Johnston, M.J.S.; Glassmoyer, G.

1989-01-01

Volumetric strain meters (Sacks-Evertson design) are installed at 15 sites along the San Andreas fault system, to monitor long-term strain changes for earthquake prediction. Deployment of portable broadband, high-resolution digital recorders (GEOS) at several of the sites extends the detection band for volumetric strain to periods shorter than 5 ?? 10-2 sec and permits the simultaneous observation of seismic radiation fields using conventional short-period pendulum seismometers. Recordings of local and regional earthquakes indicate that dilatometers respond to P energy but not direct shear energy and that straingrams can be used to resolve superimposed reflect P and S waves for inference of wave characteristics not permitted by either sensor alone. Simultaneous measurements of incident P- and S-wave amplitudes are used to introduce a technique for single-station estimates of wave field inhomogeneity, free-surface reflection coefficients and local material P velocity. -from Authors

Knocking Combustion Observed in a Spark-Ignition Engine with Simultaneous Direct and Schlieren High-Speed Motion Pictures and Pressure Records

NASA Technical Reports Server (NTRS)

Osterstrom, Gordon E

1948-01-01

Simultaneous direct and Schlieren photographs at 40,000 frames per second and correlated pressure records were taken of knocking combustion in a special spark-ignition engine to ascertain the intensity of certain end-zone reactions previously noted from Schlieren photography alone. A violent propagated homogeneous autoignition, or a similar phenomenon, previously observed, was again observed. The pressure records show autoignition of varying violence before the passage of a probable detonation wave. Extensive autoignition without occurrence of gas vibrations was seen in one explosion.

Microwave emission and scattering from Earth surface and atmosphere

NASA Technical Reports Server (NTRS)

Kong, J. A.; Lee, M. C.

1986-01-01

Nonlinear Electromagnetic (EM) wave interactions with the upper atmosphere were investigated during the period 15 December 1985 to 15 June 1986. Topics discussed include: the simultaneous excitation of ionospheric density irregularities and Earth's magnetic field fluctuations; the electron acceleration by Langmuir wave turbulence; and the occurrence of artificial spread F. The role of thermal effects in generating ionospheric irregularities by Whistler waves, intense Quasi-DC electric fields, atmospheric gravity waves, and electrojets was investigated. A model was developed to explain the discrete spectrum of the resonant ultralow frequency (ULF) waves that are commonly observed in the magnetosphere.

Joint inversion of seismic and gravity data for imaging seismic velocity structure of the crust and upper mantle beneath Utah, United States

DOE PAGES

Syracuse, Ellen Marie; Zhang, Haijiang; Maceira, Monica

2017-07-11

Here, we present a method for using any combination of body wave arrival time measurements, surface wave dispersion observations, and gravity data to simultaneously invert for three-dimensional P- and S-wave velocity models. The simultaneous use of disparate data types takes advantage of the differing sensitivities of each data type, resulting in a comprehensive and higher resolution three-dimensional geophysical model. In a case study for Utah, we combine body waves first arrivals mainly from the USArray Transportable Array, Rayleigh wave group and phase velocity dispersion data, and Bouguer gravity anomalies to invert for crustal and upper mantle structure of the region.more » Results show clear delineations, visible in both P- and S-wave velocities, between the three main tectonic provinces in the region. In conclusion, without the inclusion of the surface wave and gravity constraints, these delineations are less clear, particularly for S-wave velocities. Indeed, checkerboard tests confirm that the inclusion of the additional datasets dramatically improves S-wave velocity recovery, with more subtle improvements to P-wave velocity recovery, demonstrating the strength of the method in successfully recovering seismic velocity structure from multiple types of constraints.« less

Joint inversion of seismic and gravity data for imaging seismic velocity structure of the crust and upper mantle beneath Utah, United States

DOE Office of Scientific and Technical Information (OSTI.GOV)

Syracuse, Ellen Marie; Zhang, Haijiang; Maceira, Monica

Here, we present a method for using any combination of body wave arrival time measurements, surface wave dispersion observations, and gravity data to simultaneously invert for three-dimensional P- and S-wave velocity models. The simultaneous use of disparate data types takes advantage of the differing sensitivities of each data type, resulting in a comprehensive and higher resolution three-dimensional geophysical model. In a case study for Utah, we combine body waves first arrivals mainly from the USArray Transportable Array, Rayleigh wave group and phase velocity dispersion data, and Bouguer gravity anomalies to invert for crustal and upper mantle structure of the region.more » Results show clear delineations, visible in both P- and S-wave velocities, between the three main tectonic provinces in the region. In conclusion, without the inclusion of the surface wave and gravity constraints, these delineations are less clear, particularly for S-wave velocities. Indeed, checkerboard tests confirm that the inclusion of the additional datasets dramatically improves S-wave velocity recovery, with more subtle improvements to P-wave velocity recovery, demonstrating the strength of the method in successfully recovering seismic velocity structure from multiple types of constraints.« less

DIFFRACTION, REFRACTION, AND REFLECTION OF AN EXTREME-ULTRAVIOLET WAVE OBSERVED DURING ITS INTERACTIONS WITH REMOTE ACTIVE REGIONS

DOE Office of Scientific and Technical Information (OSTI.GOV)

Shen Yuandeng; Liu Yu; Zhao Ruijuan

2013-08-20

We present observations of the diffraction, refraction, and reflection of a global extreme-ultraviolet (EUV) wave propagating in the solar corona. These intriguing phenomena are observed when the wave interacts with two remote active regions, and together they exhibit properties of an EUV wave. When the wave approached AR11465, it became weaker and finally disappeared in the active region, but a few minutes later a new wavefront appeared behind the active region, and it was not concentric with the incoming wave. In addition, a reflected wave was also simultaneously observed on the wave incoming side. When the wave approached AR11459, itmore » transmitted through the active region directly and without reflection. The formation of the new wavefront and the transmission could be explained with diffraction and refraction effects, respectively. We propose that the different behaviors observed during the interactions may be caused by different speed gradients at the boundaries of the two active regions. We find that the EUV wave formed ahead of a group of expanding loops a few minutes after the start of the loops' expansion, which represents the initiation of the associated coronal mass ejection (CME). Based on these results, we conclude that the EUV wave should be a nonlinear magnetosonic wave or shock driven by the associated CME, which propagated faster than the ambient fast mode speed and gradually slowed down to an ordinary linear wave. Our observations support the hybrid model that includes both fast wave and slow non-wave components.« less

Numerical analysis of wavefront measurement characteristics by using plenoptic camera

NASA Astrophysics Data System (ADS)

Lv, Yang; Ma, Haotong; Zhang, Xuanzhe; Ning, Yu; Xu, Xiaojun

2016-01-01

To take advantage of the large-diameter telescope for high-resolution imaging of extended targets, it is necessary to detect and compensate the wave-front aberrations induced by atmospheric turbulence. Data recorded by Plenoptic cameras can be used to extract the wave-front phases associated to the atmospheric turbulence in an astronomical observation. In order to recover the wave-front phase tomographically, a method of completing the large Field Of View (FOV), multi-perspective wave-front detection simultaneously is urgently demanded, and it is plenoptic camera that possesses this unique advantage. Our paper focuses more on the capability of plenoptic camera to extract the wave-front from different perspectives simultaneously. In this paper, we built up the corresponding theoretical model and simulation system to discuss wave-front measurement characteristics utilizing plenoptic camera as wave-front sensor. And we evaluated the performance of plenoptic camera with different types of wave-front aberration corresponding to the occasions of applications. In the last, we performed the multi-perspective wave-front sensing employing plenoptic camera as wave-front sensor in the simulation. Our research of wave-front measurement characteristics employing plenoptic camera is helpful to select and design the parameters of a plenoptic camera, when utilizing which as multi-perspective and large FOV wave-front sensor, which is expected to solve the problem of large FOV wave-front detection, and can be used for AO in giant telescopes.

Geomagnetically conjugate observations of ionospheric and thermospheric variations accompanied with a midnight brightness wave at low latitudes

NASA Astrophysics Data System (ADS)

Fukushima, D.; Shiokawa, K.; Otsuka, Y.; Kubota, M.; Yokoyama, T.; Nishioka, M.; Komonjinda, S.; Yatini, C. Y.

2014-12-01

A midnight brightness wave (MBW) is the phenomenon that the OI (630-nm) airglow enhancement propagates poleward once at local midnight. In this study, we first conducted geomagnetically conjugate observations of 630nm airglow for an MBW at conjugate stations. An airglow enhancement which is considered to be an MBW was observed in the 630-nm airglow images at Kototabang, Indonesia (geomagnetic latitude (MLAT): 10.0S) at around local midnight from 1540 to 1730 UT (from 2240 to 2430 LT) on 7 February 2011. This MBW was propagating south-southwestward, which is geomagnetically poleward, with a velocity of 290 m/s. However, similar wave was not observed in the 630-nm airglow images at Chiang Mai, Thailand (MLAT: 8.9N), which is close to being conjugate point of Kototabang. This result indicates that the MBW does not have geomagnetic conjugacy. We simultaneously observed thermospheric neutral winds observed by a co-located Fabry-Perot interferometer at Kototabang. The observed meridional winds turned from northward (geomagnetically equatorward) to southward (geomagnetically poleward) just before the MBW was observed. The bottomside ionospheric heights observed by ionosondes rapidly decreased at Kototabang and slightly increased at Chiang Mai simultaneously with the MBW passage. In the presentation, we discuss the MBW generation by the observed poleward neutral winds at Kototabang, and the cause of the coinciding small height increase at Chiang Mai by the polarization electric field inside the observed MBW at Kototabang.

Electromagnetic and electrostatic emissions at the cusp-magnetosphere interface during substorms

NASA Technical Reports Server (NTRS)

Curtis, S. A.; Fairfield, D. H.; Wu, C. S.

1979-01-01

Strongly peaked electrostatic emissions near 10.0 kHz and electromagnetic emissions near 0.56 kHz have been observed by the VLF wave detector on board Imp 6 on crossings from the earth's magnetosphere into the polar cusp during the occurrence of large magnetospheric substorms. The electrostatic emissions were observed to be closely confined to the cusp-magnetosphere interface. The electromagnetic emissions were of somewhat broader spatial extent and were seen on higher-latitude field lines within the cusp. Using these plasma wave observations and additional information provided by plasma, magnetometer and particle measurements made simultaneously on Imp 6, theories are constructed to explain each of the two classes of emission. The electromagnetic waves are modeled as whistlers, and the electrostatic waves as electron-cyclotron harmonics. The resulting growth rates predict power spectra similar to those observed for both emission classes. The electrostatic waves may play a significant role via enhanced diffusion in the relaxation of the sharp substorm time cusp-magnetosphere boundary to a more diffuse quiet time boundary.

Direct evidence for EMIC wave scattering of relativistic electrons in space: EMIC-Driven Electron Losses in Space

DOE PAGES

Zhang, X. -J.; Li, W.; Ma, Q.; ...

2016-07-01

Electromagnetic ion cyclotron (EMIC) waves have been proposed to cause efficient losses of highly relativistic (>1 MeV) electrons via gyroresonant interactions. Simultaneous observations of EMIC waves and equatorial electron pitch angle distributions, which can be used to directly quantify the EMIC wave scattering effect, are still very limited, however. In the present study, we evaluate the effect of EMIC waves on pitch angle scattering of ultrarelativistic (>1 MeV) electrons during the main phase of a geomagnetic storm, when intense EMIC wave activity was observed in situ (in the plasma plume region with high plasma density) on both Van Allen Probes.more » EMIC waves captured by Time History of Events and Macroscale Interactions during Substorms (THEMIS) probes and on the ground across the Canadian Array for Real-time Investigations of Magnetic Activity (CARISMA) are also used to infer their magnetic local time (MLT) coverage. From the observed EMIC wave spectra and local plasma parameters, we compute wave diffusion rates and model the evolution of electron pitch angle distributions. In conclusion, by comparing model results with local observations of pitch angle distributions, we show direct, quantitative evidence of EMIC wave-driven relativistic electron losses in the Earth’s outer radiation belt.« less

Cluster Observations of Non-Time Continuous Magnetosonic Waves

NASA Technical Reports Server (NTRS)

Walker, Simon N.; Demekhov, Andrei G.; Boardsen, Scott A.; Ganushkina, Natalia Y.; Sibeck, David G.; Balikhin, Michael A.

2016-01-01

Equatorial magnetosonic waves are normally observed as temporally continuous sets of emissions lasting from minutes to hours. Recent observations, however, have shown that this is not always the case. Using Cluster data, this study identifies two distinct forms of these non temporally continuous use missions. The first, referred to as rising tone emissions, are characterized by the systematic onset of wave activity at increasing proton gyroharmonic frequencies. Sets of harmonic emissions (emission elements)are observed to occur periodically in the region +/- 10 off the geomagnetic equator. The sweep rate of these emissions maximizes at the geomagnetic equator. In addition, the ellipticity and propagation direction also change systematically as Cluster crosses the geomagnetic equator. It is shown that the observed frequency sweep rate is unlikely to result from the sideband instability related to nonlinear trapping of suprathermal protons in the wave field. The second form of emissions is characterized by the simultaneous onset of activity across a range of harmonic frequencies. These waves are observed at irregular intervals. Their occurrence correlates with changes in the spacecraft potential, a measurement that is used as a proxy for electron density. Thus, these waves appear to be trapped within regions of localized enhancement of the electron density.

Simultaneous manipulation and observation of multiple ro-vibrational eigenstates in solid para-hydrogen.

PubMed

Katsuki, Hiroyuki; Ohmori, Kenji

2016-09-28

We have experimentally performed the coherent control of delocalized ro-vibrational wave packets (RVWs) of solid para-hydrogen (p-H 2 ) by the wave packet interferometry (WPI) combined with coherent anti-Stokes Raman scattering (CARS). RVWs of solid p-H 2 are delocalized in the crystal, and the wave function with wave vector k ∼ 0 is selectively excited via the stimulated Raman process. We have excited the RVW twice by a pair of femtosecond laser pulses with delay controlled by a stabilized Michelson interferometer. Using a broad-band laser pulse, multiple ro-vibrational states can be excited simultaneously. We have observed the time-dependent Ramsey fringe spectra as a function of the inter-pulse delay by a spectrally resolved CARS technique using a narrow-band probe pulse, resolving the different intermediate states. Due to the different fringe oscillation periods among those intermediate states, we can manipulate their amplitude ratio by tuning the inter-pulse delay on the sub-femtosecond time scale. The state-selective manipulation and detection of the CARS signal combined with the WPI is a general and efficient protocol for the control of the interference of multiple quantum states in various quantum systems.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Yukhimuk, V.; Roussel-Dupre, R.

In this paper the evolution of nonlinear scattering of whistler mode waves by kinetic Alfven waves (KAW) in time and two spatial dimensions is studied analytically. The authors suggest this nonlinear process as a mechanism of kinetic Alfven wave generation in space plasmas. This mechanism can explain the dependence of Alfven wave generation on whistler waves observed in magnetospheric and ionospheric plasmas. The observational data show a dependence for the generation of long periodic pulsations Pc5 on whistler wave excitation in the auroral and subauroral zone of the magnetosphere. This dependence was first observed by Ondoh T.I. For 79 casesmore » of VLF wave excitation registered by Ondoh at College Observatory (L=64.6 N), 52 of them were followed by Pc5 geomagnetic pulsation generation. Similar results were obtained at the Loparskaia Observatory (L=64 N) for auroral and subauroral zone of the magnetosphere. Thus, in 95% of the cases when VLF wave excitation occurred the generation of long periodic geomagnetic pulsations Pc5 were observed. The observations also show that geomagnetic pulsations Pc5 are excited simultaneously or insignificantly later than VLF waves. In fact these two phenomena are associated genetically: the excitation of VLF waves leads to the generation of geomagnetic pulsations Pc5. The observations show intensive generation of geomagnetic pulsations during thunderstorms. Using an electromagnetic noise monitoring system covering the ULF range (0.01-10 Hz) A.S. Fraser-Smith observed intensive ULF electromagnetic wave during a large thunderstorm near the San-Francisco Bay area on September 23, 1990. According to this data the most significant amplification in ULF wave activity was observed for waves with a frequency of 0.01 Hz and it is entirely possible that stronger enhancements would have been measured at lower frequencies.« less

3D Structure of Iran and Surrounding Areas From The Simultaneous Inversion of Complementary Geophysical Observations

NASA Astrophysics Data System (ADS)

Ammon, C. J.; Maceira, M.; Cleveland, M.

2010-12-01

We present a three-dimensional seismic-structure model of the Arabian-Eurasian collision zone obtained via simultaneous, joint inversion of surface-wave dispersion measurements, teleseismic P-wave receiver functions, and gravity observations. We use a simple, approximate relationship between density and seismic velocities so that the three data sets may be combined in a single inversion. The sensitivity of the different data sets are well known: surface waves provide information on the smooth variations in elastic properties, receiver functions provide information on abrupt velocity contrasts, and gravity measurements provide information on broad-wavenumber shallow density variations and long-wavenumber components of deeper density structures. The combination of the data provides improved resolution of shallow-structure variations, which in turn help produce the smooth features at depth with less contamination from the strong heterogeneity often observed in the upper crust. We also explore geologically based smoothness constraints to help resolve sharp features in the underlying shallow 3D structure. Our focus is on the region surrounding Iran from east Turkey and Iraq in the west, to Pakistan and Afghanistan in the east. We use Bouguer gravity anomalies derived from the global gravity model extracted from the GRACE satellite mission. Surface-wave dispersion velocities in the period range between 7 and 150 s are taken from previously published tomographic maps for the region. Preliminary results show expected strong variations in the Caspian region as well as the deep sediment regions of the Persian Gulf. Regions constrained with receiver-function information generally show sharper crust-mantle boundary structure than that obtained by inversion of the surface waves alone (with thin layers and smoothing constraints). Final results of the simultaneous inversion will help us to better understand one of the most prominent examples of continental collision. Such models also provide an important starting model for time-consuming and fully 3D inversions.

A quantum trampoline for ultra-cold atoms

NASA Astrophysics Data System (ADS)

Robert-de-Saint-Vincent, M.; Brantut, J.-P.; Bordé, Ch. J.; Aspect, A.; Bourdel, T.; Bouyer, P.

2010-01-01

We have observed the interferometric suspension of a free-falling Bose-Einstein condensate periodically submitted to multiple-order diffraction by a vertical 1D standing wave. This scheme permits simultaneously the compensation of gravity and coherent splitting/recombination of the matter waves. It results in high-contrast interference in the number of atoms detected at constant height. For long suspension times, multiple-wave interference is revealed through a sharpening of the fringes. We characterize our atom interferometer and use it to measure the acceleration of gravity.

Dual-pumped nondegenerate four-wave mixing in semiconductor laser with a built-in external cavity

NASA Astrophysics Data System (ADS)

Wu, Jian-Wei; Qiu, Qi; Hyub Won, Yong

2017-04-01

In this paper, a semiconductor laser system consisting of a conventional multimode Fabry-Pérot laser diode with a built-in external cavity is presented and demonstrated. More than two resonance modes, whose peak levels are significantly higher than other residual modes, are simultaneously supported and output by adjusting the bias current and operating temperature of the active region. Based on this device, dual-pumped nondegenerate four-wave mixing—in which two pump waves and a single signal wave are simultaneously fed into the laser, and the injection power and wavelength of the injected pump and signal waves are changed—is observed and discussed thoroughly. The results show that while the wavelengths of pump wave A and signal wave S are kept constant, the other pump wave B jumps from about 1535 nm to 1578 nm, generating conversion signals with changed wavelengths. The achieved conversion bandwidth between the primary signal and the converted signal waves is broadly tunable in the range of several terahertz frequencies. Both the conversion efficiency and optical signal-to-noise ratio of the newly generated conversion signals are adopted to evaluate the performance of the proposed four-wave mixing process, and are strongly dependent on the wavelength and power of the injected waves. Here, the attained maximum conversion efficiency and optical signal-to-noise ratio are close to -22 dB and 15 dB, respectively.

Wind Observations of Wave Heating and/or Particle Energization at Supercritical Interplanetary Shocks

NASA Technical Reports Server (NTRS)

Wilson, Lynn Bruce, III; Szabo, Adam; Koval, Andriy; Cattell, Cynthia A.; Kellogg, Paul J.; Goetz, Keith; Breneman, Aaron; Kersten, Kris; Kasper, Justin C.; Pulupa, Marc

2011-01-01

We present the first observations at supercritical interplanetary shocks of large amplitude (> 100 mV/m pk-pk) solitary waves, approx.30 mV/m pk-pk waves exhibiting characteristics consistent with electron Bernstein waves, and > 20 nT pk-pk electromagnetic lower hybrid-like waves, with simultaneous evidence for wave heating and particle energization. The solitary waves and the Bernstein-like waves were likely due to instabilities driven by the free energy provided by reflected ions [Wilson III et al., 2010]. They were associated with strong particle heating in both the electrons and ions. We also show a case example of parallel electron energization and perpendicular ion heating due to a electromagnetic lower hybrid-like wave. Both studies provide the first experimental evidence of wave heating and/or particle energization at interplanetary shocks. Our experimental results, together with the results of recent Vlasov [Petkaki and Freeman, 2008] and PIC [Matsukyo and Scholer, 2006] simulations using realistic mass ratios provide new evidence to suggest that the importance of wave-particle dissipation at shocks may be greater than previously thought.

Does the Alfvén wave wreck the large-scale magnetic cloud structure?

NASA Astrophysics Data System (ADS)

Raghav, Anil N.; Kule, Ankita

2018-06-01

Alfvén waves are primal and pervasive in space plasmas and significantly contributes to microscale fluctuations in the solar wind and some heliospheric processes. Here, we demonstrate the first observable distinct feature of Alfvén wave while propagating from magnetic cloud to trailing solar wind. The Walén test is used to confirm their presence in selected regions. The amplitude ratio of inward to outward Alfvén waves is employed to establish their flow direction. The dominant inward flow is observed in magnetic cloud whereas trailing solar wind shows the dominant outward flow of Alfvén waves. The observed reduction in Walén slope and correlation coefficient within magnetic cloud suggest (i) the simultaneous presence of an inward & outward Alfvén waves and/or (ii) a possibility of magnetic reconnection and/or (iii) development of thermal anisotropy and/or (iv) dissipation of Alfvénic fluctuations. The study implies that either the Alfvén waves dissipate in the magnetic cloud or its presence can lead to disruption of the magnetic cloud structure.

Ocean waves and turbulence as observed with an adaptive coherent multifrequency radar

NASA Technical Reports Server (NTRS)

Gjessing, D. T.; Hjelmstad, J.

1984-01-01

An adaptive coherent multifrequency radar system is developed for several applications. The velocity distribution (Doppler spectrum) and spectral intensity of 15 different irregularity scales (waves and turbulence) can be measured simultaneously. Changing the azimuth angle of the antennas at regular intervals, the directivity of the wave/turbulence pattern on the sea surface can also be studied. A series of measurements for different air/sea conditions are carried out from a coast based platform. Experiments in the Atlantic are also performed with the same equipment making use of the NASA Electra aircraft. The multifrequency radar allows the measurement of the velocity distribution (""coherent and incoherent component'') associated with 15 different ocean irregularity scales simultaneously in a directional manner. It is possible to study the different air/sea mechanisms in some degree of detail.

Analysis of magnetometer data/wave signals in the Earth's magnetosphere

NASA Technical Reports Server (NTRS)

Engebretson, Mark J.

1993-01-01

Work on the reduction and analysis of Dynamics Explorer (DE) satellite magnetometer data with special emphasis on the ULF fluctuations and waves evident in such data is described. Research focused on the following: (1) studies of Pc 1 wave packets near the plasmapause; (2) satellite-ground pulsation study; (3) support for studies of ion energization processes; (4) search for Pc 1 wave events in 1981 DE 1 data; (5) study of Pc 3-5 events observed simultaneously by DE 1 and by AMPTE CCE; (6) support for studies of electromagnetic transients on DE 1; and (7) analysis of wave events induced by sudden impulses.

A coordinated study of 1 h mesoscale gravity waves propagating from Logan to Boulder with CRRL Na Doppler lidars and temperature mapper

NASA Astrophysics Data System (ADS)

Lu, Xian; Chen, Cao; Huang, Wentao; Smith, John A.; Chu, Xinzhao; Yuan, Tao; Pautet, Pierre-Dominique; Taylor, Mike J.; Gong, Jie; Cullens, Chihoko Y.

2015-10-01

We present the first coordinated study using two lidars at two separate locations to characterize a 1 h mesoscale gravity wave event in the mesopause region. The simultaneous observations were made with the Student Training and Atmospheric Research (STAR) Na Doppler lidar at Boulder, CO, and the Utah State University Na Doppler lidar and temperature mapper at Logan, UT, on 27 November 2013. The high precision possessed by the STAR lidar enabled these waves to be detected in vertical wind. The mean wave amplitudes are ~0.44 m/s in vertical wind and ~1% in relative temperature at altitudes of 82-107 km. Those in the zonal and meridional winds are 6.1 and 5.2 m/s averaged from 84 to 99 km. The horizontal and vertical wavelengths inferred from the mapper and lidars are ~219 ± 4 and 16.0 ± 0.3 km, respectively. The intrinsic period is ~1.3 h for the airglow layer, Doppler shifted by a mean wind of ~17 m/s. The wave packet propagates from Logan to Boulder with an azimuth angle of ~135° clockwise from north and an elevation angle of ~ 3° from the horizon. The observed phase difference between the two locations can be explained by the traveling time of the 1 h wave from Logan to Boulder, which is about ~2.4 h. The wave polarization relations are examined through the simultaneous quantifications of the three wind components and temperature. This study has developed a systematic methodology for fully characterizing mesoscale gravity waves, inspecting their intrinsic properties and validating the derivation of horizontal wave structures by applying multiple instruments from coordinated stations.

Simultaneous measurement of temperature and emissivity of lunar regolith simulant using dual-channel millimeter-wave radiometry.

PubMed

McCloy, J S; Sundaram, S K; Matyas, J; Woskov, P P

2011-05-01

Millimeter wave (MMW) radiometry can be used for simultaneous measurement of emissivity and temperature of materials under extreme environments (high temperature, pressure, and corrosive environments). The state-of-the-art dual channel MMW passive radiometer with active interferometric capabilities at 137 GHz described here allows for radiometric measurements of sample temperature and emissivity up to at least 1600 °C with simultaneous measurement of sample surface dynamics. These capabilities have been used to demonstrate dynamic measurement of melting of powders of simulated lunar regolith and static measurement of emissivity of solid samples. The paper presents the theoretical background and basis for the dual-receiver system, describes the hardware in detail, and demonstrates the data analysis. Post-experiment analysis of emissivity versus temperature allows further extraction from the radiometric data of millimeter wave viewing beam coupling factors, which provide corroboratory evidence to the interferometric data of the process dynamics observed. These results show the promise of the MMW system for extracting quantitative and qualitative process parameters for industrial processes and access to real-time dynamics of materials behavior in extreme environments.

Cloud cover classification through simultaneous ground-based measurements of solar and infrared radiation

NASA Astrophysics Data System (ADS)

Orsini, Antonio; Tomasi, Claudio; Calzolari, Francescopiero; Nardino, Marianna; Cacciari, Alessandra; Georgiadis, Teodoro

2002-04-01

Simultaneous measurements of downwelling short-wave solar irradiance and incoming total radiation flux were performed at the Reeves Nevè glacier station (1200 m MSL) in Antarctica on 41 days from late November 1994 to early January 1995, employing the upward sensors of an albedometer and a pyrradiometer. The downwelling short-wave radiation measurements were analysed following the Duchon and O'Malley [J. Appl. Meteorol. 38 (1999) 132] procedure for classifying clouds, using the 50-min running mean values of standard deviation and the ratio of scaled observed to scaled clear-sky irradiance. Comparing these measurements with the Duchon and O'Malley rectangular boundaries and the local human observations of clouds collected on 17 days of the campaign, we found that the Duchon and O'Malley classification method obtained a success rate of 93% for cirrus and only 25% for cumulus. New decision criteria were established for some polar cloud classes providing success rates of 94% for cirrus, 67% for cirrostratus and altostratus, and 33% for cumulus and altocumulus. The ratios of the downwelling short-wave irradiance measured for cloudy-sky conditions to that calculated for clear-sky conditions were analysed in terms of the Kasten and Czeplak [Sol. Energy 24 (1980) 177] formula together with simultaneous human observations of cloudiness, to determine the empirical relationship curves providing reliable estimates of cloudiness for each of the three above-mentioned cloud classes. Using these cloudiness estimates, the downwelling long-wave radiation measurements (obtained as differences between the downward fluxes of total and short-wave radiation) were examined to evaluate the downwelling long-wave radiation flux normalised to totally overcast sky conditions. Calculations of the long-wave radiation flux were performed with the MODTRAN 3.7 code [Kneizys, F.X., Abreu, L.W., Anderson, G.P., Chetwynd, J.H., Shettle, E.P., Berk, A., Bernstein, L.S., Robertson, D.C., Acharya, P., Rothman, L.S., Selby, J.E.A., Gallery, W.O., Clough, S.A., 1996. In: Abreu, L.W., Anderson, G.P. (Eds.), The MODTRAN 2/3 Report and LOWTRAN 7 MODEL. Contract F19628-91-C.0132, Phillips Laboratory, Geophysics Directorate, PL/GPOS, Hanscom AFB, MA, 261 pp.] for both clear-sky and cloudy-sky conditions, considering various cloud types characterised by different cloud base altitudes and vertical thicknesses. From these evaluations, best-fit curves of the downwelling long-wave radiation flux were defined as a function of the cloud base height for the three polar cloud classes. Using these relationship curves, average estimates of the cloud base height were obtained from the three corresponding sub-sets of long-wave radiation measurements. The relative frequency histograms of the cloud base height defined by examining these three sub-sets were found to present median values of 4.7, 1.7 and 3.6 km for cirrus, cirrostratus/altostratus and cumulus/altocumulus, respectively, while median values of 6.5, 1.8 and 2.9 km were correspondingly determined by analysing only the measurements taken together with simultaneous cloud observations.

Studies of nonlinear interactions between counter-propagating Alfv'en waves in the LAPD

NASA Astrophysics Data System (ADS)

Auerbach, D. W.; Perez, J. C.; Carter, T. A.; Boldyrev, S.

2007-11-01

From a weak turbulence point of view, nonlinear interactions between shear Alfv'en waves are fundamental to the energy cascade in low-frequency magnetic turbulence. We report here on an experimental study of counter-propagating Alfv'en wave interactions in the Large Plasma Device (LAPD) at UCLA. Colliding, orthogonally polarized kinetic Alfv'en waves are generated by two antennae, separated by 5m along the guide magnetic field. Magnetic field and langmuir probes record plasma behavior between the antennae. When each antenna is operated separately, linearly polarized Alfv'en waves propagate in opposite directions along the guide field. When two antennae simultaneously excite counter propagating waves, we observe multiple side bands in the frequency domain, whose amplitude scales quadratically with wave amplitude. In the spatial domain we observe non-linear superposition in the 2D structure of the waves and spectral broadening in the perpendicular wave-number spectrum. This indicates the presence of nonlinear interaction of the counter propagating Alfv'en waves, and opens the possiblity to investigate Alfv'enic plasma turbulence in controlled and reproducible laboratory experiments.

Simultaneous laser excitation of backward volume and perpendicular standing spin waves in full-Heusler Co2FeAl0.5Si0.5 films

PubMed Central

Chen, Zhifeng; Yan, Yong; Li, Shufa; Xu, Xiaoguang; Jiang, Yong; Lai, Tianshu

2017-01-01

Spin-wave dynamics in full-Heusler Co2FeAl0.5Si0.5 films are studied using all-optical pump-probe magneto-optical polar Kerr spectroscopy. Backward volume magnetostatic spin-wave (BVMSW) mode is observed in films with thickness ranging from 20 to 100 nm besides perpendicular standing spin-wave (PSSW) mode, and found to be excited more efficiently than the PSSW mode. The field dependence of the effective Gilbert damping parameter appears especial extrinsic origin. The relationship between the lifetime and the group velocity of BVMSW mode is revealed. The frequency of BVMSW mode does not obviously depend on the film thickness, but the lifetime and the effective damping appear to do so. The simultaneous excitation of BVMSW and PSSW in Heusler alloy films as well as the characterization of their dynamic behaviors may be of interest for magnonic and spintronic applications. PMID:28195160

Simultaneous observations of subauroral electron temperature enhancements and electromagnetic ion cyclotron waves

NASA Technical Reports Server (NTRS)

Erlandson, R. E.; Aggson, T. L.; Hogey, W. R.; Slavin, J. A.

1993-01-01

Observational results from an investigation of LF (0.5-4.0 Hz) electromagnetic ion cyclotron waves and subauroral electron temperature enhancements recorded from the DE-2 satellite are presented. Four different wave events were analyzed, all recorded at magnetic latitudes from 57-60 deg, magnetic local times from 8-14 hr, and altitudes from 600-900 km. The peak wave amplitudes during the events ranged from 8-70 nT and 5-30 mV/m in the magnetic and electric field, respectively. Te enhancements at the time of the waves were observed in three of four events. A linear relationship between the wave magnetic field spectral density and Te enhancements was found for these events. The Te enhancements were also correlated with an enhanced flux of low energy electrons. During one event (82104) an enhanced flux of electrons were observed at energies up to 50 eV and at nearly all pitch angles, although the flux was largest in the precipitating and upflowing directions. It is suggested that the waves are responsible for heating the low energy electrons which precipitate to the ionosphere and produce the observed Te enhancements. The upflowing electron population appears to be heated at ionospheric altitudes, below the DE-2 satellite.

Wave number determination of Pc 1-2 mantle waves considering He++ ions: A Cluster study

NASA Astrophysics Data System (ADS)

Grison, B.; Escoubet, C. P.; Santolík, O.; Cornilleau-Wehrlin, N.; Khotyaintsev, Y.

2014-09-01

The present case study concerns narrowband electromagnetic emission detected in the distant cusp region simultaneously with upgoing plasma flows. The wave properties match the usual properties of the Pc 1-2 mantle waves: small angle between the wave vector and the magnetic field line, left-hand polarization, and propagation toward the ionosphere. We report here the first direct wave vector measurement of these waves (about 1.2 × 10- 2 rad/km) through multi spacecraft analysis using the three magnetic components and, at the same time, through single spacecraft analysis based on the refractive index analysis using the three magnetic components and two electric components. The refractive index analysis offers a simple way to estimate wave numbers in this frequency range. Numerical calculations are performed under the observed plasma conditions. The obtained results show that the ion distribution functions are unstable to ion cyclotron instability at the observed wave vector value, due to the large ion temperature anisotropy. We thus show that these electromagnetic ion cyclotron (EMIC) waves are amplified in the distant cusp region. The Poynting flux of the waves is counterstreaming with respect to the plasma flow. This sense of propagation is consistent with the time necessary to amplify the emissions to the observed level. We point out the role of the wave damping at the He++ gyrofrequency to explain that such waves cannot be observed from the ground at the cusp foot print location.

Direct Evidence of EMIC-Driven Electron Loss in Space: Evaluation of an Electron Dropout Event

NASA Astrophysics Data System (ADS)

Zhang, X.; Li, W.; Ma, Q.; Thorne, R. M.; Angelopoulos, V.

2015-12-01

Electromagnetic ion cyclotron (EMIC) waves have been proposed as a mechanism to cause efficient losses of highly relativistic (>MeV) electrons via gyroresonant interactions. However, simultaneous observations of EMIC waves and equatorial electron pitch angle distributions, which can be used to directly quantify the EMIC wave scattering effect, are still very limited. In the present study, we evaluate the effect of EMIC waves on the pitch angle scattering of relativistic and ultrarelativistic (0.5-5 MeV) electrons during the main phase of a geomagnetic storm, when intense EMIC wave activity was observed in situ (in the plasma plume region with high plasma density) on both the Van Allen Probes and one of the THEMIS probes. EMIC waves captured on the ground across the Canadian Array for Real-time Investigations of Magnetic Activity (CARISMA) and enhanced precipitation of >~0.7 MeV electrons captured by POES are used to infer the MLT coverage of EMIC waves. Based on the observed EMIC wave spectra, local fpe and fce, we estimate the wave diffusion rates and model the evolution of electron pitch angle distributions. By comparing the modeled results with local observations of pitch angle distributions, for the first time, we are able to show direct, quantitative evidence of EMIC wave-driven relativistic electron loss in the Earth's outer radiation belt.

Coronal ``Wave'': Magnetic Footprint of a Coronal Mass Ejection?

NASA Astrophysics Data System (ADS)

Attrill, Gemma D. R.; Harra, Louise K.; van Driel-Gesztelyi, Lidia; Démoulin, Pascal

2007-02-01

We investigate the properties of two ``classical'' EUV Imaging Telescope (EIT) coronal waves. The two source regions of the associated coronal mass ejections (CMEs) possess opposite helicities, and the coronal waves display rotations in opposite senses. We observe deep core dimmings near the flare site and also widespread diffuse dimming, accompanying the expansion of the EIT wave. We also report a new property of these EIT waves, namely, that they display dual brightenings: persistent ones at the outermost edge of the core dimming regions and simultaneously diffuse brightenings constituting the leading edge of the coronal wave, surrounding the expanding diffuse dimmings. We show that such behavior is consistent with a diffuse EIT wave being the magnetic footprint of a CME. We propose a new mechanism where driven magnetic reconnections between the skirt of the expanding CME magnetic field and quiet-Sun magnetic loops generate the observed bright diffuse front. The dual brightenings and the widespread diffuse dimming are identified as innate characteristics of this process.

Onboard software of Plasma Wave Experiment aboard Arase: instrument management and signal processing of Waveform Capture/Onboard Frequency Analyzer

NASA Astrophysics Data System (ADS)

Matsuda, Shoya; Kasahara, Yoshiya; Kojima, Hirotsugu; Kasaba, Yasumasa; Yagitani, Satoshi; Ozaki, Mitsunori; Imachi, Tomohiko; Ishisaka, Keigo; Kumamoto, Atsushi; Tsuchiya, Fuminori; Ota, Mamoru; Kurita, Satoshi; Miyoshi, Yoshizumi; Hikishima, Mitsuru; Matsuoka, Ayako; Shinohara, Iku

2018-05-01

We developed the onboard processing software for the Plasma Wave Experiment (PWE) onboard the Exploration of energization and Radiation in Geospace, Arase satellite. The PWE instrument has three receivers: Electric Field Detector, Waveform Capture/Onboard Frequency Analyzer (WFC/OFA), and the High-Frequency Analyzer. We designed a pseudo-parallel processing scheme with a time-sharing system and achieved simultaneous signal processing for each receiver. Since electric and magnetic field signals are processed by the different CPUs, we developed a synchronized observation system by using shared packets on the mission network. The OFA continuously measures the power spectra, spectral matrices, and complex spectra. The OFA obtains not only the entire ELF/VLF plasma waves' activity but also the detailed properties (e.g., propagation direction and polarization) of the observed plasma waves. We performed simultaneous observation of electric and magnetic field data and successfully obtained clear wave properties of whistler-mode chorus waves using these data. In order to measure raw waveforms, we developed two modes for the WFC, `chorus burst mode' (65,536 samples/s) and `EMIC burst mode' (1024 samples/s), for the purpose of the measurement of the whistler-mode chorus waves (typically in a frequency range from several hundred Hz to several kHz) and the EMIC waves (typically in a frequency range from a few Hz to several hundred Hz), respectively. We successfully obtained the waveforms of electric and magnetic fields of whistler-mode chorus waves and ion cyclotron mode waves along the Arase's orbit. We also designed the software-type wave-particle interaction analyzer mode. In this mode, we measure electric and magnetic field waveforms continuously and transfer them to the mission data recorder onboard the Arase satellite. We also installed an onboard signal calibration function (onboard SoftWare CALibration; SWCAL). We performed onboard electric circuit diagnostics and antenna impedance measurement of the wire-probe antennas along the orbit. We utilize the results obtained using the SWCAL function when we calibrate the spectra and waveforms obtained by the PWE.[Figure not available: see fulltext.

Vector magnetic field observations with the Haleakala polarimeter

NASA Technical Reports Server (NTRS)

Mickey, D. L.

1985-01-01

Several enhancements were recently made to the Haleakala polarimeter. Linear array detectors provide simultaneous resolution over a 3-A wavelength range, with spectral resolution of 40 mA. Optical fibers are now used to carry the intensity-modulated light from the rotating quarter-wave plate polarimeter to the echelle spectrometer, permitting its removal from the spar to a more stable environment. These changes, together with improved quarter-wave plates, reduced systematic errors to a few parts in 10,000 for routine observations. Examples of Stokes profiles and derived magnetic field maps are presented.

Seismic, satellite, and site observations of internal solitary waves in the NE South China Sea.

PubMed

Tang, Qunshu; Wang, Caixia; Wang, Dongxiao; Pawlowicz, Rich

2014-06-20

Internal solitary waves (ISWs) in the NE South China Sea (SCS) are tidally generated at the Luzon Strait. Their propagation, evolution, and dissipation processes involve numerous issues still poorly understood. Here, a novel method of seismic oceanography capable of capturing oceanic finescale structures is used to study ISWs in the slope region of the NE SCS. Near-simultaneous observations of two ISWs were acquired using seismic and satellite imaging, and water column measurements. The vertical and horizontal length scales of the seismic observed ISWs are around 50 m and 1-2 km, respectively. Wave phase speeds calculated from seismic observations, satellite images, and water column data are consistent with each other. Observed waveforms and vertical velocities also correspond well with those estimated using KdV theory. These results suggest that the seismic method, a new option to oceanographers, can be further applied to resolve other important issues related to ISWs.

Observations of Electromagnetic Whistler Precursors at Supercritical Interplanetary Shocks

NASA Technical Reports Server (NTRS)

Wilson, L. B., III; Koval, A.; Szabo, Adam; Breneman, A.; Cattell, C. A.; Goetz, K.; Kellogg, P. J.; Kersten, K.; Kasper, J. C.; Maruca, B. A.;

Z mode radiation in Jupiter's magnetosphere - The source of Jovian continuum radiation

NASA Technical Reports Server (NTRS)

Barbosa, D. D.; Kurth, W. S.; Moses, S. L.; Scarf, F. L.

1990-01-01

Observations of Z-mode waves in Jupiter's magnetosphere are analyzed. The assumption that the frequency of the intensity minimum, which isolates the signal, corresponds to the electron plasma frequency provides a consistent interpretation of all spectral features in terms of plasma resonances and cutoffs. It is shown that the continuum radiation is composed of both left-hand and right-hand polarized waves with distinct cutoffs observed at the plasma frequency and right-hand cutoff frequency, respectively. It is found that the Z-mode peak frequency lies close to the left-hand cutoff frequency, suggesting that the observed characteristics of the emission are the result of wave reflection at the cutoff layer. Another distinct emission occurring near the upper hybrid resonance frequency is detected simultaneously with the Z mode. The entire set of observations gives strong support to the linear mode theory of the conversion of upper hybrid waves to continuum radiation mediated by the Z mode via the Budden radio window mechanism.

Observation and theory of Pc 5 waves with harmonically related transverse and compressional components

NASA Astrophysics Data System (ADS)

Takahashi, K.; Cheng, C. Z.; McEntire, R. W.; Kistler, L. M.

1990-02-01

The properties of 23 magnetic pulsation events observed by the AMPTE CCE spacecraft are studied. These events are selected on the basis of the field magnitude which oscillated at the second harmonic of a simultaneously present transverse oscillation. The events have a second harmonic period of 80-600 s (roughly the Pc 5 range), are observed in cluster in the dawn (0300-0800 magnetic local time, MLT) and dusk (1600-2100 MLT) sectors, and are localized near the magnetic equator. Although the azimuthal wave number estimated from an ion finite Larmor radius effect, is generally large (about 50), there is a marked difference between the events observed in the dawn and dusk sectors. In the dawn sector the waves have low frequencies (1-5 mHz), indicate left-hand polarization with respect to the ambient magnetic field, and propagate eastward with respect to the spacecraft. In the dusk sector the waves have high frequencies (5-15 mHz), indicate right-hand polarization, and propagate westward. It is suggested that the waves are all westward propagating in the plasma rest frame and that local-time-dependent Doppler shift is the reason for the local time dependence of the wave properties.

Observation and theory of Pc 5 waves with harmonically related transverse and compressional components

NASA Technical Reports Server (NTRS)

Takahashi, K.; Mcentire, R. W.; Cheng, C. Z.; Kistler, L. M.

1990-01-01

The properties of 23 magnetic pulsation events observed by the AMPTE CCE spacecraft are studied. These events are selected on the basis of the field magnitude which oscillated at the second harmonic of a simultaneously present transverse oscillation. The events have a second harmonic period of 80-600 s (roughly the Pc 5 range), are observed in cluster in the dawn (0300-0800 magnetic local time, MLT) and dusk (1600-2100 MLT) sectors, and are localized near the magnetic equator. Although the azimuthal wave number estimated from an ion finite Larmor radius effect, is generally large (about 50), there is a marked difference between the events observed in the dawn and dusk sectors. In the dawn sector the waves have low frequencies (1-5 mHz), indicate left-hand polarization with respect to the ambient magnetic field, and propagate eastward with respect to the spacecraft. In the dusk sector the waves have high frequencies (5-15 mHz), indicate right-hand polarization, and propagate westward. It is suggested that the waves are all westward propagating in the plasma rest frame and that local-time-dependent Doppler shift is the reason for the local time dependence of the wave properties.

Evidence of Ubiquitous Large-Amplitude Alfven waves in the Global Field-Aligned Current System

NASA Astrophysics Data System (ADS)

Pakhotin, I.; Mann, I.; Lysak, R. L.; Knudsen, D. J.; Burchill, J. K.; Gjerloev, J. W.; Rae, J.; Forsyth, C.; Murphy, K. R.; Miles, D.; Ozeke, L.; Balasis, G.

2017-12-01

Large-amplitude non-stationarities have been observed during an analysis of a quiescent field-aligned current system crossing using the multi-satellite Swarm constellation. Using simultaneous electric and magnetic field measurements it has been determined that these non-stationarities, reaching tens to hundreds of nanoteslas, are Alfvenic in nature. Evidence suggests that these large-amplitude Alfven waves are a ubiquitous, fundamentally inherent feature of and exist in a continuum with larger-scale field-aligned currents, and both can be explained using the same physical paradigm of reflected Alfven waves.

ULF waves in the Martian foreshock: MAVEN observations

NASA Astrophysics Data System (ADS)

Shan, Lican; Mazelle, Christian; Meziane, Karim; Ruhunusiri, Suranga; Espley, Jared; Halekas, Jasper; Connerney, Jack; McFadden, Jim; Mitchell, Dave; Larson, Davin; Brain, Dave; Jakosky, Bruce; Ge, Yasong; Du, Aimin

2016-04-01

Foreshock ULF waves constitute a significant physical phenomenon of the plasma environment for terrestrial planets. The occurrence of these ULF waves, associated with backstreaming ions reflected and accelerated at the bow shock, implies specific conditions and properties of the shock and its foreshock. Using measurements from MAVEN, we report clear observations of this type of ULF waves in the Martian foreshock. We show from different case studies that the peak frequency of the wave case in spacecraft frame is too far from the local ion cyclotron frequency to be associated with local pickup ions taking into account the Doppler shifted frequency from a cyclotron resonance, the obliquity of the mode, resonance broadening and experimental uncertainties. On the opposite their properties fit very well with foreshock waves driven unstable by backtreaming field-aligned ion beams. The propagation angle is usually less than 30 degrees from ambient magnetic field. The waves also display elliptical and left-hand polarizations with respect to interplanetary magnetic field in the spacecraft frame. It is clear for these cases that foreshock ions are simultaneous present for the ULF wave interval. Such observation is important in order to discriminate with the already well-reported pickup ion (protons) waves associated with exospheric hydrogen in order to quantitatively use the later to study seasonal variations of the hydrogen corona.

Non-stationary Alfvén resonator: new results on Pc1 pearls and IPDP events

NASA Astrophysics Data System (ADS)

Mursula, K.; Prikner, K.; Feygin, F. Z.; Bräysy, T.; Kangas, J.; Kerttula, R.; Pollari, P.; Pikkarainen, T.; Pokhotelov, O. A.

2000-03-01

We analyse a Pc1 pearl event observed by the Finnish search-coil magnetometer network on 15 December 1984, which subsequently developed into a structured IPDP after a substorm onset. The EISCAT radar was simultaneously monitoring the mid- to high-latitude ionosphere. We have calculated the ionospheric resonator properties during the different phases of the event using EISCAT observations. Contrary to the earlier results, we find that the Pc1/IPDP (Interval of Pulsations of Diminishing Period) frequency observed on the ground corresponds to the maximum of the transmission coefficient rather than that of the reflection coefficient. This casts strong doubts on the bouncing wave packet model of Pc1 pearls. Instead, we present evidence for an alternative model of pearl formation in which long-period ULF waves modulate the Pc1 growth rate. Moreover, we propose a new model for IPDP formation, whereby the ionosphere acts as an active agent in forming the IPDP signal on the ground. The model calculations show that the ionospheric resonator properties can be modified during the event so that the resonator eigenfrequency increases according to the observed frequency increase during the IPDP phase. We suggest that the IPDP signal on the ground is a combined effect of the frequency increase in the magnetospheric wave source and the simultaneous increase of the resonator eigenfrequency. The need for such a complicated matching of the two factors explains the rarity of IPDPs on the ground despite the ubiquitous occurrence of EMIC waves in the magnetosphere and the continuous substorm cycle.

Hybrid simulations of positively and negatively charged pickup ions and cyclotron wave generation at Europa

DOE Office of Scientific and Technical Information (OSTI.GOV)

Desai, Ravindra T.; Cowee, Misa; Wei, Hanying

In the vicinity of Europa, Galileo observed bursty Alfvén-cyclotron wave power at the gyrofrequencies of a number of species including K +, math formula, Na +, and Cl +, indicating the localised pickup of these species. Additional evidence for the presence of Chlorine was the occurrence of both left-hand (LH) and right-hand (RH) polarised transverse wave power near the Cl + gyrofrequency, thought to be due to the pickup of both Cl + and the easily formed Chlorine anion, Cl –. To test this hypothesis we use one-dimensional hybrid (kinetic ion, massless fluid electron) simulations for both positive and negativemore » pickup ions and self-consistently reproduce the growth of both LH and RH Alfvén-cyclotron waves in agreement with linear theory. We show how the simultaneous generation of LH and RH waves can result in non-gyrotropic ion distributions and increased wave amplitudes, and how even trace quantities of negative pickup ions are able to generate an observable RH signal. Here, through comparing simulated and observed wave amplitudes, we are able to place the first constraints on the densities of Chlorine pickup ions in localised regions at Europa.« less

Hybrid simulations of positively and negatively charged pickup ions and cyclotron wave generation at Europa

DOE PAGES

Desai, Ravindra T.; Cowee, Misa; Wei, Hanying; ...

2017-09-19

In the vicinity of Europa, Galileo observed bursty Alfvén-cyclotron wave power at the gyrofrequencies of a number of species including K +, math formula, Na +, and Cl +, indicating the localised pickup of these species. Additional evidence for the presence of Chlorine was the occurrence of both left-hand (LH) and right-hand (RH) polarised transverse wave power near the Cl + gyrofrequency, thought to be due to the pickup of both Cl + and the easily formed Chlorine anion, Cl –. To test this hypothesis we use one-dimensional hybrid (kinetic ion, massless fluid electron) simulations for both positive and negativemore » pickup ions and self-consistently reproduce the growth of both LH and RH Alfvén-cyclotron waves in agreement with linear theory. We show how the simultaneous generation of LH and RH waves can result in non-gyrotropic ion distributions and increased wave amplitudes, and how even trace quantities of negative pickup ions are able to generate an observable RH signal. Here, through comparing simulated and observed wave amplitudes, we are able to place the first constraints on the densities of Chlorine pickup ions in localised regions at Europa.« less

Hybrid Simulations of Positively and Negatively Charged Pickup Ions and Cyclotron Wave Generation at Europa.

PubMed

Desai, R T; Cowee, M M; Wei, H; Fu, X; Gary, S P; Volwerk, M; Coates, A J

2017-10-01

In the vicinity of Europa, Galileo observed bursty Alfvén-cyclotron wave power at the gyrofrequencies of a number of species including K + , O 2+, Na + , and Cl + , indicating the localized pickup of these species. Additional evidence for the presence of chlorine was the occurrence of both left-hand (LH) and right-hand (RH) polarized transverse wave power near the Cl + gyrofrequency, thought to be due to the pickup of both Cl + and the easily formed chlorine anion, Cl - . To test this hypothesis, we use one-dimensional hybrid (kinetic ion, massless fluid electron) simulations for both positive and negative pickup ions and self-consistently reproduce the growth of both LH and RH Alfvén-cyclotron waves in agreement with linear theory. We show how the simultaneous generation of LH and RH waves can result in nongyrotropic ion distributions and increased wave amplitudes, and how even trace quantities of negative pickup ions are able to generate an observable RH signal. Through comparing simulated and observed wave amplitudes, we are able to place the first constraints on the densities of Chlorine pickup ions in localized regions at Europa.

Substorm Related ULF waves Observed in the Magnetosphere by BD-IES and Van Allan Probes

NASA Astrophysics Data System (ADS)

Zong, Q.

2017-12-01

By using the data return from the BD-IES instrument onboard an inclined (55°) geosynchronous orbit (IGSO) satellite together with geo-transfer orbit (GTO) Van Allen Probe A&B satellite, we analysis a substorm related ULF waves occurred on Feb 5, 2016 in the dawnside of the magnetosphere. Immediately after the substorm injection followed by energetic electron drift echoes, the electron flux was clearly and strongly varying on the ULF wave time scale. It is found that both toroidal and poloidal mode ULF waves with a period of 320 s. During the substorm injection, the IES onboard IGSO is outbound while both Van Allen Probe A&B satellites are inbound. This configuration of multiple satellite trajectories provides an unique opportunity to investigate substorm related ULF waves. When substorm injections are observed simultaneously with multiple spacecraft, they help elucidate potential mechanisms for particle transport and energization, a topic of great importance for understanding and modeling the magnetosphere. Two possible scenaria on ULF wave triggering are discussed: fast-mode compressional waves -driven field line resonance and ULF wave growth through drift resonance.

Statistical analysis of mesospheric gravity waves over King Sejong Station, Antarctica (62.2°S, 58.8°W)

NASA Astrophysics Data System (ADS)

Kam, Hosik; Jee, Geonhwa; Kim, Yong; Ham, Young-bae; Song, In-Sun

2017-03-01

We have investigated the characteristics of mesospheric short period (<1 h) gravity waves which were observed with all-sky images of OH Meinel band and OI 557 nm airglows over King Sejong Station (KSS) (62.22°S, 58.78°W) during a period of 2008-2015. By applying 2-dimensional FFT to time differenced images, we derived horizontal wavelengths, phase speeds, and propagating directions (188 and 173 quasi-monochromatic waves from OH and OI airglow images, respectively). The majority of the observed waves propagated predominantly westward, implying that eastward waves were filtered out by strong eastward stratospheric winds. In order to obtain the intrinsic properties of the observed waves, we utilized winds simultaneously measured by KSS Meteor Radar and temperatures from Aura Microwave Limb Sounder (MLS). More than half the waves propagated horizontally, as waves were in Doppler duct or evanescent in the vertical direction. This might be due to strong eastward background wind field in the mesosphere over KSS. For freely propagating waves, the vertical wavelengths were in the interquartile range of 9-33 km with a median value of 15 km. The vertical wavelengths are shorter than those observed at Halley station (76°S, 27°W) where the majority of the observed waves were freely propagating. The difference in the wave propagating characteristics between KSS and Halley station suggests that gravity waves may affect mesospheric dynamics in this part of the Antarctic Peninsula more strongly than over the Antarctic continent. Furthermore, strong wind shear over KSS played an important role in changing the vertical wavenumbers as the waves propagated upward between two airglow layers (87 and 96 km).

Nonlinear excitation of fast magnetosonic waves via quasi-electrostatic whistler wave mixing

NASA Astrophysics Data System (ADS)

Zechar, Nathan; Sotnikov, Vladimir; Caplinger, James; Chu, Arthur

2017-10-01

We report on experiments of nonlinear simultaneous generation of low frequency fast magnetosonic waves and electromagnetic whistler waves using two loop antennas in the afterglow of a cold magnetized helium plasma. The exciting antennas each have a frequency that is below half the electron cyclotron frequency, and the difference between the two is just below the lower hybrid frequency. They both directly excite whistler waves, however their nonlinear interaction excite the low frequency fast magnetosonic waves at the frequency given by their difference. Plasma is generated using a helicon plasma source in a one meter length cylindrical chamber. The spatial and temporal data of the electromagnetic and electrostatic components of the plasma waves are then captured with developed diagnostic techniques. Wave spectra, general structure and time domain frequencies observed will be reported.

ELF/VLF Wave Generation and Scattering from Modulated Heating of the Ionosphere at Arecibo Observatory

NASA Astrophysics Data System (ADS)

Maxworth, A. S.; Golkowski, M.; McCormick, J.; Cohen, M.; Hosseini, P.; Bittle, J.

2017-12-01

The recently completed ionospheric heater at Arecibo Observatory is used for modulated HF (5 or 8 MHz) heating of the ionosphere, to generate ELF/VLF (3 Hz - 30 kHz) waves. Observation of ramp and tone signals at frequencies from hundreds of Hz to several kHz at multiple receivers confirms the ability of the heater to modulate D region currents and create an ELF/VLF antenna in the ionosphere. Observed ELF/VLF signal amplitudes are lower than for similar experiments performed at high latitudes at the HAARP and Tromso facilities, for a variety of reasons including the reduced natural currents at mid latitudes, and the lower HF power of the Arecibo heater. The heating of the overhead ionosphere is also observed to change the Earth-ionosphere waveguide propagation characteristics as is evident from simultaneous observations of lightning induced sferics and VLF transmitter signals that propagate under the heated region. The active heating of the ionosphere modifies the reflection of incident VLF (3-30 kHz) waves. We present initial observations of HF heating of the D-region and resulting ELF/VLF wave generation.

Ulysses radio and plasma wave observations in the Jupiter environment

NASA Technical Reports Server (NTRS)

Stone, R. G.; Pedersen, B. M.; Harvey, C. C.; Canu, P.; Cornilleau-Wehrlin, N.; Desch, M. D.; De Villedary, C.; Fainberg, J.; Farrell, W. M.; Goetz, K.

1992-01-01

The Unified Radio and Plasma Wave (URAP) experiment has produced new observations of the Jupiter environment, owing to the unique capabilities of the instrument and the traversal of high Jovian latitudes. Broad-band continuum radio emission from Jupiter and in situ plasma waves have proved valuable in delineating the magnetospheric boundaries. Simultaneous measurements of electric and magnetic wave fields have yielded new evidence of whistler-mode radiation within the magnetosphere. Observations of auroral-like hiss provided evidence of a Jovian cusp. The source direction and polarization capabilities of URAP have demonstrated that the outer region of the Io plasma torus supported at least five separate radio sources that reoccurred during successive rotations with a measurable corotation lag. Thermal noise measurements of the Io torus densities yielded values in the densest portion that are similar to models suggested on the basis of Voyager observations of 13 years ago. The URAP measurements also suggest complex beaming and polarization characteristics of Jovian radio components. In addition, a new class of kilometer-wavelength striated Jovian bursts has been observed.

Liquid-assisted tunable metasurface for simultaneous manipulation of surface elastic and acoustic waves

NASA Astrophysics Data System (ADS)

Yuan, Si-Min; Ma, Tian-Xue; Chen, A.-Li; Wang, Yue-Sheng

2018-03-01

A tunable and multi-functional one-dimensional metasurface, which is formed by engraving periodic semi-ellipse grooves on the surface of an aluminum half-space, is proposed in this paper. One characteristic of the metasurface is the manipulation of multi-physical fields, i.e. it could be utilized to manipulate surface elastic and acoustic waves simultaneously. The dispersion curves of the elastic and acoustic waves can be effectively tuned by adding liquids into the grooves. Based on the tunability different applications can be realized by adding different volumes of different liquids into the grooves. As an example, simultaneous rainbow trapping of the surface elastic and acoustic waves is demonstrated in the metasurface. Moreover, a resonant cavity where the elastic and acoustic waves are highly confined is reported. The proposed metasurface paves the way to the design of multi-functional devices for simultaneous control of elastic and acoustic waves.

Sodium Lidar-observed Strong Inertia-gravity Wave Activities in the Mesopause Region over Fort Collins, Colorado (41 deg N, 105 deg W)

NASA Technical Reports Server (NTRS)

Li, Tao; She, C. -Y.; Liu, Han-Li; Leblanc, Thierry; McDermid, I. Stuart

2007-01-01

In December 2004, the Colorado State University sodium lidar system at Fort Collins, Colorado (41 deg N, 105 deg W), conducted an approximately 80-hour continuous campaign for the simultaneous observations of mesopause region sodium density, temperature, and zonal and meridional winds. This data set reveals the significant inertia-gravity wave activities with a period of approximately 18 hours, which are strong in both wind components since UT day 338 (second day of the campaign), and weak in temperature and sodium density. The considerable variability of wave activities was observed with both wind amplitudes growing up to approximately 40 m/s at 95-100 km in day 339 and then decreasing dramatically in day 340. We also found that the sodium density wave perturbation is correlated in phase with temperature perturbation below 90 km, and approximately 180 deg out of phase above. Applying the linear wave theory, we estimated the wave horizontal propagation direction, horizontal wavelength, and apparent horizontal phase speed to be approximately 25 deg south of west, approximately 1800 +/- 150 km, and approximately 28 +/- 2 m/s, respectively of wave intrinsic period, intrinsic phase speed, and vertical wavelength were also estimated. While the onset of enhanced inertia-gravity wave amplitude in the night of 338 was observed to be in coincidence with short-period gravity wave breaking via convective instability, the decrease of inertia-gravity wave amplitude after noon of day 339 was also observed to coincide with the development of atmospheric dynamical instability layers with downward phase progression clearly correlated with the 18-hour inertia-gravity wave, suggesting likely breaking of this inertia-gravity wave via dynamical (shear) instability.

Foreshock waves as observed in energetic ion flux

NASA Astrophysics Data System (ADS)

Petrukovich, A. A.; Chugunova, O. M.; Inamori, T.; Kudela, K.; Stetiarova, J.

2017-05-01

Oscillations of energetic ion fluxes with periods 10-100 s are often present in the Earth's foreshock. Detailed analysis of wave properties with Time History of Events and Macroscale Interactions during Substorms data and comparisons with other data sets confirm that these oscillations are the previously unnoticed part of well-known "30 s" waves but are observed mainly for higher-speed solar wind. Simultaneous magnetic oscillations have similar periods, large amplitudes, and nonharmonic unstable waveforms or shocklet-type appearance, suggesting their nonlinearity, also typical for high solar wind speed. Analysis of the general foreshock data set of Interball project shows that the average flux of the backstreaming energetic ions increases more than 1 order of magnitude, when solar wind speed increases from 400 to 500 km/s.

Fly Eye radar: detection through high scattered media

NASA Astrophysics Data System (ADS)

Molchanov, Pavlo; Gorwara, Ashok

2017-05-01

Longer radio frequency waves better penetrating through high scattered media than millimeter waves, but imaging resolution limited by diffraction at longer wavelength. Same time frequency and amplitudes of diffracted waves (frequency domain measurement) provides information of object. Phase shift of diffracted waves (phase front in time domain) consists information about shape of object and can be applied for reconstruction of object shape or even image by recording of multi-frequency digital hologram. Spectrum signature or refracted waves allows identify the object content. Application of monopulse method with overlap closely spaced antenna patterns provides high accuracy measurement of amplitude, phase, and direction to signal source. Digitizing of received signals separately in each antenna relative to processor time provides phase/frequency independence. Fly eye non-scanning multi-frequency radar system provides simultaneous continuous observation of multiple targets and wide possibilities for stepped frequency, simultaneous frequency, chaotic frequency sweeping waveform (CFS), polarization modulation for reliable object detection. Proposed c-band fly eye radar demonstrated human detection through 40 cm concrete brick wall with human and wall material spectrum signatures and can be applied for through wall human detection, landmines, improvised explosive devices detection, underground or camouflaged object imaging.

Occurrence features of simultaneous H+- and He+-band EMIC emissions in the outer radiation belt

NASA Astrophysics Data System (ADS)

Fu, Song; He, Fengming; Gu, Xudong; Ni, Binbin; Xiang, Zheng; Liu, Jiang

2018-04-01

As an important loss mechanism of radiation belt electrons, electromagnetic ion cyclotron (EMIC) waves show up as three distinct frequency bands below the hydrogen (H+), helium (He+), and oxygen (O+) ion gyrofrequencies. Compared to O+-band EMIC waves, H+- and He+-band emissions generally occur more frequently and result in more efficient scattering removal of <∼5 MeV relativistic electrons. Therefore, knowledge about the occurrence of these two bands is important for understanding the evolution of the relativistic electron population. To evaluate the occurrence pattern and wave properties of H+- and He+-band EMIC waves when they occur concurrently, we investigate 64 events of multi-band EMIC emissions identified from high quality Van Allen Probes wave data. Our quantitative results demonstrate a strong occurrence dependence of the multi-band EMIC emissions on magnetic local time (MLT) and L-shell to mainly concentrate on the dayside region of L = ∼4-6. We also find that the average magnetic field amplitude of H+-band waves is larger than that of He+-band waves only when L < 4.5 and AE∗ < 300 nT, and He+-band emissions are more intense under all other conditions. In contrast to 5 events that have average H+-band amplitude over 2 nT, 19 events exhibit >2 nT He+-band amplitude, indicating that the He+-band waves can be more easily amplified than the H+-band waves under the same circumstances. For simultaneous occurrences of the two EMIC wave bands, their frequencies vary with L-shell and geomagnetic activity: the peak wave frequency of H+-band emissions varies between 0.25 and 0.8 fcp with the average between 0.25 and 0.6 fcp, while that of He+-band emissions varies between 0.03 and 0.23 fcp with the average between 0.05 and 0.15 fcp. These newly observed occurrence features of simultaneous H+- and He+-band EMIC emissions provide improved information to quantify the overall contribution of multi-band EMIC waves to the loss processes of radiation belt electrons.

Simultaneous measurement of temperature and emissivity of lunar regolith simulant using dual-channel millimeter-wave radiometry

DOE Office of Scientific and Technical Information (OSTI.GOV)

McCloy, J. S.; Sundaram, S. K.; Matyas, J.

Millimeter wave (MMW) radiometry can be used for simultaneous measurement of emissivity and temperature of materials under extreme environments (high temperature, pressure, and corrosive environments). The state-of-the-art dual channel MMW passive radiometer with active interferometric capabilities at 137 GHz described here allows for radiometric measurements of sample temperature and emissivity up to at least 1600 °C with simultaneous measurement of sample surface dynamics. These capabilities have been used to demonstrate dynamic measurement of melting of powders of simulated lunar regolith and static measurement of emissivity of solid samples. The paper presents the theoretical background and basis for the dual-receiver system,more » describes the hardware in detail, and demonstrates the data analysis. Post-experiment analysis of emissivity versus temperature allows further extraction from the radiometric data of millimeter wave viewing beam coupling factors, which provide corroboratory evidence to the interferometric data of the process dynamics observed. Finally, these results show the promise of the MMW system for extracting quantitative and qualitative process parameters for industrial processes and access to real-time dynamics of materials behavior in extreme environments.« less

A case study of A mesoscale gravity wave in the MLT region using simultaneous multi-instruments in Beijing

NASA Astrophysics Data System (ADS)

Jia, Mingjiao; Xue, Xianghui; Dou, Xiankang; Tang, Yihuan; Yu, Chao; Wu, Jianfei; Xu, Jiyao; Yang, Guotao; Ning, Baiqi; Hoffmann, Lars

2016-03-01

In this work, we used observational data from an all-sky airglow imager at Xinglong (40.2 °N, 117.4 °E), a sodium lidar at Yanqing (40.4 °N, 116.0 °E) and a meteor radar at Shisanling (40.3 °N, 116.2 °E) to study the propagation of a mesoscale gravity wave. During the night of March 1, 2011, the imager identified a mesoscale gravity wave structure in the OH airglow that had a wave period of 2 hours, propagated along an azimuthal direction (clockwise) with an angle of 163°, a phase speed of 73 m/s, and a horizontal wavelength of 566 km. Simultaneous measurements provided by the sodium lidar also showed a perturbation in the sodium layer with a 2-hour period. Based on the SABER/TIMED and radar data, we estimated that the momentum flux and the energy flux of the gravity wave were approximately 0.59 m2/s2 and 0.22 mW/m2, respectively. Ray-tracing analysis showed that the gravity wave was likely generated in the center of Lake Baikal owing to the existence of a jet- front system in the upper troposphere at that time.

Turbulence of electrostatic electron cyclotron harmonic waves observed by Ogo 5.

NASA Technical Reports Server (NTRS)

Oya, H.

1972-01-01

Analysis of VLF emissions that have been observed near 3/2, 5/2, and 7/2 f sub H by Ogo 5 in the magnetosphere (f sub H is the electron cyclotron frequency) in the light of the mechanism used for the diffuse plasma resonance f sub Dn observed by Alouette 2 and Isis 1. The VLF emission is considered to be generated by nonlinear coupling mechanisms in certain portions of the observation as the f sub Dn is enhanced by its association with nonlinear wave-particle interaction of the electrostatic electron cyclotron harmonic wave, including the instability due to the nonlinear inverse Landau damping mechanism in the turbulence. The difference between the two observations is in the excitation mechanism of the turbulence; the turbulence in the plasma trough detected by Ogo 5 is due to natural origins, whereas the ionospheric topside sounder makes the plasma wave turbulence artificially by submitting strong stimulation pulses. Electron density values in the plasma trough are deduced by applying the f sub Dn-f sub N/f sub H relationship obtained from the Alouette 2 experiment as well as by applying the condition for the wave-particle nonlinear interactions. The electron density values reveal good agreement with the ion density values observed simultaneously by the highly sensitive ion mass spectrometer.

Simultaneous large band gaps and localization of electromagnetic and elastic waves in defect-free quasicrystals.

PubMed

Yu, Tianbao; Wang, Zhong; Liu, Wenxing; Wang, Tongbiao; Liu, Nianhua; Liao, Qinghua

2016-04-18

We report numerically large and complete photonic and phononic band gaps that simultaneously exist in eight-fold phoxonic quasicrystals (PhXQCs). PhXQCs can possess simultaneous photonic and phononic band gaps over a wide range of geometric parameters. Abundant localized modes can be achieved in defect-free PhXQCs for all photonic and phononic polarizations. These defect-free localized modes exhibit multiform spatial distributions and can confine simultaneously electromagnetic and elastic waves in a large area, thereby providing rich selectivity and enlarging the interaction space of optical and elastic waves. The simulated results based on finite element method show that quasiperiodic structures formed of both solid rods in air and holes in solid materials can simultaneously confine and tailor electromagnetic and elastic waves; these structures showed advantages over the periodic counterparts.

Climatology of the quasi-2-day waves observed in the MLS/Aura measurements (2005-2014)

NASA Astrophysics Data System (ADS)

Pancheva, Dora; Mukhtarov, Plamen; Siskind, David E.

2018-06-01

The paper presents the climatology and interannual variability of both eastward- and westward-propagating ∼2-day waves (QTDW) observed in the MLS/Aura geopotential height data for a period of 10 full years (2005-2014). The climatology of the QTDWs has been studied in two steps: (i) by using average 2D-wavelet spectra both the dominant modes of variability and how these modes vary in time and space have been determined, and (ii) by applying a 2D decomposition procedure, where all planetary waves are simultaneously extracted from the data, the average global spatio-temporal distributions of all defined by the 2D-wavelet analysis modes have been obtained. It is found that the westward-propagating waves at mid-high latitudes have zonal wave numbers 2, 3 and 4 and are observed mainly in summer hemisphere. Two different types of eastward-propagating waves have been identified: (i) waves at mid-high latitudes with zonal wave numbers 2 and 3 observed in the winter hemisphere, and (ii) waves observed predominantly over the equator with zonal wave number 2, which do not have a well-defined seasonal variability but show some enhancement in both solstices. While the climatological features of the MLS/Aura QTDWs for the considered period are robust the interannual variations have to be adopted cautiously. The primary reason is that the length of the considered period of 10 years is not enough for finding clear variability pattern. The only long-term variability which appears to have some robustness is that of the W3 wave in the Southern Hemisphere where the influence of the solar cycle has been distinguished.

Linking source region and ocean wave parameters with the observed primary microseismic noise

NASA Astrophysics Data System (ADS)

Juretzek, C.; Hadziioannou, C.

2017-12-01

In previous studies, the contribution of Love waves to the primary microseismic noise field was found to be comparable to those of Rayleigh waves. However, so far only few studies analysed both wave types present in this microseismic noise band, which is known to be generated in shallow water and the theoretical understanding has mainly evolved for Rayleigh waves only. Here, we study the relevance of different source region parameters on the observed primary microseismic noise levels of Love and Rayleigh waves simultaneously. By means of beamforming and correlation of seismic noise amplitudes with ocean wave heights in the period band between 12 and 15 s, we analysed how source areas of both wave types compare with each other around Europe. The generation effectivity in different source regions was compared to ocean wave heights, peak ocean gravity wave propagation direction and bathymetry. Observed Love wave noise amplitudes correlate comparably well with near coastal ocean wave parameters as Rayleigh waves. Some coastal regions serve as especially effective sources for one or the other wave type. These coincide not only with locations of high wave heights but also with complex bathymetry. Further, Rayleigh and Love wave noise amplitudes seem to depend equally on the local ocean wave heights, which is an indication for a coupled variation with swell height during the generation of both wave types. However, the wave-type ratio varies directionally. This observation likely hints towards a spatially varying importance of different source mechanisms or structural influences. Further, the wave-type ratio is modulated depending on peak ocean wave propagation directions which could indicate a variation of different source mechanism strengths but also hints towards an imprint of an effective source radiation pattern. This emphasizes that the inclusion of both wave types may provide more constraints for the understanding of acting generation mechanisms.

Modelling multi-hazard hurricane damages on an urbanized coast with a Bayesian Network approach

USGS Publications Warehouse

van Verseveld, H.C.W.; Van Dongeren, A. R.; Plant, Nathaniel G.; Jäger, W.S.; den Heijer, C.

2015-01-01

Hurricane flood impacts to residential buildings in coastal zones are caused by a number of hazards, such as inundation, overflow currents, erosion, and wave attack. However, traditional hurricane damage models typically make use of stage-damage functions, where the stage is related to flooding depth only. Moreover, these models are deterministic and do not consider the large amount of uncertainty associated with both the processes themselves and with the predictions. This uncertainty becomes increasingly important when multiple hazards (flooding, wave attack, erosion, etc.) are considered simultaneously. This paper focusses on establishing relationships between observed damage and multiple hazard indicators in order to make better probabilistic predictions. The concept consists of (1) determining Local Hazard Indicators (LHIs) from a hindcasted storm with use of a nearshore morphodynamic model, XBeach, and (2) coupling these LHIs and building characteristics to the observed damages. We chose a Bayesian Network approach in order to make this coupling and used the LHIs ‘Inundation depth’, ‘Flow velocity’, ‘Wave attack’, and ‘Scour depth’ to represent flooding, current, wave impacts, and erosion related hazards.The coupled hazard model was tested against four thousand damage observations from a case site at the Rockaway Peninsula, NY, that was impacted by Hurricane Sandy in late October, 2012. The model was able to accurately distinguish ‘Minor damage’ from all other outcomes 95% of the time and could distinguish areas that were affected by the storm, but not severely damaged, 68% of the time. For the most heavily damaged buildings (‘Major Damage’ and ‘Destroyed’), projections of the expected damage underestimated the observed damage. The model demonstrated that including multiple hazards doubled the prediction skill, with Log-Likelihood Ratio test (a measure of improved accuracy and reduction in uncertainty) scores between 0.02 and 0.17 when only one hazard is considered and a score of 0.37 when multiple hazards are considered simultaneously. The LHIs with the most predictive skill were ‘Inundation depth’ and ‘Wave attack’. The Bayesian Network approach has several advantages over the market-standard stage-damage functions: the predictive capacity of multiple indicators can be combined; probabilistic predictions can be obtained, which include uncertainty; and quantitative as well as descriptive information can be used simultaneously.

Observations of Secondary Waves Generated from Interaction Between the 2-Day Wave and the Migrating Diurnal Tide.

NASA Astrophysics Data System (ADS)

Lieberman, R. S.; Riggin, D. M.; Siskind, D. E.; Nguyen, V.; Palo, S. E.; Mitchell, N. J.; Livesey, N. J.; Stober, G.; Wilhelm, S.; Jacobi, C.

2015-12-01

Nonlinear coupling between the migrating diurnal tide and the westward traveling quasi-2-day wave yields a westward-traveling "sum" wave with zonal wavenumber 4 and a period of 16 hours, and an eastward-traveling "difference" wave with a zonal wavenumber 2 and a period of 2 days. While the eastward 2-day wave has been reported in TIMED/SABER temperatures, the westward 16-hour wave lies outside SABER's Nyquist limits of resolution. To obtain simultaneous definitions of the parent and child waves, we examine hourly output from NOGAPS-ALPHA during January 2005, 2006 and 2008. The westward 16-hour wave maximizes in the winter hemisphere, and behaves like an inertia-gravity wave. The eastward 2-day wave maximizes at low latitudes, and exhibits a mixture of Kelvin and higher-order modes. The 16-hour and the eastward 2-day waves are of comparable magnitude, and alias to the same apparent frequency when viewed from the satellite perspective.

Implications of elastic wave velocities for Apollo 17 rock powders

NASA Technical Reports Server (NTRS)

Talwani, P.; Nur, A.; Kovach, R. L.

1974-01-01

Ultrasonic P- and S-wave velocities of lunar rock powders 172701, 172161, 170051, and 175081 were measured at room temperature and to 2.5 kb confining pressure. The results compare well with those of terrestrial volcanic ash and powdered basalt. P-wave velocity values up to pressures corresponding to a lunar depth of 1.4 km preclude cold compaction alone as an explanation for the observed seismic velocity structure at the Apollo 17 site. Application of small amounts of heat with simultaneous application of pressure causes rock powders to achieve equivalence of seismic velocities for competent rocks.

Ground-based ELF/VLF chorus observations at subauroral latitudes—VLF-CHAIN Campaign

NASA Astrophysics Data System (ADS)

Shiokawa, Kazuo; Yokoyama, Yu; Ieda, Akimasa; Miyoshi, Yoshizumi; Nomura, Reiko; Lee, Sungeun; Sunagawa, Naoki; Miyashita, Yukinaga; Ozaki, Mitsunori; Ishizaka, Kazumasa; Yagitani, Satoshi; Kataoka, Ryuho; Tsuchiya, Fuminori; Schofield, Ian; Connors, Martin

2014-09-01

We report observations of very low frequency (VLF) and extremely low frequency (ELF) chorus waves taken during the ELF/VLF Campaign observation with High-resolution Aurora Imaging Network (VLF-CHAIN) of 17-25 February 2012 at subauroral latitudes at Athabasca (L=4.3), Canada. ELF/VLF waves were measured continuously with a sampling rate of 100 kHz to monitor daily variations in ELF/VLF emissions and derive their detailed structures. We found quasiperiodic (QP) emissions whose repetition period changes rapidly within a period of 1 h without corresponding magnetic pulsations. QP emissions showed positive correlation between amplitude and frequency sweep rate, similarly to rising-tone elements. We found an event of nearly simultaneous enhancements of QP emissions and Pc1/electromagnetic ion cyclotron wave intensities, suggesting that the temperature anisotropy of electrons and ions developed simultaneously at the equatorial plane of the magnetosphere. We also found QP emissions whose intensity suddenly increased in association with storm sudden commencement without changing their frequency. Falling-tone ELF/VLF emissions were observed with their rate of frequency change varying from 0.7 to 0.05 kHz/s over 10 min. Bursty-patch emissions in the lower and upper frequency bands are often observed during magnetically disturbed periods. Clear systematic correlation between these various ELF/VLF emissions and cosmic noise absorption was not obtained throughout the campaign period. These observations indicate several previously unknown features of ELF/VLF emissions in subauroral latitudes and demonstrate the importance of continuous measurements for monitoring temporal variations in these emissions.

Numerical modeling of a multiscale gravity wave event and its airglow signatures over Mount Cook, New Zealand, during the DEEPWAVE campaign

NASA Astrophysics Data System (ADS)

Heale, C. J.; Bossert, K.; Snively, J. B.; Fritts, D. C.; Pautet, P.-D.; Taylor, M. J.

2017-01-01

A 2-D nonlinear compressible model is used to simulate a large-amplitude, multiscale mountain wave event over Mount Cook, NZ, observed as part of the Deep Propagating Gravity Wave Experiment (DEEPWAVE) campaign and to investigate its observable signatures in the hydroxyl (OH) layer. The campaign observed the presence of a λx=200 km mountain wave as part of the 22nd research flight with amplitudes of >20 K in the upper stratosphere that decayed rapidly at airglow heights. Advanced Mesospheric Temperature Mapper (AMTM) showed the presence of small-scale (25-28 km) waves within the warm phase of the large mountain wave. The simulation results show rapid breaking above 70 km altitude, with the preferential formation of almost-stationary vortical instabilities within the warm phase front of the mountain wave. An OH airglow model is used to identify the presence of small-scale wave-like structures generated in situ by the breaking of the mountain wave that are consistent with those seen in the observations. While it is easy to interpret these feature as waves in OH airglow data, a considerable fraction of the features are in fact instabilities and vortex structures. Simulations suggest that a combination of a large westward perturbation velocity and shear, in combination with strong perturbation temperature gradients, causes both dynamic and convective instability conditions to be met particularly where the wave wind is maximized and the temperature gradient is simultaneously minimized. This leads to the inevitable breaking and subsequent generation of smaller-scale waves and instabilities which appear most prominent within the warm phase front of the mountain wave.

Seismic, satellite, and site observations of internal solitary waves in the NE South China Sea

PubMed Central

Tang, Qunshu; Wang, Caixia; Wang, Dongxiao; Pawlowicz, Rich

2014-01-01

Internal solitary waves (ISWs) in the NE South China Sea (SCS) are tidally generated at the Luzon Strait. Their propagation, evolution, and dissipation processes involve numerous issues still poorly understood. Here, a novel method of seismic oceanography capable of capturing oceanic finescale structures is used to study ISWs in the slope region of the NE SCS. Near-simultaneous observations of two ISWs were acquired using seismic and satellite imaging, and water column measurements. The vertical and horizontal length scales of the seismic observed ISWs are around 50 m and 1–2 km, respectively. Wave phase speeds calculated from seismic observations, satellite images, and water column data are consistent with each other. Observed waveforms and vertical velocities also correspond well with those estimated using KdV theory. These results suggest that the seismic method, a new option to oceanographers, can be further applied to resolve other important issues related to ISWs. PMID:24948180

New Experimental Setup for High-Pressure High-Temperature Gigahertz Ultrasonic Interferometry

NASA Astrophysics Data System (ADS)

Kantor, A. P.; Kantor, I. Y.; Dubrovinsky, L. S.; Jacobsen, S. D.

2005-12-01

The only direct information about Earth's interior comes from seismological observations of sound wave velocities. In order to create compositional and mineralogical model from seismological data knowledge of the elastic properties and crystal chemistry of minerals is necessary. Gigahertz ultrasonic interferometry (GUI) is a relatively new tool used to measure single-crystal compressional and shear-wave travel times, which are converted to sound velocities and elastic moduli for direct application to problems in geophysics. Although possibility of simultaneous high-pressure and high-temperature GUI measurements in diamond anvil cell was demonstrated before up to temperature of 250°C, in situ pressure measurements were not possible. We developed new experimental setup for simultaneous GUI and pressure determination using a ruby fluorescence gouge. A diamond anvil cell is equipped with a miniature internal resistive heater with thermocouple fixed at a very small distance from the sample chamber. DAC is mounted at the rotating stage with 5 degrees of freedom (XYZ and two tilting degrees), that can be fixed in three different positions: on top of a P-buffer rod for compressional wave velocities measurement, on top of S-buffer rod for shear wave velocities measurement and under the microscope, equipped with laser and portable high-resolution spectrometer for ruby fluorescence measurement. DAC under high temperature could be moved between these three positions, and independent pressure, temperature, S and P wave velocities measurements could be done simultaneously at each data point. In addition to single-crystal elasticity measurements, ability of GUI for elasticity measurements of liquids was demonstrated. Compressional wave velocities in liquid argon were measured at high pressures and temperatures, showing the ability of GUI for studies equation of state of a liquid.

Observation of Gravitational Waves from a Binary Black Hole Merger

NASA Astrophysics Data System (ADS)

Abbott, B. P.; Abbott, R.; Abbott, T. D.; Abernathy, M. R.; Acernese, F.; Ackley, K.; Adams, C.; Adams, T.; Addesso, P.; Adhikari, R. X.; Adya, V. B.; Affeldt, C.; Agathos, M.; Agatsuma, K.; Aggarwal, N.; Aguiar, O. D.; Aiello, L.; Ain, A.; Ajith, P.; Allen, B.; Allocca, A.; Altin, P. A.; Anderson, S. B.; Anderson, W. G.; Arai, K.; Arain, M. A.; Araya, M. C.; Arceneaux, C. C.; Areeda, J. S.; Arnaud, N.; Arun, K. G.; Ascenzi, S.; Ashton, G.; Ast, M.; Aston, S. M.; Astone, P.; Aufmuth, P.; Aulbert, C.; Babak, S.; Bacon, P.; Bader, M. K. M.; Baker, P. T.; Baldaccini, F.; Ballardin, G.; Ballmer, S. W.; Barayoga, J. C.; Barclay, S. E.; Barish, B. C.; Barker, D.; Barone, F.; Barr, B.; Barsotti, L.; Barsuglia, M.; Barta, D.; Bartlett, J.; Barton, M. A.; Bartos, I.; Bassiri, R.; Basti, A.; Batch, J. C.; Baune, C.; Bavigadda, V.; Bazzan, M.; Behnke, B.; Bejger, M.; Belczynski, C.; Bell, A. S.; Bell, C. J.; Berger, B. K.; Bergman, J.; Bergmann, G.; Berry, C. P. L.; Bersanetti, D.; Bertolini, A.; Betzwieser, J.; Bhagwat, S.; Bhandare, R.; Bilenko, I. A.; Billingsley, G.; Birch, J.; Birney, R.; Birnholtz, O.; Biscans, S.; Bisht, A.; Bitossi, M.; Biwer, C.; Bizouard, M. A.; Blackburn, J. K.; Blair, C. D.; Blair, D. G.; Blair, R. M.; Bloemen, S.; Bock, O.; Bodiya, T. P.; Boer, M.; Bogaert, G.; Bogan, C.; Bohe, A.; Bojtos, P.; Bond, C.; Bondu, F.; Bonnand, R.; Boom, B. A.; Bork, R.; Boschi, V.; Bose, S.; Bouffanais, Y.; Bozzi, A.; Bradaschia, C.; Brady, P. R.; Braginsky, V. B.; Branchesi, M.; Brau, J. E.; Briant, T.; Brillet, A.; Brinkmann, M.; Brisson, V.; Brockill, P.; Brooks, A. F.; Brown, D. A.; Brown, D. D.; Brown, N. M.; Buchanan, C. C.; Buikema, A.; Bulik, T.; Bulten, H. J.; Buonanno, A.; Buskulic, D.; Buy, C.; Byer, R. L.; Cabero, M.; Cadonati, L.; Cagnoli, G.; Cahillane, C.; Bustillo, J. Calderón; Callister, T.; Calloni, E.; Camp, J. B.; Cannon, K. C.; Cao, J.; Capano, C. D.; Capocasa, E.; Carbognani, F.; Caride, S.; Casanueva Diaz, J.; Casentini, C.; Caudill, S.; Cavaglià, M.; Cavalier, F.; Cavalieri, R.; Cella, G.; Cepeda, C. B.; Baiardi, L. Cerboni; Cerretani, G.; Cesarini, E.; Chakraborty, R.; Chalermsongsak, T.; Chamberlin, S. J.; Chan, M.; Chao, S.; Charlton, P.; Chassande-Mottin, E.; Chen, H. Y.; Chen, Y.; Cheng, C.; Chincarini, A.; Chiummo, A.; Cho, H. S.; Cho, M.; Chow, J. H.; Christensen, N.; Chu, Q.; Chua, S.; Chung, S.; Ciani, G.; Clara, F.; Clark, J. A.; Cleva, F.; Coccia, E.; Cohadon, P.-F.; Colla, A.; Collette, C. G.; Cominsky, L.; Constancio, M.; Conte, A.; Conti, L.; Cook, D.; Corbitt, T. R.; Cornish, N.; Corsi, A.; Cortese, S.; Costa, C. A.; Coughlin, M. W.; Coughlin, S. B.; Coulon, J.-P.; Countryman, S. T.; Couvares, P.; Cowan, E. E.; Coward, D. M.; Cowart, M. J.; Coyne, D. C.; Coyne, R.; Craig, K.; Creighton, J. D. E.; Creighton, T. D.; Cripe, J.; Crowder, S. G.; Cruise, A. M.; Cumming, A.; Cunningham, L.; Cuoco, E.; Dal Canton, T.; Danilishin, S. L.; D'Antonio, S.; Danzmann, K.; Darman, N. S.; Da Silva Costa, C. F.; Dattilo, V.; Dave, I.; Daveloza, H. P.; Davier, M.; Davies, G. S.; Daw, E. J.; Day, R.; De, S.; DeBra, D.; Debreczeni, G.; Degallaix, J.; De Laurentis, M.; Deléglise, S.; Del Pozzo, W.; Denker, T.; Dent, T.; Dereli, H.; Dergachev, V.; DeRosa, R. T.; De Rosa, R.; DeSalvo, R.; Dhurandhar, S.; Díaz, M. C.; Di Fiore, L.; Di Giovanni, M.; Di Lieto, A.; Di Pace, S.; Di Palma, I.; Di Virgilio, A.; Dojcinoski, G.; Dolique, V.; Donovan, F.; Dooley, K. L.; Doravari, S.; Douglas, R.; Downes, T. P.; Drago, M.; Drever, R. W. P.; Driggers, J. C.; Du, Z.; Ducrot, M.; Dwyer, S. E.; Edo, T. B.; Edwards, M. C.; Effler, A.; Eggenstein, H.-B.; Ehrens, P.; Eichholz, J.; Eikenberry, S. S.; Engels, W.; Essick, R. C.; Etzel, T.; Evans, M.; Evans, T. M.; Everett, R.; Factourovich, M.; Fafone, V.; Fair, H.; Fairhurst, S.; Fan, X.; Fang, Q.; Farinon, S.; Farr, B.; Farr, W. M.; Favata, M.; Fays, M.; Fehrmann, H.; Fejer, M. M.; Feldbaum, D.; Ferrante, I.; Ferreira, E. C.; Ferrini, F.; Fidecaro, F.; Finn, L. S.; Fiori, I.; Fiorucci, D.; Fisher, R. P.; Flaminio, R.; Fletcher, M.; Fong, H.; Fournier, J.-D.; Franco, S.; Frasca, S.; Frasconi, F.; Frede, M.; Frei, Z.; Freise, A.; Frey, R.; Frey, V.; Fricke, T. T.; Fritschel, P.; Frolov, V. V.; Fulda, P.; Fyffe, M.; Gabbard, H. A. G.; Gair, J. R.; Gammaitoni, L.; Gaonkar, S. G.; Garufi, F.; Gatto, A.; Gaur, G.; Gehrels, N.; Gemme, G.; Gendre, B.; Genin, E.; Gennai, A.; George, J.; Gergely, L.; Germain, V.; Ghosh, Abhirup; Ghosh, Archisman; Ghosh, S.; Giaime, J. A.; Giardina, K. D.; Giazotto, A.; Gill, K.; Glaefke, A.; Gleason, J. R.; Goetz, E.; Goetz, R.; Gondan, L.; González, G.; Castro, J. M. Gonzalez; Gopakumar, A.; Gordon, N. A.; Gorodetsky, M. L.; Gossan, S. E.; Gosselin, M.; Gouaty, R.; Graef, C.; Graff, P. B.; Granata, M.; Grant, A.; Gras, S.; Gray, C.; Greco, G.; Green, A. C.; Greenhalgh, R. J. S.; Groot, P.; Grote, H.; Grunewald, S.; Guidi, G. M.; Guo, X.; Gupta, A.; Gupta, M. K.; Gushwa, K. E.; Gustafson, E. K.; Gustafson, R.; Hacker, J. J.; Hall, B. R.; Hall, E. D.; Hammond, G.; Haney, M.; Hanke, M. M.; Hanks, J.; Hanna, C.; Hannam, M. D.; Hanson, J.; Hardwick, T.; Harms, J.; Harry, G. M.; Harry, I. W.; Hart, M. J.; Hartman, M. T.; Haster, C.-J.; Haughian, K.; Healy, J.; Heefner, J.; Heidmann, A.; Heintze, M. C.; Heinzel, G.; Heitmann, H.; Hello, P.; Hemming, G.; Hendry, M.; Heng, I. S.; Hennig, J.; Heptonstall, A. W.; Heurs, M.; Hild, S.; Hoak, D.; Hodge, K. A.; Hofman, D.; Hollitt, S. E.; Holt, K.; Holz, D. E.; Hopkins, P.; Hosken, D. J.; Hough, J.; Houston, E. A.; Howell, E. J.; Hu, Y. M.; Huang, S.; Huerta, E. A.; Huet, D.; Hughey, B.; Husa, S.; Huttner, S. H.; Huynh-Dinh, T.; Idrisy, A.; Indik, N.; Ingram, D. R.; Inta, R.; Isa, H. N.; Isac, J.-M.; Isi, M.; Islas, G.; Isogai, T.; Iyer, B. R.; Izumi, K.; Jacobson, M. B.; Jacqmin, T.; Jang, H.; Jani, K.; Jaranowski, P.; Jawahar, S.; Jiménez-Forteza, F.; Johnson, W. W.; Johnson-McDaniel, N. K.; Jones, D. I.; Jones, R.; Jonker, R. J. G.; Ju, L.; Haris, K.; Kalaghatgi, C. V.; Kalogera, V.; Kandhasamy, S.; Kang, G.; Kanner, J. B.; Karki, S.; Kasprzack, M.; Katsavounidis, E.; Katzman, W.; Kaufer, S.; Kaur, T.; Kawabe, K.; Kawazoe, F.; Kéfélian, F.; Kehl, M. S.; Keitel, D.; Kelley, D. B.; Kells, W.; Kennedy, R.; Keppel, D. G.; Key, J. S.; Khalaidovski, A.; Khalili, F. Y.; Khan, I.; Khan, S.; Khan, Z.; Khazanov, E. A.; Kijbunchoo, N.; Kim, C.; Kim, J.; Kim, K.; Kim, Nam-Gyu; Kim, Namjun; Kim, Y.-M.; King, E. J.; King, P. J.; Kinzel, D. L.; Kissel, J. S.; Kleybolte, L.; Klimenko, S.; Koehlenbeck, S. M.; Kokeyama, K.; Koley, S.; Kondrashov, V.; Kontos, A.; Koranda, S.; Korobko, M.; Korth, W. Z.; Kowalska, I.; Kozak, D. B.; Kringel, V.; Krishnan, B.; Królak, A.; Krueger, C.; Kuehn, G.; Kumar, P.; Kumar, R.; Kuo, L.; Kutynia, A.; Kwee, P.; Lackey, B. D.; Landry, M.; Lange, J.; Lantz, B.; Lasky, P. D.; Lazzarini, A.; Lazzaro, C.; Leaci, P.; Leavey, S.; Lebigot, E. O.; Lee, C. H.; Lee, H. K.; Lee, H. M.; Lee, K.; Lenon, A.; Leonardi, M.; Leong, J. R.; Leroy, N.; Letendre, N.; Levin, Y.; Levine, B. M.; Li, T. G. F.; Libson, A.; Littenberg, T. B.; Lockerbie, N. A.; Logue, J.; Lombardi, A. L.; London, L. T.; Lord, J. E.; Lorenzini, M.; Loriette, V.; Lormand, M.; Losurdo, G.; Lough, J. D.; Lousto, C. O.; Lovelace, G.; Lück, H.; Lundgren, A. P.; Luo, J.; Lynch, R.; Ma, Y.; MacDonald, T.; Machenschalk, B.; MacInnis, M.; Macleod, D. M.; Magaña-Sandoval, F.; Magee, R. M.; Mageswaran, M.; Majorana, E.; Maksimovic, I.; Malvezzi, V.; Man, N.; Mandel, I.; Mandic, V.; Mangano, V.; Mansell, G. L.; Manske, M.; Mantovani, M.; Marchesoni, F.; Marion, F.; Márka, S.; Márka, Z.; Markosyan, A. S.; Maros, E.; Martelli, F.; Martellini, L.; Martin, I. W.; Martin, R. M.; Martynov, D. V.; Marx, J. N.; Mason, K.; Masserot, A.; Massinger, T. J.; Masso-Reid, M.; Matichard, F.; Matone, L.; Mavalvala, N.; Mazumder, N.; Mazzolo, G.; McCarthy, R.; McClelland, D. E.; McCormick, S.; McGuire, S. C.; McIntyre, G.; McIver, J.; McManus, D. J.; McWilliams, S. T.; Meacher, D.; Meadors, G. D.; Meidam, J.; Melatos, A.; Mendell, G.; Mendoza-Gandara, D.; Mercer, R. A.; Merilh, E.; Merzougui, M.; Meshkov, S.; Messenger, C.; Messick, C.; Meyers, P. M.; Mezzani, F.; Miao, H.; Michel, C.; Middleton, H.; Mikhailov, E. E.; Milano, L.; Miller, J.; Millhouse, M.; Minenkov, Y.; Ming, J.; Mirshekari, S.; Mishra, C.; Mitra, S.; Mitrofanov, V. P.; Mitselmakher, G.; Mittleman, R.; Moggi, A.; Mohan, M.; Mohapatra, S. R. P.; Montani, M.; Moore, B. C.; Moore, C. J.; Moraru, D.; Moreno, G.; Morriss, S. R.; Mossavi, K.; Mours, B.; Mow-Lowry, C. M.; Mueller, C. L.; Mueller, G.; Muir, A. W.; Mukherjee, Arunava; Mukherjee, D.; Mukherjee, S.; Mukund, N.; Mullavey, A.; Munch, J.; Murphy, D. J.; Murray, P. G.; Mytidis, A.; Nardecchia, I.; Naticchioni, L.; Nayak, R. K.; Necula, V.; Nedkova, K.; Nelemans, G.; Neri, M.; Neunzert, A.; Newton, G.; Nguyen, T. T.; Nielsen, A. B.; Nissanke, S.; Nitz, A.; Nocera, F.; Nolting, D.; Normandin, M. E. N.; Nuttall, L. K.; Oberling, J.; Ochsner, E.; O'Dell, J.; Oelker, E.; Ogin, G. H.; Oh, J. J.; Oh, S. H.; Ohme, F.; Oliver, M.; Oppermann, P.; Oram, Richard J.; O'Reilly, B.; O'Shaughnessy, R.; Ott, C. D.; Ottaway, D. J.; Ottens, R. S.; Overmier, H.; Owen, B. J.; Pai, A.; Pai, S. A.; Palamos, J. R.; Palashov, O.; Palomba, C.; Pal-Singh, A.; Pan, H.; Pan, Y.; Pankow, C.; Pannarale, F.; Pant, B. C.; Paoletti, F.; Paoli, A.; Papa, M. A.; Paris, H. R.; Parker, W.; Pascucci, D.; Pasqualetti, A.; Passaquieti, R.; Passuello, D.; Patricelli, B.; Patrick, Z.; Pearlstone, B. L.; Pedraza, M.; Pedurand, R.; Pekowsky, L.; Pele, A.; Penn, S.; Perreca, A.; Pfeiffer, H. P.; Phelps, M.; Piccinni, O.; Pichot, M.; Pickenpack, M.; Piergiovanni, F.; Pierro, V.; Pillant, G.; Pinard, L.; Pinto, I. M.; Pitkin, M.; Poeld, J. H.; Poggiani, R.; Popolizio, P.; Post, A.; Powell, J.; Prasad, J.; Predoi, V.; Premachandra, S. S.; Prestegard, T.; Price, L. R.; Prijatelj, M.; Principe, M.; Privitera, S.; Prix, R.; Prodi, G. A.; Prokhorov, L.; Puncken, O.; Punturo, M.; Puppo, P.; Pürrer, M.; Qi, H.; Qin, J.; Quetschke, V.; Quintero, E. A.; Quitzow-James, R.; Raab, F. J.; Rabeling, D. S.; Radkins, H.; Raffai, P.; Raja, S.; Rakhmanov, M.; Ramet, C. R.; Rapagnani, P.; Raymond, V.; Razzano, M.; Re, V.; Read, J.; Reed, C. M.; Regimbau, T.; Rei, L.; Reid, S.; Reitze, D. H.; Rew, H.; Reyes, S. D.; Ricci, F.; Riles, K.; Robertson, N. A.; Robie, R.; Robinet, F.; Rocchi, A.; Rolland, L.; Rollins, J. G.; Roma, V. J.; Romano, J. D.; Romano, R.; Romanov, G.; Romie, J. H.; Rosińska, D.; Rowan, S.; Rüdiger, A.; Ruggi, P.; Ryan, K.; Sachdev, S.; Sadecki, T.; Sadeghian, L.; Salconi, L.; Saleem, M.; Salemi, F.; Samajdar, A.; Sammut, L.; Sampson, L. M.; Sanchez, E. J.; Sandberg, V.; Sandeen, B.; Sanders, G. H.; Sanders, J. R.; Sassolas, B.; Sathyaprakash, B. S.; Saulson, P. R.; Sauter, O.; Savage, R. L.; Sawadsky, A.; Schale, P.; Schilling, R.; Schmidt, J.; Schmidt, P.; Schnabel, R.; Schofield, R. M. S.; Schönbeck, A.; Schreiber, E.; Schuette, D.; Schutz, B. F.; Scott, J.; Scott, S. M.; Sellers, D.; Sengupta, A. S.; Sentenac, D.; Sequino, V.; Sergeev, A.; Serna, G.; Setyawati, Y.; Sevigny, A.; Shaddock, D. A.; Shaffer, T.; Shah, S.; Shahriar, M. S.; Shaltev, M.; Shao, Z.; Shapiro, B.; Shawhan, P.; Sheperd, A.; Shoemaker, D. H.; Shoemaker, D. M.; Siellez, K.; Siemens, X.; Sigg, D.; Silva, A. D.; Simakov, D.; Singer, A.; Singer, L. P.; Singh, A.; Singh, R.; Singhal, A.; Sintes, A. M.; Slagmolen, B. J. J.; Smith, J. R.; Smith, M. R.; Smith, N. D.; Smith, R. J. E.; Son, E. J.; Sorazu, B.; Sorrentino, F.; Souradeep, T.; Srivastava, A. K.; Staley, A.; Steinke, M.; Steinlechner, J.; Steinlechner, S.; Steinmeyer, D.; Stephens, B. C.; Stevenson, S. P.; Stone, R.; Strain, K. A.; Straniero, N.; Stratta, G.; Strauss, N. A.; Strigin, S.; Sturani, R.; Stuver, A. L.; Summerscales, T. Z.; Sun, L.; Sutton, P. J.; Swinkels, B. L.; Szczepańczyk, M. J.; Tacca, M.; Talukder, D.; Tanner, D. B.; Tápai, M.; Tarabrin, S. P.; Taracchini, A.; Taylor, R.; Theeg, T.; Thirugnanasambandam, M. P.; Thomas, E. G.; Thomas, M.; Thomas, P.; Thorne, K. A.; Thorne, K. S.; Thrane, E.; Tiwari, S.; Tiwari, V.; Tokmakov, K. V.; Tomlinson, C.; Tonelli, M.; Torres, C. V.; Torrie, C. I.; Töyrä, D.; Travasso, F.; Traylor, G.; Trifirò, D.; Tringali, M. C.; Trozzo, L.; Tse, M.; Turconi, M.; Tuyenbayev, D.; Ugolini, D.; Unnikrishnan, C. S.; Urban, A. L.; Usman, S. A.; Vahlbruch, H.; Vajente, G.; Valdes, G.; Vallisneri, M.; van Bakel, N.; van Beuzekom, M.; van den Brand, J. F. J.; Van Den Broeck, C.; Vander-Hyde, D. C.; van der Schaaf, L.; van Heijningen, J. V.; van Veggel, A. A.; Vardaro, M.; Vass, S.; Vasúth, M.; Vaulin, R.; Vecchio, A.; Vedovato, G.; Veitch, J.; Veitch, P. J.; Venkateswara, K.; Verkindt, D.; Vetrano, F.; Viceré, A.; Vinciguerra, S.; Vine, D. J.; Vinet, J.-Y.; Vitale, S.; Vo, T.; Vocca, H.; Vorvick, C.; Voss, D.; Vousden, W. D.; Vyatchanin, S. P.; Wade, A. R.; Wade, L. E.; Wade, M.; Waldman, S. J.; Walker, M.; Wallace, L.; Walsh, S.; Wang, G.; Wang, H.; Wang, M.; Wang, X.; Wang, Y.; Ward, H.; Ward, R. L.; Warner, J.; Was, M.; Weaver, B.; Wei, L.-W.; Weinert, M.; Weinstein, A. J.; Weiss, R.; Welborn, T.; Wen, L.; Weßels, P.; Westphal, T.; Wette, K.; Whelan, J. T.; Whitcomb, S. E.; White, D. J.; Whiting, B. F.; Wiesner, K.; Wilkinson, C.; Willems, P. A.; Williams, L.; Williams, R. D.; Williamson, A. R.; Willis, J. L.; Willke, B.; Wimmer, M. H.; Winkelmann, L.; Winkler, W.; Wipf, C. C.; Wiseman, A. G.; Wittel, H.; Woan, G.; Worden, J.; Wright, J. L.; Wu, G.; Yablon, J.; Yakushin, I.; Yam, W.; Yamamoto, H.; Yancey, C. C.; Yap, M. J.; Yu, H.; Yvert, M.; ZadroŻny, A.; Zangrando, L.; Zanolin, M.; Zendri, J.-P.; Zevin, M.; Zhang, F.; Zhang, L.; Zhang, M.; Zhang, Y.; Zhao, C.; Zhou, M.; Zhou, Z.; Zhu, X. J.; Zucker, M. E.; Zuraw, S. E.; Zweizig, J.; LIGO Scientific Collaboration; Virgo Collaboration

2016-02-01

On September 14, 2015 at 09:50:45 UTC the two detectors of the Laser Interferometer Gravitational-Wave Observatory simultaneously observed a transient gravitational-wave signal. The signal sweeps upwards in frequency from 35 to 250 Hz with a peak gravitational-wave strain of 1.0 ×10-21. It matches the waveform predicted by general relativity for the inspiral and merger of a pair of black holes and the ringdown of the resulting single black hole. The signal was observed with a matched-filter signal-to-noise ratio of 24 and a false alarm rate estimated to be less than 1 event per 203 000 years, equivalent to a significance greater than 5.1 σ . The source lies at a luminosity distance of 41 0-180+160 Mpc corresponding to a redshift z =0.0 9-0.04+0.03 . In the source frame, the initial black hole masses are 3 6-4+5M⊙ and 2 9-4+4M⊙ , and the final black hole mass is 6 2-4+4M⊙ , with 3. 0-0.5+0.5M⊙ c2 radiated in gravitational waves. All uncertainties define 90% credible intervals. These observations demonstrate the existence of binary stellar-mass black hole systems. This is the first direct detection of gravitational waves and the first observation of a binary black hole merger.

Observation of Gravitational Waves from a Binary Black Hole Merger

NASA Technical Reports Server (NTRS)

Abbott, B. P.; Abbott, R.; Abbott, T. D.; Abernathy, M. R.; Acernese, F.; Ackley, K.; Adams, C.; Adams, T.; Addesso, P.; Camp, Jordan B.;

Observation of Gravitational Waves from a Binary Black Hole Merger.

PubMed

Abbott, B P; Abbott, R; Abbott, T D; Abernathy, M R; Acernese, F; Ackley, K; Adams, C; Adams, T; Addesso, P; Adhikari, R X; Adya, V B; Affeldt, C; Agathos, M; Agatsuma, K; Aggarwal, N; Aguiar, O D; Aiello, L; Ain, A; Ajith, P; Allen, B; Allocca, A; Altin, P A; Anderson, S B; Anderson, W G; Arai, K; Arain, M A; Araya, M C; Arceneaux, C C; Areeda, J S; Arnaud, N; Arun, K G; Ascenzi, S; Ashton, G; Ast, M; Aston, S M; Astone, P; Aufmuth, P; Aulbert, C; Babak, S; Bacon, P; Bader, M K M; Baker, P T; Baldaccini, F; Ballardin, G; Ballmer, S W; Barayoga, J C; Barclay, S E; Barish, B C; Barker, D; Barone, F; Barr, B; Barsotti, L; Barsuglia, M; Barta, D; Bartlett, J; Barton, M A; Bartos, I; Bassiri, R; Basti, A; Batch, J C; Baune, C; Bavigadda, V; Bazzan, M; Behnke, B; Bejger, M; Belczynski, C; Bell, A S; Bell, C J; Berger, B K; Bergman, J; Bergmann, G; Berry, C P L; Bersanetti, D; Bertolini, A; Betzwieser, J; Bhagwat, S; Bhandare, R; Bilenko, I A; Billingsley, G; Birch, J; Birney, R; Birnholtz, O; Biscans, S; Bisht, A; Bitossi, M; Biwer, C; Bizouard, M A; Blackburn, J K; Blair, C D; Blair, D G; Blair, R M; Bloemen, S; Bock, O; Bodiya, T P; Boer, M; Bogaert, G; Bogan, C; Bohe, A; Bojtos, P; Bond, C; Bondu, F; Bonnand, R; Boom, B A; Bork, R; Boschi, V; Bose, S; Bouffanais, Y; Bozzi, A; Bradaschia, C; Brady, P R; Braginsky, V B; Branchesi, M; Brau, J E; Briant, T; Brillet, A; Brinkmann, M; Brisson, V; Brockill, P; Brooks, A F; Brown, D A; Brown, D D; Brown, N M; Buchanan, C C; Buikema, A; Bulik, T; Bulten, H J; Buonanno, A; Buskulic, D; Buy, C; Byer, R L; Cabero, M; Cadonati, L; Cagnoli, G; Cahillane, C; Calderón Bustillo, J; Callister, T; Calloni, E; Camp, J B; Cannon, K C; Cao, J; Capano, C D; Capocasa, E; Carbognani, F; Caride, S; Casanueva Diaz, J; Casentini, C; Caudill, S; Cavaglià, M; Cavalier, F; Cavalieri, R; Cella, G; Cepeda, C B; Cerboni Baiardi, L; Cerretani, G; Cesarini, E; Chakraborty, R; Chalermsongsak, T; Chamberlin, S J; Chan, M; Chao, S; Charlton, P; Chassande-Mottin, E; Chen, H Y; Chen, Y; Cheng, C; Chincarini, A; Chiummo, A; Cho, H S; Cho, M; Chow, J H; Christensen, N; Chu, Q; Chua, S; Chung, S; Ciani, G; Clara, F; Clark, J A; Cleva, F; Coccia, E; Cohadon, P-F; Colla, A; Collette, C G; Cominsky, L; Constancio, M; Conte, A; Conti, L; Cook, D; Corbitt, T R; Cornish, N; Corsi, A; Cortese, S; Costa, C A; Coughlin, M W; Coughlin, S B; Coulon, J-P; Countryman, S T; Couvares, P; Cowan, E E; Coward, D M; Cowart, M J; Coyne, D C; Coyne, R; Craig, K; Creighton, J D E; Creighton, T D; Cripe, J; Crowder, S G; Cruise, A M; Cumming, A; Cunningham, L; Cuoco, E; Dal Canton, T; Danilishin, S L; D'Antonio, S; Danzmann, K; Darman, N S; Da Silva Costa, C F; Dattilo, V; Dave, I; Daveloza, H P; Davier, M; Davies, G S; Daw, E J; Day, R; De, S; DeBra, D; Debreczeni, G; Degallaix, J; De Laurentis, M; Deléglise, S; Del Pozzo, W; Denker, T; Dent, T; Dereli, H; Dergachev, V; DeRosa, R T; De Rosa, R; DeSalvo, R; Dhurandhar, S; Díaz, M C; Di Fiore, L; Di Giovanni, M; Di Lieto, A; Di Pace, S; Di Palma, I; Di Virgilio, A; Dojcinoski, G; Dolique, V; Donovan, F; Dooley, K L; Doravari, S; Douglas, R; Downes, T P; Drago, M; Drever, R W P; Driggers, J C; Du, Z; Ducrot, M; Dwyer, S E; Edo, T B; Edwards, M C; Effler, A; Eggenstein, H-B; Ehrens, P; Eichholz, J; Eikenberry, S S; Engels, W; Essick, R C; Etzel, T; Evans, M; Evans, T M; Everett, R; Factourovich, M; Fafone, V; Fair, H; Fairhurst, S; Fan, X; Fang, Q; Farinon, S; Farr, B; Farr, W M; Favata, M; Fays, M; Fehrmann, H; Fejer, M M; Feldbaum, D; Ferrante, I; Ferreira, E C; Ferrini, F; Fidecaro, F; Finn, L S; Fiori, I; Fiorucci, D; Fisher, R P; Flaminio, R; Fletcher, M; Fong, H; Fournier, J-D; Franco, S; Frasca, S; Frasconi, F; Frede, M; Frei, Z; Freise, A; Frey, R; Frey, V; Fricke, T T; Fritschel, P; Frolov, V V; Fulda, P; Fyffe, M; Gabbard, H A G; Gair, J R; Gammaitoni, L; Gaonkar, S G; Garufi, F; Gatto, A; Gaur, G; Gehrels, N; Gemme, G; Gendre, B; Genin, E; Gennai, A; George, J; Gergely, L; Germain, V; Ghosh, Abhirup; Ghosh, Archisman; Ghosh, S; Giaime, J A; Giardina, K D; Giazotto, A; Gill, K; Glaefke, A; Gleason, J R; Goetz, E; Goetz, R; Gondan, L; González, G; Gonzalez Castro, J M; Gopakumar, A; Gordon, N A; Gorodetsky, M L; Gossan, S E; Gosselin, M; Gouaty, R; Graef, C; Graff, P B; Granata, M; Grant, A; Gras, S; Gray, C; Greco, G; Green, A C; Greenhalgh, R J S; Groot, P; Grote, H; Grunewald, S; Guidi, G M; Guo, X; Gupta, A; Gupta, M K; Gushwa, K E; Gustafson, E K; Gustafson, R; Hacker, J J; Hall, B R; Hall, E D; Hammond, G; Haney, M; Hanke, M M; Hanks, J; Hanna, C; Hannam, M D; Hanson, J; Hardwick, T; Harms, J; Harry, G M; Harry, I W; Hart, M J; Hartman, M T; Haster, C-J; Haughian, K; Healy, J; Heefner, J; Heidmann, A; Heintze, M C; Heinzel, G; Heitmann, H; Hello, P; Hemming, G; Hendry, M; Heng, I S; Hennig, J; Heptonstall, A W; Heurs, M; Hild, S; Hoak, D; Hodge, K A; Hofman, D; Hollitt, S E; Holt, K; Holz, D E; Hopkins, P; Hosken, D J; Hough, J; Houston, E A; Howell, E J; Hu, Y M; Huang, S; Huerta, E A; Huet, D; Hughey, B; Husa, S; Huttner, S H; Huynh-Dinh, T; Idrisy, A; Indik, N; Ingram, D R; Inta, R; Isa, H N; Isac, J-M; Isi, M; Islas, G; Isogai, T; Iyer, B R; Izumi, K; Jacobson, M B; Jacqmin, T; Jang, H; Jani, K; Jaranowski, P; Jawahar, S; Jiménez-Forteza, F; Johnson, W W; Johnson-McDaniel, N K; Jones, D I; Jones, R; Jonker, R J G; Ju, L; Haris, K; Kalaghatgi, C V; Kalogera, V; Kandhasamy, S; Kang, G; Kanner, J B; Karki, S; Kasprzack, M; Katsavounidis, E; Katzman, W; Kaufer, S; Kaur, T; Kawabe, K; Kawazoe, F; Kéfélian, F; Kehl, M S; Keitel, D; Kelley, D B; Kells, W; Kennedy, R; Keppel, D G; Key, J S; Khalaidovski, A; Khalili, F Y; Khan, I; Khan, S; Khan, Z; Khazanov, E A; Kijbunchoo, N; Kim, C; Kim, J; Kim, K; Kim, Nam-Gyu; Kim, Namjun; Kim, Y-M; King, E J; King, P J; Kinzel, D L; Kissel, J S; Kleybolte, L; Klimenko, S; Koehlenbeck, S M; Kokeyama, K; Koley, S; Kondrashov, V; Kontos, A; Koranda, S; Korobko, M; Korth, W Z; Kowalska, I; Kozak, D B; Kringel, V; Krishnan, B; Królak, A; Krueger, C; Kuehn, G; Kumar, P; Kumar, R; Kuo, L; Kutynia, A; Kwee, P; Lackey, B D; Landry, M; Lange, J; Lantz, B; Lasky, P D; Lazzarini, A; Lazzaro, C; Leaci, P; Leavey, S; Lebigot, E O; Lee, C H; Lee, H K; Lee, H M; Lee, K; Lenon, A; Leonardi, M; Leong, J R; Leroy, N; Letendre, N; Levin, Y; Levine, B M; Li, T G F; Libson, A; Littenberg, T B; Lockerbie, N A; Logue, J; Lombardi, A L; London, L T; Lord, J E; Lorenzini, M; Loriette, V; Lormand, M; Losurdo, G; Lough, J D; Lousto, C O; Lovelace, G; Lück, H; Lundgren, A P; Luo, J; Lynch, R; Ma, Y; MacDonald, T; Machenschalk, B; MacInnis, M; Macleod, D M; Magaña-Sandoval, F; Magee, R M; Mageswaran, M; Majorana, E; Maksimovic, I; Malvezzi, V; Man, N; Mandel, I; Mandic, V; Mangano, V; Mansell, G L; Manske, M; Mantovani, M; Marchesoni, F; Marion, F; Márka, S; Márka, Z; Markosyan, A S; Maros, E; Martelli, F; Martellini, L; Martin, I W; Martin, R M; Martynov, D V; Marx, J N; Mason, K; Masserot, A; Massinger, T J; Masso-Reid, M; Matichard, F; Matone, L; Mavalvala, N; Mazumder, N; Mazzolo, G; McCarthy, R; McClelland, D E; McCormick, S; McGuire, S C; McIntyre, G; McIver, J; McManus, D J; McWilliams, S T; Meacher, D; Meadors, G D; Meidam, J; Melatos, A; Mendell, G; Mendoza-Gandara, D; Mercer, R A; Merilh, E; Merzougui, M; Meshkov, S; Messenger, C; Messick, C; Meyers, P M; Mezzani, F; Miao, H; Michel, C; Middleton, H; Mikhailov, E E; Milano, L; Miller, J; Millhouse, M; Minenkov, Y; Ming, J; Mirshekari, S; Mishra, C; Mitra, S; Mitrofanov, V P; Mitselmakher, G; Mittleman, R; Moggi, A; Mohan, M; Mohapatra, S R P; Montani, M; Moore, B C; Moore, C J; Moraru, D; Moreno, G; Morriss, S R; Mossavi, K; Mours, B; Mow-Lowry, C M; Mueller, C L; Mueller, G; Muir, A W; Mukherjee, Arunava; Mukherjee, D; Mukherjee, S; Mukund, N; Mullavey, A; Munch, J; Murphy, D J; Murray, P G; Mytidis, A; Nardecchia, I; Naticchioni, L; Nayak, R K; Necula, V; Nedkova, K; Nelemans, G; Neri, M; Neunzert, A; Newton, G; Nguyen, T T; Nielsen, A B; Nissanke, S; Nitz, A; Nocera, F; Nolting, D; Normandin, M E N; Nuttall, L K; Oberling, J; Ochsner, E; O'Dell, J; Oelker, E; Ogin, G H; Oh, J J; Oh, S H; Ohme, F; Oliver, M; Oppermann, P; Oram, Richard J; O'Reilly, B; O'Shaughnessy, R; Ott, C D; Ottaway, D J; Ottens, R S; Overmier, H; Owen, B J; Pai, A; Pai, S A; Palamos, J R; Palashov, O; Palomba, C; Pal-Singh, A; Pan, H; Pan, Y; Pankow, C; Pannarale, F; Pant, B C; Paoletti, F; Paoli, A; Papa, M A; Paris, H R; Parker, W; Pascucci, D; Pasqualetti, A; Passaquieti, R; Passuello, D; Patricelli, B; Patrick, Z; Pearlstone, B L; Pedraza, M; Pedurand, R; Pekowsky, L; Pele, A; Penn, S; Perreca, A; Pfeiffer, H P; Phelps, M; Piccinni, O; Pichot, M; Pickenpack, M; Piergiovanni, F; Pierro, V; Pillant, G; Pinard, L; Pinto, I M; Pitkin, M; Poeld, J H; Poggiani, R; Popolizio, P; Post, A; Powell, J; Prasad, J; Predoi, V; Premachandra, S S; Prestegard, T; Price, L R; Prijatelj, M; Principe, M; Privitera, S; Prix, R; Prodi, G A; Prokhorov, L; Puncken, O; Punturo, M; Puppo, P; Pürrer, M; Qi, H; Qin, J; Quetschke, V; Quintero, E A; Quitzow-James, R; Raab, F J; Rabeling, D S; Radkins, H; Raffai, P; Raja, S; Rakhmanov, M; Ramet, C R; Rapagnani, P; Raymond, V; Razzano, M; Re, V; Read, J; Reed, C M; Regimbau, T; Rei, L; Reid, S; Reitze, D H; Rew, H; Reyes, S D; Ricci, F; Riles, K; Robertson, N A; Robie, R; Robinet, F; Rocchi, A; Rolland, L; Rollins, J G; Roma, V J; Romano, J D; Romano, R; Romanov, G; Romie, J H; Rosińska, D; Rowan, S; Rüdiger, A; Ruggi, P; Ryan, K; Sachdev, S; Sadecki, T; Sadeghian, L; Salconi, L; Saleem, M; Salemi, F; Samajdar, A; Sammut, L; Sampson, L M; Sanchez, E J; Sandberg, V; Sandeen, B; Sanders, G H; Sanders, J R; Sassolas, B; Sathyaprakash, B S; Saulson, P R; Sauter, O; Savage, R L; Sawadsky, A; Schale, P; Schilling, R; Schmidt, J; Schmidt, P; Schnabel, R; Schofield, R M S; Schönbeck, A; Schreiber, E; Schuette, D; Schutz, B F; Scott, J; Scott, S M; Sellers, D; Sengupta, A S; Sentenac, D; Sequino, V; Sergeev, A; Serna, G; Setyawati, Y; Sevigny, A; Shaddock, D A; Shaffer, T; Shah, S; Shahriar, M S; Shaltev, M; Shao, Z; Shapiro, B; Shawhan, P; Sheperd, A; Shoemaker, D H; Shoemaker, D M; Siellez, K; Siemens, X; Sigg, D; Silva, A D; Simakov, D; Singer, A; Singer, L P; Singh, A; Singh, R; Singhal, A; Sintes, A M; Slagmolen, B J J; Smith, J R; Smith, M R; Smith, N D; Smith, R J E; Son, E J; Sorazu, B; Sorrentino, F; Souradeep, T; Srivastava, A K; Staley, A; Steinke, M; Steinlechner, J; Steinlechner, S; Steinmeyer, D; Stephens, B C; Stevenson, S P; Stone, R; Strain, K A; Straniero, N; Stratta, G; Strauss, N A; Strigin, S; Sturani, R; Stuver, A L; Summerscales, T Z; Sun, L; Sutton, P J; Swinkels, B L; Szczepańczyk, M J; Tacca, M; Talukder, D; Tanner, D B; Tápai, M; Tarabrin, S P; Taracchini, A; Taylor, R; Theeg, T; Thirugnanasambandam, M P; Thomas, E G; Thomas, M; Thomas, P; Thorne, K A; Thorne, K S; Thrane, E; Tiwari, S; Tiwari, V; Tokmakov, K V; Tomlinson, C; Tonelli, M; Torres, C V; Torrie, C I; Töyrä, D; Travasso, F; Traylor, G; Trifirò, D; Tringali, M C; Trozzo, L; Tse, M; Turconi, M; Tuyenbayev, D; Ugolini, D; Unnikrishnan, C S; Urban, A L; Usman, S A; Vahlbruch, H; Vajente, G; Valdes, G; Vallisneri, M; van Bakel, N; van Beuzekom, M; van den Brand, J F J; Van Den Broeck, C; Vander-Hyde, D C; van der Schaaf, L; van Heijningen, J V; van Veggel, A A; Vardaro, M; Vass, S; Vasúth, M; Vaulin, R; Vecchio, A; Vedovato, G; Veitch, J; Veitch, P J; Venkateswara, K; Verkindt, D; Vetrano, F; Viceré, A; Vinciguerra, S; Vine, D J; Vinet, J-Y; Vitale, S; Vo, T; Vocca, H; Vorvick, C; Voss, D; Vousden, W D; Vyatchanin, S P; Wade, A R; Wade, L E; Wade, M; Waldman, S J; Walker, M; Wallace, L; Walsh, S; Wang, G; Wang, H; Wang, M; Wang, X; Wang, Y; Ward, H; Ward, R L; Warner, J; Was, M; Weaver, B; Wei, L-W; Weinert, M; Weinstein, A J; Weiss, R; Welborn, T; Wen, L; Weßels, P; Westphal, T; Wette, K; Whelan, J T; Whitcomb, S E; White, D J; Whiting, B F; Wiesner, K; Wilkinson, C; Willems, P A; Williams, L; Williams, R D; Williamson, A R; Willis, J L; Willke, B; Wimmer, M H; Winkelmann, L; Winkler, W; Wipf, C C; Wiseman, A G; Wittel, H; Woan, G; Worden, J; Wright, J L; Wu, G; Yablon, J; Yakushin, I; Yam, W; Yamamoto, H; Yancey, C C; Yap, M J; Yu, H; Yvert, M; Zadrożny, A; Zangrando, L; Zanolin, M; Zendri, J-P; Zevin, M; Zhang, F; Zhang, L; Zhang, M; Zhang, Y; Zhao, C; Zhou, M; Zhou, Z; Zhu, X J; Zucker, M E; Zuraw, S E; Zweizig, J

2016-02-12

On September 14, 2015 at 09:50:45 UTC the two detectors of the Laser Interferometer Gravitational-Wave Observatory simultaneously observed a transient gravitational-wave signal. The signal sweeps upwards in frequency from 35 to 250 Hz with a peak gravitational-wave strain of 1.0×10(-21). It matches the waveform predicted by general relativity for the inspiral and merger of a pair of black holes and the ringdown of the resulting single black hole. The signal was observed with a matched-filter signal-to-noise ratio of 24 and a false alarm rate estimated to be less than 1 event per 203,000 years, equivalent to a significance greater than 5.1σ. The source lies at a luminosity distance of 410(-180)(+160)  Mpc corresponding to a redshift z=0.09(-0.04)(+0.03). In the source frame, the initial black hole masses are 36(-4)(+5)M⊙ and 29(-4)(+4)M⊙, and the final black hole mass is 62(-4)(+4)M⊙, with 3.0(-0.5)(+0.5)M⊙c(2) radiated in gravitational waves. All uncertainties define 90% credible intervals. These observations demonstrate the existence of binary stellar-mass black hole systems. This is the first direct detection of gravitational waves and the first observation of a binary black hole merger.

A STUDY OF THE η^'π^- SYSTEM PRODUCED IN THE REACTION π^-parrowη^'π^- p AT 18 GeV/c

NASA Astrophysics Data System (ADS)

Ivanov-Tatar, Emil

2000-04-01

The η^'π^- system has been studied in the reaction π^-parrowη^'π^- p at 18 GeV/c. The partial wave analysis of 6040 kinematically-identified events shows that the reaction is dominated by natural parity exchange. The production of an exotic isovector state π_1(1600) is observed in the I^G(J^PC) = 1^-(1^-+) wave. The mass and the width of that state are estimated via simultaneous mass-dependent fits of the I^G(J^PC) = 1^-(1^-+) and I^G(J^PC) = 1^-(2^++) waves. The a_2^-(1320) and a wide structure at 1.8 GeV/c^2 are observed in the I^G(J^PC) = 1^-(2^++) wave. The amplitude analysis of the mass interval above 1.8 GeV/c^2 indicates an interference between I^G(J^PC) = 1^-(2^++) and I^G(J^PC) = 1^-(4^++) waves.

Characterizing crustal and uppermost mantle anisotropy with a depth-dependent tilted hexagonally symmetric elastic tensor: theory and examples

NASA Astrophysics Data System (ADS)

Feng, L.; Xie, J.; Ritzwoller, M. H.

2017-12-01

Two major types of surface wave anisotropy are commonly observed by seismologists but are only rarely interpreted jointly: apparent radial anisotropy, which is the difference in propagation speed between horizontally and vertically polarized waves inferred from Love and Rayleigh waves, and apparent azimuthal anisotropy, which is the directional dependence of surface wave speeds (usually Rayleigh waves). We describe a method of inversion that interprets simultaneous observations of radial and azimuthal anisotropy under the assumption of a hexagonally symmetric elastic tensor with a tilted symmetry axis defined by dip and strike angles. With a full-waveform numerical solver based on the spectral element method (SEM), we verify the validity of the forward theory used for the inversion. We also present two examples, in the US and Tibet, in which we have successfully applied the tomographic method to demonstrate that the two types of apparent anisotropy can be interpreted jointly as a tilted hexagonally symmetric medium.

Topologically protected edge states for out-of-plane and in-plane bulk elastic waves.

PubMed

Huo, Shao-Yong; Chen, Jiu-Jiu; Huang, Hong-Bo

2018-04-11

Topological phononic insulators (TPnIs) show promise for application in the manipulation of acoustic waves for the design of low-loss transmission and perfectly integrated communication devices. Since solid phononic crystals exist as a transverse polarization mode and a mixed longitudinal-transverse polarization mode, the realization of topological edge states for both out-of-plane and in-plane bulk elastic waves is desirable to enhance the controllability of the edge waves in solid systems. In this paper, a two-dimensional (2D) solid/solid hexagonal-latticed phononic system that simultaneously supports the topologically protected edge states for out-of-plane and in-plane bulk elastic waves is investigated. Firstly, two pairs of two-fold Dirac cones, respectively corresponding to the out-of-plane and in-plane waves, are obtained at the same frequency by tuning the crystal parameters. Then, a strategy of zone folding is invoked to form double Dirac cones. By shrinking and expanding the steel scatterer, the lattice symmetry is broken, and band inversions induced, giving rise to an intriguing topological phase transition. Finally, the topologically protected edge states for both out-of-plane and in-plane bulk elastic waves, which can be simultaneously located at the frequency range from 1.223 to 1.251 MHz, are numerically observed. Robust pseudospin-dependent elastic edge wave propagation along arbitrary paths is further demonstrated. Our results will significantly broaden its practical application in the engineering field.

Topologically protected edge states for out-of-plane and in-plane bulk elastic waves

NASA Astrophysics Data System (ADS)

Huo, Shao-Yong; Chen, Jiu-Jiu; Huang, Hong-Bo

2018-04-01

Topological phononic insulators (TPnIs) show promise for application in the manipulation of acoustic waves for the design of low-loss transmission and perfectly integrated communication devices. Since solid phononic crystals exist as a transverse polarization mode and a mixed longitudinal-transverse polarization mode, the realization of topological edge states for both out-of-plane and in-plane bulk elastic waves is desirable to enhance the controllability of the edge waves in solid systems. In this paper, a two-dimensional (2D) solid/solid hexagonal-latticed phononic system that simultaneously supports the topologically protected edge states for out-of-plane and in-plane bulk elastic waves is investigated. Firstly, two pairs of two-fold Dirac cones, respectively corresponding to the out-of-plane and in-plane waves, are obtained at the same frequency by tuning the crystal parameters. Then, a strategy of zone folding is invoked to form double Dirac cones. By shrinking and expanding the steel scatterer, the lattice symmetry is broken, and band inversions induced, giving rise to an intriguing topological phase transition. Finally, the topologically protected edge states for both out-of-plane and in-plane bulk elastic waves, which can be simultaneously located at the frequency range from 1.223 to 1.251 MHz, are numerically observed. Robust pseudospin-dependent elastic edge wave propagation along arbitrary paths is further demonstrated. Our results will significantly broaden its practical application in the engineering field.

Generation and propagation of electromagnetic waves in the magnetosphere. Ph.D. Thesis

NASA Technical Reports Server (NTRS)

Taylor, W. W. L.

1973-01-01

Characteristics of broadband ELF, VLF, and LF emissions in the magnetosphere were calculated assuming incoherent Cerenkov radiation from magnetospheric electrons with energies from 50 eV to 50 keV. Calculations were included to determine the ray paths of the emitted waves. A diffusive equilibrium model of the magnetosphere with an ionosphere, plasmapause, and a centered dipole magnetic field was used. Ray path calculations were done in three dimensions. Using simultaneous energetic electron and VLF data, comparisons were made between calculated and observed VLF hiss. Assuming a wave normal angle six degrees from the resonance cone angle, the calculated spectral densities are both two orders of magnitude below the observed spectral densities. It seems unlikely that VLF hiss is produced by incoherent Cerenkov radiation. The observed spectral shape of V-shaped VLF hiss is similar to that calculated from incoherent Cerenkov radiation.

Micro X-ray CT imaging of pore-scale changes in unconsolidated sediment under confining pressure

NASA Astrophysics Data System (ADS)

Schindler, M.; Prasad, M.

2017-12-01

Micro X-ray computed tomography was used to image confining-pressure induced changes in a dry, unconsolidated quartz sand pack while simultaneously recording ultrasonic P-wave velocities. The experiments were performed under in-situ pressure of up to 4000 psi. The majority of digital rock physics studies rely on micro CT images obtained under ambient pressure and temperature conditions although effective rock properties strongly depend on in situ conditions. Goal of this work is to be able to obtain micro CT images of rock samples while pore and confining pressure is applied. Simultaneously we recorded ultrasonic P-wave velocities. The combination of imaging and velocity measurements provides insight in pore-scale changes in the rock and their influence on elastic properties. We visually observed a reduction in porosity by more than a third of the initial value as well as extensive grain damage, changes in pore and grain size distribution and an increase in contact number and contact radius with increasing confining pressure. An increase in measured ultrasonic P-wave velocities with increasing pressure was observed. We used porosity, contact number and contact radius obtained from micro CT images to model P-wave velocity with the contact-radius model by Bachrach et al. (1998). Our observations showed that the frame of unconsolidated sediments is significantly altered starting at pressures of only 1000 psi. This finding indicates that common assumptions in rock physics models (the solid frame remains unchanged) are violated for unconsolidated sediments. The effects on the solid frame should be taken into account when modeling the pressure dependence of elastic rock properties.

Simultaneous transverse oscillations of a prominence and a filament and longitudinal oscillation of another filament induced by a single shock wave

DOE Office of Scientific and Technical Information (OSTI.GOV)

Shen, Yuandeng; Liu, Ying D.; Chen, P. F.

2014-11-10

We present the first stereoscopic and Doppler observations of simultaneous transverse oscillations of a prominence and a filament and longitudinal oscillation of another filament launched by a single shock wave. Using Hα Doppler observations, we derive the three-dimensional oscillation velocities at different heights along the prominence axis. The results indicate that the prominence has a larger oscillation amplitude and damping time at higher altitude, but the periods at different heights are the same (i.e., 13.5 minutes). This suggests that the prominence oscillates like a linear vertical rigid body with one end anchored on the Sun. One of the filaments showsmore » weak transverse oscillation after the passing of the shock, which is possibly due to the low altitude of the filament and the weakening (due to reflection) of the shock wave before the interaction. Large-amplitude longitudinal oscillation is observed in the other filament after the passing of the shock wave. The velocity amplitude and period are about 26.8 km s{sup –1} and 80.3 minutes, respectively. We propose that the orientation of a filament or prominence relative to the normal vector of the incoming shock should be an important factor for launching transverse or longitudinal filament oscillations. In addition, the restoring forces of the transverse prominence are most likely due to the coupling of gravity and magnetic tension of the supporting magnetic field, while that for the longitudinal filament oscillation is probably the resultant force of gravity and magnetic pressure.« less

Negative refraction of elastic waves at the deep-subwavelength scale in a single-phase metamaterial.

PubMed

Zhu, R; Liu, X N; Hu, G K; Sun, C T; Huang, G L

2014-11-24

Negative refraction of elastic waves has been studied and experimentally demonstrated in three- and two-dimensional phononic crystals, but Bragg scattering is impractical for low-frequency wave control because of the need to scale the structures to manageable sizes. Here we present an elastic metamaterial with chiral microstructure made of a single-phase solid material that aims to achieve subwavelength negative refraction of elastic waves. Both negative effective mass density and modulus are observed owing to simultaneous translational and rotational resonances. We experimentally demonstrate negative refraction of the longitudinal elastic wave at the deep-subwavelength scale in the metamaterial fabricated in a stainless steel plate. The experimental measurements are in good agreement with numerical simulations. Moreover, wave mode conversion related with negative refraction is revealed and discussed. The proposed elastic metamaterial may thus be used as a flat lens for elastic wave focusing.

Coherent generation of the auroral kilometric radiation by nonlinear beatings between electrostatic waves

DOE Office of Scientific and Technical Information (OSTI.GOV)

Pellat, R.; Roux, A.

1979-09-01

The propagation of electrostatic plasma waves in an inhomogeneous and magnetized plasma is studied analytically. These waves, which are driven unstable by auroral beams of electrons, are shown to suffer a further geometrical amplification while they propagate toward cut-off. Simultaneously their group velocities tend to be aligned with the geomagnetic field. Then it is shown that the electrostatic energy tends to accumulate at or near ..omega../sub L/H and ..omega../sub U/H, the local lower and upper hybrid frequencies. Due to this process, large amplitude electrostatic waves with very narrow spectra should be observed near these frequencies at any place along themore » auroral field lines where intense beam driven instability takes place. These intense quasi-monochromatic electrostatic waves are then shown to give rise by a coherent nonlinear three wave process to an intense electromagnetic radiation. Provided that the ratio ..omega../sub p/e/..omega../sub c/e tends to be smaller than unity, it is shown that the most intense radiation should be observed at 2..omega../sub U/H in the extraordinary mode.« less

Ocean-ice interaction in the marginal ice zone using synthetic aperture radar imagery

NASA Technical Reports Server (NTRS)

Liu, Antony K.; Peng, Chich Y.; Weingartner, Thomas J.

1994-01-01

Ocean-ice interaction processes in the marginal ice zone (MIZ) by wind, waves, and mesoscale features, such as up/downwelling and eddies are studied using Earth Remote-Sensing Satellite (ERS) 1 synthetic aperture radar (SAR) images and an ocean-ice interaction model. A sequence of seven SAR images of the MIZ in the Chukchi Sea with 3 or 6 days interval are investigated for ice edge advance/retreat. Simultaneous current measurements from the northeast Chukchi Sea, as well as the Barrow wind record, are used to interpret the MIZ dynamics. SAR spectra of waves in ice and ocean waves in the Bering and Chukchi Sea are compared for the study of wave propagation and dominant SAR imaging mechanism. By using the SAR-observed ice edge configuration and wind and wave field in the Chukchi Sea as inputs, a numerical simulation has been performed with the ocean-ice interaction model. After 3 days of wind and wave forcing the resulting ice edge configuration, eddy formation, and flow velocity field are shown to be consistent with SAR observations.

The joint search for gravitational wave and low energy neutrino signals from core-collapse supernovae: methodology and status report

NASA Astrophysics Data System (ADS)

Gromov, M. B.; Casentini, C.

2017-09-01

The detection of gravitational waves opens a new era in physics. Now it's possible to observe the Universe using a fundamentally new way. Gravitational waves potentially permit getting insight into the physics of Core-Collapse Supernovae (CCSNe). However, due to significant uncertainties on the theoretical models of gravitational wave emission associated with CCSNe, benefits may come from multi-messenger observations of CCSNe. Such benefits include increased confidence in detection, extending the astrophysical reach of the detectors and allowing deeper understanding of the nature of the phenomenon. Fortunately, CCSNe have a neutrino signature confirmed by the observation of SN1987A. The gravitational and neutrino signals propagate with the speed of light and without significant interaction with interstellar matter. So that they must reach an observer on the Earth almost simultaneously. These facts open a way to search for the correlation between the signals. However, this method is limited by the sensitivity of modern neutrino detectors that allow to observe CCSNe only in the Local Group of galaxies. The methodology and status of a proposed joint search for the correlation signals are presented here.

The joint search for gravitational wave and low energy neutrino signals from core-collapse supernovae: methodology and status report

NASA Astrophysics Data System (ADS)

Gromov, M. B.; Casentini, C.

2017-09-01

The detection of gravitational waves opens a new era in physics. Now it's possible to observe the Universe using a fundamentally new way. Gravitational waves potentially permit getting insight into the physics of Core-Collapse Supernovae (CCSNe). However, due to signi cant uncertainties on the theoretical models of gravitational wave emission associated with CCSNe, bene ts may come from multi-messenger observations of CCSNe. Such bene ts include increased con dence in detection, extending the astrophysical reach of the detectors and allowing deeper understanding of the nature of the phenomenon. Fortunately, CCSNe have a neutrino signature con rmed by the observation of SN1987A. The gravitational and neutrino signals propagate with the speed of light and without signi cant interaction with interstellar matter. So that they must reach an observer on the Earth almost simultaneously. These facts open a way to search for the correlation between the signals. However, this method is limited by the sensitivity of modern neutrino detectors that allow to observe CCSNe only in the Local Group of galaxies. The methodology and status of a proposed joint search for the correlation signals are presented here.

Simultaneous generation of high-efficiency broadband asymmetric anomalous refraction and reflection waves with few-layer anisotropic metasurface

PubMed Central

Li, Zhancheng; Liu, Wenwei; Cheng, Hua; Liu, Jieying; Chen, Shuqi; Tian, Jianguo

2016-01-01

Optical metasurfaces consisting of single-layer nanostructures have immensely promising applications in wavefront control because they can be used to arbitrarily manipulate wave phase, and polarization. However, anomalous refraction and reflection waves have not yet been simultaneously and asymmetrically generated, and the limited efficiency and bandwidth of pre-existing single-layer metasurfaces hinder their practical applications. Here, a few-layer anisotropic metasurface is presented for simultaneously generating high-efficiency broadband asymmetric anomalous refraction and reflection waves. Moreover, the normal transmission and reflection waves are low and the anomalous waves are the predominant ones, which is quite beneficial for practical applications such as beam deflectors. Our work provides an effective method of enhancing the performance of anomalous wave generation, and the asymmetric performance of the proposed metasurface shows endless possibilities in wavefront control for nanophotonics device design and optical communication applications. PMID:27762286

Gravity Wave Seeding of Equatorial Plasma Bubbles

NASA Technical Reports Server (NTRS)

Singh, Sardul; Johnson, F. S.; Power, R. A.

1997-01-01

Some examples from the Atmosphere Explorer E data showing plasma bubble development from wavy ion density structures in the bottomside F layer are described. The wavy structures mostly had east-west wavelengths of 150-800 km, in one example it was about 3000 km. The ionization troughs in the wavy structures later broke up into either a multiple-bubble patch or a single bubble, depending upon whether, in the precursor wavy structure, shorter wavelengths were superimposed on the larger scale wavelengths. In the multiple bubble patches, intrabubble spacings vaned from 55 km to 140 km. In a fully developed equatorial spread F case, east-west wavelengths from 690 km down to about 0.5 km were present simultaneously. The spacings between bubble patches or between bubbles in a patch appear to be determined by the wavelengths present in the precursor wave structure. In some cases, deeper bubbles developed on the western edge of a bubble patch, suggesting an east-west asymmetry. Simultaneous horizontal neutral wind measurements showed wavelike perturbations that were closely associated with perturbations in the plasma horizontal drift velocity. We argue that the wave structures observed here that served as the initial seed ion density perturbations were caused by gravity waves, strengthening the view that gravity waves seed equatorial spread F irregularities.

AMPTE CCE observations of Pi 2 pulsations in the inner magnetosphere

NASA Technical Reports Server (NTRS)

Takahashi, Kazue; Ohtani, Shin-Ichi; Yumoto, Kiyohumi

1992-01-01

Magnetic field data acquired with the AMPTE Charge Composition Explorer satellite in the inner magnetosphere (L = 2-5) often show Pi 2 pulsations whose waveforms match Pi 2 pulsations simultaneously observed on the ground at Kakioka (L = 1.2). From a study such events, it is found that the magnetic pulsations in the equatorial magnetosphere are dominated by poloidal-mode oscillations. The relative phase between the compressional component at CCE and the horizontal component at Kakioka is either near zero or near 180 deg, with the 180 lag observed only when the satellite is at L greater than 3. This observation implies that there is a node of a radial standing wave at L greater than 3. It is argued that the nodal structure arises from reflection of MHD fast-mode waves at some inner boundary of the magnetosphere and discuss the relevance of the nodal structure to cavity-mode resonances and oscillations in the inner magnetosphere forced by a source wave external to the inner magnetosphere.

On the connection between the 3HE-enrichment and spectral index of solar energetic particles

NASA Technical Reports Server (NTRS)

Kocharov, L. G.; Dvoryanchikov, Y. V.

1985-01-01

A model is presented which explains the observed tendency of events with large 3He/4He ratios to have steeper spectra. In this model preferential injection of 3He, acceleration by Alfven waves and Coulomb deceleration of ions are considered simultaneously. The observed tendency may be obtained as a result of competition between injection and acceleration processes.

Vibration of a single microcapsule with a hard plastic shell in an acoustic standing wave field.

PubMed

Koyama, Daisuke; Kotera, Hironori; Kitazawa, Natsuko; Yoshida, Kenji; Nakamura, Kentaro; Watanabe, Yoshiaki

2011-04-01

Observation techniques for measuring the small vibration of a single microcapsule of tens of nanometers in an acoustic standing wave field are discussed. First, simultaneous optical observation of a microbubble vibration by two methods is investigated, using a high-speed video camera, which permits two-dimensional observation of the bubble vibration, and a laser Doppler vibrometer (LDV), which can observe small bubble vibration amplitudes at high frequency. Bubbles of tens of micrometers size were trapped at the antinode of an acoustic standing wave generated in an observational cell. Bubble vibration at 27 kHz could be observed and the experimental results for the two methods showed good agreement. The radial vibration of microcapsules with a hard plastic shell was observed using the LDV and the measurement of the capsule vibration with radial oscillation amplitude of tens of nanometers was successful. The acoustic radiation force acting on microcapsules in the acoustic standing wave was measured from the trapped position of the standing wave and the radial oscillation amplitude of the capsules was estimated from the theoretical equation of the acoustic radiation force, giving results in good agreement with the LDV measurements. The radial oscillation amplitude of a capsule was found to be proportional to the amplitude of the driving sound pressure. A larger expansion ratio was observed for capsules closer to the resonance condition under the same driving sound pressure and frequency. © 2011 IEEE

Experimental demonstration of the vertical spin existence in evanescent waves

NASA Astrophysics Data System (ADS)

Maksimyak, P. P.; Maksimyak, A. P.; Ivanskyi, D. I.

2018-01-01

Physical existence of the recently discovered vertical spin arising in an evanescent light wave due to the total internal reflection of a linearly polarized probing beam with azimuthal angle 45° is experimentally verified. Mechanical action, caused by optical force, associated with the extraordinary transverse component of the spin in evanescent wave is demonstrated. The motion of a birefringent plate in a direction controlled by simultaneous action of the canonical momentum and the transversal spin momentum is observed. The contribution of the canonical and spin momenta in determination of the trajectory of the resulting motion occur commensurable under exceptionally delicately determined experimental conditions.

A case study of lightning, whistlers, and associated ionospheric effects during a substorm particle injection event

NASA Technical Reports Server (NTRS)

Rodriguez, J. V.; Inan, U. S.; Li, Y. Q.; Holzworth, R. H.; Smith, A. J.; Orville, R. E.; Rosenberg, T. J.

1992-01-01

The relationships among cloud-to-ground (CG) lightning, sferics, whistlers, VLF amplitude perturbations, and other ionospheric phenomena occurring during substorm events were investigated using data from simultaneous ground-based observations of narrow-band and broad-band VLF radio waves and of CG lightning made during the 1987 Wave-Induced Particle Precipitation campaign conducted from Wallops Island (Virginia). Results suggest that the data collected on ionospheric phenomena during this event may represent new evidence of direct coupling of lightning energy to the lower ionosphere, either in conjunction with or in the absence of gyroresonant interactions between whistler mode waves and electrons in the magnetosphere.

GW170817 falsifies dark matter emulators

NASA Astrophysics Data System (ADS)

Boran, S.; Desai, S.; Kahya, E. O.; Woodard, R. P.

2018-02-01

On August 17, 2017 the LIGO interferometers detected the gravitational wave (GW) signal (GW170817) from the coalescence of binary neutron stars. This signal was also simultaneously seen throughout the electromagnetic (EM) spectrum from radio waves to gamma rays. We point out that this simultaneous detection of GW and EM signals rules out a class of modified gravity theories, termed "dark matter emulators," which dispense with the need for dark matter by making ordinary matter couple to a different metric from that of GW. We discuss other kinds of modified gravity theories which dispense with the need for dark matter and are still viable. This simultaneous observation also provides the first observational test of Einstein's weak equivalence principle (WEP) between gravitons and photons. We estimate the Shapiro time delay due to the gravitational potential of the total dark matter distribution along the line of sight (complementary to the calculation by Abbott et al. [Astrophys. J. Lett. 848, L13 (2017)], 10.3847/2041-8213/aa920c) to be about 400 days. Using this estimate for the Shapiro delay and from the time difference of 1.7 seconds between the GW signal and gamma rays, we can constrain violations of the WEP using the parametrized post-Newtonian parameter γ , and it is given by |γGW-γEM|<9.8 ×10-8.

Simultaneous observations of F2 layer stratification and spread F at postmidnight over a northern equatorial anomaly region

NASA Astrophysics Data System (ADS)

Jiang, Chunhua; Yang, Guobin; Deng, Chi; Zhou, Chen; Zhu, Peng; Yokoyama, Tatsuhiro; Song, Huan; Lan, Ting; Ni, Binbin; Zhao, Zhengyu; Zhang, Yuannong

2015-12-01

Simultaneous observations of F2 layer stratification and spread F at postmidnight (00:00 LT to 05:00 LT) were carried out on 22, 23, and 28 November 2013, using ionosondes distributed over a northern equatorial anomaly region at three specific locations, i.e., Puer (PUR, 22.7°N, 101.05°E, dip latitude 12.9°N), Chiang Mai (CMU, 18.8°N, 98.9°E, dip latitude 9.04°N), and Chumphon (CPN, 10.7°N, 99.4°E, dip latitude 0.93°N). The results show that both the PUR and CMU stations observed the F2 layer stratification at postmidnight in the Northern Hemisphere, frequently accompanied with gravity waves (the periods~30-100 min). It is reported that F2 layer stratification at postmidnight can be observed in the Northern Hemisphere for the first time. It is suggested that the thermospheric neutral wind triggered by gravity waves strongly contribute to the altitude dependence of the combined vertical plasma velocity, which consequently poses significant impacts on the occurrence of the low-latitude F2 layer stratification at postmidnight. In addition, the spread F other than F2 layer stratification was observed at the CPN station located at the geomagnetic equator, suggesting that smaller geomagnetic inclination tend to inhibit the postmidnight F2 layer stratification in the equatorial region. Furthermore, on 23 November 2013 a good correlation was identified between the F2 layer stratification at PUR and the spread F at both CMU and CPN, possibly due to that the large-scale gravity waves originating at middle latitudes contribute to the nighttime spread F observed in the low-latitude and equatorial regions.

Magnetosphere on May 11, 1999, the day the solar wind almost disappeared: II. Magnetic pulsations in space and on the ground

NASA Astrophysics Data System (ADS)

Le, G.; Chi, P. J.; Goedecke, W.; Russell, C. T.; Szabo, A.; Petrinec, S. M.; Angelopoulos, V.; Reeves, G. D.; Chun, F. K.

2000-08-01

Simultaneous observations by Wind and IMP-8 in the upstream region on May 11, 1999, when the solar wind density was well below its usual values and the IMF was generally weakly northward, indicate there were upstream waves present in the foreshock, but wave power was an order of magnitude weaker than usual due to an extremely weak bow shock and tenuous solar wind plasma. Magnetic pulsations in the magnetosphere have been observed in the magnetic field data from Polar and at mid-latitude ground stations. By comparing May 11 with a control day under normal solar wind conditions and with a similar foreshock geometry, we find that the magnetosphere was much quieter than usual. The Pc 3-4 waves were nearly absent in the dayside magnetosphere both at Polar and as seen at mid-latitude ground stations even through the foreshock geometry was favorable for the generation of these waves. Since the solar wind speed was not unusual on this day, these observations suggest that it is the Mach number of the solar wind flow relative to the magnetosphere that controls the amplitude of Pc 3-4 waves in the magnetosphere.

Collaborative analysis of Planetary Waves in the Mesospheric Neutral Winds with SuperDARN and TIMED Observations

NASA Astrophysics Data System (ADS)

Ruohoniemi, J. M.

2004-12-01

The SuperDARN HF radars are best known for observing the ExB drift of ionospheric plasma in the high-latitude F region. At mesospheric altitudes the trails of ionization produced by meteors provide another kind of target for radar backscatter, and the motions imparted to these trails by winds in the neutral atmosphere can be measured. In the northern hemisphere the coverage of mesospheric winds currently extends over a 180 deg longitude sector but is confined by propagation conditions to latitudes near 55 deg geographic. We have analyzed several extended periods of simultaneous observations of the neutral wind involving SuperDARN and the TIMED suite of instruments. Often, the winds show clear evidence of large-scale wave events. The quasi 2-day planetary waves are prominent and their occurrence is seen to depend on season. By comparing the wave characteristics between the satellite and ground observations we obtain a complete breakdown of the wave activity in terms of wave periods and zonal wavenumbers. In addition, the semidiurnal tide is a ubiquitous feature of the mid-latitude mesosphere. A single radar station cannot resolve the sun-synchronous component from other contributions at the semidiurnal frequency. We show that with a chain of radars along a latitude band, the true sun-synchronous, or migrating, component can be inferred. Joint analysis can be performed chiefly with data from the SABRE and TIDI instruments.

Simultaneous Traveling Convection Vortex (TCV) Events and Pc 1-2 Wave Bursts at Cusp/Cleft Latitudes observed in Arctic Canada and Svalbard

NASA Astrophysics Data System (ADS)

Posch, J. L.; Witte, A. J.; Engebretson, M. J.; Murr, D.; Lessard, M.; Raita, T.; Singer, H. J.

2010-12-01

Traveling convection vortices (TCVs), which appear in ground magnetometer records at near-cusp latitudes as solitary ~5 mHz pulses, are now known to originate in instabilities in the ion foreshock just upstream of Earth’s bow shock. They can also stimulate compressions or relaxations of the dayside magnetosphere (evident in geosynchronous satellite data). These transient compressions can in turn sharply increase the growth rate of electromagnetic ion cyclotron (EMIC) waves, which also appear in ground records at near-cusp latitudes as bursts of Pc 1-2 pulsations. In this study we have identified simultaneous TCV - Pc 1-2 burst events occurring from 2008 through the first 7 months of 2010 in Eastern Arctic Canada and Svalbard, using a combination of fluxgate magnetometers (MACCS and IMAGE) and search coil magnetometers in each region. Magnetometer observations at GOES 10 and 12, at longitudes near the MACCS sites, are also used to characterize the strength of the magnetic perturbations. There is no direct proportion between the amplitude of TCV and Pc 1-2 wave events in either region, consistent with the highly variable densities and pitch angle distributions of plasma of ring current / plasma sheet energies in the outer dayside magnetosphere.

Simultaneous Observations of Atmospheric Tides from Combined in Situ and Remote Observations at Mars from the MAVEN Spacecraft

NASA Technical Reports Server (NTRS)

England, Scott L.; Liu, Guiping; Withers, Paul; Yigit, Erdal; Lo, Daniel; Jain, Sonal; Schneider, Nicholas M. (Inventor); Deighan, Justin; McClintock, William E.; Mahaffy, Paul R.;

Impact analysis of air gap motion with respect to parameters of mooring system for floating platform

NASA Astrophysics Data System (ADS)

Shen, Zhong-xiang; Huo, Fa-li; Nie, Yan; Liu, Yin-dong

2017-04-01

In this paper, the impact analysis of air gap concerning the parameters of mooring system for the semi-submersible platform is conducted. It is challenging to simulate the wave, current and wind loads of a platform based on a model test simultaneously. Furthermore, the dynamic equivalence between the truncated and full-depth mooring system is still a tuff work. However, the wind and current loads can be tested accurately in wind tunnel model. Furthermore, the wave can be simulated accurately in wave tank test. The full-scale mooring system and the all environment loads can be simulated accurately by using the numerical model based on the model tests simultaneously. In this paper, the air gap response of a floating platform is calculated based on the results of tunnel test and wave tank. Meanwhile, full-scale mooring system, the wind, wave and current load can be considered simultaneously. In addition, a numerical model of the platform is tuned and validated by ANSYS AQWA according to the model test results. With the support of the tuned numerical model, seventeen simulation cases about the presented platform are considered to study the wave, wind, and current loads simultaneously. Then, the impact analysis studies of air gap motion regarding the length, elasticity, and type of the mooring line are performed in the time domain under the beam wave, head wave, and oblique wave conditions.

A pulse coding and decoding strategy to perform Lamb wave inspections using simultaneously multiple actuators

NASA Astrophysics Data System (ADS)

De Marchi, Luca; Marzani, Alessandro; Moll, Jochen; Kudela, Paweł; Radzieński, Maciej; Ostachowicz, Wiesław

2017-07-01

The performance of Lamb wave based monitoring systems, both in terms of diagnosis time and data complexity, can be enhanced by increasing the number of transducers used to actuate simultaneously the guided waves in the inspected medium. However, in case of multiple simultaneously-operated actuators the interference among the excited wave modes within the acquired signals has to be considered for the further processing. To this aim, in this work a code division strategy based on the Warped Frequency Transform is presented. At first, the proposed procedure encodes actuation pulses using Gold sequences. Next, for each considered actuator the acquired signals are compensated from dispersion by cross correlating the warped version of the actuated and received signals. Compensated signals form the base for a final wavenumber imaging meant at emphasizing defects and or anomalies by removing incident wavefield and edge reflections. The proposed strategy is tested numerically, and validated through an experiment in which guided waves are actuated in a plate by four piezoelectric transducers operating simultaneously.

Simultaneous investigation of intracellular Ca2+ increase and morphological events upon fertilization in the sand dollar egg.

PubMed

Hamaguchi, Y; Hamaguchi, M S

1990-06-01

An increase in intracellular Ca2+ concentration ([Ca2+]) and morphological were simultaneously observed by epifluorescence and differential interference contrast (DIC) microscopy during fertilization of the sand dollar, Clypeaster japonicus. [Ca2+], which was detected by a Ca2+ indicator, Fluo-3, initially increased just beneath the sperm-attached site on the egg surface 8.6 sec after attachment. The increase spread into the egg as a concentric sphere to the egg center and, thereafter, propagated in the egg cytoplasm as a planar wave rather than a spherical wave. It reached the site opposite the initiation site across the egg 24.2 sec after initiation. The fertilization envelope (FE) began to elevate 10.3 sec after the initiation of the increase in [Ca2+] and 21.2 sec after sperm attachment.

Simultaneous observation of free and defect-bound excitons in CH3NH3PbI3 using four-wave mixing spectroscopy

NASA Astrophysics Data System (ADS)

March, Samuel A.; Clegg, Charlotte; Riley, Drew B.; Webber, Daniel; Hill, Ian G.; Hall, Kimberley C.

2016-12-01

Solar cells incorporating organic-inorganic perovskite, which may be fabricated using low-cost solution-based processing, have witnessed a dramatic rise in efficiencies yet their fundamental photophysical properties are not well understood. The exciton binding energy, central to the charge collection process, has been the subject of considerable controversy due to subtleties in extracting it from conventional linear spectroscopy techniques due to strong broadening tied to disorder. Here we report the simultaneous observation of free and defect-bound excitons in CH3NH3PbI3 films using four-wave mixing (FWM) spectroscopy. Due to the high sensitivity of FWM to excitons, tied to their longer coherence decay times than unbound electron- hole pairs, we show that the exciton resonance energies can be directly observed from the nonlinear optical spectra. Our results indicate low-temperature binding energies of 13 meV (29 meV) for the free (defect-bound) exciton, with the 16 meV localization energy for excitons attributed to binding to point defects. Our findings shed light on the wide range of binding energies (2-55 meV) reported in recent years.

Simultaneous Dual Species Matter Wave Interferometry

NASA Astrophysics Data System (ADS)

Schlippert, Dennis; Albers, Henning; Richardson, Logan; Meiners, Christian; Hartwig, Jonas; Ertmer, Wolfgang; Rasel, Ernst

2014-05-01

We report on the first realization of a simultaneous 39K-87Rb-dual species matter wave interferometer measuring gravitational acceleration with the aim to test Einstein's Equivalence Principle (EEP). Compared to classical tests such as torsion pendulum experiments and Lunar Laser Ranging, chemical elements suitable for performing matter wave interferometry can provide complementary information. We show the performance of our apparatus and discuss current limitations and future improvements towards highly sensitive matter wave tests of EEP.

Assessing waveform predictions of recent three-dimensional velocity models of the Tibetan Plateau

NASA Astrophysics Data System (ADS)

Bao, Xueyang; Shen, Yang

2016-04-01

Accurate velocity models are essential for both the determination of earthquake locations and source moments and the interpretation of Earth structures. With the increasing number of three-dimensional velocity models, it has become necessary to assess the models for accuracy in predicting seismic observations. Six models of the crustal and uppermost mantle structures in Tibet and surrounding regions are investigated in this study. Regional Rayleigh and Pn (or Pnl) waveforms from two ground truth events, including one nuclear explosion and one natural earthquake located in the study area, are simulated by using a three-dimensional finite-difference method. Synthetics are compared to observed waveforms in multiple period bands of 20-75 s for Rayleigh waves and 1-20 s for Pn/Pnl waves. The models are evaluated based on the phase delays and cross-correlation coefficients between synthetic and observed waveforms. A model generated from full-wave ambient noise tomography best predicts Rayleigh waves throughout the data set, as well as Pn/Pnl waves traveling from the Tarim Basin to the stations located in central Tibet. In general, the models constructed from P wave tomography are not well suited to predict Rayleigh waves, and vice versa. Possible causes of the differences between observed and synthetic waveforms, and frequency-dependent variations of the "best matching" models with the smallest prediction errors are discussed. This study suggests that simultaneous prediction for body and surface waves requires an integrated velocity model constructed with multiple seismic waveforms and consideration of other important properties, such as anisotropy.

Alfvén Wave Turbulence as a Coronal Heating Mechanism: Simultaneously Predicting the Heating Rate and the Wave-induced Emission Line Broadening

DOE Office of Scientific and Technical Information (OSTI.GOV)

Oran, R.; Landi, E.; Holst, B. van der

We test the predictions of the Alfvén Wave Solar Model (AWSoM), a global wave-driven magnetohydrodynamic (MHD) model of the solar atmosphere, against high-resolution spectra emitted by the quiescent off-disk solar corona. AWSoM incorporates Alfvén wave propagation and dissipation in both closed and open magnetic field lines; turbulent dissipation is the only heating mechanism. We examine whether this mechanism is consistent with observations of coronal EUV emission by combining model results with the CHIANTI atomic database to create synthetic line-of-sight spectra, where spectral line widths depend on thermal and wave-related ion motions. This is the first time wave-induced line broadening ismore » calculated from a global model with a realistic magnetic field. We used high-resolution SUMER observations above the solar west limb between 1.04 and 1.34 R {sub ⊙} at the equator, taken in 1996 November. We obtained an AWSoM steady-state solution for the corresponding period using a synoptic magnetogram. The 3D solution revealed a pseudo-streamer structure transversing the SUMER line of sight, which contributes significantly to the emission; the modeled electron temperature and density in the pseudo-streamer are consistent with those observed. The synthetic line widths and the total line fluxes are consistent with the observations for five different ions. Further, line widths that include the contribution from the wave-induced ion motions improve the correspondence with observed spectra for all ions. We conclude that the turbulent dissipation assumed in the AWSoM model is a viable candidate for explaining coronal heating, as it is consistent with several independent measured quantities.« less

Correlated Pc4-5 ULF waves, whistler-mode chorus, and pulsating aurora observed by the Van Allen Probes and ground-based systems

DOE Office of Scientific and Technical Information (OSTI.GOV)

Jaynes, A. N.; Lessard, M. R.; Takahashi, K.

Theory and observations have linked equatorial VLF waves with pulsating aurora for decades, invoking the process of pitch angle scattering of tens of keV electrons in the equatorial magnetosphere. Recently published satellite studies have strengthened this argument, by showing strong correlation between pulsating auroral patches and both lower-band chorus and tens of keV electron modulation in the vicinity of geosynchronous orbit. Additionally, a previous link has been made between Pc4–5 compressional pulsations and modulation of whistler-mode chorus using Time History of Events and Macroscale Interactions during Substorms. In the current study, we present simultaneous in situ observations of structured chorusmore » waves and an apparent field line resonance (in the Pc4–5 range) as a result of a substorm injection, observed by Van Allen Probes, along with ground-based observations of pulsating aurora. We demonstrate the likely scenario being one of substorm-driven Pc4–5 ULF pulsations modulating chorus waves, and thus providing the driver for pulsating particle precipitation into the Earth's atmosphere. Interestingly, the modulated chorus wave and ULF wave periods are well correlated, with chorus occurring at half the periodicity of the ULF waves. We also show, for the first time, a particular few-Hz modulation of individual chorus elements that coincides with the same modulation in a nearby pulsating aurora patch. As a result, such modulation has been noticed as a high-frequency component in ground-based camera data of pulsating aurora for decades and may be a result of nonlinear chorus wave interactions in the equatorial region.« less

Correlated Pc4-5 ULF waves, whistler-mode chorus, and pulsating aurora observed by the Van Allen Probes and ground-based systems

DOE PAGES

Jaynes, A. N.; Lessard, M. R.; Takahashi, K.; ...

2015-10-28

Theory and observations have linked equatorial VLF waves with pulsating aurora for decades, invoking the process of pitch angle scattering of tens of keV electrons in the equatorial magnetosphere. Recently published satellite studies have strengthened this argument, by showing strong correlation between pulsating auroral patches and both lower-band chorus and tens of keV electron modulation in the vicinity of geosynchronous orbit. Additionally, a previous link has been made between Pc4–5 compressional pulsations and modulation of whistler-mode chorus using Time History of Events and Macroscale Interactions during Substorms. In the current study, we present simultaneous in situ observations of structured chorusmore » waves and an apparent field line resonance (in the Pc4–5 range) as a result of a substorm injection, observed by Van Allen Probes, along with ground-based observations of pulsating aurora. We demonstrate the likely scenario being one of substorm-driven Pc4–5 ULF pulsations modulating chorus waves, and thus providing the driver for pulsating particle precipitation into the Earth's atmosphere. Interestingly, the modulated chorus wave and ULF wave periods are well correlated, with chorus occurring at half the periodicity of the ULF waves. We also show, for the first time, a particular few-Hz modulation of individual chorus elements that coincides with the same modulation in a nearby pulsating aurora patch. As a result, such modulation has been noticed as a high-frequency component in ground-based camera data of pulsating aurora for decades and may be a result of nonlinear chorus wave interactions in the equatorial region.« less

Ground and Satellite Observations of ULF Waves Artificially Produced by HAARP

NASA Astrophysics Data System (ADS)

Chang, C.; Labenski, J.; Shroff, H.; Doxas, I.; Papadopoulos, D.; Milikh, G.; Parrot, M.

2008-12-01

Modulated ionospheric heating at ULF frequencies using the HAARP heater was performed from April 28 to May 3, 2008 (http://www.haarp.alaska.edu). Simultaneous ground-based ULF measurements were made locally at Gakona, AK and at Lake Ozette, WA that is 2000 km away. The ground-based results showed that ULF amplitudes measured at Gakona are mostly proportional to the electrojet strength above HAARP, indicating electrojet modulation to be the source of the local ULF waves. However, the timing of ULF events recorded at Lake Ozette did not correlated with the electrojet strength at Gakona, indicating that modulation of F region pressure is the more likely source for distant ULF waves. These observations are consistent with the theoretical understanding that ULF waves generated by current modulation are shear Alfven waves propagating along the magnetic field line, thus at high latitude their observations are limited to the vicinity of the heated spot. On the other hand, propagation of ULF waves at significant lateral distances requires generation of magnetosonic waves since they are the only mode that propagates isotropically and can thus couple efficiently in the Alfvenic duct. In addition to ground-based observations, the DEMETER satellite also provided space measurements of the heating effects during its passes over HAARP. The DEMETER results showed direct detection of HAARP ULF waves at 0.1 Hz. Moreover, density dips were observed every time HAARP was operated at CW mode, which provides clear evidence of duct formation by direct HF heating at F peak. Details of these results will be presented at the meeting. We would like to acknowledge the support provided by the HAARP facility during our ULF experiments.

Simultaneous realization of slow and fast acoustic waves using a fractal structure of Koch curve.

PubMed

Ding, Jin; Fan, Li; Zhang, Shu-Yi; Zhang, Hui; Yu, Wei-Wei

2018-01-24

An acoustic metamaterial based on a fractal structure, the Koch curve, is designed to simultaneously realize slow and fast acoustic waves. Owing to the multiple transmitting paths in the structure resembling the Koch curve, the acoustic waves travelling along different paths interfere with each other. Therefore, slow waves are created on the basis of the resonance of a Koch-curve-shaped loop, and meanwhile, fast waves even with negative group velocities are obtained due to the destructive interference of two acoustic waves with opposite phases. Thus, the transmission of acoustic wave can be freely manipulated with the Koch-curve shaped structure.

First Simultaneous and Common-Volume Lidar Observations of Na and Fe Metals, Temperatures, and Vertical Winds in Antarctica

NASA Astrophysics Data System (ADS)

Chu, X.

2017-12-01

A new STAR Na Doppler lidar will be installed to Arrival Heights near McMurdo Station, Antarctica in October 2017. This new lidar will be operated next to an existing Fe Boltzmann lidar to make simultaneous and common-volume measurements of metal Na and Fe layers, neutral temperatures, and vertical winds in the mesosphere and thermosphere, up to nearly 200 km. These measurements will be used to study a variety of science topics, e.g., the meteoric metal layers, wave dynamics, polar mesospheric clouds, constituent and heat fluxes, and cosmic dust. The discoveries of thermospheric neutral Fe layers and persistent gravity waves by the Fe Boltzmann lidar observations has opened a new door to explore the space-atmosphere interactions with ground-based instruments, especially in the least understood but crucially important altitude range of 100-200 km. These neutral metal layers provide excellent tracers for modern resonance lidars to measure the neutral wind and temperature directly. Even more exciting, the neutral metal layers in the thermosphere provide a natural laboratory to test our fundamental understandings of the atmosphere-ionosphere-magnetosphere coupling and processes. This paper will report the first summer results from the simultaneous Na and Fe lidar observations from Antarctica, and highlight important discoveries made by the Fe lidar during its first seven years of campaign at McMurdo. A thermosphere-ionosphere Fe/Fe+ (TIFe) model will be introduced to explain the TIFe layers in Antarctica.

Magnetoacoustic Wave Energy from Numerical Simulations of an Observed Sunspot Umbra

NASA Astrophysics Data System (ADS)

Felipe, T.; Khomenko, E.; Collados, M.

2011-07-01

We aim at reproducing the height dependence of sunspot wave signatures obtained from spectropolarimetric observations through three-dimensional MHD numerical simulations. A magnetostatic sunspot model based on the properties of the observed sunspot is constructed and perturbed at the photosphere, introducing the fluctuations measured with the Si I λ10827 line. The results of the simulations are compared with the oscillations observed simultaneously at different heights from the He I λ10830 line, the Ca II H core, and the Fe I blends in the wings of the Ca II H line. The simulations show a remarkable agreement with the observations. They reproduce the velocity maps and power spectra at the formation heights of the observed lines, as well as the phase and amplification spectra between several pairs of lines. We find that the stronger shocks at the chromosphere are accompanied with a delay between the observed signal and the simulated one at the corresponding height, indicating that shocks shift the formation height of the chromospheric lines to higher layers. Since the simulated wave propagation matches very well the properties of the observed one, we are able to use the numerical calculations to quantify the energy contribution of the magnetoacoustic waves to the chromospheric heating in sunspots. Our findings indicate that the energy supplied by these waves is too low to balance the chromospheric radiative losses. The energy contained at the formation height of the lowermost Si I λ10827 line in the form of slow magnetoacoustic waves is already insufficient to heat the higher layers, and the acoustic energy which reaches the chromosphere is around 3-9 times lower than the required amount of energy. The contribution of the magnetic energy is even lower.

Using MLT Composition Observations to Evaluate Transport in a Comprehensive High Top Model

NASA Astrophysics Data System (ADS)

Smith, A. K.

2016-12-01

Gravity waves play an outsized role in the MLT: driving the mean meridional circulation, exerting a large degree of control over the mean winds and seasonal variations in temperature, and leading to diffusive vertical transport of heat and trace species. These waves are represented using a parameterization in the NCAR Whole Atmosphere Community Climate Model (WACCM), as in many other GCMs. To evaluate their impact, we need to consider not just the mean temperature and wind but the distributions of trace species that are affected by advection due to resolved winds and waves and diffusion associated with gravity wave dissipation. The responses of chemical species to changes in the gravity wave forcing are complex and sometimes unexpected. Transport and diffusion simultaneously affect all species and the heat and momentum budgets; subsequent interactions, and the strong dependence of reaction rates on temperature, affect the net impact of transport on the composition. In evaluating the model, we evaluate the simulations using a range of available observations of composition, including O, O3, CO, CO2, NO, NO2, OH, and H2O.

Unraveling the excitation mechanisms of highly oblique lower-band chorus waves

DOE PAGES

Li, Wen; Mourenas, D.; Artemyev, A. V.; ...

2016-08-17

Excitation mechanisms of highly oblique, quasi-electrostatic lower band chorus waves are investigated using Van Allen Probes observations near the equator of the Earth's magnetosphere. Linear growth rates are evaluated based on in situ, measured electron velocity distributions and plasma conditions and compared with simultaneously observed wave frequency spectra and wave normal angles. Accordingly, two distinct excitation mechanisms of highly oblique lower band chorus have been clearly identified for the first time. The first mechanism relies on cyclotron resonance with electrons possessing both a realistic temperature anisotropy at keV energies and a plateau at 100–500 eV in the parallel velocity distribution.more » The second mechanism corresponds to Landau resonance with a 100–500 eV beam. In both cases, a small low-energy beam-like component is necessary for suppressing an otherwise dominating Landau damping. In conclusion, our new findings suggest that small variations in the electron distribution could have important impacts on energetic electron dynamics.« less

RATIR Follow-up of LIGO/Virgo Gravitational Wave Events

NASA Astrophysics Data System (ADS)

Golkhou, V. Zach; Butler, Nathaniel R.; Strausbaugh, Robert; Troja, Eleonora; Kutyrev, Alexander; Lee, William H.; Román-Zúñiga, Carlos G.; Watson, Alan M.

2018-04-01

We have recently witnessed the first multi-messenger detection of colliding neutron stars through gravitational waves (GWs) and electromagnetic (EM) waves (GW 170817) thanks to the joint efforts of LIGO/Virgo and Space/Ground-based telescopes. In this paper, we report on the RATIR follow-up observation strategies and show the results for the trigger G194575. This trigger is not of astrophysical interest; however, it is of great interest to the robust design of a follow-up engine to explore large sky-error regions. We discuss the development of an image-subtraction pipeline for the six-color, optical/NIR imaging camera RATIR. Considering a two-band (i and r) campaign in the fall of 2015, we find that the requirement of simultaneous detection in both bands leads to a factor ∼10 reduction in false alarm rate, which can be further reduced using additional bands. We also show that the performance of our proposed algorithm is robust to fluctuating observing conditions, maintaining a low false alarm rate with a modest decrease in system efficiency that can be overcome utilizing repeat visits. Expanding our pipeline to search for either optical or NIR detections (three or more bands), considering separately the optical riZ and NIR YJH bands, should result in a false alarm rate ≈1% and an efficiency ≈90%. RATIR’s simultaneous optical/NIR observations are expected to yield about one candidate transient in the vast 100 deg2 LIGO error region for prioritized follow-up with larger aperture telescopes.

Characterization of complementary patterned metallic membranes produced simultaneously by a dual fabrication process

NASA Astrophysics Data System (ADS)

Hao, Qingzhen; Zeng, Yong; Wang, Xiande; Zhao, Yanhui; Wang, Bei; Chiang, I.-Kao; Werner, Douglas H.; Crespi, Vincent; Huang, Tony Jun

2010-11-01

An efficient technique is developed to fabricate optically thin metallic films with subwavelength patterns and their complements simultaneously. By comparing the spectra of the complementary films, we show that Babinet's principle nearly holds for these structures in the optical domain. Rigorous full-wave simulations are employed to verify the experimental observations. It is further demonstrated that a discrete-dipole approximation can qualitatively describe the spectral dependence of the metallic membranes on the geometry of the constituent particles as well as the illuminating polarization.

Guided-wave high-performance spectrometers for the MEOS miniature earth observation satellite

NASA Astrophysics Data System (ADS)

Kruzelecky, Roman V.; Wong, Brian; Zou, Jing; Jamroz, Wes; Sloan, James; Cloutis, Edward

2017-11-01

The MEOS Miniature Earth Observing Satellite is a low-cost mission being developed for the Canadian Space Agency with international collaborations that will innovatively combine remote correlated atmospheric/land-cover measurements with the corresponding atmospheric and ecosystem modelling in near real-time to obtain simultaneous variations in lower tropospheric GHG mixing ratios and the resulting responses of the surface ecosystems. MEOS will provide lower tropospheric CO2, CH4, CO, N2O, H2O and aerosol mixing ratios over natural sources and sinks using two kinds of synergistic observations; a forward limb measurement and a follow-on nadir measurement over the same geographical tangent point. The measurements will be accomplished using separate limb and nadir suites of innovative miniature line-imaging spectrometers and will be spatially coordinated such that the same air mass is observed in both views within a few minutes. The limb data will consist of 16-pixel vertical spectral line imaging to provide 1-km vertical resolution, while the corresponding nadir measurements will view sixteen 5 by 10 km2 ground pixels with a 160-km East-West swath width. To facilitate the mission accommodation on a low-cost microsat with a net payload mass under 22 kg, groundbreaking miniature guided-wave spectrometers with advanced optical filtering and coding technologies will be employed based on MPBC's patented IOSPEC technologies. The data synergy requirements for each view will be innovatively met using two complementary miniature line-imaging spectrometers to provide broad-band measurements from 1200 to 2450 nm at about 1.2 nm/pixel bandwidth using a multislit binary-coded MEMS-IOSPEC and simultaneous high-resolution multiple microchannels at 0.03 nm FWHM using the revolutionary FP-IOSPEC Fabry-Perot guided-wave spectrometer concept. The guided-wave spectrometer integration provides an order of magnitude reduction in the mass and volume relative to traditional bulk-optic spectrometers while also providing significant performance advantages; including an optically immersed master grating for minimal optical aberrations, robust optical alignment using a low-loss dielectric IR waveguide, and simultaneous broad-band spectral acquisition using advanced infrared linear arrays and multiplexing electronics. This paper describes the trial bread-boarding of the groundbreaking new spectrometer concepts and associated technologies towards the MEOS mission requirements.

The wave-field from an array of periodic emitters driven simultaneously by a broadband pulse.

PubMed

Dixon, Steve; Hill, Samuel; Fan, Yichao; Rowlands, George

2013-06-01

The use of phased array methods are commonplace in ultrasonic applications, where controlling the variation of the phase between the narrowband emitters in an array facilitates beam steering and focusing of ultrasonic waves. An approach is presented here whereby emitters of alternating polarity arranged in a one-dimensional array are pulsed simultaneously, and have sufficiently wide, controlled bandwidth to emit a two-dimensional wave. This pulsed approach provides a rapid means of simultaneously covering a region of space with a wave-front, whereby any wave that scatters or reflects off a body to a detector will have a distinct arrival time and frequency. This is a general wave phenomenon with a potential application in radar, sonar, and ultrasound. The key result is that one can obtain a smooth, continuous wave-front emitted from the array, over a large solid angle, whose frequency varies as a function of angle to the array. Analytic and finite element models created to describe this phenomenon have been validated with experimental results using ultrasonic waves in metal samples.

Multi-Species Test of Ion Cyclotron Resonance Heating at High Altitudes

NASA Technical Reports Server (NTRS)

Persoon, A. M.; Peterson, W. K.; Andre, M.; Chang, T.; Gurnett, D. A.; Retterer, J. M.; Crew, G. B.

1997-01-01

Observations of ion distributions and plasma waves obtained by the Dynamics Explorer 1 satellite in the high-altitude, nightside auroral zone are used to study ion energization for three ion species. A number of theoretical models have been proposed to account for the transverse heating of these ion populations. One of these, the ion cyclotron resonance heating (ICRH) mechanism, explains ion conic formation through ion cyclotron resonance with broadband electromagnetic wave turbulence in the vicinity of the characteristic ion cyclotron frequency. The cyclotron resonant heating of the ions by low- frequency electromagnetic waves is an important energy source for the transport of ions from the ionosphere to the magnetosphere. In this paper we test the applicability of the ICRH mechanism to three simultaneously heated and accelerated ion species by modelling the ion conic formation in terms of a resonant wave-particle interaction in which the ions extract energy from the portion of the broadband electromagnetic wave spectrum which includes the ion cyclotron frequency. Using a Monte Carlo technique we evaluate the ion heating produced by the electromagnetic turbulence at low frequencies and find that the wave amplitudes near the ion cyclotron frequencies are sufficient to explain the observed ion energies.

Multi-Species Test of Ion Cyclotron Resonance Heating at High Altitudes

NASA Technical Reports Server (NTRS)

Persoon, A. M.; Peterson, W. K.; Andre, M.; Chang, T.; Gurnett, D. A.; Retterer, J. M.; Crew, G. B.

1997-01-01

Observations of ion distributions and plasma waves obtained by the Dynamics Explorer 1 satellite in the high-altitude, nightside auroral zone are used to study ion energization for three ion species. A number of theoretical models have been proposed to account for the transverse heating of these ion populations. One of these, the ion cyclotron resonance heating (ICRH) mechanism, explains ion conic formation through ion cyclotron resonance with broadband electromagnetic wave turbulence in the vicinity of the characteristic ion cyclotron frequency. The cyclotron resonant heating of the ions by low-frequency electromagnetic waves is an important energy source for the transport of ions from the ionosphere to the magnetosphere. In this paper we test the applicability of the ICRH mechanism to three simultaneously heated and accelerated ion species by modelling the ion conic formation in terms of a resonant wave-particle interaction in which the ions extract energy from the portion of the broadband electromagnetic wave spectrum which includes the ion cyclotron frequency. Using a Monte Carlo technique we evaluate the ion heating produced by the electromagnetic turbulence at low frequencies and find that the wave amplitudes near the ion cyclotron frequencies are sufficient to explain the observed ion energies.

Acoustic multipath arrivals in the horizontal plane due to approaching nonlinear internal waves.

PubMed

Badiey, Mohsen; Katsnelson, Boris G; Lin, Ying-Tsong; Lynch, James F

2011-04-01

Simultaneous measurements of acoustic wave transmissions and a nonlinear internal wave packet approaching an along-shelf acoustic path during the Shallow Water 2006 experiment are reported. The incoming internal wave packet acts as a moving frontal layer reflecting (or refracting) sound in the horizontal plane. Received acoustic signals are filtered into acoustic normal mode arrivals. It is shown that a horizontal multipath interference is produced. This has previously been called a horizontal Lloyd's mirror. The interference between the direct path and the refracted path depends on the mode number and frequency of the acoustic signal. A mechanism for the multipath interference is shown. Preliminary modeling results of this dynamic interaction using vertical modes and horizontal parabolic equation models are in good agreement with the observed data.

Exploring the relative boundaries of the patchy pulsating aurora

NASA Astrophysics Data System (ADS)

Carlisle, E.; Donovan, E.; Jackel, B. J.

2017-12-01

Pulsating aurora is a common auroral feature that occurs most frequently on the nightside, in the equatorward part of the auroral oval. It is caused by pitch angle scattering of electrons due to wave-particle interactions near the equatorial plane. As such, observations of pulsating aurora provide information about the distribution of the plasma waves in the magnetosphere. Anecdotal evidence suggests that pulsating aurora occur equatorward of the proton aurora, and hence in the largely dipolar region at or inside the inner edge of the plasma sheet. Here we present results of a statistical survey of photometer observations of proton aurora and simultaneous all-sky imager observations of electron aurora. Our objective is to provide a definitive statement regarding the location of pulsating aurora relative to the proton aurora.

Reduction and analysis of data from the plasma wave instruments on the IMP-6 and IMP-8 spacecraft

NASA Technical Reports Server (NTRS)

Gurnett, D. A.; Anderson, R. R.

1983-01-01

The primary data reduction effort during the reporting period was to process summary plots of the IMP 8 plasma wave data and to submit these data to the National Space Science Data Center. Features of the electrostatic noise are compared with simultaneous observations of the magnetic field, plasma and energetic electrons. Spectral characteristics of the noise and the results of this comparison both suggest that in its high frequency part at least the noise does not belong to normal modes of plasma waves but represents either quasi-thermal noise in the non-Maxwellian plasma or artificial noise generated by spacecraft interaction with the medium.

First simultaneous observations of local moon aurora and the moon footprints in Jupiter's polar aurora

NASA Astrophysics Data System (ADS)

Hue, V.; Roth, L.; Grodent, D. C.; Gladstone, R.; Saur, J.; Bonfond, B.

2017-12-01

The interaction of the co-rotating magnetospheric plasma with Jupiter's Galilean moons generates local perturbations and auroral emissions in the moons' tenuous atmospheres. Alfvén waves are launched by this local interaction and travel along Jupiter's field lines triggering various effects that finally lead to the auroral moon footprints far away in Jupiter's polar regions. Within the large Hubble Space Telescope aurora program in support of the NASA Juno mission (HST GO-14634, PI D. Grodent), HST observed the local aurora at the moons Io and Ganymede on three occasions in 2017 while the Juno Ultraviolet Spectrograph simultaneously observed Jupiter's aurora and the moon footprints. In this presentation, we will provide first results from the first-ever simultaneous moon and footprint observations for the case of Io. We compare the temporal variability of the local moon aurora and the Io footprint, addressing the question how much of the footprint variability originates from changes at the moon source and how much originates from processes in the regions that lie in between the moon and Jupiter's poles.

A New Method to Comprehensively Diagnose Shock Waves in the Solar Atmosphere Based on Simultaneous Spectroscopic and Imaging Observations

NASA Astrophysics Data System (ADS)

Ruan, Wenzhi; Yan, Limei; He, Jiansen; Zhang, Lei; Wang, Linghua; Wei, Yong

2018-06-01

Shock waves are believed to play an important role in plasma heating. The shock-like temporal jumps in radiation intensity and Doppler shift have been identified in the solar atmosphere. However, a quantitative diagnosis of the shocks in the solar atmosphere is still lacking, seriously hindering the understanding of shock dissipative heating of the solar atmosphere. Here, we propose a new method to realize the goal of the shock quantitative diagnosis, based on Rankine–Hugoniot equations and taking the advantages of simultaneous imaging and spectroscopic observations from, e.g., IRIS (Interface Region Imaging Spectrograph). Because of this method, the key parameters of shock candidates can be derived, such as the bulk velocity and temperature of the plasma in the upstream and downstream, the propagation speed and direction. The method is applied to the shock candidates observed by IRIS, and the overall characteristics of the shocks are revealed quantitatively for the first time. This method is also tested with the help of forward modeling, i.e., virtual observations of simulated shocks. The parameters obtained from the method are consistent with the parameters of the shock formed in the model and are independent of the viewing direction. Therefore, the method we proposed here is applicable to the quantitative and comprehensive diagnosis of the observed shocks in the solar atmosphere.

Chemical detection demonstrated using an evanescent wave graphene optical sensor

DOE Office of Scientific and Technical Information (OSTI.GOV)

Maliakal, Ashok; Reith, Leslie; Cabot, Steve

Graphene devices have been constructed on silicon mirrors, and the graphene is optically probed through an evanescent wave interaction in an attenuated total reflectance configuration using an infrared spectrometer. The graphene is electrically biased in order to tune its optical properties. Exposure of the device to the chemicals iodine and ammonia causes observable and reversible changes to graphene's optical absorption spectra in the mid to near infrared range which can be utilized for the purpose of sensing. Electrical current measurements through the graphene are made simultaneously with optical measurements allowing for simultaneous sensing using two separate detection modalities. Our currentmore » results reveal sub-ppm detection limits for iodine and approximately 100 ppm detection limits for ammonia. We have also demonstrated that this approach will work at 1.55 μm, which opens up the possibility for graphene optical sensors that leverage commercial telecom light sources.« less

Relationship between Alfvén Wave and Quasi-Static Acceleration in Earth's Auroral Zone

NASA Astrophysics Data System (ADS)

Mottez, Fabrice

2016-02-01

There are two main categories of acceleration processes in the Earth's auroral zone: those based on quasi-static structures, and those based on Alfvén wave (AW). AWs play a nonnegligible role in the global energy budget of the plasma surrounding the Earth because they participate in auroral acceleration, and because auroral acceleration conveys a large portion of the energy flux across the magnetosphere. Acceleration events by double layers (DLs) and by AW have mostly been investigated separately, but many studies cited in this chapter show that they are not independent: these processes can occur simultaneously, and one process can be the cause of the other. The quasi-simultaneous occurrences of acceleration by AW and by quasi-static structures have been observed predominantly at the polar cap boundary of auroral arc systems, where often new bright arcs develop or intensify.

Simultaneous Rayleigh lidar and airglow measurements of middle atmospheric waves over low latitudes in India

NASA Astrophysics Data System (ADS)

Taori, A.; Kamalakar, V.; Raghunath, K.; Rao, S. V. B.; Russell, J. M.

2012-04-01

We utilize simultaneous Rayleigh lidar and mesospheric OH and O2 airglow measurements to identify the dominant and propagating waves within 40-95 km altitude regions over a low latitude station Gadanki (13.8° N, 79.2 °E). It is found that waves with 0.4-0.6 h periodicity are common throughout the altitude range of 40-95 km with significant amplitudes. The ground based temperature measurements with lidar and airglow monitoring are found to compare well with SABER data. With simultaneous Rayleigh lidar (temperature) and mesospheric airglow (emission intensity and temperature) measurements, we estimate the amplitude growth and Krassovsky parameters to characterize the propagation and dissipation of these upward propagating waves.

Signature of 3-4 day planetary waves in the equatorial ionospheric F layer height and medium frequency radar winds over Tirunelveli (8.7oN)

NASA Astrophysics Data System (ADS)

Sundararaman, Sathishkumar

Signature of 3-4 day planetary waves in the equatorial ionospheric F layer height and medium frequency radar winds over Tirunelveli (8.7oN) S. Sathishkumar1, R. Dhanya1, K. Emperumal1, D. Tiwari2, S. Gurubaran1 and A. Bhattacharyya2 1. Equatorial Geophysical Research Laboratory, Indian Institute of Geomagnetism, Tirunelveli, India 2. Indian Institute of Geomagnetism, Navi Mumbai, India Email: sathishmaths@gmail.com Abstract The equatorial atmosphere-ionosphere system has been studied theoretically and observationally in the past. In the equatorial atmosphere, oscillations with periods of 3-4 days are often observed in the medium frequency (MF) radar over Tirunelveli (8.7oN, 77.8oE, 1.34oN geomag. lat.). Earlier observations show the clear evidence that these waves can propagate from the stratosphere to ionosphere. A digital ionosonde has been providing useful information on several ionospheric parameters from the same site. Simultaneous observations of mesospheric winds using medium frequency radar and F-layer height (h'F) from ionosonde reveal that the 3-4 day wave was evident in both the component during the 01 June 2007 and 31 July 2007. The 3-4 day wave could have an important role in the day to day variability of the equatorial ionosphere evening uplift. Results from an extensive analysis that is being carried out in the direction of 3-4 day wave present in the ionosphere will be presented.

Simultaneous versus Sequential Accelerated Corneal Collagen Cross-Linking and Wave Front Guided PRK for Treatment of Keratoconus: Objective and Subjective Evaluation

PubMed Central

El Emam, Dalia Sabry; Farag, Rania Kamel; Abouelkheir, Hossam Youssef

2016-01-01

Aim. To compare objective and subjective outcome after simultaneous wave front guided (WFG) PRK and accelerated corneal cross-linking (CXL) in patients with progressive keratoconus versus sequential WFG PRK 6 months after CXL. Methods. 62 eyes with progressive keratoconus were divided into two groups; the first including 30 eyes underwent simultaneous WFG PRK with accelerated CXL. The second including 32 eyes underwent subsequent WFG PRK performed 6 months later after accelerated CXL. Visual, refractive, topographic, and aberrometric data were determined preoperatively and during 1-year follow-up period and the results compared in between the 2 studied groups. Results. All evaluated visual, refractive, and aberrometric parameters demonstrated highly significant improvement in both studied groups (all P < 0.001). A significant improvement was observed in keratometric and Q values. The improvement in all parameters was stable till the end of follow-up. Likewise, no significant difference was determined in between the 2 groups in any of recorded parameters. Subjective data revealed similarly significant improvement in both groups. Conclusions. WFG PRK and accelerated CXL is an effective and safe option to improve the vision in mild to moderate keratoconus. In one-year follow-up, there is no statistically significant difference between the simultaneous and sequential procedure. PMID:28127465

Simultaneous versus Sequential Accelerated Corneal Collagen Cross-Linking and Wave Front Guided PRK for Treatment of Keratoconus: Objective and Subjective Evaluation.

PubMed

Abou Samra, Waleed Ali; El Emam, Dalia Sabry; Farag, Rania Kamel; Abouelkheir, Hossam Youssef

2016-01-01

Aim . To compare objective and subjective outcome after simultaneous wave front guided (WFG) PRK and accelerated corneal cross-linking (CXL) in patients with progressive keratoconus versus sequential WFG PRK 6 months after CXL. Methods . 62 eyes with progressive keratoconus were divided into two groups; the first including 30 eyes underwent simultaneous WFG PRK with accelerated CXL. The second including 32 eyes underwent subsequent WFG PRK performed 6 months later after accelerated CXL. Visual, refractive, topographic, and aberrometric data were determined preoperatively and during 1-year follow-up period and the results compared in between the 2 studied groups. Results . All evaluated visual, refractive, and aberrometric parameters demonstrated highly significant improvement in both studied groups (all P < 0.001). A significant improvement was observed in keratometric and Q values. The improvement in all parameters was stable till the end of follow-up. Likewise, no significant difference was determined in between the 2 groups in any of recorded parameters. Subjective data revealed similarly significant improvement in both groups. Conclusions . WFG PRK and accelerated CXL is an effective and safe option to improve the vision in mild to moderate keratoconus. In one-year follow-up, there is no statistically significant difference between the simultaneous and sequential procedure.

REFLECTION OF PROPAGATING SLOW MAGNETO-ACOUSTIC WAVES IN HOT CORONAL LOOPS: MULTI-INSTRUMENT OBSERVATIONS AND NUMERICAL MODELING

DOE Office of Scientific and Technical Information (OSTI.GOV)

Mandal, Sudip; Banerjee, Dipankar; Pant, Vaibhav

Slow MHD waves are important tools for understanding coronal structures and dynamics. In this paper, we report a number of observations from the X-Ray Telescope (XRT) on board HINODE and Solar Dynamic Observatory /Atmospheric Imaging Assembly (AIA) of reflecting longitudinal waves in hot coronal loops. To our knowledge, this is the first report of this kind as seen from the XRT and simultaneously with the AIA. The wave appears after a micro-flare occurs at one of the footpoints. We estimate the density and temperature of the loop plasma by performing differential emission measure (DEM) analysis on the AIA image sequence.more » The estimated speed of propagation is comparable to or lower than the local sound speed, suggesting it to be a propagating slow wave. The intensity perturbation amplitude, in every case, falls very rapidly as the perturbation moves along the loop and eventually vanishes after one or more reflections. To check the consistency of such reflection signatures with the obtained loop parameters, we perform a 2.5D MHD simulation, which uses the parameters obtained from our observation as inputs, and perform forward modeling to synthesize AIA 94 Å images. Analyzing the synthesized images, we obtain the same properties of the observables as for the real observation. From the analysis we conclude that a footpoint heating can generate a slow wave which then reflects back and forth in the coronal loop before fading. Our analysis of the simulated data shows that the main agent for this damping is anisotropic thermal conduction.« less

Optical Emissions Enhanced by O and X Mode Ionosphere HF Pumping: Similarities and Differences

NASA Astrophysics Data System (ADS)

Sergienko, T.; Brandstrom, U.; Gustavsson, B.; Blagoveshchenskaya, N. F.

2013-12-01

Strong enhancement of the optical emissions with excitation thresholds from 1.96 eV up to 18.75 eV have been observed during experiments of ionosphere modification by high power HF radio waves since the early 1970s. Up to now all these emissions were observed only during the interaction of the O-mode HF radio wave with the ionospheric plasma. On 19 October 2012, during an EISCAT heating experiment, strong optical emissions were observed by ALIS, in first time, for X-mode ionosphere pumping. While for O-mode heating the optical emission enhancements can be explained by the ionospheric electron heating and acceleration due to the nonlinear interaction of the powerful radio wave with ionosphere, the mechanism responsible for the emission enhancements during the X-mode heating is not known. In the experiment optical emissions have been measured in three different wave-lengths simultaneously from four ALIS stations. The emission intensity ratios as well as the characteristics of the spatial distribution of the enhanced optical emissions provide important information on the possible mechanisms of the radio wave - ionosphere interaction. In this report we present the results of comparison of the characteristics of the optical emissions caused by X-mode heating with the characteristics of the emissions enhanced by O-mode measured during same experiment.

Inverse procedure for simultaneous evaluation of viscosity and density of Newtonian liquids from dispersion curves of Love waves

NASA Astrophysics Data System (ADS)

Kiełczyński, P.; Szalewski, M.; Balcerzak, A.

2014-07-01

Simultaneous determination of the viscosity and density of liquids is of great importance in the monitoring of technological processes in the chemical, petroleum, and pharmaceutical industry, as well as in geophysics. In this paper, the authors present the application of Love waves for simultaneous inverse determination of the viscosity and density of liquids. The inversion procedure is based on measurements of the dispersion curves of phase velocity and attenuation of ultrasonic Love waves. The direct problem of the Love wave propagation in a layered waveguide covered by a viscous liquid was formulated and solved. Love waves propagate in an elastic layered waveguide covered on its surface with a viscous (Newtonian) liquid. The inverse problem is formulated as an optimization problem with appropriately constructed objective function that depends on the material properties of an elastic waveguide of the Love wave, material parameters of a liquid (i.e., viscosity and density), and the experimental data. The results of numerical calculations show that Love waves can be efficiently applied to determine simultaneously the physical properties of liquids (i.e., viscosity and density). Sensors based on this method can be very attractive for industrial applications to monitor on-line the parameters (density and viscosity) of process liquid during the course of technological processes, e.g., in polymer industry.

Gravity waves in Titan's atmosphere

NASA Technical Reports Server (NTRS)

Friedson, A. James

1994-01-01

Scintillations (high frequency variations) observed in the radio signal during the occultation of Voyager 1 by Titan (Hinson and Tyler, 1983) provide information concerning neutral atmospheric density fluctuations on scales on hundreds of meters to a few kilometers. Those seen at altitudes higher than 25 km above the surface were interpreted by Hinson and Tyler as being caused by linear, freely propagating (energy-conserving) gravity waves, but this interpretation was found to be inconsistent with the scintillation data below the 25-km altitude level. Here an attempt is made to interpret the entire scintillation profile between the surface and the 90-km altitude level in terms of gravity waves generated at the surface. Numerical calculations of the density fluctuations caused by two-dimensional, nonhydrostatic, finite-amplitude gravity waves propagating vertically through Titan's atmosphere are performed to produce synthetic scintillation profiles for comparison with the observations. The numerical model accurately treats the effects of wave transience, nonlinearity, and breakdown due to convective instability in the overturned part of the wave. The high-altitude scintillation data were accurately recovered with a freely propagating wave solution, confirming the analytic model of Hinson and Tyler. It is found that the low-altitude scintillation data can be fit by a model where a component of the gravity waves becomes convectively unstable and breaks near the 15 km level. The large-scale structure of the observed scintillation profile in the entire altitude range between 5 and 85 km can be simulated by a model where the freely propagating and breaking waves are forced at the surface simultaneously. Further analysis of the Voyager 1 Titan low-altitude scintillation data, using inversion theory appropriate for strong scattering, could potentially remove some of the ambiguities remaining in this analysis and allow a better determination of the strength and source of the waves.

Coronal "wave": Magnetic Footprint Of A Cme?

NASA Astrophysics Data System (ADS)

Attrill, Gemma; Harra, L. K.; van Driel-Gesztelyi, L.; Demoulin, P.; Wuelser, J.

2007-05-01

We propose a new mechanism for the generation of "EUV coronal waves". This work is based on new analysis of data from SOHO/EIT, SOHO/MDI & STEREO/EUVI. Although first observed in 1997, the interpretation of coronal waves as flare-induced or CME-driven remains a debated topic. We investigate the properties of two "classical" SOHO/EIT coronal waves in detail. The source regions of the associated CMEs possess opposite helicities & the coronal waves display rotations in opposite senses. We observe deep dimmings near the flare site & also widespread diffuse dimming, accompanying the expansion of the EIT wave. We report a new property of these EIT waves, namely, that they display dual brightenings: persistent ones at the outermost edge of the core dimming regions & simultaneously diffuse brightenings constituting the leading edge of the coronal wave, surrounding the expanding diffuse dimmings. We show that such behaviour is consistent with a diffuse EIT wave being the magnetic footprint of a CME. We propose a new mechanism where driven magnetic reconnections between the skirt of the expanding CME & quiet-Sun magnetic loops generate the observed bright diffuse front. The dual brightenings & widespread diffuse dimming are identified as innate characteristics of this process. In addition we present some of the first analysis of a STEREO/EUVI limb coronal wave. We show how the evolution of the diffuse bright front & dimmings can be understood in terms of the model described above. We show that an apparently stationary part of the bright front can be understood in terms of magnetic interchange reconnections between the expanding CME & the "open" magnetic field of a low-latitude coronal hole. We use both the SOHO/EIT & STEREO/EUVI events to demonstrate that through successive reconnections, this new model provides a natural mechanism via which CMEs can become large-scale in the lower corona.

Cassini RSS occultation observations of density waves in Saturn's rings

NASA Astrophysics Data System (ADS)

McGhee, C. A.; French, R. G.; Marouf, E. A.; Rappaport, N. J.; Schinder, P. J.; Anabtawi, A.; Asmar, S.; Barbinis, E.; Fleischman, D.; Goltz, G.; Johnston, D.; Rochblatt, D.

2005-08-01

On May 3, 2005, the first of a series of eight nearly diametric occultations by Saturn's rings and atmosphere took place, observed by the Cassini Radio Science (RSS) team. Simultaneous high SNR measurements at the Deep Space Network (DSN) at S, X, and Ka bands (λ = 13, 3.6, and 0.9 cm) have provided a remarkably detailed look at the radial structure and particle scattering behavior of the rings. By virtue of the relatively large ring opening angle (B=-23.6o), the slant path optical depth of the rings was much lower than during the Voyager epoch (B=5.9o), making it possible to detect many density waves and other ring features in the Cassini RSS data that were lost in the noise in the Voyager RSS experiment. Ultimately, diffraction correction of the ring optical depth profiles will yield radial resolution as small as tens of meters for the highest SNR data. At Ka band, the Fresnel scale is only 1--1.5 km, and thus even without diffraction correction, the ring profiles show a stunning array of density waves. The A ring is replete with dozens of Pandora and Prometheus inner Lindblad resonance features, and the Janus 2:1 density wave in the B ring is revealed with exceptional clarity for the first time at radio wavelengths. Weaker waves are abundant as well, and multiple occultation chords sample a variety of wave phases. We estimate the surface mass density of the rings from linear density wave models of the weaker waves. For stronger waves, non-linear models are required, providing more accurate estimates of the wave dispersion relation, the ring surface mass density, and the angular momentum exchange between the rings and satellite. We thank the DSN staff for their superb support of these complex observations.

STEREO Observations of Waves in the Ramp Regions of Interplanetary Shocks

NASA Astrophysics Data System (ADS)

Cohen, Z.; Breneman, A. W.; Cattell, C. A.; Davis, L.; Grul, P.; Kersten, K.; Wilson, L. B., III

2017-12-01

Determining the role of plasma waves in providing energy dissipation at shock waves is of long-standing interest. Interplanetary (IP) shocks serve as a large database of low Mach number shocks. We examine electric field waveforms captured by the Time Domain Sampler (TDS) on the STEREO spacecraft during the ramps of IP shocks, with emphasis on captures lasting 2.1 seconds. Previous work has used captures of shorter duration (66 and 131 ms on STEREO, and 17 ms on WIND), which allowed for observation of waves with maximum (minimum) frequencies of 125 kHz (15 Hz), 62.5 kHz (8 Hz), and 60 kHz (59 Hz), respectively. The maximum frequencies are comparable to 2-8 times the plasma frequency in the solar wind, enabling observation of Langmuir waves, ion acoustic, and some whistler-mode waves. The 2 second captures resolve lower frequencies ( few Hz), which allows us to analyze packet structure of the whistler-mode waves and some ion acoustic waves. The longer capture time also improves the resolvability of simultaneous wave modes and of waves with frequencies on the order of 10s of Hz. Langmuir waves, however, cannot be identified at this sampling rate, since the plasma frequency is usually higher than 3.9 kHz. IP shocks are identified from multiple databases (Helsinki heliospheric shock database at http://ipshocks.fi, and the STEREO level 3 shock database at ftp://stereoftp.nascom.nasa.gov/pub/ins_data/impact/level3/). Our analysis focuses on TDS captures in shock ramp regions, with ramp durations determined from magnetic field data taken at 8 Hz. Software is used to identify multiple wave modes in any given capture and classify waves as Langmuir, ion acoustic, whistler, lower hybrid, electron cyclotron drift instability, or electrostatic solitary waves. Relevant frequencies are determined from density and magnetic field data collected in situ. Preliminary results suggest that large amplitude (≥ 5 mV/m) ion acoustic waves are most prevalent in the ramp, in agreement with Wilson, et al. Other modes are also observed. Statistical results will be presented and compared with previous studies and theoretical predictions.

RADIATION WAVE DETECTION

DOEpatents

Wouters, L.F.

1960-08-30

Radiation waves can be detected by simultaneously measuring radiation- wave intensities at a plurality of space-distributed points and producing therefrom a plot of the wave intensity as a function of time. To this end. a detector system is provided which includes a plurality of nuclear radiation intensity detectors spaced at equal radial increments of distance from a source of nuclear radiation. Means are provided to simultaneously sensitize the detectors at the instant a wave of radiation traverses their positions. the detectors producing electrical pulses indicative of wave intensity. The system further includes means for delaying the pulses from the detectors by amounts proportional to the distance of the detectors from the source to provide an indication of radiation-wave intensity as a function of time.

Wind and wave dataset for Matara, Sri Lanka

NASA Astrophysics Data System (ADS)

Luo, Yao; Wang, Dongxiao; Priyadarshana Gamage, Tilak; Zhou, Fenghua; Madusanka Widanage, Charith; Liu, Taiwei

2018-01-01

We present a continuous in situ hydro-meteorology observational dataset from a set of instruments first deployed in December 2012 in the south of Sri Lanka, facing toward the north Indian Ocean. In these waters, simultaneous records of wind and wave data are sparse due to difficulties in deploying measurement instruments, although the area hosts one of the busiest shipping lanes in the world. This study describes the survey, deployment, and measurements of wind and waves, with the aim of offering future users of the dataset the most comprehensive and as much information as possible. This dataset advances our understanding of the nearshore hydrodynamic processes and wave climate, including sea waves and swells, in the north Indian Ocean. Moreover, it is a valuable resource for ocean model parameterization and validation. The archived dataset (Table 1) is examined in detail, including wave data at two locations with water depths of 20 and 10 m comprising synchronous time series of wind, ocean astronomical tide, air pressure, etc. In addition, we use these wave observations to evaluate the ERA-Interim reanalysis product. Based on Buoy 2 data, the swells are the main component of waves year-round, although monsoons can markedly alter the proportion between swell and wind sea. The dataset (Luo et al., 2017) is publicly available from Science Data Bank (https://doi.org/10.11922/sciencedb.447).

Myocardial effects of local shock wave therapy in a Langendorff model.

PubMed

Becker, M; Goetzenich, A; Roehl, A B; Huebel, C; de la Fuente, M; Dietz-Laursonn, K; Radermacher, K; Rossaint, R; Hein, M

2014-01-01

Applying shock waves to the heart has been reported to stimulate the heart and alter cardiac function. We hypothesized that shock waves could be used to diagnose regional viability. We used a Langendorff model to investigate the acute effects of shock waves at different energy levels and times related to systole, cycle duration and myocardial function. We found only a small time window to use shock waves. Myocardial fibrillation or extrasystolic beats will occur if the shock wave is placed more than 15 ms before or 30 ms after the onset of systole. Increased contractility and augmented relaxation were observed after the second beat, and these effects decreased after prolonging the shock wave delay from 15 ms before to 30 ms after the onset of systole. An energy dependency could be found only after short delays (-15 ms). The involved processes might include post-extrasystolic potentiation and simultaneous pacing. In summary, we found that low-energy shock waves can be a useful tool to stimulate the myocardium at a distance and influence function. Copyright © 2013 Elsevier B.V. All rights reserved.

'Two go together': Near-simultaneous moment release of two asperities during the 2016 Mw 6.6 Muji, China earthquake

NASA Astrophysics Data System (ADS)

Bie, Lidong; Hicks, Stephen; Garth, Thomas; Gonzalez, Pablo; Rietbrock, Andreas

2018-06-01

On 25 November 2016, a Mw 6.6 earthquake ruptured the Muji fault in western Xinjiang, China. We investigate the earthquake rupture independently using geodetic observations from Interferometric Synthetic Aperture Radar (InSAR) and regional seismic recordings. To constrain the fault geometry and slip distribution, we test different combinations of fault dip and slip direction to reproduce InSAR observations. Both InSAR observations and optimal distributed slip model suggest buried rupture of two asperities separated by a gap of greater than 5 km. Additional seismic gaps exist at the end of both asperities that failed in the 2016 earthquake. To reveal the dynamic history of asperity failure, we inverted regional seismic waveforms for multiple centroid moment tensors and construct a moment rate function. The results show a small centroid time gap of 2.6 s between the two sub-events. Considering the >5 km gap between the two asperities and short time interval, we propose that the two asperities failed near-simultaneously, rather than in a cascading rupture propagation style. The second sub-event locates ∼39 km to the east of the epicenter and the centroid time is at 10.7 s. It leads to an estimate of average velocity of 3.7 km/s as an upper bound, consistent with upper crust shear wave velocity in this region. We interpret that the rupture front is propagating at sub-shear wave velocities, but that the second sub-event has a reduced or asymmetric rupture time, leading to the apparent near-simultaneous moment release of the two asperities.

Multichannel analysis of surface wave method with the autojuggie

USGS Publications Warehouse

Tian, G.; Steeples, D.W.; Xia, J.; Miller, R.D.; Spikes, K.T.; Ralston, M.D.

2003-01-01

The shear (S)-wave velocity of near-surface materials and its effect on seismic-wave propagation are of fundamental interest in many engineering, environmental, and groundwater studies. The multichannel analysis of surface wave (MASW) method provides a robust, efficient, and accurate tool to observe near-surface S-wave velocity. A recently developed device used to place large numbers of closely spaced geophones simultaneously and automatically (the 'autojuggie') is shown here to be applicable to the collection of MASW data. In order to demonstrate the use of the autojuggie in the MASW method, we compared high-frequency surface-wave data acquired from conventionally planted geophones (control line) to data collected in parallel with the automatically planted geophones attached to steel bars (test line). The results demonstrate that the autojuggie can be applied in the MASW method. Implementation of the autojuggie in very shallow MASW surveys could drastically reduce the time required and costs incurred in such surveys. ?? 2003 Elsevier Science Ltd. All rights reserved.

Lightning-generated whistler waves observed by probes on the Communication/Navigation Outage Forecast System satellite at low latitudes

NASA Astrophysics Data System (ADS)

Holzworth, R. H.; McCarthy, M. P.; Pfaff, R. F.; Jacobson, A. R.; Willcockson, W. L.; Rowland, D. E.

2011-06-01

Direct evidence is presented for a causal relationship between lightning and strong electric field transients inside equatorial ionospheric density depletions. In fact, these whistler mode plasma waves may be the dominant electric field signal within such depletions. Optical lightning data from the Communication/Navigation Outage Forecast System (C/NOFS) satellite and global lightning location information from the World Wide Lightning Location Network are presented as independent verification that these electric field transients are caused by lightning. The electric field instrument on C/NOFS routinely measures lightning-related electric field wave packets or sferics, associated with simultaneous measurements of optical flashes at all altitudes encountered by the satellite (401-867 km). Lightning-generated whistler waves have abundant access to the topside ionosphere, even close to the magnetic equator.

Lightning-Generated Whistler Waves Observed by Probes On The Communication/Navigation Outage Forecast System Satellite at Low Latitudes

NASA Technical Reports Server (NTRS)

Holzworth, R. H.; McCarthy, M. P.; Pfaff, R. F.; Jacobson, A. R.; Willcockson, W. L.; Rowland, D. E.

2011-01-01

Direct evidence is presented for a causal relationship between lightning and strong electric field transients inside equatorial ionospheric density depletions. In fact, these whistler mode plasma waves may be the dominant electric field signal within such depletions. Optical lightning data from the Communication/Navigation Outage Forecast System (C/NOFS) satellite and global lightning location information from the World Wide Lightning Location Network are presented as independent verification that these electric field transients are caused by lightning. The electric field instrument on C/NOFS routinely measures lightning ]related electric field wave packets or sferics, associated with simultaneous measurements of optical flashes at all altitudes encountered by the satellite (401.867 km). Lightning ]generated whistler waves have abundant access to the topside ionosphere, even close to the magnetic equator.

PROPAGATING DISTURBANCES IN THE SOLAR CORONA AND SPICULAR CONNECTION

DOE Office of Scientific and Technical Information (OSTI.GOV)

Samanta, Tanmoy; Pant, Vaibhav; Banerjee, Dipankar, E-mail: tsamanta@iiap.res.in

Spicules are small, hairy-like structures seen at the solar limb, mainly at chromospheric and transition region lines. They generally live for 3–10 minutes. We study these spicules in a south polar region of the Sun with coordinated observations using the Interface Region Imaging Spectrograph (IRIS) and the Atmospheric Imaging Assembly (AIA) instruments on board the Solar Dynamics Observatory. Propagating disturbances (PDs) are observed everywhere in the polar off-limb regions of the Sun at coronal heights. From these simultaneous observations, we show that the spicules and the PDs may have originated through a common process. From spacetime maps, we find thatmore » the start of the trajectory of PDs is almost cotemporal with the time of the rise of the spicular envelope as seen by IRIS slit-jaw images at 2796 and 1400 Å. During the return of spicular material, brightenings are seen in AIA 171 and 193 Å images. The quasi-periodic nature of the spicular activity, as revealed by the IRIS spectral image sequences, and its relation to coronal PDs, as recorded by the coronal AIA channels, suggest that they share a common origin. We propose that reconnection-like processes generate the spicules and waves simultaneously. The waves escape while the cool spicular material falls back.« less

Propagating Disturbances in the Solar Corona and Spicular Connection

NASA Astrophysics Data System (ADS)

Samanta, Tanmoy; Pant, Vaibhav; Banerjee, Dipankar

2015-12-01

Spicules are small, hairy-like structures seen at the solar limb, mainly at chromospheric and transition region lines. They generally live for 3-10 minutes. We study these spicules in a south polar region of the Sun with coordinated observations using the Interface Region Imaging Spectrograph (IRIS) and the Atmospheric Imaging Assembly (AIA) instruments on board the Solar Dynamics Observatory. Propagating disturbances (PDs) are observed everywhere in the polar off-limb regions of the Sun at coronal heights. From these simultaneous observations, we show that the spicules and the PDs may have originated through a common process. From spacetime maps, we find that the start of the trajectory of PDs is almost cotemporal with the time of the rise of the spicular envelope as seen by IRIS slit-jaw images at 2796 and 1400 Å. During the return of spicular material, brightenings are seen in AIA 171 and 193 Å images. The quasi-periodic nature of the spicular activity, as revealed by the IRIS spectral image sequences, and its relation to coronal PDs, as recorded by the coronal AIA channels, suggest that they share a common origin. We propose that reconnection-like processes generate the spicules and waves simultaneously. The waves escape while the cool spicular material falls back.

Evidence of spectrally broad Gravity Wave packet propagation and dispersion in the mesopause region observed by the Na lidar and Mesospheric Temperature Mapper above Logan, Utah

NASA Astrophysics Data System (ADS)

Yuan, T.; Heale, C. J.; Snively, J. B.

2016-12-01

Utilizing observations from the Na lidar at Utah State University and the nearby Mesospheric Temperature Mapper (MTM) at Bear Lake Observatory (BLO) [41.9°N, 111.4°W], we investigate a unique case of vertical dispersion for a spectrally broad gravity wave packet in the mesopause region over Logan, Utah (41.7°N, 111.8°W) that occurred on September 2nd, 2011, to study the waves' evolution as a packet propagates upward. The lidar observed temperature perturbation was dominated by close to a 1-hour modulation at 100 km during the early hours, but gradually evolved into a 1.5-hour modulation during the second half of the night. The vertical wavelength also decreased simultaneously, while the vertical group and phase velocities of the packet apparently slowed, as it was approaching a critical level during the second half of the night. A two-dimensional numerical model is utilized to simulate the observed GW processes, finding that the location of the lidar relative to the source can strongly influence which portion of the spectrum can be observed at a particular location relative to a source.

Seismic structure of the European upper mantle based on adjoint tomography

NASA Astrophysics Data System (ADS)

Zhu, Hejun; Bozdağ, Ebru; Tromp, Jeroen

2015-04-01

We use adjoint tomography to iteratively determine seismic models of the crust and upper mantle beneath the European continent and the North Atlantic Ocean. Three-component seismograms from 190 earthquakes recorded by 745 seismographic stations are employed in the inversion. Crustal model EPcrust combined with mantle model S362ANI comprise the 3-D starting model, EU00. Before the structural inversion, earthquake source parameters, for example, centroid moment tensors and locations, are reinverted based on global 3-D Green's functions and Fréchet derivatives. This study consists of three stages. In stage one, frequency-dependent phase differences between observed and simulated seismograms are used to constrain radially anisotropic wave speed variations. In stage two, frequency-dependent phase and amplitude measurements are combined to simultaneously constrain elastic wave speeds and anelastic attenuation. In these two stages, long-period surface waves and short-period body waves are combined to simultaneously constrain shallow and deep structures. In stage three, frequency-dependent phase and amplitude anomalies of three-component surface waves are used to simultaneously constrain radial and azimuthal anisotropy. After this three-stage inversion, we obtain a new seismic model of the European curst and upper mantle, named EU60. Improvements in misfits and histograms in both phase and amplitude help us to validate this three-stage inversion strategy. Long-wavelength elastic wave speed variations in model EU60 compare favourably with previous body- and surface wave tomographic models. Some hitherto unidentified features, such as the Adria microplate, naturally emerge from the smooth starting model. Subducting slabs, slab detachments, ancient suture zones, continental rifts and backarc basins are well resolved in model EU60. We find an anticorrelation between shear wave speed and anelastic attenuation at depths < 100 km. At greater depths, this anticorrelation becomes relatively weak, in agreement with previous global attenuation studies. Furthermore, enhanced attenuation is observed within the mantle transition zone beneath the North Atlantic Ocean. Consistent with typical radial anisotropy in 1-D reference models, the European continent is dominated by features with a radially anisotropic parameter ξ > 1, indicating predominantly horizontal flow within the upper mantle. In addition, subduction zones, such as the Apennines and Hellenic arcs, are characterized by vertical flow with ξ < 1 at depths greater than 150 km. We find that the direction of the fast anisotropic axis is closely tied to the tectonic evolution of the region. Averaged radial peak-to-peak anisotropic strength profiles identify distinct brittle-ductile deformation in lithospheric strength beneath oceans and continents. Finally, we use the `point-spread function' to assess image quality and analyse trade-offs between different model parameters.

Microtremors study applying the SPAC method in Colima state, Mexico.

NASA Astrophysics Data System (ADS)

Vázquez Rosas, R.; Aguirre González, J.; Mijares Arellano, H.

2007-05-01

One of the main parts of seismic risk studies is to determine the site effect. This can be estimated by means of the microtremors measurements. From the H/V spectral ratio (Nakamura, 1989), the predominant period of the site can be estimated. Although the predominant period by itself can not represent the site effect in a wide range of frequencies and doesn't provide information of the stratigraphy. The SPAC method (Spatial Auto-Correlation Method, Aki 1957), on the other hand, is useful to estimate the stratigraphy of the site. It is based on the simultaneous recording of microtremors in several stations deployed in an instrumental array. Through the spatial autocorrelation coefficient computation, the Rayleigh wave dispersion curve can be cleared. Finally the stratigraphy model (thickness, S and P wave velocity, and density of each layer) is estimated by fitting the theoretical dispersion curve with the observed one. The theoretical dispersion curve is initially computed using a proposed model. That model is modified several times until the theoretical curve fit the observations. This method requires of a minimum of three stations where the microtremors are observed simultaneously in all the stations. We applied the SPAC method to six sites in Colima state, Mexico. Those sites are Santa Barbara, Cerro de Ortega, Tecoman, Manzanillo and two in Colima city. Totally 16 arrays were carried out using equilateral triangles with different apertures with a minimum of 5 m and a maximum of 60 m. For recording microtremors we used short period (5 seconds) velocity type vertical sensors connected to a K2 (Kinemetrics) acquisition system. We could estimate the velocities of the most superficial layers reaching different depths in each site. For Santa Bárbara site the exploration depth was about 30 m, for Tecoman 12 m, for Manzanillo 35 m, for Cerro de Ortega 68 m, and the deepest site exploration was obtained in Colima city with a depth of around 73 m. The S wave velocities fluctuate between 230 m/s and 420 m/s for the most superficial layer. It means that, in general, the most superficial layers are quite competent. The superficial layer with smaller S wave velocity was observed in Tecoman, while that of largest S wave velocity was observed in Cerro de Ortega. Our estimations are consistent with down-hole velocity records obtained in Santa Barbara by previous studies.

Volumetric strain in relation to particle displacements for body and surface waves in a general viscoelastic half-space

USGS Publications Warehouse

Borcherdt, R.D.

1988-01-01

Dilatational earth strain, associated with the radiation fields for several hundred local, regional, and teleseismic earthquakes, has been recorded over an extended bandwidth and dynamic range at four borehole sites near the San Andreas fault, CA. The general theory of linear viscoelasticity is applied to account for anelasticity of the near-surface materials and to provide a mathematical basis for interpretation of seismic radiation fields as detected simultaneously by co-located volumetric strain meters and seismometers. The general theory is applied to describe volumetric strain and displacement for general (homogeneous or inhomogeneous) P and S waves in an anelastic whole space. Solutions to the free-surface reflection problems for incident general P and S-I waves are used to evaluate the effect of the free surface on observations from co-located sensors. Corresponding expressions are derived for a Rayleigh-type surface wave on a linear viscoelastic half-space. The theory predicts a number of anelastic wave field characteristics that can be inferred from observation of volumetric strains and displacement fields as detected by co-located sensors that cannot be inferred from either sensor alone. -from Author

Coordinated Polar Spacecraft, Geosynchronous Spacecraft, and Ground-based Observations of Magnetopause Oscillations and Pc5 Waves in the Magnetosphere

NASA Technical Reports Server (NTRS)

Le, G.; Chen, S.; Zheng, Y.; Russell, C. T.; Slavin, J. A.; Huang, C.-S.; Petrinec, S. S.; Moore, T. E.; Samson, J.; Singer, H. J.

2005-01-01

In this paper, we present in situ observations of surface waves at the magnetopause and oscillatory magnetospheric field lines, and coordinated observations Pc5 waves at geosynchronous orbit by the GOES spacecraft, and on the ground by CANOPUS and 210 Degree Magnetic Meridian (210MMJ magnetometer arrays. On February 7,2002 during a highspeed solar wind stream, the Polar spacecraft was skimming the magnetopause in a post-noon meridian plane for approximately 3 hours. During this interval, it made two short excursions and a few partial crossings into the magnetosheath and observed quasi-periodic cold ion bursts in the region adjacent to the magnetopause current layer. The multiple magnetopause crossings as well as the velocity of the cold ion bursts indicate that the magnetopause was oscillating with about 6 minute period. Simultaneous observations of Pc5 waves at geosynchronous orbit by the GOES spacecraft and on the ground by the CANOPUS magnetometer array reveal that these magnetospheric pulsations were forced oscillations of magnetic field lines directly driven by the magnetopause oscillations. The magnetospheric pulsations occurred only in a limited longitudinal region in the post-noon dayside sector, and were not a global phenomenon as one would expect for global field line resonance. Thus, the magnetopause oscillations at the source were also limited to a localized region spanning about 4 hours in local time.

Investigation of the Presence of Charge Order in Magnetite by Measurement of the Sprin Wave Spectrum

DOE Office of Scientific and Technical Information (OSTI.GOV)

McQueeny, R. J.; Yethiraj, Mohana; Montfrooij, W.

Inelastic neutron scattering results on magnetite (Fe{sub 3}O{sub 4}) show a large splitting in the acoustic spin wave branch, producing a 7 meV gap midway to the Brillouin zone boundary at q = (0,0,1/2) and {h_bar}{omega} = 43 meV. The splitting occurs below the Verwey transition temperature, where a metal-insulator transition occurs simultaneously with a structural transformation, supposedly caused by the charge ordering on the iron sublattice. The wavevector (0,0,1/2) corresponds to the superlattice peak in the low symmetry structure. The dependence of the magnetic superexchange on changes in the crystal structure and ionic configurations that occur below the Verweymore » transition affect the spin wave dispersion. To better understand the origin of the observed splitting, several Heisenberg models intended to reproduce the pair-wise variation of the magnetic superexchange arising from both small crystalline distortions and charge ordering were studied. None of the models studied predicts the observed splitting, whose origin may arise from charge-density wave formation or magnetoelastic coupling.« less

Ion Acoustic Wave Frequencies and Onset Times During Type 3 Solar Radio Bursts

NASA Technical Reports Server (NTRS)

Cairns, Iver H.; Robinson, P. A.

1995-01-01

Conflicting interpretations exist for the low-frequency ion acoustic (S) waves often observed by ISEE 3 in association with intense Langmuir (L) waves in the source regions of type III solar radio bursts near 1 AU. Two indirect lines of observational evidence, as well as plasma theory, suggest they are produced by the electrostatic (ES) decay L yields L(PRIME) + S. However, contrary to theoretical predictions, an existing analysis of the wave frequencies instead favors the electromagnetic (EM) decays L yields T + S, where T denotes an EM wave near the plasma frequency. This conflict is addressed here by comparing the observed wave frequencies and onset times with theoretical predictions for the ES and EM decays, calculated using the time-variable electron beam and magnetic field orientation data, rather than the nominal values used previously. Field orientation effects and beam speed variations are shown analytically to produce factor-of-three effects, greater than the difference in wave frequencies predicted for the ES and EM decays; effects of similar magnitude occur in the events analyzed here. The S-wave signals are extracted by hand from a sawtooth noise background, greatly improving the association between S waves and intense L waves. Very good agreement exists between the time-varying predictions for the ES decay and the frequencies of most (but not all) wave bursts. The waves occur only after the ES decay becomes kinematically allowed, which is consistent with the ES decay proceeding and producing most of the observed signals. Good agreement exists between the EM decay's predictions and a significant fraction of the S-wave observations while the EM decay is kinematically allowed. The wave data are not consistent, however, with the EM decay being the dominant nonlinear process. Often the observed waves are sufficiently broadband to overlap simultaneously the frequency ranges predicted for the ES and EM decays. Coupling the dominance of the ES decay with this frequency overlap provides support for a previous suggestion that fundamental emission occurs when the EM decay is stimulated by the ES decay product waves. The periods in which the ES and EM decays produce observable S waves are consistent with the observed and (independently) predicted times of fundamental and harmonic radio emission. This supports interpretation of fundamental emission as stimulated EM decay and harmonic emission as the coalescence L + L(prime) yields T of beam-generated L waves and L(prime) waves produced by the ES decay, where T denotes an electromagnetic wave at twice the plasma frequency. Analysis of the electron beam data reveals that the time-varying beam speed is consistent with ballistic beam propagation with minimal energy loss, implying that the beam propagates in a state close to time- and volume-averaged marginal stability. This confirms a central tenet of the stochastic growth theory for type III bursts.

Case study of simultaneous observations of sporadic sodium layer, E-region field-aligned irregularities and sporadic E layer at low latitude of China

NASA Astrophysics Data System (ADS)

Xie, H. Y.; Ning, B. Q.; Zhao, X. K.; Hu, L. H.

2017-03-01

Using the Na lidar at Haikou (20.0°N, 110.3°E), the VHF coherent radar and the digital ionosonde both at Sanya (18.4°N, 109.6°E), cases of simultaneous observations of sporadic sodium layer (SSL), E-region field-aligned irregularities (FAI) and sporadic E layer (Es) in the mesosphere and lower thermosphere (MLT) region at low latitude of China are studied. It is found that SSL occurs simultaneously or follows the enhancement of Es and FAI. The Es, FAI and SSL descend slowly with time which is mostly controlled by the diurnal tide (DT). Besides, the interaction of gravity wave (GW) with tides can cause oscillations in FAI and SSL. Our observations support the neutralization of ions for SSL formation: when the metallic ions layer descents to the altitudes where models predict, the sodium ions convert rapidly to atomic Na that may form an SSL event. Moreover, the SSL peak density will increase (decrease) in the convergence (divergence) vertical shear region of zonal wind.

Oscillations and patterns in a model of simultaneous CO and C2H2 oxidation and NO(x) reduction in a cross-flow reactor.

PubMed

Hadač, Otto; Kohout, Martin; Havlica, Jaromír; Schreiber, Igor

2015-03-07

A model describing simultaneous catalytic oxidation of CO and C2H2 and reduction of NOx in a cross-flow tubular reactor is explored with the aim of relating spatiotemporal patterns to specific pathways in the mechanism. For that purpose, a detailed mechanism proposed for three-way catalytic converters is split into two subsystems, (i) simultaneous oxidation of CO and C2H2, and (ii) oxidation of CO combined with NOx reduction. The ability of these two subsystems to display mechanism-specific dynamical effects is studied initially by neglecting transport phenomena and applying stoichiometric network and bifurcation analyses. We obtain inlet temperature - inlet oxygen concentration bifurcation diagrams, where each region possessing specific dynamics - oscillatory, bistable and excitable - is associated with a dominant reaction pathway. Next, the spatiotemporal behaviour due to reaction kinetics combined with transport processes is studied. The observed spatiotemporal patterns include phase waves, travelling fronts, pulse waves and spatiotemporal chaos. Although these types of pattern occur generally when the kinetic scheme possesses autocatalysis, we find that some of their properties depend on the underlying dominant reaction pathway. The relation of patterns to specific reaction pathways is discussed.

Quasi-periodic Radio Bursts Associated with Fast-mode Waves near a Magnetic Null Point

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kumar, Pankaj; Nakariakov, Valery M.; Cho, Kyung-Suk, E-mail: pankaj.kumar@nasa.gov

This paper presents an observation of quasi-periodic rapidly propagating waves observed in the Atmospheric Image Assembly (AIA) 171/193 Å channels during the impulsive phase of an M1.9 flare that occurred on 2012 May 7. The instant period was found to decrease from 240 to 120 s, and the speed of the wavefronts was in the range of ∼664–1416 km s{sup −1}. Almost simultaneously, quasi-periodic bursts with similar instant periods, ∼70 and ∼140 s, occur in the microwave emission and in decimetric type IV and type III radio bursts, and in the soft X-ray emission. The magnetic field configuration of themore » flare site was consistent with a breakout topology, i.e., a quadrupolar field along with a magnetic null point. The quasi-periodic rapidly propagating wavefronts of the EUV emission are interpreted as a fast magnetoacoustic wave train. The observations suggest that the fast-mode waves are generated during the quasi-periodic magnetic reconnection in the cusp region above the flare arcade loops. For the first time, we provide evidence of a tadpole wavelet signature at about 70–140 s in decimetric (245/610 MHz) radio bursts, along with the direct observation of a coronal fast-mode wave train in EUV. In addition, at AIA 131/193 Å we observed quasi-periodic EUV disturbances with periods of 95 and 240 s propagating downward at apparent speeds of 172–273 km s{sup −1}. The nature of these downward propagating disturbances is not revealed, but they could be connected to magnetoacoustic waves or periodically shrinking loops.« less

Van Allen Probes observation and modeling of chorus excitation and propagation during weak geomagnetic activities

DOE PAGES

He, Yihua; Xiao, Fuliang; Zhou, Qinghua; ...

2015-08-20

We report correlated data on nightside chorus waves and energetic electrons during two small storm periods: 1 November 2012 (Dst ≈ –45) and 14 January 2013 (Dst ≈ –18). The Van Allen Probes simultaneously observed strong chorus waves at locations L = 5.8 – 6.3, with a lower frequency band 0.1–0.5fce and a peak spectral density ~10 –4 nT 2/Hz. In the same period, the fluxes and anisotropy of energetic (~10–300 keV) electrons were greatly enhanced in the interval of large negative interplanetary magnetic field Bz. Using a bi-Maxwellian distribution to model the observed electron distribution, we perform ray tracingmore » simulations to show that nightside chorus waves are indeed produced by the observed electron distribution with a peak growth for a field-aligned propagation approximately between 0.3f ce and 0.4f ce, at latitude <7°. Moreover, chorus waves launched with initial normal angles either θ < 90° or > 90° propagate along the field either northward or southward and then bounce back either away from Earth for a lower frequency or toward Earth for higher frequencies. The current results indicate that nightside chorus waves can be excited even during weak geomagnetic activities in cases of continuous injection associated with negative Bz. Furthermore, we examine a dayside event during a small storm C on 8 May 2014 (Dst ≈ –45) and find that the observed anisotropic energetic electron distributions potentially contribute to the generation of dayside chorus waves, but this requires more thorough studies in the future.« less

Simultaneous observations of ice motion, calving and seismicity on the Yahtse Glacier, Alaska. (Invited)

NASA Astrophysics Data System (ADS)

Larsen, C. F.; Bartholomaus, T. C.; O'Neel, S.; West, M. E.

2010-12-01

We observe ice motion, calving and seismicity simultaneously and with high-resolution on an advancing tidewater glacier in Icy Bay, Alaska. Icy Bay’s tidewater glaciers dominate regional glacier-generated seismicity in Alaska. Yahtse emanates from the St. Elias Range near the Bering-Bagley-Seward-Malaspina Icefield system, the most extensive glacier cover outside the polar regions. Rapid rates of change and fast flow (>16 m/d near the terminus) at Yahtse Glacier provide a direct analog to the disintegrating outlet systems in Greenland. Our field experiment co-locates GPS and seismometers on the surface of the glacier, with a greater network of bedrock seismometers surrounding the glacier. Time-lapse photogrammetry, fjord wave height sensors, and optical survey methods monitor iceberg calving and ice velocity near the terminus. This suite of geophysical instrumentation enables us to characterize glacier motion and geometry changes while concurrently listening for seismic energy release. We are performing a close examination of calving as a seismic source, and the associated mechanisms of energy transfer to seismic waves. Detailed observations of ice motion (GPS and optical surveying), glacier geometry and iceberg calving (direct observations and timelapse photogrammetry) have been made in concert with a passive seismic network. Combined, the observations form the basis of a rigorous analysis exploring the relationship between glacier-generated seismic events and motion, glacier-fiord interactions, calving and hydraulics. Our work is designed to demonstrate the applicability and utility of seismology to study the impact of climate forcing on calving glaciers.

Transmitral flow velocity-contour variation after premature ventricular contractions: a novel test of the load-independent index of diastolic filling.

PubMed

Boskovski, Marko T; Shmuylovich, Leonid; Kovács, Sándor J

2008-12-01

The new echocardiography-based, load-independent index of diastolic filling (LIIDF) M was assessed using load-/shape-varying E-waves after premature ventricular contractions (PVCs). Twenty-six PVCs in 15 subjects from a preexisting simultaneous echocardiography-catheterization database were selected. Perturbed load-state beats, defined as the first two post-PVC E-waves, and steady-state E-waves, were subjected to conventional and model-based analysis. M, a dimensionless index, defined by the slope of the peak driving-force vs. peak (filling-opposing) resistive-force regression, was determined from steady-state E-waves alone, and from load-perturbed E-waves combined with a matched number of subsequent beats. Despite high degrees of E-wave shape variation, M derived from load-varying, perturbed beats and M derived from steady-state beats alone were indistinguishable. Because the peak driving-force vs. peak resistive-force relation determining M remains highly linear in the extended E-wave shape and load variation regime observed, we conclude that M is a robust LIIDF.

Parametric decay of current-driven Langmuir oscillations and wave packet formation in plateau plasmas: Relevance to type III bursts

NASA Astrophysics Data System (ADS)

Sauer, K.; Malaspina, D.; Pulupa, M.

2016-12-01

Instead of starting with an unstable electron beam, our focus is directed on the nonlinear response of Langmuir oscillations which are driven after beam stabilization by the still persisting current of the (stable) two-electron plasma. The velocity distribution function of the second population forms a plateau with weak damping over a more or less extended wave number range k. As shown by PIC simulations, this so-called plateau plasma drives primarily Langmuir oscillations at the plasma frequency ωe with k=0 over long times without remarkable change of the distribution function. The Langmuir oscillations, however, act as pump wave for parametric decay by which an electron-acoustic wave slightly below ωe and a counter-streaming ion-acoustic wave are generated. Both high-frequency waves have nearly the same amplitude which is simply given by the product of plateau density and velocity. Beating of these two wave types leads to pronounced Langmuir amplitude modulation, in good agreement with solar wind and foreshock WIND observations where waveforms and electron distribution functions have simultaneously been analyzed.

Ion Upwelling and Height-Resolved Electrodynamic Response of the Ionosphere to ULF Waves and Precipitation: Comparison Between Simulation and EISCAT Observations

NASA Astrophysics Data System (ADS)

Sydorenko, D.; Rankin, R.

2013-12-01

We have developed a comprehensive two-dimensional (meridional) model of coupling between the magnetosphere and ionosphere that covers an altitude range from ~100 km to few thousand km at high latitudes [Sydorenko and Rankin, 2013]. The model describes propagation of inertial scale Alfven waves, including ponderomotive forces, and has a parametric model of energetic electron precipitation; it includes vertical ion flows and chemical reactions between ions and neutrals. Model results are presented that reproduce EISCAT radar observations of electron and ion temperatures, height integrated conductivity, ion densities, and ion flows during a period of ULF activity described in [Lester, Davies, and Yeoman, 2000]. We performed simulations where the precipitation and the Alfven wave perturb the ionosphere simultaneously. By adjusting parameters of the wave and the precipitation we have achieved qualitative, and sometimes even reasonable quantitative agreement between the observations and the simulation. The model results are discussed in the context of new results anticipated from the Canadian small satellite mission ePOP "Enhanced Polar Outflow Probe", scheduled for launch on September 9, 2013. Sydorenko D. and R. Rankin, 'Simulation of O+ upflows created by electron precipitation and Alfvén waves in the ionosphere' submitted to Journal of Geophysical Research, 2013. Lester M., J. A. Davies, and T. K. Yeoman, 'The ionospheric response during an interval of PC5 ULF wave activity', Ann. Geophysicae, v.18, p.257-261 (2000).

Observations of EMIC Waves in the Exterior Cusp Region and in the Nearby Magnetosheath

NASA Astrophysics Data System (ADS)

Grison, B.; Escoubet, C. P.; Santolik, O.; Lavraud, B.; Cornilleau-Wehrlin, N.

2014-12-01

In the early years (2000-2004) of the mission, Cluster crossed the most distant part of the polar cusps. On 05/01/2002, Cluster enters the distant cusp region on the duskside of the southern hemisphere (inbound). The spacecraft are successively crossing the magnetopause between 19:50 UT (SC4) and 20:15 UT (SC3). The interplanetary conditions during the crossing were stable with a dominant negative By. The magnetometer (FGM) data indicates that the entry into the cusp takes place in a region where the magnetic field lines in the magnetosheath are anti-parallel with the field lines in the magnetosphere. Despite this clear picture, the global encounter is rather complex: one can notice partial magnetopause crossings, magnetic null points, and intense monochromatic waves on both sides of the magnetopause.We investigate electromagnetic ion cyclotron (EMIC) waves observed in the cusp and in the nearby magnetosheath, just before the magnetopause crossing by the spacecraft. Left-handed monochromatic waves observed in the cusp display different duration and frequency (below and above the local proton gyrofrequency) on each spacecraft. Both the Poynting flux of these emissions and the simultaneously recorded ion flows propagate in the same direction - toward the Earth. The wavenumber are determined in two ways: considering the Doppler shift and from direct measurements of the refractive index. We analyze these wave parameters and the local plasma conditions to explain the wave generation process on each side of the magnetopause.

Parenting Behavior Mediates the Intergenerational Association of Parent and Child Offspring ADHD Symptoms

PubMed Central

Tung, Irene; Brammer, Whitney A.; Li, James J.; Lee, Steve S.

2015-01-01

Although there are likely to be multiple mechanisms underlying parent attention-deficit/hyperactivity disorder (ADHD) symptoms as a key risk factor for offspring ADHD, potential explanatory factors have yet to be reliably identified. Given that parent ADHD symptoms independently predict parenting behavior and child ADHD symptoms, we tested whether individual differences in multiple dimensions of positive and negative parenting behavior (i.e., corporal punishment, inconsistent discipline, positive parenting behavior, observed negative talk, and observed praise) mediated the association between parental and offspring ADHD. We used a prospective design that featured predictors (i.e., parent ADHD symptoms) and mediators (i.e., parenting behavior) that temporally preceded the outcome (i.e., offspring ADHD symptoms). Using a well-characterized sample of 120 children with and without ADHD (ages 5–10 at Wave 1, 7–12 at Wave 2) and their biological parents, we examined multimethod (i.e., observed, self-report) measures of positive and negative parenting behavior as simultaneous mediators of the association of Wave 1 parent and Wave 2 offspring ADHD symptoms. Using a multiple mediation framework, consisting of rigorous bootstrapping procedures and controlling for parent depression, child’s baseline ADHD and oppositional defiant disorder, and child’s age, corporal punishment significantly and uniquely mediated the association of Wave 1 parent ADHD symptoms and Wave 2 offspring ADHD. We consider the role of parenting behavior in the intergenerational transmission of ADHD as well as implications of these findings for the intervention and prevention of childhood ADHD. PMID:24926775

Modeling Gravitational Radiation Waveforms from Black Hole Mergers

NASA Technical Reports Server (NTRS)

Baker, J. G.; Centrelia, J. M.; Choi, D.; Koppitz, M.; VanMeter, J.

2006-01-01

Gravitational radiation from merging binary black hole systems is anticipated as a key source for gravitational wave observations. Ground-based instruments, such as the Laser Interferometer Gravitational-wave Observatory (LIGO) may observe mergers of stellar-scale black holes, while the space-based Laser Interferometer Space Antenna (LISA) observatory will be sensitive to mergers of massive galactic-center black holes over a broad range of mass scales. These cataclysmic events may emit an enormous amount of energy in a brief time. Gravitational waves from comparable mass mergers carry away a few percent of the system's mass-energy in just a few wave cycles, with peak gravitational wave luminosities on the order of 10^23 L_Sun. Optimal analysis and interpretation of merger observation data will depend on developing a detailed understanding, based on general relativistic modeling, of the radiation waveforms. We discuss recent progress in modeling radiation from equal mass mergers using numerical simulations of Einstein's gravitational field equations, known as numerical relativity. Our simulations utilize Adaptive Mesh Refinement (AMR) to allow high-resolution near the black holes while simultaneously keeping the outer boundary of the computational domain far from the black holes, and making it possible to read out gravitational radiation waveforms in the weak-field wave zone. We discuss the results from simulations beginning with the black holes orbiting near the system's innermost stable orbit, comparing the recent simulations with earlier "Lazarus" waveform estimates based on an approximate hybrid numerical/perturbative technique.

Parenting Behavior Mediates the Intergenerational Association of Parent and Child Offspring ADHD Symptoms.

PubMed

Tung, Irene; Brammer, Whitney A; Li, James J; Lee, Steve S

2015-01-01

Although there are likely to be multiple mechanisms underlying parent attention-deficit/hyperactivity disorder (ADHD) symptoms as a key risk factor for offspring ADHD, potential explanatory factors have yet to be reliably identified. Given that parent ADHD symptoms independently predict parenting behavior and child ADHD symptoms, we tested whether individual differences in multiple dimensions of positive and negative parenting behavior (i.e., corporal punishment, inconsistent discipline, positive parenting behavior, observed negative talk, and observed praise) mediated the association between parental and offspring ADHD. We used a prospective design that featured predictors (i.e., parent ADHD symptoms) and mediators (i.e., parenting behavior) that temporally preceded the outcome (i.e., offspring ADHD symptoms). Using a well-characterized sample of 120 children with and without ADHD (ages 5-10 at Wave 1, 7-12 at Wave 2) and their biological parents, we examined multimethod (i.e., observed, self-report) measures of positive and negative parenting behavior as simultaneous mediators of the association of Wave 1 parent and Wave 2 offspring ADHD symptoms. Using a multiple mediation framework, consisting of rigorous bootstrapping procedures and controlling for parent depression, child's baseline ADHD and oppositional defiant disorder, and child's age, corporal punishment significantly and uniquely mediated the association of Wave 1 parent ADHD symptoms and Wave 2 offspring ADHD. We consider the role of parenting behavior in the intergenerational transmission of ADHD as well as implications of these findings for the intervention and prevention of childhood ADHD.

Wave-Particle Interactions Involving Correlated Electron Bursts and Whistler Chorus in Earth's Radiation Belts

NASA Astrophysics Data System (ADS)

Echterling, N.; Schriver, D.; Roeder, J. L.; Fennell, J. F.

2017-12-01

During the recovery phase of substorm plasma injections, the Van Allen Probes commonly observe events of quasi-periodic energetic electron bursts correlating with simultaneously detected upper-band, whistler-mode chorus emissions. These electron bursts exhibit narrow ranges of pitch angles (75-80° and 100-105°) and energies (20-40 keV). Electron cyclotron harmonic (ECH) emissions are also commonly detected, but typically do not display correlation with the electron bursts. To examine sources of free energy and the generation of these wave emissions, an observed electron velocity distribution on January 13, 2013 is used as the starting condition for a particle in cell (PIC) simulation. Effects of temperature anisotropy (perpendicular temperature greater than parallel temperature), the presence of a loss cone and a cold electron population on the generation of whistler and ECH waves are examined to understand wave generation and nonlinear interactions with the particle population. These nonlinear interactions produce energy diffusion along with strong pitch angle scattering into the loss cone on the order of milliseconds, which is faster than a typical bounce period of seconds. To examine the quasi-periodic nature of the electron bursts, a loss-cone recycling technique is implemented to model the effects of the periodic emptying of the loss cone and electron injection on the growth of whistler and ECH waves. The results of the simulations are compared to the Van Allen Probe observations to determine electron acceleration, heating and transport in Earth's radiation belts due to wave-particle interactions.

Localizing gravitational wave sources with single-baseline atom interferometers

NASA Astrophysics Data System (ADS)

Graham, Peter W.; Jung, Sunghoon

2018-02-01

Localizing sources on the sky is crucial for realizing the full potential of gravitational waves for astronomy, astrophysics, and cosmology. We show that the midfrequency band, roughly 0.03 to 10 Hz, has significant potential for angular localization. The angular location is measured through the changing Doppler shift as the detector orbits the Sun. This band maximizes the effect since these are the highest frequencies in which sources live for several months. Atom interferometer detectors can observe in the midfrequency band, and even with just a single baseline they can exploit this effect for sensitive angular localization. The single-baseline orbits around the Earth and the Sun, causing it to reorient and change position significantly during the lifetime of the source, and making it similar to having multiple baselines/detectors. For example, atomic detectors could predict the location of upcoming black hole or neutron star merger events with sufficient accuracy to allow optical and other electromagnetic telescopes to observe these events simultaneously. Thus, midband atomic detectors are complementary to other gravitational wave detectors and will help complete the observation of a broad range of the gravitational spectrum.

Temporal coordination of olfactory cortex sharp-wave activity with up- and downstates in the orbitofrontal cortex during slow-wave sleep.

PubMed

Onisawa, Naomi; Manabe, Hiroyuki; Mori, Kensaku

2017-01-01

During slow-wave sleep, interareal communications via coordinated, slow oscillatory activities occur in the large-scale networks of the mammalian neocortex. Because olfactory cortex (OC) areas, which belong to paleocortex, show characteristic sharp-wave (SPW) activity during slow-wave sleep, we examined whether OC SPWs in freely behaving rats occur in temporal coordination with up- and downstates of the orbitofrontal cortex (OFC) slow oscillation. Simultaneous recordings of local field potentials and spike activities in the OC and OFC showed that during the downstate in the OFC, the OC also exhibited downstate with greatly reduced neuronal activity and suppression of SPW generation. OC SPWs occurred during two distinct phases of the upstate of the OFC: early-phase SPWs occurred at the start of upstate shortly after the down-to-up transition in the OFC, whereas late-phase SPWs were generated at the end of upstate shortly before the up-to-down transition. Such temporal coordination between neocortical up- and downstates and olfactory system SPWs was observed between the prefrontal cortex areas (OFC and medial prefrontal cortex) and the OC areas (anterior piriform cortex and posterior piriform cortex). These results suggest that during slow-wave sleep, OC and OFC areas communicate preferentially in specific time windows shortly after the down-to-up transition and shortly before the up-to-down transition. Simultaneous recordings of local field potentials and spike activities in the anterior piriform cortex (APC) and orbitofrontal cortex (OFC) during slow-wave sleep showed that APC sharp waves tended to occur during two distinct phases of OFC upstate: early phase, shortly after the down-to-up transition, and late phase, shortly before the up-to-down transition, suggesting that during slow-wave sleep, olfactory cortex and OFC areas communicate preferentially in the specific time windows. Copyright © 2017 the American Physiological Society.

Temporal coordination of olfactory cortex sharp-wave activity with up- and downstates in the orbitofrontal cortex during slow-wave sleep

PubMed Central

Onisawa, Naomi; Mori, Kensaku

2016-01-01

During slow-wave sleep, interareal communications via coordinated, slow oscillatory activities occur in the large-scale networks of the mammalian neocortex. Because olfactory cortex (OC) areas, which belong to paleocortex, show characteristic sharp-wave (SPW) activity during slow-wave sleep, we examined whether OC SPWs in freely behaving rats occur in temporal coordination with up- and downstates of the orbitofrontal cortex (OFC) slow oscillation. Simultaneous recordings of local field potentials and spike activities in the OC and OFC showed that during the downstate in the OFC, the OC also exhibited downstate with greatly reduced neuronal activity and suppression of SPW generation. OC SPWs occurred during two distinct phases of the upstate of the OFC: early-phase SPWs occurred at the start of upstate shortly after the down-to-up transition in the OFC, whereas late-phase SPWs were generated at the end of upstate shortly before the up-to-down transition. Such temporal coordination between neocortical up- and downstates and olfactory system SPWs was observed between the prefrontal cortex areas (OFC and medial prefrontal cortex) and the OC areas (anterior piriform cortex and posterior piriform cortex). These results suggest that during slow-wave sleep, OC and OFC areas communicate preferentially in specific time windows shortly after the down-to-up transition and shortly before the up-to-down transition. NEW & NOTEWORTHY Simultaneous recordings of local field potentials and spike activities in the anterior piriform cortex (APC) and orbitofrontal cortex (OFC) during slow-wave sleep showed that APC sharp waves tended to occur during two distinct phases of OFC upstate: early phase, shortly after the down-to-up transition, and late phase, shortly before the up-to-down transition, suggesting that during slow-wave sleep, olfactory cortex and OFC areas communicate preferentially in the specific time windows. PMID:27733591

Evidence of Boundary Reflection of Kelvin and First-Mode Rossby Waves from Topex/Poseidon Sea Level Data

NASA Technical Reports Server (NTRS)

Boulanger, Jean-Philippe; Fu, Lee-Lueng

1996-01-01

The TOPEX/POSEIDON sea level data lead to new opportunities to investigate some theoretical mechanisms suggested to be involved in the El Nino-Southern Oscillation phenomenon in the tropical Pacific ocean. In particular, we are interested in studying the western boundary reflection, a process crucial for the delayed action oscillator theory, by using the TOPEX/POSEIDON data from November 1992 to May 1995. We first projected the sea level data onto Kelvin and first-mode Ross waves. Then we estimated the contribution of wind forcing to these waves by using a single baroclinic mode simple wave model forced by the ERS-1 wind data. Wave propagation was clearly observed with amplitudes well explained by the wind forcing in the ocean interior. Evidence of wave reflection was detected at both the western and eastern boundaries of the tropical Pacific ocean. At the eastern boundary, Kelvin waves were seen to reflect as first-mode Rossby waves during the entire period. The reflection efficiency (in terms of wave amplitude) of the South American coasts was estimated to be 80% of that of an infinite meridional wall. At the western boundary, reflection was observed in April-August 1993, in January-June 1994, and, later, in December 1994 to February 1995. Although the general roles of these reflection events in the variability observed in the equatorial Pacific ocean are not clear, the data suggest that the reflections in January-June 1994 have played a role in the onset of the warm conditions observed in late 1994 to early 1995. Indeed, during the January-June 1994 period, as strong downwelling first-mode Rossby waves reflected into downwelling Kelvin waves, easterly wind and cold sea surface temperature anomalies located near the date line weakened and eventually reversed in June-July 1994. The presence of the warm anomalies near the date line then favored convection and westerly wind anomalies that triggered strong downwelling Kelvin waves propagating throughout the basin simultaneously with the beginning of the 1994-1995 warm conditions.

Dual-channel near-field control by polarizations using isotropic and inhomogeneous metasurface.

PubMed

Wan, Xiang; Cai, Ben Geng; Li, Yun Bo; Cui, Tie Jun

2015-11-03

We propose a method for dual-channel near-field manipulations by designing isotropic but inhomogeneous metasurfaces. As example, we present a dual-channel near-field focusing metasurface device. When the device is driven by surface waves from different channels on the metasurface, the near fields will be focused at the same spatial point with different polarizations. Conversely, if a linearly polarized source is radiated at the spatial focal point, different channels will be evoked on the metasurface controlled by polarization. We fabricated and measured the metasurface device in the microwave frequency. Well agreements between the simulation and measurement results are observed. The proposed method exhibits great flexibility in controlling the surface waves and spatial waves simultaneously. It is expected that the proposed method and dual-channel device will facilitate the manipulation of near electromagnetic or optical waves in different frequency regimes.

Hydraulic and Wave Aspects of Novorossiysk Bora

NASA Astrophysics Data System (ADS)

Shestakova, Anna A.; Moiseenko, Konstantin B.; Toropov, Pavel A.

2018-02-01

Bora in Novorossiysk (seaport on the Black Sea coast of the Caucasus) is one of the strongest and most prominent downslope windstorms on the territory of Russia. In this paper, we evaluate the applicability of the hydraulic and wave hypotheses, which are widely used for downslope winds around the world, to Novorossiysk bora on the basis of observational data, reanalysis, and mesoscale numerical modeling with WRF-ARW. It is shown that mechanism of formation of Novorossiysk bora is essentially mixed, which is expressed in the simultaneous presence of gravity waves breaking and a hydraulic jump, as well as in the significant variability of the contribution of wave processes to the windstorm dynamics. Effectiveness of each mechanism depends on the elevated inversion intensity and mean state critical level height. Most favorable conditions for both mechanisms working together are moderate or weak inversion and high or absent critical level.

Independent control of differently-polarized waves using anisotropic gradient-index metamaterials

PubMed Central

Ma, Hui Feng; Wang, Gui Zhen; Jiang, Wei Xiang; Cui, Tie Jun

2014-01-01

We propose a kind of anisotropic gradient-index (GRIN) metamaterials, which can be used to control differently-polarized waves independently. We show that two three- dimensional (3D) planar lenses made of such anisotropic GRIN metamaterials are able to make arbitrary beam deflections for the vertical (or horizontal) polarization but have no response to the horizontal (or vertical) polarization. Then the vertically- and horizontally-polarized waves are separated and controlled independently to deflect to arbitrarily different directions by designing the anisotropic GRIN planar lenses. We make experimental verifications of the lenses using such a special metamaterial, which has both electric and magnetic responses simultaneously to reach approximately equal permittivity and permeability. Hence excellent impedance matching is obtained between the GRIN planar lenses and the air. The measurement results demonstrate good performance on the independent controls of differently-polarized waves, as observed in the numerical simulations. PMID:25231412

Manipulating one-way space wave and its refraction by time-reversal and parity symmetry breaking

PubMed Central

Poo, Yin; He, Cheng; Xiao, Chao; Lu, Ming-Hui; Wu, Rui-Xin; Chen, Yan-Feng

2016-01-01

One-way transmission and negative refraction are the exotic wave properties founded in photonic crystals which attract a great attention due to their promising applications in photonic devices. How to integrate such two phenomena in one material or device is interesting and valuable. In this work, we theoretically and experimentally demonstrate that one-way electromagnetic space wave can be realized by means of two-dimensional magnetic photonic crystals. Simultaneously breaking the time-reversal and parity symmetries of the magnetic photonic crystals designed, we observe oblique incident space wave propagating one-way in the magnetic photonic crystals with positive or negative refraction occurring at interfaces, which can be manipulated upon the incident angle and operating frequency. Our work may offer a potential platform to realize some exotic photoelectronic and microwave devices such as one-way imaging and one-way cloaking. PMID:27387438

Femtosecond laser excitation of multiple spin waves and composition dependence of Gilbert damping in full-Heusler Co{sub 2}Fe{sub 1−x}Mn{sub x}Al films

DOE Office of Scientific and Technical Information (OSTI.GOV)

Cheng, Chuyuan; Li, Shufa; Lai, Tianshu, E-mail: stslts@mail.sysu.edu.cn, E-mail: jhzhao@red.semi.ac.cn

2013-12-02

Spin-wave dynamics in 30 nm thick Co{sub 2}Fe{sub 1−x}Mn{sub x}Al full-Heusler films is investigated using time-resolved magneto-optical polar Kerr spectroscopy under an external field perpendicular to films. Damon-Eshbach (DE) and the first-order perpendicular standing spin-wave (PSSW) modes are observed simultaneously in four samples with x = 0, 0.3, 0.7, and 1. The frequency of DE and PSSW modes does not apparently depend on composition x, but damping of DE mode significantly on x and reaches the minimum as x = 0.7. The efficient coherent excitation of DE spin wave exhibits the promising application of Co{sub 2}Fe{sub 0.3}Mn{sub 0.7}Al films in magnonic devices.

Geomagnetically conjugate observations of ionospheric and thermospheric variations accompanied by a midnight brightness wave at low latitudes

NASA Astrophysics Data System (ADS)

Fukushima, D.; Shiokawa, K.; Otsuka, Y.; Kubota, M.; Yokoyama, T.; Nishioka, M.; Komonjinda, S.; Yatini, C. Y.

2017-08-01

We conducted geomagnetically conjugate observations of 630-nm airglow for a midnight brightness wave (MBW) at Kototabang, Indonesia [geomagnetic latitude (MLAT): 10.0°S], and Chiang Mai, Thailand (MLAT: 8.9°N), which are geomagnetically conjugate points at low latitudes. An airglow enhancement that was considered to be an MBW was observed in OI (630-nm) airglow images at Kototabang around local midnight from 2240 to 2430 LT on February 7, 2011. This MBW propagated south-southwestward, which is geomagnetically poleward, at a velocity of 290 m/s. However, a similar wave was not observed in the 630-nm airglow images at Chiang Mai. This is the first evidence of an MBW that does not have geomagnetic conjugacy, which also implies generation of MBW only in one side of the hemisphere from the equator. We simultaneously observed thermospheric neutral winds observed by a co-located Fabry-Perot interferometer at Kototabang. The observed meridional winds turned from northward (geomagnetically equatorward) to southward (geomagnetically poleward) just before the wave was observed. This indicates that the observed MBW was generated by the poleward winds which push ionospheric plasma down along geomagnetic field lines, thereby increasing the 630-nm airglow intensity. The bottomside ionospheric heights observed by ionosondes rapidly decreased at Kototabang and slightly increased at Chiang Mai. We suggest that the polarization electric field inside the observed MBW is projected to the northern hemisphere, causing the small height increase observed at Chiang Mai. This implies that electromagnetic coupling between hemispheres can occur even though the original disturbance is caused purely by the neutral wind.[Figure not available: see fulltext.

Measurements of a Lee Wave in the Southern Ocean: Energy and Momentum Fluxes and Mixing

NASA Astrophysics Data System (ADS)

Cusack, J. M.; Naveira Garabato, A.; Smeed, D.; Girton, J. B.

2016-02-01

Lee waves, internal waves generated by stratified flow over topographic features are thought to break and generate a significant proportion of the turbulent mixing required to close the abyssal overturning circulation. A lack of observations means that there is large uncertainty in the magnitude of contribution that lee waves make to turbulent transformations, as well as their importance in local and global momentum and energy budgets. Two EM-APEX profiling floats deployed in the Drake Passage during the Diapycnal and Isopycnal Mixing Experiment (DIMES) independently measured a large lee wave over the Shackleton Fracture Zone. A model for steady EM-APEX motion is presented and used to calculate absolute vertical water velocity in addition to horizontal velocity measurements made by the floats. The wave is observed to have velocity fluctuations in all three directions of over 15 cm s-1 and a frequency close to the local buoyancy frequency. Furthermore, the wave has a measured peak vertical flux of horizontal momentum of 6 N m-2, a value that is two orders of magnitude larger than the time mean wind forcing on the Southern Ocean. Linear internal wave theory was used to estimate wave energy density and fluxes, while a mixing parameterisation was used to estimate the magnitude of turbulent kinetic energy dissipation, which was found to be elevated above typical background levels by two orders of magnitude. This work provides the first direct measurement of a lee wave generated by ACC flow over topography with simultaneous estimates of energy fluxes and mixing.

A resonance approach to cochlear mechanics.

PubMed

Bell, Andrew

2012-01-01

How does the cochlea analyse sound into its component frequencies? In the 1850s Helmholtz thought it occurred by resonance, whereas a century later Békésy's work indicated a travelling wave. The latter answer seemed to settle the question, but with the discovery in 1978 that the cochlea emits sound, the mechanics of the cochlea was back on the drawing board. Recent studies have raised questions about whether the travelling wave, as currently understood, is adequate to explain observations. Applying basic resonance principles, this paper revisits the question. A graded bank of harmonic oscillators with cochlear-like frequencies and quality factors is simultaneously excited, and it is found that resonance gives rise to similar frequency responses, group delays, and travelling wave velocities as observed by experiment. The overall effect of the group delay gradient is to produce a decelerating wave of peak displacement moving from base to apex at characteristic travelling wave speeds. The extensive literature on chains of coupled oscillators is considered, and the occurrence of travelling waves, pseudowaves, phase plateaus, and forced resonance in such systems is noted. This alternative approach to cochlear mechanics shows that a travelling wave can simply arise as an apparently moving amplitude peak which passes along a bank of resonators without carrying energy. This highlights the possible role of the fast pressure wave and indicates how phase delays and group delays of a set of driven harmonic oscillators can generate an apparent travelling wave. It is possible to view the cochlea as a chain of globally forced coupled oscillators, and this model incorporates fundamental aspects of both the resonance and travelling wave theories.

Simultaneous Ocean Wave Measurements by the Jason and Topex Satellites, With Buoy and Model Comparisons

NASA Technical Reports Server (NTRS)

Ray, Richard D.; Beckley, B. D.

2003-01-01

The verification phase of the Jason-1 satellite altimeter mission presents a unique opportunity for comparing near-simultaneous, independent satellite measurements. We here examine simultaneous significant wave height measurements by the Jason-1 and Topex/Poseidon altimeters. These data are also compared with in-situ measurements from deep-ocean buoys and with predicted wave heights from the Wave Watch 111 operational model. The rms difference between Jason and Topex wave heights is 21 cm, and this can be further lowered by application of median filters to reduce high-frequency noise. This noise is slightly larger in the Jason dataset, amounting to about 7 cm rms for frequencies above 0.05 Hz, which is the frequency at which the coherence between Topex and Jason measurements drops to zero. The probability density function for Jason shows a dearth of small waves relative to Topex. Buoy comparisons confirm that this problem lies with the Jason measurements. The buoy comparisons confirm previous reports that Topex wave heights are roughly 5% smaller than buoy measurements for waves between 2 and 5m; Jason heights in general are 2.7% smaller than Topex. Spurious dips in the Topex density function for 3- and 6-meter waves, a problem that has existed since the beginning of the mission, can be solved by waveform retracking..

Probing the Milky Way electron density using multi-messenger astronomy

NASA Astrophysics Data System (ADS)

Breivik, Katelyn; Larson, Shane

2015-04-01

Multi-messenger observations of ultra-compact binaries in both gravitational waves and electromagnetic radiation supply highly complementary information, providing new ways of characterizing the internal dynamics of these systems, as well as new probes of the galaxy itself. Electron density models, used in pulsar distance measurements via the electron dispersion measure, are currently not well constrained. Simultaneous radio and gravitational wave observations of pulsars in binaries provide a method of measuring the average electron density along the line of sight to the pulsar, thus giving a new method for constraining current electron density models. We present this method and assess its viability with simulations of the compact binary component of the Milky Way using the public domain binary evolution code, BSE. This work is supported by NASA Award NNX13AM10G.

Three-component ambient noise beamforming in the Parkfield area

NASA Astrophysics Data System (ADS)

Löer, Katrin; Riahi, Nima; Saenger, Erik H.

2018-06-01

We apply a three-component beamforming algorithm to an ambient noise data set recorded at a seismic array to extract information about both isotropic and anisotropic surface wave velocities. In particular, we test the sensitivity of the method with respect to the array geometry as well as to seasonal variations in the distribution of noise sources. In the earth's crust, anisotropy is typically caused by oriented faults or fractures and can be altered when earthquakes or human activities cause these structures to change. Monitoring anisotropy changes thus provides time-dependent information on subsurface processes, provided they can be distinguished from other effects. We analyse ambient noise data at frequencies between 0.08 and 0.52 Hz recorded at a three-component array in the Parkfield area, California (US), between 2001 November and 2002 April. During this time, no major earthquakes were identified in the area and structural changes are thus not expected. We compute dispersion curves of Love and Rayleigh waves and estimate anisotropy parameters for Love waves. For Rayleigh waves, the azimuthal source coverage is too limited to perform anisotropy analysis. For Love waves, ambient noise sources are more widely distributed and we observe significant and stable surface wave anisotropy for frequencies between 0.2 and 0.4 Hz. Synthetic data experiments indicate that the array geometry introduces apparent anisotropy, especially when waves from multiple sources arrive simultaneously at the array. Both the magnitude and the pattern of apparent anisotropy, however, differ significantly from the anisotropy observed in Love wave data. Temporal variations of anisotropy parameters observed at frequencies below 0.2 Hz and above 0.4 Hz correlate with changes in the source distribution. Frequencies between 0.2 and 0.4 Hz, however, are less affected by these variations and provide relatively stable results over the period of study.

Location of EMIC Wave Events Relative to the Plasmapause: Van Allen Probes Observations

NASA Astrophysics Data System (ADS)

Tetrick, S.; Engebretson, M. J.; Posch, J. L.; Kletzing, C.; Smith, C. W.; Wygant, J. R.; Gkioulidou, M.; Reeves, G. D.; Fennell, J. F.

2015-12-01

Many early theoretical studies of electromagnetic ion cyclotron (EMIC) waves generated in Earth's magnetosphere predicted that the equatorial plasmapause (PP) would be a preferred location for their generation. However, several large statistical studies in the past two decades, most notably Fraser and Nguyen [2001], have provided little support for this location. In this study we present a survey of the most intense EMIC waves observed by the EMFISIS fluxgate magnetometer on the Van Allen Probes-A spacecraft (with apogee at 5.9 RE) from its launch through the end of 2014, and have compared their location with simultaneous electron density data obtained by the EFW electric field instrument and ring current ion flux data obtained by the HOPE and RBSPICE instruments. We show distributions of these waves as a function of distance inside or outside the PP as a function of local time sector, frequency band (H+, He+, or both), and timing relative to magnetic storms and substorms. Most EMIC waves in this data set occurred within 1 RE of the PP in all local time sectors, but very few were limited to ± 0.1 RE, and most of these occurred in the 06-12 MLT sector during non-storm conditions. The majority of storm main phase waves in the dusk sector occurred inside the PP. He+ band waves dominated at most local times inside the PP, and H+ band waves were never observed there. Although the presence of elevated fluxes of ring current protons was common to all events, the configuration of lower energy ion populations varied as a function of geomagnetic activity and storm phase.

Interplanetary shocks, Plasma waves and turbulence, Kinetic waves and instabilities, STEREO spacecraft

NASA Astrophysics Data System (ADS)

Cohen, Z.; Breneman, A. W.; Cattell, C. A.; Davis, L.; Grul, P.; Kersten, K.; Wilson, L. B., III

2017-12-01

Determining the role of plasma waves in providing energy dissipation at shock waves is of long-standing interest. Interplanetary (IP) shocks serve as a large database of low Mach number shocks. We examine electric field waveforms captured by the Time Domain Sampler (TDS) on the STEREO spacecraft during the ramps of IP shocks, with emphasis on captures lasting 2.1 seconds. Previous work has used captures of shorter duration (66 and 131 ms on STEREO, and 17 ms on WIND), which allowed for observation of waves with maximum (minimum) frequencies of 125 kHz (15 Hz), 62.5 kHz (8 Hz), and 60 kHz (59 Hz), respectively. The maximum frequencies are comparable to 2-8 times the plasma frequency in the solar wind, enabling observation of Langmuir waves, ion acoustic, and some whistler-mode waves. The 2 second captures resolve lower frequencies ( few Hz), which allows us to analyze packet structure of the whistler-mode waves and some ion acoustic waves. The longer capture time also improves the resolvability of simultaneous wave modes and of waves with frequencies on the order of 10s of Hz. Langmuir waves, however, cannot be identified at this sampling rate, since the plasma frequency is usually higher than 3.9 kHz. IP shocks are identified from multiple databases (Helsinki heliospheric shock database at http://ipshocks.fi, and the STEREO level 3 shock database at ftp://stereoftp.nascom.nasa.gov/pub/ins_data/impact/level3/). Our analysis focuses on TDS captures in shock ramp regions, with ramp durations determined from magnetic field data taken at 8 Hz. Software is used to identify multiple wave modes in any given capture and classify waves as Langmuir, ion acoustic, whistler, lower hybrid, electron cyclotron drift instability, or electrostatic solitary waves. Relevant frequencies are determined from density and magnetic field data collected in situ. Preliminary results suggest that large amplitude (∼ 5 mV/m) ion acoustic waves are most prevalent in the ramp, in agreement with Wilson, et al. Other modes are also observed. Statistical results will be presented and compared with previous studies and theoretical predictions.

Direct multiple path magnetospheric propagation - A fundamental property of nonducted VLF waves

NASA Technical Reports Server (NTRS)

Sonwalkar, V. S.; Bell, T. F.; Helliwell, R. A.; Inan, U. S.

1984-01-01

An elongation of 20-200 ms, attributed to closely spaced multiple propagation paths between the satellite and the ground, is noted in well defined pulses observed by the ISEE 1 satellite in nonducted whistler mode signals from the Siple Station VLF transmitter. Electric field measurements show a 2 to 10 dB amplitude variation in the observed amplitude fading pattern which is also consistent with direct multiple path propagation. The results obtained for two cases, one outside and one inside the plasmapause, establish that the direct signals transmitted from the ground arrive almost simultaneously at any point in the magnetosphere along two or more closely spaced direct ray paths. It is also shown that multiple paths can be explained by assuming field-aligned irregularities, and the implications of these results for nonducted wave-particle interaction in the magnetosphere are discussed. For reasonable parameters of nonducted, multiple path propagation, a cyclotron-resonant electron will experience a wave Doppler broadening of a few tens to a few hundreds of Hz.

Temperature-mediated transition from Dyakonov-Tamm surface waves to surface-plasmon-polariton waves

NASA Astrophysics Data System (ADS)

Chiadini, Francesco; Fiumara, Vincenzo; Mackay, Tom G.; Scaglione, Antonio; Lakhtakia, Akhlesh

2017-08-01

The effect of changing the temperature on the propagation of electromagnetic surface waves (ESWs), guided by the planar interface of a homogeneous isotropic temperature-sensitive material (namely, InSb) and a temperature-insensitive structurally chiral material (SCM) was numerically investigated in the terahertz frequency regime. As the temperature rises, InSb transforms from a dissipative dielectric material to a dissipative plasmonic material. Correspondingly, the ESWs transmute from Dyakonov-Tamm surface waves into surface-plasmon-polariton waves. The effects of the temperature change are clearly observed in the phase speeds, propagation distances, angular existence domains, multiplicity, and spatial profiles of energy flow of the ESWs. Remarkably large propagation distances can be achieved; in such instances the energy of an ESW is confined almost entirely within the SCM. For certain propagation directions, simultaneous excitation of two ESWs with (i) the same phase speeds but different propagation distances or (ii) the same propagation distances but different phase speeds are also indicated by our results.

Collapse of optical wave arrested by cross-phase modulation in nonlinear metamaterials

NASA Astrophysics Data System (ADS)

Zhang, Jinggui; Li, Ying; Xiang, Yuanjiang; Lei, Dajun; Zhang, Lifu

2016-03-01

In this article, we put forward a novel strategy to realize the management of wave collapse through designing probe-pump configuration where probe wave is assumed to propagate in the positive-index region of metamaterials (MMs), while pump wave is assumed to propagate in the negative-index region. We disclose that cross-phase modulation (XPM) in MMs as a new physical mechanism that can be used to arrest the collapse of probe wave in the positive-index region by copropagating it together with pump wave in the negative-index region. Further, we observe that pump wave will evolve into a ring while probe wave will develop a side lob in the wings during the course of coupled waves propagation, different from the corresponding counterpart in the ordinary positive-index materials (OMs) where they simultaneously exhibit the catastrophic self-focusing behavior. Meanwhile, we also discuss how to control the collapse of probe wave by adjusting intensity-detuned pump wave. Our analysis is performed by directly numerically solving the coupled nonlinear Schrödinger equations, as well as using the variational approximation, both showing consistent results. The finding demonstrates XPM as a specific physical mechanism in MMs can provide us unique opportunities unattainable in OMs to manipulate self-focusing of high-power laser.

Reproducibility of Regional Pulse Wave Velocity in Healthy Subjects

PubMed Central

Lee, Nak Bum

2009-01-01

Background/Aims Despite the clinical importance and widespread use of pulse wave velocity (PWV), there are no standards for pulse sensors or for system requirements to ensure accurate pulse wave measurement. We assessed the reproducibility of PWV values using a newly developed PWV measurement system. Methods The system used in this study was the PP-1000, which simultaneously provides regional PWV values from arteries at four different sites (carotid, femoral, radial, and dorsalis pedis). Seventeen healthy male subjects without any cardiovascular disease participated in this study. Two observers performed two consecutive measurements in the same subject in random order. To evaluate the reproducibility of the system, two sets of analyses (within-observer and between-observer) were performed. Results The means±SD of PWV for the aorta, arm, and leg were 7.0±1.48, 8.43±1.14, and 8.09±0.98 m/s as measured by observer A and 6.76±1.00, 7.97±0.80, and 7.97±0.72 m/s by observer B, respectively. Between-observer differences for the aorta, arm, and leg were 0.14±0.62, 0.18±0.84, and 0.07±0.86 m/s, respectively, and the correlation coefficients were high, especially for aortic PWV (r=0.93). All the measurements showed significant correlation coefficients, ranging from 0.94 to 0.99. Conclusions The PWV measurement system used in this study provides accurate analysis results with high reproducibility. It is necessary to provide an accurate algorithm for the detection of additional features such as flow wave, reflection wave, and dicrotic notch from a pulse waveform. PMID:19270477

An experimental investigation on the subcritical instability in plane Poieseuille flow

NASA Technical Reports Server (NTRS)

Nishioka, T.; Honda, S.; Kamibayashi, S.

1981-01-01

The relationship between the three dimensional properties of the fundamental flow of a plane Poieseuille flow and subcritical stability was studied. An S-T wave was introduced into the flow and the three dimensional development of the wave observed. Results indicate that: (1) the T-S wave has three dimensional properties which are synchronous with the fundamental flow, but there is damping at microamplitude; (2) when the amplitude reaches a certain threshold, subcritical instability and peak valley bifurcation occur simultaneously and a peak valley structure is formed; (3) this threshold depends to a great extent on the frequency; and (4) after the peak valley bifurcation there is a transition to a turbulent flow by the process of laminar flow collapse identical to that in Blasius flow.

Swope Supernova Survey 2017a (SSS17a), the optical counterpart to a gravitational wave source.

PubMed

Coulter, D A; Foley, R J; Kilpatrick, C D; Drout, M R; Piro, A L; Shappee, B J; Siebert, M R; Simon, J D; Ulloa, N; Kasen, D; Madore, B F; Murguia-Berthier, A; Pan, Y-C; Prochaska, J X; Ramirez-Ruiz, E; Rest, A; Rojas-Bravo, C

2017-12-22

On 17 August 2017, the Laser Interferometer Gravitational-Wave Observatory (LIGO) and the Virgo interferometer detected gravitational waves (GWs) emanating from a binary neutron star merger, GW170817. Nearly simultaneously, the Fermi and INTEGRAL (INTErnational Gamma-Ray Astrophysics Laboratory) telescopes detected a gamma-ray transient, GRB 170817A. At 10.9 hours after the GW trigger, we discovered a transient and fading optical source, Swope Supernova Survey 2017a (SSS17a), coincident with GW170817. SSS17a is located in NGC 4993, an S0 galaxy at a distance of 40 megaparsecs. The precise location of GW170817 provides an opportunity to probe the nature of these cataclysmic events by combining electromagnetic and GW observations. Copyright © 2017, American Association for the Advancement of Science.

Oscillations and waves in a spatially distributed system with a 1/f spectrum

NASA Astrophysics Data System (ADS)

Koverda, V. P.; Skokov, V. N.

2018-02-01

A spatially distributed system with a 1/f power spectrum is described by two nonlinear stochastic equations. Conditions for the formation of auto-oscillations have been found using numerical methods. The formation of a 1/f and 1/k spectrum simultaneously with the formation and motion of waves under the action of white noise has been demonstrated. The large extreme fluctuations with 1/f and 1/k spectra correspond to the maximum entropy, which points to the stability of such processes. It is shown that on the background of formation and motion of waves at an external periodic action there appears spatio-temporal stochastic resonance, at which one can observe the expansion of the region of periodic pulsations under the action of white noise.

Evidence for {100}<011> slip in ferropericlase in Earth's lower mantle from high-pressure/high-temperature experiments

NASA Astrophysics Data System (ADS)

Immoor, J.; Marquardt, H.; Miyagi, L.; Lin, F.; Speziale, S.; Merkel, S.; Buchen, J.; Kurnosov, A.; Liermann, H.-P.

2018-05-01

Seismic anisotropy in Earth's lowermost mantle, resulting from Crystallographic Preferred Orientation (CPO) of elastically anisotropic minerals, is among the most promising observables to map mantle flow patterns. A quantitative interpretation, however, is hampered by the limited understanding of CPO development in lower mantle minerals at simultaneously high pressures and temperatures. Here, we experimentally determine CPO formation in ferropericlase, one of the elastically most anisotropic deep mantle phases, at pressures of the lower mantle and temperatures of up to 1400 K using a novel experimental setup. Our data reveal a significant contribution of slip on {100} to ferropericlase CPO in the deep lower mantle, contradicting previous inferences based on experimental work at lower mantle pressures but room temperature. We use our results along with a geodynamic model to show that deformed ferropericlase produces strong shear wave anisotropy in the lowermost mantle, where horizontally polarized shear waves are faster than vertically polarized shear waves, consistent with seismic observations. We find that ferropericlase alone can produce the observed seismic shear wave splitting in D″ in regions of downwelling, which may be further enhanced by post-perovskite. Our model further shows that the interplay between ferropericlase (causing VSH > VSV) and bridgmanite (causing VSV > VSH) CPO can produce a more complex anisotropy patterns as observed in regions of upwelling at the margin of the African Large Low Shear Velocity Province.

Evidence at Mesospheric Altitude of Deeply Propagating Atmospheric Gravity Waves Created by Orographic Forcing over the Auckland Islands (50.5ºS) During the Deepwave Project

NASA Astrophysics Data System (ADS)

Pautet, P. D.; Ma, J.; Taylor, M. J.; Bossert, K.; Doyle, J. D.; Eckermann, S. D.; Williams, B. P.; Fritts, D. C.

2014-12-01

The DEEPWAVE project recently took place in New Zealand during the months of June and July 2014. This international program focused on investigating the generation and deep propagation of atmospheric gravity waves. A series of instruments was operated at several ground-based locations and on-board the NSF Gulfstream V aircraft. 26 research flights were performed to explore possible wave sources and their effects on the middle and upper atmosphere. On July 14th, a research flight was conducted over the Auckland Islands, a small sub Antarctic archipelago located ~450km south of New Zealand. Moderate southwesterly tropospheric wind (~25m/s) was blowing over the rugged topography of the islands, generating mountain wave signature at the flight altitude. Spectacular small-scale gravity waves were simultaneously observed at the mesopause level using the USU Advanced Mesospheric Temperature Mapper (AMTM). Their similarity with the model-predicted waves was striking. This presentation will describe this remarkable case of deep wave propagation and compare the measurements obtained with the instruments on-board the aircraft with forecasting and wave propagation models.

Determining wave direction using curvature parameters.

PubMed

de Queiroz, Eduardo Vitarelli; de Carvalho, João Luiz Baptista

2016-01-01

The curvature of the sea wave was tested as a parameter for estimating wave direction in the search for better results in estimates of wave direction in shallow waters, where waves of different sizes, frequencies and directions intersect and it is difficult to characterize. We used numerical simulations of the sea surface to determine wave direction calculated from the curvature of the waves. Using 1000 numerical simulations, the statistical variability of the wave direction was determined. The results showed good performance by the curvature parameter for estimating wave direction. Accuracy in the estimates was improved by including wave slope parameters in addition to curvature. The results indicate that the curvature is a promising technique to estimate wave directions.•In this study, the accuracy and precision of curvature parameters to measure wave direction are analyzed using a model simulation that generates 1000 wave records with directional resolution.•The model allows the simultaneous simulation of time-series wave properties such as sea surface elevation, slope and curvature and they were used to analyze the variability of estimated directions.•The simultaneous acquisition of slope and curvature parameters can contribute to estimates wave direction, thus increasing accuracy and precision of results.

Blood pulse wave velocity measured by photoacoustic microscopy

NASA Astrophysics Data System (ADS)

Yeh, Chenghung; Hu, Song; Maslov, Konstantin; Wang, Lihong V.

2013-03-01

Blood pulse wave velocity (PWV) is an important indicator for vascular stiffness. In this letter, we present electrocardiogram-synchronized photoacoustic microscopy for in vivo noninvasive quantification of the PWV in the peripheral vessels of mice. Interestingly, strong correlation between blood flow speed and ECG were clearly observed in arteries but not in veins. PWV is measured by the pulse travel time and the distance between two spot of a chose vessel, where simultaneously recorded electrocardiograms served as references. Statistical analysis shows a linear correlation between the PWV and the vessel diameter, which agrees with known physiology. Keywords: photoacoustic microscopy, photoacoustic spectroscopy, bilirubin, scattering medium.

Evolution of chorus emissions into plasmaspheric hiss observed by Van Allen Probes

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zhou, Qinghua; Xiao, Fuliang; Yang, Chang

The two classes of whistler mode waves (chorus and hiss) play different roles in the dynamics of radiation belt energetic electrons. Chorus can efficiently accelerate energetic electrons, and hiss is responsible for the loss of energetic electrons. Previous studies have proposed that chorus is the source of plasmaspheric hiss, but this still requires an observational confirmation because the previously observed chorus and hiss emissions were not in the same frequency range in the same time. In this paper, we report simultaneous observations form Van Allen Probes that chorus and hiss emissions occurred in the same range ~300–1500 Hz with themore » peak wave power density about 10 -5 nT 2/Hz during a weak storm on 3 July 2014. Chorus emissions propagate in a broad region outside the plasmapause. Meanwhile, hiss emissions are confined inside the plasmasphere, with a higher intensity and a broader area at a lower frequency. A sum of bi-Maxwellian distribution is used to model the observed anisotropic electron distributions and to evaluate the instability of waves. A three-dimensional ray tracing simulation shows that a portion of chorus emission outside the plasmasphere can propagate into the plasmasphere and evolve into plasmaspheric hiss. Moreover, hiss waves below 1 kHz are more intense and propagate over a broader area than those above 1 kHz, consistent with the observation. Finally, the current results can explain distributions of the observed hiss emission and provide a further support for the mechanism of evolution of chorus into hiss emissions.« less

Evolution of chorus emissions into plasmaspheric hiss observed by Van Allen Probes

DOE PAGES

Zhou, Qinghua; Xiao, Fuliang; Yang, Chang; ...

2016-05-09

The two classes of whistler mode waves (chorus and hiss) play different roles in the dynamics of radiation belt energetic electrons. Chorus can efficiently accelerate energetic electrons, and hiss is responsible for the loss of energetic electrons. Previous studies have proposed that chorus is the source of plasmaspheric hiss, but this still requires an observational confirmation because the previously observed chorus and hiss emissions were not in the same frequency range in the same time. In this paper, we report simultaneous observations form Van Allen Probes that chorus and hiss emissions occurred in the same range ~300–1500 Hz with themore » peak wave power density about 10 -5 nT 2/Hz during a weak storm on 3 July 2014. Chorus emissions propagate in a broad region outside the plasmapause. Meanwhile, hiss emissions are confined inside the plasmasphere, with a higher intensity and a broader area at a lower frequency. A sum of bi-Maxwellian distribution is used to model the observed anisotropic electron distributions and to evaluate the instability of waves. A three-dimensional ray tracing simulation shows that a portion of chorus emission outside the plasmasphere can propagate into the plasmasphere and evolve into plasmaspheric hiss. Moreover, hiss waves below 1 kHz are more intense and propagate over a broader area than those above 1 kHz, consistent with the observation. Finally, the current results can explain distributions of the observed hiss emission and provide a further support for the mechanism of evolution of chorus into hiss emissions.« less

Simultaneous Determination of Structure and Event Location Using Body and Surface Wave Measurements at a Single Station: Preparation for Mars Data from the InSight Mission

NASA Astrophysics Data System (ADS)

Panning, M. P.; Banerdt, W. B.; Beucler, E.; Blanchette-Guertin, J. F.; Boese, M.; Clinton, J. F.; Drilleau, M.; James, S. R.; Kawamura, T.; Khan, A.; Lognonne, P. H.; Mocquet, A.; van Driel, M.

2015-12-01

An important challenge for the upcoming InSight mission to Mars, which will deliver a broadband seismic station to Mars along with other geophysical instruments in 2016, is to accurately determine event locations with the use of a single station. Locations are critical for the primary objective of the mission, determining the internal structure of Mars, as well as a secondary objective of measuring the activity of distribution of seismic events. As part of the mission planning process, a variety of techniques have been explored for location of marsquakes and inversion of structure, and preliminary procedures and software are already under development as part of the InSight Mars Quake and Mars Structure Services. One proposed method, involving the use of recordings of multiple-orbit surface waves, has already been tested with synthetic data and Earth recordings. This method has the strength of not requiring an a priori velocity model of Mars for quake location, but will only be practical for larger events. For smaller events where only first orbit surface waves and body waves are observable, other methods are required. In this study, we implement a transdimensional Bayesian inversion approach to simultaneously invert for basic velocity structure and location parameters (epicentral distance and origin time) using only measurements of body wave arrival times and dispersion of first orbit surface waves. The method is tested with synthetic data with expected Mars noise and Earth data for single events and groups of events and evaluated for errors in both location and structural determination, as well as tradeoffs between resolvable parameters and the effect of 3D crustal variations.

VERTICAL KINK OSCILLATION OF A MAGNETIC FLUX ROPE STRUCTURE IN THE SOLAR CORONA

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kim, S.; Cho, K.-S.; Nakariakov, V. M., E-mail: sjkim@kasi.re.kr

2014-12-20

Vertical transverse oscillations of a coronal magnetic rope, observed simultaneously in the 171 Å and 304 Å bandpasses of the Atmospheric Imaging Assembly on board the Solar Dynamics Observatory (SDO), are detected. The oscillation period is about 700 s and the displacement amplitude is about 1 Mm. The oscillation amplitude remains constant during the observation. Simultaneous observation of the rope in the bandpasses corresponding to the coronal and chromospheric temperatures suggests that it has a multi-thermal structure. Oscillatory patterns in 171 Å and 304 Å are coherent, which indicates that the observed kink oscillation is collective, in which the ropemore » moves as a single entity. We interpret the oscillation as a fundamental standing vertically polarized kink mode of the rope, while the interpretation in terms of a perpendicular fast wave could not be entirely ruled out. In addition, the arcade situated above the rope and seen in the 171 Å bandpass shows an oscillatory motion with the period of about 1000 s.« less

Path planning on cellular nonlinear network using active wave computing technique

NASA Astrophysics Data System (ADS)

Yeniçeri, Ramazan; Yalçın, Müstak E.

2009-05-01

This paper introduces a simple algorithm to solve robot path finding problem using active wave computing techniques. A two-dimensional Cellular Neural/Nonlinear Network (CNN), consist of relaxation oscillators, has been used to generate active waves and to process the visual information. The network, which has been implemented on a Field Programmable Gate Array (FPGA) chip, has the feature of being programmed, controlled and observed by a host computer. The arena of the robot is modelled as the medium of the active waves on the network. Active waves are employed to cover the whole medium with their own dynamics, by starting from an initial point. The proposed algorithm is achieved by observing the motion of the wave-front of the active waves. Host program first loads the arena model onto the active wave generator network and command to start the generation. Then periodically pulls the network image from the generator hardware to analyze evolution of the active waves. When the algorithm is completed, vectorial data image is generated. The path from any of the pixel on this image to the active wave generating pixel is drawn by the vectors on this image. The robot arena may be a complicated labyrinth or may have a simple geometry. But, the arena surface always must be flat. Our Autowave Generator CNN implementation which is settled on the Xilinx University Program Virtex-II Pro Development System is operated by a MATLAB program running on the host computer. As the active wave generator hardware has 16, 384 neurons, an arena with 128 × 128 pixels can be modeled and solved by the algorithm. The system also has a monitor and network image is depicted on the monitor simultaneously.

Development of Electric Field and Plasma Wave Investigations for Future Space Weather Missions: ERG, SCOPE, and beyond

NASA Astrophysics Data System (ADS)

Kasaba, Y.; Kumamoto, A.; Ono, T.; Misawa, H.; Kojima, H.; Yagitani, S.; Kasahara, Y.; Ishisaka, K.

2009-04-01

The electric field and plasma wave investigation is important for the clarification of global plasma dynamics and energetic processes in the planetary Magnetospheric studies. We have several missions which will contribute those objectives. the small-sized radiation belt mission, ERG (Energization and Radiation in Geospace), the cross-scale formation flight mission, SCOPE, the BepiColombo mission to Mercury, and the small-sized and full-scale Jovian mission in future. Those will prevail the universal plasma mechanism and processes in the space laboratory. The main purposes of electric field and plasma wave observation for those missions are: (1) Examination of the theories of high-energy particle acceleration by plasma waves, (2) identification of the origin of electric fields in the magnetosphere associated with cross-scale coupling processes, (3) diagnosis of plasma density, temperature and composition, and (4) investigation of wave-particle interaction and mode conversion processes. Simultaneous observation of plasma waves and energetic particles with high resolution will enable us to investigate the wave-particle interaction based on quasi-linear theory and non-linear models. In this paper, we will summarize the current plan and efforts for those future activities. In order to achieve those objectives, the instrument including sensitive sensors (the long wire / stem antennae, the search-coil / loop antennae) and integrated receiver systems are now in development, including the direct identification of nonlinear wave-particle interactions associated will be tried by Wave-particle Correlator. And, as applications of those development, we will mention to the space interferometer and the radar sounder technologies.

Laboratory Studies of the Nonlinear Interactions of Kink-Unstable Flux Ropes and Shear Alfvén Waves

NASA Astrophysics Data System (ADS)

Vincena, S. T.; Tripathi, S.; Gekelman, W. N.; DeHaas, T.; Pribyl, P.

2017-12-01

Magnetic flux ropes and shear Alfvén waves occur simultaneously in plasmas ranging from solar prominences, to the solar wind, to planetary magnetospheres. If the flux ropes evolve to become unstable to the kink mode, interactions between the kink oscillations and the shear waves can arise, and may even lead to nonlinear phenomena. Experiments aimed at elucidating such interactions are performed in the upgraded Large Plasma Device at UCLA. Flux ropes are generated using a 20 cm x 20 cm LaB6 cathode-anode discharge (with L = 18 m and β ˜ 0.1.) The ropes are embedded in a larger, otherwise current-free, cylindrical (r = 30cm) ambient plasma produced by a second cathode. Shear Alfvén waves are launched using externally fed antennas having three separate polarizations (azimuthal mode numbers.) The counter-propagating, kink-unstable oscillations and driven shear waves are observed to nonlinearly generate sidebands about the higher, shear wave frequency (evident in power spectra) via three-wave coupling. This is demonstrated though bi-coherence calculations and k-matching. With a fixed kink-mode polarization, a total of six daughter wave patterns are presented. Energy flow is shown to proceed from larger to smaller perpendicular wavelengths. Future work will focus on increasing the plasma beta and wave amplitudes in the quest to observe an evolution to a turbulent state. Work is performed at the US Basic Plasma Science Facility, which is supported by the US Department of Energy and the National Science Foundation.

Tsunami simulation using submarine displacement calculated from simulation of ground motion due to seismic source model

NASA Astrophysics Data System (ADS)

Akiyama, S.; Kawaji, K.; Fujihara, S.

2013-12-01

Since fault fracturing due to an earthquake can simultaneously cause ground motion and tsunami, it is appropriate to evaluate the ground motion and the tsunami by single fault model. However, several source models are used independently in the ground motion simulation or the tsunami simulation, because of difficulty in evaluating both phenomena simultaneously. Many source models for the 2011 off the Pacific coast of Tohoku Earthquake are proposed from the inversion analyses of seismic observations or from those of tsunami observations. Most of these models show the similar features, which large amount of slip is located at the shallower part of fault area near the Japan Trench. This indicates that the ground motion and the tsunami can be evaluated by the single source model. Therefore, we examine the possibility of the tsunami prediction, using the fault model estimated from seismic observation records. In this study, we try to carry out the tsunami simulation using the displacement field of oceanic crustal movements, which is calculated from the ground motion simulation of the 2011 off the Pacific coast of Tohoku Earthquake. We use two fault models by Yoshida et al. (2011), which are based on both the teleseismic body wave and on the strong ground motion records. Although there is the common feature in those fault models, the amount of slip near the Japan trench is lager in the fault model from the strong ground motion records than in that from the teleseismic body wave. First, the large-scale ground motion simulations applying those fault models used by the voxel type finite element method are performed for the whole eastern Japan. The synthetic waveforms computed from the simulations are generally consistent with the observation records of K-NET (Kinoshita (1998)) and KiK-net stations (Aoi et al. (2000)), deployed by the National Research Institute for Earth Science and Disaster Prevention (NIED). Next, the tsunami simulations are performed by the finite difference calculation based on the shallow water theory. The initial wave height for tsunami generation is estimated from the vertical displacement of ocean bottom due to the crustal movements, which is obtained from the ground motion simulation mentioned above. The results of tsunami simulations are compared with the observations of the GPS wave gauges to evaluate the validity for the tsunami prediction using the fault model based on the seismic observation records.

The Observation of Gravitational Waves from a Binary Black Hole Merger

NASA Astrophysics Data System (ADS)

Reitze, David

2016-03-01

On September 14, 2015, the two LIGO detectors operating at Hanford, WA and Livingston, LA nearly simultaneously recorded a strong trigger consistent with the passage of gravitational waves. An extensive and thorough analysis by the LIGO Scientific Collaboration and the Virgo Collaboration over the following months determined the gravitational waves to originate from the final stage of the inspiral of two black holes with masses approximately 36 and 29 Msun merging to form a 62 Msun black hole located at a distance of roughly 410 Mpc.This discovery is remarkable in many ways. In addition to being the first direct measurement of a gravitational wave by an earth-based detector, this is the first observation of coalescing binary black hole system and the first evidence that ``heavy'' stellar mass black holes exist. The measured gravitational waveform was determined to be highly consistent with that predicted by general relativity for the merger of two black holes. In this talk, the first of two in this special session on the discovery of GW150914, I'll cover a number of topics related to the detection, including a brief description of the operation and performance of the Advanced LIGO detectors during the first `O1' Observing Run as well as the data quality verification methods used to determine the validity of the detection. I'll also present the searches that were used to find and establish the statistical confidence of the event, as well as provide an estimate of its sky localization. Finally, I will discuss the plans for future observations by LIGO, Virgo and other gravitational wave detectors over the next few years and, time permitting, present the short term and longer term programs for improving the sensitivity and range of gravitational wave detectors over the next ten years.

Polarization analysis of VLF/ELF waves observed at subauroral latitudes during the VLF-CHAIN campaign

NASA Astrophysics Data System (ADS)

Martinez-Calderon, Claudia; Shiokawa, Kazuo; Miyoshi, Yoshizumi; Ozaki, Mitsunori; Schofield, Ian; Connors, Martin

2015-02-01

Chorus wave emissions are one of the most intense naturally occurring phenomena in the very low (VLF) and extremely low frequency (ELF) ranges. They are believed to be one of the major contributors to acceleration and loss of electrons in the radiation belts. During the VLF Campaign observation with High-resolution Aurora Imaging Network (VLF-CHAIN) from 17 to 25 February 2012, several types of VLF/ELF emissions, including chorus, were observed at subauroral latitudes in Athabasca, Canada. To our knowledge, there has not been any comprehensive study of the physical properties of such emissions at these latitudes. In this study, we calculate spectral and polarization parameters of VLF/ELF waves with high temporal resolution. We found that the polarization angle of several emissions depended on both frequency and time. We suggest that the frequency-dependent events, which usually last several tens of minutes, might be the consequence of the broadening of the ray path that the waves follow from their generation region to the ground. Furthermore, time-dependent events, also lasting tens of minutes, have a polarization angle that changes from negative to positive values (or vice versa) every few minutes. We suggest that this could be due to variations of the wave duct, either near the generation region or along the wave propagation path. Using another ground station in Fort Vermillion, Canada, about 450 km northwest of Athabasca, we tracked the movements of the ionospheric exit point of three chorus emissions observed simultaneously at both stations. Although we found that movement of the ionospheric exit point does not follow a general direction, it is subject to hovering motion, suggesting that the exit point can be affected by small-scale plasma processes.

VLF wave injections from the ground

NASA Technical Reports Server (NTRS)

Helliwell, R. A.

1983-01-01

Experiments on wave-particle interactions using VLF whistler-mode waves injected into the magnetosphere from Antartica are described. The injected signals are single-frequency coherent waves whose amplitudes and frequencies may be changed slowly with time, or else two or more coherent wave trains transmitted simultaneously to determine the nature of the response to multifrequency excitation. The waves may be amplified 30 dB or more and may trigger intense emissions having bandwidths that vary from a few to several hundred Hertz. In most cases significant growth and triggering occur only when the driving signal is essentially monochromatic (bandwidth 10 Hz). If two frequencies are transmitted simultaneously the signal at the lower frequency tends to be suppressed by 20 dB or more. These results are interpreted in terms of a feedback interaction between the waves and counter-streaming cyclotron resonant electrons in a region several hundred wavelengths long, centered on the magnetic equator.

Case study of convective instability observed in airglow images over the Northeast of Brazil

NASA Astrophysics Data System (ADS)

Carvalho, A. J. A.; Paulino, I.; Medeiros, A. F.; Lima, L. M.; Buriti, R. A.; Paulino, A. R.; Wrasse, C. M.; Takahashi, H.

2017-02-01

An intense activity of ripples during the nighttime was observed in airglow images over São João do Cariri (36.5° W, 7.4° S) on 10 October 2004 which lasted for two hours. Those ripples appeared simultaneously with the crossing of a mesospheric front and medium scale gravity waves. The ripples occurred ahead of the mesospheric front and their phase front were almost parallel to the phase of the mesospheric front and were almost perpendicular to the phase front of the gravity wave. Using wind measurements from a meteor radar located at São João do Cariri and simultaneous vertical temperature profiles from the TIMED/SABER satellite, on the night of the events and within the imager field of view, the atmospheric background environment in the mesosphere and lower thermosphere (MLT) was investigated in order to understand the instability process that caused the appearance of the ripples. Dynamic and convective instabilities have been pointed out as responsible for creation of ripples in the MLT. The observed ripples were advected by the neutral wind, they occurred into a region with negative lapse rate of the potential temperature and the Richardson number was negative as well. According to these characteristics, the ripple structures could be generated in the MLT region due to the predominance of convective instability.

A semi-analytical method for near-trapped mode and fictitious frequencies of multiple scattering by an array of elliptical cylinders in water waves

NASA Astrophysics Data System (ADS)

Chen, Jeng-Tzong; Lee, Jia-Wei

2013-09-01

In this paper, we focus on the water wave scattering by an array of four elliptical cylinders. The null-field boundary integral equation method (BIEM) is used in conjunction with degenerate kernels and eigenfunctions expansion. The closed-form fundamental solution is expressed in terms of the degenerate kernel containing the Mathieu and the modified Mathieu functions in the elliptical coordinates. Boundary densities are represented by using the eigenfunction expansion. To avoid using the addition theorem to translate the Mathieu functions, the present approach can solve the water wave problem containing multiple elliptical cylinders in a semi-analytical manner by introducing the adaptive observer system. Regarding water wave problems, the phenomena of numerical instability of fictitious frequencies may appear when the BIEM/boundary element method (BEM) is used. Besides, the near-trapped mode for an array of four identical elliptical cylinders is observed in a special layout. Both physical (near-trapped mode) and mathematical (fictitious frequency) resonances simultaneously appear in the present paper for a water wave problem by an array of four identical elliptical cylinders. Two regularization techniques, the combined Helmholtz interior integral equation formulation (CHIEF) method and the Burton and Miller approach, are adopted to alleviate the numerical resonance due to fictitious frequency.

Ponderomotive Force and Lower Hybrid Turbulence Effects in Space Plasmas Subjected to Large-Amplitude Low-Frequency Waves

NASA Technical Reports Server (NTRS)

Khazanov, G. V.; Khazanov, George; Liemohn, M. W.; Stone, N. H.; Coffey, V. N.

1997-01-01

In the auroral region, simultaneous occurrences of upward-flowing ions and field-aligned electrons have been observed by the Viking satellite. The occurrence is strongly correlated with large amplitude low frequency fluctuations of the electric field. Large-amplitude shear Alfven waves have also been observed by sounding rockets in the auroral ionosphere. When such LF waves are propagating in a plasma, a ponderomotive force and other types of waves are produced which may lead to significant effects on the plasma. This force is directed toward decreasing density, providing the electromagnetic lift of the background plasma and an increase of collisionless plasma expansion. We find that even for modest wave strengths, the influence on the outflowing oxygen ions can be dramatic, increasing the high-altitude density by orders of magnitude. It is also demonstrated that large-amplitude low-frequency waves (LFW) may generate lower hybrid waves (LHW) in the auroral zone. The excitation of LHW by a LF wave may lead to the appearance of an additional channel of energy transfer from, for example, Alfven or fast magnetosonic waves, to particles. This process then influences the formation of the plasma distribution function at the expense of acceleration in the tail of the distribution during the collapse of the LHW. The ion energization due to the LHW can be comparable with that produced by the ponderomotive force of the LFW. It is shown that the LH turbulence leads to equalization of the ponderomotive acceleration of the different ion species. The mechanism of LHW excitation due to the oxygen ion relative drift in a plasma subjected to low-frequency waves is used for analysis of Viking satellite data for events in the cusp/cleft region. It is found that, in some cases, such a mechanism leads to LHW energy densities and ion distribution functions close to those observed.

Ionospheric signatures of cusp latitude Pc 3 pulsations

NASA Technical Reports Server (NTRS)

Engebretson, M. J.; Anderson, B. J.; Cahill, L. J., Jr.; Arnoldy, R. L.; Rosenberg, T. J.

1990-01-01

Search coil magnetometer, riometer, photometer, and ELF-VLF receiver data obtained at South Pole Station and McMurdo, Antarctica during selected days in March and April 1986 are compared. Narrow-band magnetic pulsations in the Pc 3 period range are observed simultaneously at both stations in the dayside sector during times of low IMF cone angle, but are considerably stronger at South Pole, which is located at a latitude near the nominal foot point of the dayside cusp/cleft region. Pulsations in auroral light at 427.8 nm wavelength are often observed with magnetic pulsations at South Pole, but such optical pulsations are not observed at McMurdo. The observations suggest that precipitating magnetosheathlike electrons at nominal dayside cleft latitudes are at times modulated with frequencies similar to those of upstream waves. These particles may play an important role, via modification of ionospheric currents and conductivities, in the transmission of upstream wave signals into the magnetosphere and in the generation of dayside high-latitude Pc 3 pulsations.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Trubilko, A. I., E-mail: trubilko.andrey@gmail.com

Coherent scattering of a two-level atom in the field of a quantized standing wave of a micromaser is considered under conditions of initial quantum correlation between the atom and the field. Such a correlation can be produced by a broadband parametric source. The interaction leading to scattering of the atom from the nonuniform field occurs in the dispersion limit or in the wing of the absorption line of the atom. Apart from the quantized field, the atom simultaneously interacts with two classical counterpropagating waves with different frequencies, which are acting in the plane perpendicular to the atom’s propagation velocity andmore » to the wavevector of the standing wave. Joint action of the quantized field and two classical waves induces effective two-photon and Raman resonance interaction on the working transition. The effective Hamiltonian of the interaction is derived using the unitary transformation method developed for a moving atom. A strong effect is detected, which makes it possible to distinguish the correlated initial state of the atom and the field in the scattering of atom from the state of independent systems. For all three waves, scattering is not observed when systems with quantum correlation are prepared using a high-intensity parametric source. Conversely, when the atom interacts only with the nonuniform field of the standing wave, scattering is not observed in the case of the initial factorized state.« less

Progress Report on the GROWTH (GNSS Reflectometry for Ocean Waves, Tides, and Height) Research Project

NASA Astrophysics Data System (ADS)

Ichikawa, Kaoru; Akiyama, Hiroaki; Ebinuma, Takuji; Isoguchi, Osamu; Kimura, Noriaki; Kitazawa, Yukihito; Konda, Masanori; Kouguchi, Nobuyuki; Tamura, Hitoshi; Tomita, Hiroyuki; Yoshikawa, Yutaka; Waseda, Takuji

2016-04-01

There has been considerable interest in GNSS Reflectometry (GNSS-R) as a new remote-sensing method. We have started a research program for GNSS-R applications on oceanographic observations under the contract with MEXT (Ministry of Education Culture, Sports, Science and Technology, JAPAN) and launched a Japanese research consortium, GROWTH. It is aiming to evaluate the capabilities of GNSS-R observations for oceanographic phenomena with different time scales, such as ocean waves (1/10 to tens of seconds), tides (one or half days), and sea surface dynamic height (a few days to years). In situ observations of ocean wave spectrum, wind speed vertical profile, and sea surface height will be quantitatively compared with equivalent estimates from simultaneous GNSS-R measurements. The GROWTH project will utilize different types of observation platforms; marine observation towers (about 20 m height), multi-copters (about 100 to 200 m height), and much higher-altitude CYGNSS data. Cross-platform data, together with in situ oceanographic observations, will be compared after adequate temporal averaging that accounts differences of the footprint sizes and temporal and spatial scales of oceanographic phenomena. This paper will provide overview of the GROWTH project, preliminary test results obtained by the multi-sensor platform at observation towers, and preparation status of a ground station that will be supplied to receive CYGNSS data at Japan.

Detection of Acoustic/Infrasonic/Seismic Waves Generated by Hypersonic Re-Entry of the HAYABUSA Capsule and Fragmented Parts of the Spacecraft

NASA Astrophysics Data System (ADS)

Yamamoto, Masa-Yuki; Ishihara, Yoshiaki; Hiramatsu, Yoshihiro; Kitamura, Kazuki; Ueda, Masayoshi; Shiba, Yasuo; Furumoto, Muneyoshi; Fujita, Kazuhisa

2011-10-01

Acoustic/infrasonic/seismic waves were observed during the re-entry of the Japanese asteroid explorer ``HAYABUSA'' at 6 ground sites in Woomera, Australia, on 2010 June 13. Overpressure values of infrasound waves were detected at 3 ground sites in a range from 1.3 Pa, 1.0 Pa, and 0.7 Pa with each distance of 36.9 km, 54.9 km, and 67.8 km, respectively, apart from the SRC trajectory. Seismic waveforms through air-to-ground coupling processes were also detected at 6 sites, showing a one-to-one correspondence to infrasound waves at all simultaneous observation sites. Audible sound up to 1 kHz was recorded at one site with a distance of 67.8 km. The mother spacecraft was fragmented from 75 km down to 38 km with a few explosive enhancements of emissions. A persistent train of HAYABUSA re-entry was confirmed at an altitude range of between 92 km down to 82 km for about 3 minutes. Light curves of 136 fragmented parts of the spacecraft were analyzed in detail based on video observations taken at multiple ground sites, being classified into three types of fragmentations, i.e., melting, explosive, and re-fragmented types. In a comparison between infrasonic waves and video-image analyses, regarding the generation of sonic-boom type shock waves by hypersonically moving artificial meteors, both the sample return capsule and fragmented parts of the mother spacecraft, at an altitude of 40 ± 1 km were confirmed with a one-to-one correspondence with each other.

Revisiting a magnetopause Kelvin-Helmholtz event seen by the MMS spacecraft on 8 September 2015: Large-scale context and wave properties

NASA Astrophysics Data System (ADS)

Hasegawa, H.; Nakamura, T.; Kitamura, N.; Hoshi, Y.; Saito, Y.; Figueroa-Vinas, A.; Giles, B. L.; Lavraud, B.; Khotyaintsev, Y. V.; Ergun, R.

2017-12-01

The Kelvin-Helmholtz (KH) instability is known to grow along the Earth's magnetopause, but its role in transporting solar wind mass and energy into the magnetosphere is not fully understood. On 8 September 2015, the Magnetospheric Multiscale (MMS) spacecraft, located at the postnoon, southern-hemisphere magnetopause, encountered thin low-shear current sheets at the trailing edge of the KH waves, where KH-induced reconnection, one of the plasma transport processes, was occurring [Eriksson et al., GRL, 2016; Li et al., GRL, 2016]. The event was observed during a prolonged period of northward interplanetary magnetic field, and was characterized by an extended region of the low-latitude boundary layer (LLBL) immediately earthward of the KH unstable magnetopause, which appeared to have been formed through magnetopause reconnection poleward of the cusp. In this LLBL, MMS observed plasma turbulence, another agent for the plasma transport [Stawarz et al., JGR, 2016]. Key features are that (i) significant magnetic shears were seen only at the trailing edges of the KH surface waves, (ii) for both the leading and trailing edge traversals, both field-aligned and anti-field-aligned streaming D-shaped ion populations, which are consistent with reconnection on the southward and northward sides, respectively, of MMS, were observed on either the magnetosheath or LLBL side of the magnetopause, though not always simultaneously, and (iii) the field-aligned Poynting flux was positive in some parts of the LLBL but was negative in other parts. Based on these observations and further wave analysis, we address the questions of how the current sheets at the KH wave trailing edges were generated, and what could have been the driver of the turbulent fluctuations observed within the KH vortices.

A Resonance Approach to Cochlear Mechanics

PubMed Central

Bell, Andrew

2012-01-01

Background How does the cochlea analyse sound into its component frequencies? In the 1850s Helmholtz thought it occurred by resonance, whereas a century later Békésy's work indicated a travelling wave. The latter answer seemed to settle the question, but with the discovery in 1978 that the cochlea emits sound, the mechanics of the cochlea was back on the drawing board. Recent studies have raised questions about whether the travelling wave, as currently understood, is adequate to explain observations. Approach Applying basic resonance principles, this paper revisits the question. A graded bank of harmonic oscillators with cochlear-like frequencies and quality factors is simultaneously excited, and it is found that resonance gives rise to similar frequency responses, group delays, and travelling wave velocities as observed by experiment. The overall effect of the group delay gradient is to produce a decelerating wave of peak displacement moving from base to apex at characteristic travelling wave speeds. The extensive literature on chains of coupled oscillators is considered, and the occurrence of travelling waves, pseudowaves, phase plateaus, and forced resonance in such systems is noted. Conclusion and significance This alternative approach to cochlear mechanics shows that a travelling wave can simply arise as an apparently moving amplitude peak which passes along a bank of resonators without carrying energy. This highlights the possible role of the fast pressure wave and indicates how phase delays and group delays of a set of driven harmonic oscillators can generate an apparent travelling wave. It is possible to view the cochlea as a chain of globally forced coupled oscillators, and this model incorporates fundamental aspects of both the resonance and travelling wave theories. PMID:23144835

A Link between Variability of the Semidiurnal Tide and Planetary Waves in the Opposite Hemisphere

NASA Technical Reports Server (NTRS)

Smith, Anne K.; Pancheva, Dora V.; Mitchell, Nicholas J.; Marsh, Daniel R.; Russell, James M., III; Mlynczak, Martin G.

2007-01-01

Horizontal wind observations over four years from the meteor radar at Esrange (68 deg N) are analyzed to determine the variability of the semidiurnal tide. Simultaneous global observations of temperature and geopotential from the SABER satellite instrument are used to construct time series of planetary wave amplitudes and geostrophic mean zonal wind. During NH summer and fall, the temporal variability of the semidiurnal tide at Esrange is found to be well correlated with the amplitude of planetary wavenumber 1 in the stratosphere in high southern latitudes (i.e., in the opposite hemisphere). The correlations indicate that a significant part of the tidal variations at Esrange is due to dynamical interactions in the Southern Hemisphere. Other times of the year do not indicate a corresponding robust correlation pattern for the Esrange tides over multiple years.

A mechanism for sustained groundwater pressure changes induced by distant earthquakes

USGS Publications Warehouse

Brodsky, E.E.; Roeloffs, E.; Woodcock, D.; Gall, I.; Manga, M.

2003-01-01

Large sustained well water level changes (>10 cm) in response to distant (more than hundreds of kilometers) earthquakes have proven enigmatic for over 30 years. Here we use high sampling rates at a well near Grants Pass, Oregon, to perform the first simultaneous analysis of both the dynamic response of water level and sustained changes, or steps. We observe a factor of 40 increase in the ratio of water level amplitude to seismic wave ground velocity during a sudden coseismic step. On the basis of this observation we propose a new model for coseismic pore pressure steps in which a temporary barrier deposited by groundwater flow is entrained and removed by the more rapid flow induced by the seismic waves. In hydrothermal areas, this mechanism could lead to 4 ?? 10-2 MPa pressure changes and triggered seismicity.

Polarization characteristics of Whispering-Gallery-Mode fiber lasers based on evanescent-wave-coupled gain.

PubMed

Zhang, Yuan-Xian; Pu, Xiao-Yun; Feng, Li; Han, De-Yu; Ren, Yi-Tao

2013-05-20

The polarization characteristics of Whispering-Gallery-Mode (WGM) fiber lasers based on evanescent-wave-coupled gain are investigated. For the laser gain is excited by side-pumping scheme, it is found that the polarization property of lasing emission is simply dependent on the polarized states of the pump beams. The polarization property of lasing emission depends on the propagating situation of the pump beams in an optical fiber if the laser gain is excited by evanescent-wave pumping scheme, that is, if the pump beams within the fiber are meridional beams, the lasing emission is a transverse electric (TE) wave that forms a special radial polarization emission. However, if the pump beams within the fiber are skew beams, both transverse magnetic (TM) and TE waves exist simultaneously in lasing emission that forms a special axially and radially mixed polarization emission. Pumped by skew beams, the wave-number differences between TE and TM waves are also investigated quantitatively, the results demonstrate that the wave-number difference decreases with the increase of the fiber diameter and the refractive index (RI) of the cladding solution. The observed polarization characteristics have been well explained based on lasing radiation mechanism of WGM fiber laser of gain coupled by evanescent wave.

Imaging two-dimensional mechanical waves of skeletal muscle contraction.

PubMed

Grönlund, Christer; Claesson, Kenji; Holtermann, Andreas

2013-02-01

Skeletal muscle contraction is related to rapid mechanical shortening and thickening. Recently, specialized ultrasound systems have been applied to demonstrate and quantify transient tissue velocities and one-dimensional (1-D) propagation of mechanical waves during muscle contraction. Such waves could potentially provide novel information on musculoskeletal characteristics, function and disorders. In this work, we demonstrate two-dimensional (2-D) mechanical wave imaging following the skeletal muscle contraction. B-mode image acquisition during multiple consecutive electrostimulations, speckle-tracking and a time-stamp sorting protocol were used to obtain 1.4 kHz frame rate 2-D tissue velocity imaging of the biceps brachii muscle contraction. The results present novel information on tissue velocity profiles and mechanical wave propagation. In particular, counter-propagating compressional and shear waves in the longitudinal direction were observed in the contracting tissue (speed 2.8-4.4 m/s) and a compressional wave in the transverse direction of the non-contracting muscle tissue (1.2-1.9 m/s). In conclusion, analysing transient 2-D tissue velocity allows simultaneous assessment of both active and passive muscle tissue properties. Copyright © 2013 World Federation for Ultrasound in Medicine & Biology. Published by Elsevier Inc. All rights reserved.

Simultaneous observations of traveling convection vortices: Ionosphere-thermosphere coupling

NASA Astrophysics Data System (ADS)

Kim, Hyomin; Lessard, Marc R.; Jones, Sarah L.; Lynch, Kristina A.; Fernandes, Philip A.; Aruliah, Anasuya L.; Engebretson, Mark J.; Moen, Jøran I.; Oksavik, Kjellmar; Yahnin, Alexander G.; Yeoman, Timothy K.

2017-05-01

We present simultaneous observations of magnetosphere-ionosphere-thermosphere coupling over Svalbard during a traveling convection vortex (TCV) event. Various spaceborne and ground-based instruments made coordinated measurements, including magnetometers, particle detectors, an all-sky camera, European Incoherent Scatter (EISCAT) Svalbard Radar, Super Dual Auroral Radar Network (SuperDARN), and SCANning Doppler Imager (SCANDI). The instruments recorded TCVs associated with a sudden change in solar wind dynamic pressure. The data display typical features of TCVs including vortical ionospheric convection patterns seen by the ground magnetometers and SuperDARN radars and auroral precipitation near the cusp observed by the all-sky camera. Simultaneously, electron and ion temperature enhancements with corresponding density increase from soft precipitation are also observed by the EISCAT Svalbard Radar. The ground magnetometers also detected electromagnetic ion cyclotron waves at the approximate time of the TCV arrival. This implies that they were generated by a temperature anisotropy resulting from a compression on the dayside magnetosphere. SCANDI data show a divergence in thermospheric winds during the TCVs, presumably due to thermospheric heating associated with the current closure linked to a field-aligned current system generated by the TCVs. We conclude that solar wind pressure impulse-related transient phenomena can affect even the upper atmospheric dynamics via current systems established by a magnetosphere-ionosphere-thermosphere coupling process.

A new point contact surface acoustic wave transducer for measurement of acoustoelastic effect of polymethylmethacrylate.

PubMed

Lee, Yung-Chun; Kuo, Shi Hoa

2004-01-01

A new acoustic transducer and measurement method have been developed for precise measurement of surface wave velocity. This measurement method is used to investigate the acoustoelastic effects for waves propagating on the surface of a polymethylmethacrylate (PMMA) sample. The transducer uses two miniature conical PZT elements for acoustic wave transmitter and receiver on the sample surface; hence, it can be viewed as a point-source/point-receiver transducer. Acoustic waves are excited and detected with the PZT elements, and the wave velocity can be accurately determined with a cross-correlation waveform comparison method. The transducer and its measurement method are particularly sensitive and accurate in determining small changes in wave velocity; therefore, they are applied to the measurement of acoustoelastic effects in PMMA materials. Both the surface skimming longitudinal wave and Rayleigh surface wave can be simultaneously excited and measured. With a uniaxial-loaded PMMA sample, both acoustoelastic effects for surface skimming longitudinal wave and Rayleigh waves of PMMA are measured. The acoustoelastic coefficients for both types of surface wave motions are simultaneously determined. The transducer and its measurement method provide a practical way for measuring surface stresses nondestructively.

Gamma-Ray Astronomy Across 6 Decades of Energy: Synergy between Fermi, IACTs, and HAWC

NASA Technical Reports Server (NTRS)

Hui, C. Michelle

2017-01-01

Gamma Ray Observatories, Gamma-Ray Astrophysics, GeV TeV Sky Survey, Galaxy, Galactic Plane, Source Distribution, The gamma-ray sky is currently well-monitored with good survey coverage. Many instruments from different waveband/messenger (X rays, gamma rays, neutrinos, gravitational waves) available for simultaneous observations. Both wide-field and pointing instruments in development and coming online in the next decade LIGO

Comparison of fine structures of electron cyclotron harmonic emissions in aurora

NASA Astrophysics Data System (ADS)

LaBelle, J.; Dundek, M.

2015-10-01

Recent discoveries of higher harmonic cyclotron emissions in aurora occurring under daylight conditions motivated the modification of radio receivers at South Pole Station, Antarctica, to measure fine structure of such emissions during two consecutive austral summers, 2013-2014 and 2014-2015. The experiment recorded 347 emission events over 376 days of observation. The seasonal distribution of these events reveals that successively higher harmonics require higher solar zenith angles for occurrence, as expected if they are generated at the matching condition fuh = Nfce, which for higher N requires higher electron densities which are associated with higher solar zenith angles. This result implies that generation of higher harmonics from lower harmonics via wave-wave processes explains only a minority of events. Detailed examination of 21 cases in which two harmonics occur simultaneously shows that in almost all events the higher harmonic comes from higher altitudes, and only for a small fraction of events is it plausible that the frequencies of the fine structures of the emissions are correlated and in exact integer ratio. This observation puts an upper bound of 15-20% on the fraction of emissions which can be explained by wave-wave interactions involving Z mode waves at fce and, combined with consideration of source altitudes, puts an upper bound of 75% on the fraction explained by coalescence of Z mode waves at 2fce. Taken together, these results suggest that the dominant mechanism for the higher harmonics is independent generation at the matching points fuh = Nfce and that the wave-wave interaction mechanisms explain a relatively small fraction of events.

Theory of hydrodynamic transport in fluctuating electronic charge density wave states

NASA Astrophysics Data System (ADS)

Delacrétaz, Luca V.; Goutéraux, Blaise; Hartnoll, Sean A.; Karlsson, Anna

2017-11-01

We describe the collective hydrodynamic motion of an incommensurate charge density wave state in a clean electronic system. Our description simultaneously incorporates the effects of both pinning due to weak disorder and also phase relaxation due to proliferating dislocations. We show that the interplay between these two phenomena has important consequences for charge and momentum transport. For instance, it can lead to metal-insulator transitions. We furthermore identify signatures of fluctuating density waves in frequency and spatially resolved conductivities. Phase disordering is well known to lead to a large viscosity. We derive a precise formula for the phase relaxation rate in terms of the viscosity in the dislocation cores. We thereby determine the viscosity of the superconducting state of BSCCO from the observed melting dynamics of Abrikosov lattices and show that the result is consistent with dissipation into Bogoliubov quasiparticles.

SU-G-IeP4-09: Method of Human Eye Aberration Measurement Using Plenoptic Camera Over Large Field of View

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lv, Yang; Wang, Ruixing; Ma, Haotong

Purpose: The measurement based on Shack-Hartmann wave-front sensor(WFS), obtaining both the high and low order wave-front aberrations simultaneously and accurately, has been applied in the detection of human eyes aberration in recent years. However, Its application is limited by the small field of view (FOV), slight eye movement leads the optical bacon image exceeds the lenslet array which result in uncertain detection error. To overcome difficulties of precise eye location, the capacity of detecting eye wave-front aberration over FOV much larger than simply a single conjugate Hartmann WFS accurately and simultaneously is demanded. Methods: Plenoptic camera’s lenslet array subdivides themore » aperture light-field in spatial frequency domain, capture the 4-D light-field information. Data recorded by plenoptic cameras can be used to extract the wave-front phases associated to the eyes aberration. The corresponding theoretical model and simulation system is built up in this article to discuss wave-front measurement performance when utilizing plenoptic camera as wave-front sensor. Results: The simulation results indicate that the plenoptic wave-front method can obtain both the high and low order eyes wave-front aberration with the same accuracy as conventional system in single visual angle detectionand over FOV much larger than simply a single conjugate Hartmann systems. Meanwhile, simulation results show that detection of eye aberrations wave-front in different visual angle can be achieved effectively and simultaneously by plenoptic method, by both point and extended optical beacon from the eye. Conclusion: Plenoptic wave-front method possesses the feasibility in eye aberrations wave-front detection. With larger FOV, the method can effectively reduce the detection error brought by imprecise eye location and simplify the eye aberrations wave-front detection system comparing with which based on Shack-Hartmann WFS. Unique advantage of the plenoptic method lies in obtaining wave-front in different visual angle simultaneously, which provides an approach in building up 3-D model of eye refractor tomographically. Funded by the key Laboratory of High Power Laser and Physics, CAS Research Project of National University of Defense Technology No. JC13-07-01; National Natural Science Foundation of China No. 61205144.« less

Localizing gravitational wave sources with single-baseline atom interferometers

DOE PAGES

Graham, Peter W.; Jung, Sunghoon

2018-01-31

Localizing sources on the sky is crucial for realizing the full potential of gravitational waves for astronomy, astrophysics, and cosmology. Here in this paper, we show that the midfrequency band, roughly 0.03 to 10 Hz, has significant potential for angular localization. The angular location is measured through the changing Doppler shift as the detector orbits the Sun. This band maximizes the effect since these are the highest frequencies in which sources live for several months. Atom interferometer detectors can observe in the midfrequency band, and even with just a single baseline they can exploit this effect for sensitive angular localization.more » The single-baseline orbits around the Earth and the Sun, causing it to reorient and change position significantly during the lifetime of the source, and making it similar to having multiple baselines/detectors. For example, atomic detectors could predict the location of upcoming black hole or neutron star merger events with sufficient accuracy to allow optical and other electromagnetic telescopes to observe these events simultaneously. Thus, midband atomic detectors are complementary to other gravitational wave detectors and will help complete the observation of a broad range of the gravitational spectrum.« less

Localizing gravitational wave sources with single-baseline atom interferometers

DOE Office of Scientific and Technical Information (OSTI.GOV)

Graham, Peter W.; Jung, Sunghoon

Localizing sources on the sky is crucial for realizing the full potential of gravitational waves for astronomy, astrophysics, and cosmology. Here in this paper, we show that the midfrequency band, roughly 0.03 to 10 Hz, has significant potential for angular localization. The angular location is measured through the changing Doppler shift as the detector orbits the Sun. This band maximizes the effect since these are the highest frequencies in which sources live for several months. Atom interferometer detectors can observe in the midfrequency band, and even with just a single baseline they can exploit this effect for sensitive angular localization.more » The single-baseline orbits around the Earth and the Sun, causing it to reorient and change position significantly during the lifetime of the source, and making it similar to having multiple baselines/detectors. For example, atomic detectors could predict the location of upcoming black hole or neutron star merger events with sufficient accuracy to allow optical and other electromagnetic telescopes to observe these events simultaneously. Thus, midband atomic detectors are complementary to other gravitational wave detectors and will help complete the observation of a broad range of the gravitational spectrum.« less

Relative Timing of Substorm-Associated Processes in the Near-Earth Magnetotail and Development of Auroral Onset Arc

NASA Astrophysics Data System (ADS)

Miyashita, Y.; Ieda, A.; Machida, S.; Hiraki, Y.; Angelopoulos, V.; McFadden, J. P.; Auster, H. U.; Mende, S. B.; Donovan, E.; Larson, D. E.

2014-12-01

We have studied the relative timing of the processes in the near-Earth magnetotail and development of auroral onset arc at the beginning of the expansion phase, based on substorm events observed by the THEMIS spacecraft and ground-based all-sky imagers. The THEMIS all-sky imagers can observe auroras over a wide area with temporal and spacial resolutions higher than spacecraft-borne cameras. This enables us to investigate the timing of auroral development in more detail than before. A few min after the appearance and intensification of an auroral onset arc, it begins to form wave-like structure. Then auroral poleward expansion begins another few min later. THEMIS magnetotail observations clearly show that magnetic reconnection is initiated at X~-20 Re at least 1-2 min before the intensification of auroral onset arc. Then low-frequency waves are excited in the plasma sheet at X~-10 Re 2 min before dipolarization, which is simultaneous with the formation of auroral wave-like structure. Dipolarization begins at the same time as the auroral poleward expansion. These results suggest that near-Earth magnetic reconnection plays some role in the development of dipolarization and auroral onset arc.

Model-Data Assimilation of Internal Waves during ASIAEX-2001

NASA Technical Reports Server (NTRS)

Liu, Antony; Zhao, Yun-He; Tang, T. Y.; Ramp, Steven R.

2003-01-01

In recent Asian Seas International Acoustics Experiment (ASIAEX), extensive moorings have been deployed around the continental shelf break area in the northeast of South China Sea in May 2001. Simultaneous RADARSAT SAR images have been collected during the field test to integrate with the in-situ measurements from moorings, ship-board sensors, and CTD casts. Besides it provides synoptic information, satellite imagery is very useful for tracking the internal waves, and locating surface fronts and mesoscale features. During ASIAEX in May 2001, many large internal waves were observed at the test area and were the major oceanic features for acoustic volume interaction. Based on the internal wave distribution maps compiled from satellite data, the wave crest can be as long as 200 km with amplitude of 100 m. Environmental parameters have been calculated based on extensive CTD casts data near the ASIAEX area. Nonlinear internal wave models have been applied to integrate and assimilate both SAR and mooring data. Using SAR data in deep water as an initial condition, numerical simulations produce the wave evolution on the continental shelf and compared reasonably well with the mooring measurements at the downstream station. The shoaling, turning, and dissipation of large internal waves on the shelf break, elevation solitons, and wave-wave interaction have been studied and are very important issues for acoustic propagation. The internal wave effects on acoustic modal coupling has been implicated and discussed.

The height variation of supergranular velocity fields determined from simultaneous OSO 8 satellite and ground-based observations

NASA Technical Reports Server (NTRS)

November, L. J.; Toomre, J.; Gebbie, K. B.; Simon, G. W.

1979-01-01

Results are reported for simultaneous satellite and ground-based observations of supergranular velocities in the sun, which were made using a UV spectrometer aboard OSO 8 and a diode-array instrument operating at the exit slit of an echelle spectrograph attached to a vacuum tower telescope. Observations of the steady Doppler velocities seen toward the limb in the middle chromosphere and the photosphere are compared; the observed spectral lines of Si II at 1817 A and Fe I at 5576 A are found to differ in height of formation by about 1400 km. The results show that supergranular motions are able to penetrate at least 11 density scale heights into the middle chromosphere, that the patterns of motion correlate well with the cellular structure seen in the photosphere, and that the motion increases from about 800 m/s in the photosphere to at least 3000 m/s in the middle chromosphere. These observations imply that supergranular velocities should be evident in the transition region and that strong horizontal shear layers in supergranulation should produce turbulence and internal gravity waves.

Passively Q-switched and mode-locked dual-wavelength Nd:GGG laser with Cr4+:YAG as a saturable absorber

NASA Astrophysics Data System (ADS)

Chu, Hongwei; Zhao, Shengzhi; Li, Yufei; Yang, Kejian; Li, Guiqiu; Li, Dechun; Zhao, Jia; Qiao, Wenchao; Li, Tao; Feng, Chuansheng; Zhang, Haijuan

2014-03-01

By using neodymium-doped gadolinium gallium garnet (Nd:GGG) as a laser medium, a simultaneously passively Q-switched and mode-locked (QML) dual-wavelength laser with Cr4+:YAG as a saturable absorber is presented. The laser simultaneously oscillated at 1061 nm and 1063 nm, corresponding to a frequency difference of 0.53 THz. QML pulses with nearly 100% modulation depth were observed. The mode-locked pulse duration underneath the Q-switched envelope was estimated to be about 908 ps. The experimental results indicated that the dual-wavelength QML Nd:GGG laser can be an excellent candidate for the generation of THz waves.

Observations and Numerical Modelling of Strong Meteotsunami of 13 June 2013 on the East Coast of the USA

NASA Astrophysics Data System (ADS)

Fine, I.; Sepic, J.; Rabinovich, A.; Thomson, R.

2014-12-01

A strong "derecho" (rapidly moving lines of convectively induced intense thunderstorms) was generated over the Midwestern United States on 12-13 June 2013 and propagated across the Appalachian Mountains to the Atlantic Ocean. Three hours after the derecho crossed the Atlantic coast, a ~2-m high meteotsunami wave was reported to have hit the New Jersey coast. Significant tsunami-like oscillations, with wave heights of ~0.6 m, were also recorded by a number of tide-gauges located along the eastern seaboard from Nova Scotia to South Carolina, at Bermuda, and by open-ocean DART 44402. These observations triggered the tsunami-alert mode of the DART station. Intense air pressure disturbances (with pressure change of 3-6 hPa in 20 min) and strong winds were observed at a number of National Oceanic and Atmospheric Administration (NOAA) and Automated Surface Observing System (ASOS) stations to be propagating simultaneously with the derecho system, indicating that the pressure disturbances were the primary cause for the sea level oscillations in Chesapeake and Delaware bays. The air pressure disturbance continued to propagate seaward over the continental shelf, thereby generating long waves via Proudman resonance at those areas of the shelf where the propagation speed of the air pressure disturbance matched the long wave speed. Upon reaching the shelf break, the long-waves were partly transmitted (reaching Bermuda 5 hours later) and partly reflected (returning to the east coast of the US and Canada 3 to 6 hours later). A numerical barotropic ocean model forced with idealized air pressure and wind fields was used successfully to simulate the event. The meteotsunami arrival times and maximum wave heights obtained from the model closely match the measured values and confirm initial assumptions regarding the partitioning between transmitted and reflected meteotsunami waves.

Imaging San Jacinto Fault damage zone structure using dense linear arrays: application of ambient noise tomography, Rayleigh wave ellipticity, and site amplification

NASA Astrophysics Data System (ADS)

Wang, Y.; Lin, F. C.; Allam, A. A.; Ben-Zion, Y.

2017-12-01

The San Jacinto fault is presently the most seismically active component of the San Andreas Transform system in Southern California. To study the damage zone structure, two dense linear geophone arrays (BS and RR) were deployed across the Clark segment of the San Jacinto Fault between Anza and Hemet during winter 2015 and Fall 2016, respectively. Both arrays were 2 km long with 20 m station spacing. Month-long three-component ambient seismic noise data were recorded and used to calculate multi-channel cross-correlation functions. All three-component noise records of each array were normalized simultaneously to retain relative amplitude information between different stations and different components. We observed clear Rayleigh waves and Love waves on the cross-correlations of both arrays at 0.3 - 1 s period. The phase travel times of the Rayleigh waves on both arrays were measured by frequency-time analysis (FTAN), and inverted for Rayleigh wave phase velocity profiles of the upper 500 m depth. For both arrays, we observe prominent asymmetric low velocity zones which narrow with depth. At the BS array near the Hemet Stepover, an approximately 250m wide slow zone is observed to be offset by 75m to the northeast of the surface fault trace. At the RR array near the Anza segment of the fault, a similar low velocity zone width and offset are observed, along with a 10% across-fault velocity contrast. Analyses of Rayleigh wave ellipticity (H/V ratio), Love wave phase travel times, and site amplification are in progress. By using multiple measurements from ambient noise cross-correlations, we can obtain strong constraints on the local damage zone structure of the San Jacinto Fault. The results contribute to improved understanding of rupture directivity, maximum earthquake magnitude and more generally seismic hazard associated with the San Jacinto fault zone.

Gravity wave life cycle (GW-LCYCLE): Initial results from a coordinated field program to trace gravity waves from the troposphere to the MLT-region

NASA Astrophysics Data System (ADS)

Rapp, Markus

Gravity waves (GW) play an important role in the coupling between the troposphere and the middle atmosphere (˜10 - 120 km). GWs couple different atmospheric regions both in the vertical as well as in the horizontal directions by means of momentum and energy transport. Notably, this coupling is effective both from the troposphere upwards, and also in the opposite direction by indirect effects on circulation patterns. While the importance of GW for understanding atmospheric structure, dynamics and climate is now widely recognized, surprisingly little is still known about the details of the GW life cycle, i.e., the processes of GW excitation, propagation and dissipation. To address this issue a coordinated field program - named GW-LCYCLE - has been established in which ground based observations with radars, lidars and airglow imagers are combined with airborne observations, balloon soundings, and modelling to trace GWs from their source in the troposphere to their area of dissipation in the middle atmosphere. Within GW-LCYCLE an initial field campaign was conducted in December 2013 in Northern Scandinavia. The research aircraft DLR-FALCON was deployed to Kiruna, Sweden, from where several flights (with a total of 25 flight hours) were conducted to study mountain wave generation by flow over the Scandinavian mountain ridge. The FALCON was equipped with a downward looking wind lidar operating at a wavelength of 2 mum as well as with an in-flight system to measure winds, temperatures and pressures and with several in-situ instruments to detect wave signatures in trace gases like H _{2}O, CO _{2}, CO, CH _{4}, N _{2}O, HNO _{3} and SO _{2}. Ground based observations of winds and temperatures from the troposphere to the mesosphere/lower thermosphere (MLT-) region were conducted from Kiruna as well as from Andenes, Norway. These measurements were augmented by balloon soundings from the same places as well as from Sodankylä in Finland. Coordinated observations were conducted during five intensive observations periods, IOPs, where during two IOPs strong mountain wave generation was observed. In this paper we present an overview of the initial preliminary results of this first GW-LCYCLE campaign contrasting results from selected IOPs with and without strong mountain wave generation. We will discuss in how far observed tropospheric and lower stratospheric wave signatures can be reconciled with regional modelling and whether simultaneously observed mesospheric waves can be attributed to dedicated GW sources in the troposphere using GW ray tracing as well as high-resolution idealized modelling.

Examining Coherency Scales, Substructure, and Propagation of Whistler Mode Chorus Elements With Magnetospheric Multiscale (MMS)

NASA Astrophysics Data System (ADS)

Turner, D. L.; Lee, J. H.; Claudepierre, S. G.; Fennell, J. F.; Blake, J. B.; Jaynes, A. N.; Leonard, T.; Wilder, F. D.; Ergun, R. E.; Baker, D. N.; Cohen, I. J.; Mauk, B. H.; Strangeway, R. J.; Hartley, D. P.; Kletzing, C. A.; Breuillard, H.; Le Contel, O.; Khotyaintsev, Yu. V.; Torbert, R. B.; Allen, R. C.; Burch, J. L.; Santolik, O.

2017-11-01

Whistler mode chorus waves are a naturally occurring electromagnetic emission observed in Earth's magnetosphere. Here, for the first time, data from NASA's Magnetospheric Multiscale (MMS) mission were used to analyze chorus waves in detail, including the calculation of chorus wave normal vectors, fi>k. A case study was examined from a period of substorm activity around the time of a conjunction between the MMS constellation and NASA's Van Allen Probes mission on 07 April 2016. Chorus wave activity was simultaneously observed by all six spacecraft over a broad range of L shells (5.5 < L < 8.5), magnetic local time (06:00 < MLT < 09:00), and magnetic latitude (-32° < MLAT < -15°), implying a large chorus active region. Eight chorus elements and their substructure were analyzed in detail with MMS. These chorus elements were all lower band and rising tone emissions, right-handed and nearly circularly polarized, and propagating away from the magnetic equator when they were observed at MMS (MLAT -31°). Most of the elements had "hook"-like signatures on their wave power spectra, characterized by enhanced wave power at flat or falling frequency following the peak, and all the elements exhibited complex and well-organized substructure observed consistently at all four MMS spacecraft at separations up to 70 km (60 km perpendicular and 38 km parallel to the background magnetic field). The waveforms in field-aligned coordinates also demonstrated that these waves were all phase coherent, allowing for the direct calculation of fi>k. Error estimates on calculated fi>k revealed that the plane wave approximation was valid for six of the eight elements and most of the subelements. The wave normal vectors were within 20-30° from the direction antiparallel to the background field for all elements and changed from subelement to subelement through at least two of the eight elements. The azimuthal angle of fi>k in the perpendicular plane was oriented earthward and was oblique to that of the Poynting vector, which has implications for the validity of cold plasma theory.

Pulsating aurora from electron scattering by chorus waves

NASA Astrophysics Data System (ADS)

Kasahara, S.; Miyoshi, Y.; Yokota, S.; Mitani, T.; Kasahara, Y.; Matsuda, S.; Kumamoto, A.; Matsuoka, A.; Kazama, Y.; Frey, H. U.; Angelopoulos, V.; Kurita, S.; Keika, K.; Seki, K.; Shinohara, I.

2018-02-01

Auroral substorms, dynamic phenomena that occur in the upper atmosphere at night, are caused by global reconfiguration of the magnetosphere, which releases stored solar wind energy. These storms are characterized by auroral brightening from dusk to midnight, followed by violent motions of distinct auroral arcs that suddenly break up, and the subsequent emergence of diffuse, pulsating auroral patches at dawn. Pulsating aurorae, which are quasiperiodic, blinking patches of light tens to hundreds of kilometres across, appear at altitudes of about 100 kilometres in the high-latitude regions of both hemispheres, and multiple patches often cover the entire sky. This auroral pulsation, with periods of several to tens of seconds, is generated by the intermittent precipitation of energetic electrons (several to tens of kiloelectronvolts) arriving from the magnetosphere and colliding with the atoms and molecules of the upper atmosphere. A possible cause of this precipitation is the interaction between magnetospheric electrons and electromagnetic waves called whistler-mode chorus waves. However, no direct observational evidence of this interaction has been obtained so far. Here we report that energetic electrons are scattered by chorus waves, resulting in their precipitation. Our observations were made in March 2017 with a magnetospheric spacecraft equipped with a high-angular-resolution electron sensor and electromagnetic field instruments. The measured quasiperiodic precipitating electron flux was sufficiently intense to generate a pulsating aurora, which was indeed simultaneously observed by a ground auroral imager.

Electric Field Observations of Plasma Convection, Shear, Alfven Waves, and other Phenomena Observed on Sounding Rockets in the Cusp and Boundary Layer

NASA Technical Reports Server (NTRS)

Pfaff, R. F.

2009-01-01

On December 14,2002, a NASA Black Brant X sounding rocket was launched equatorward from Ny Alesund, Spitzbergen (79 N) into the dayside cusp and subsequently cut across the open/closed field line boundary, reaching an apogee of771 km. The launch occurred during Bz negative conditions with strong By negative that was changing during the flight. SuperDarn (CUTLASS) radar and subsequent model patterns reveal a strong westward/poleward convection, indicating that the rocket traversed a rotational reversal in the afternoon merging cell. The payload returned DC electric and magnetic fields, plasma waves, energetic particle, suprathermal electron and ion, and thermal plasma data. We provide an overview of the main observations and focus on the DC electric field results, comparing the measured E x B plasma drifts in detail with the CUTLASS radar observations of plasma drifts gathered simultaneously in the same volume. The in situ DC electric fields reveal steady poleward flows within the cusp with strong shears at the interface of the closed/open field lines and within the boundary layer. We use the observations to discuss ionospheric signatures of the open/closed character of the cusp/low latitude boundary layer as a function of the IMF. The electric field and plasma density data also reveal the presence of very strong plasma irregularities with a large range of scales (10 m to 10 km) that exist within the open field line cusp region yet disappear when the payload was equatorward of the cusp on closed field lines. These intense low frequency wave observations are consistent with strong scintillations observed on the ground at Ny Alesund during the flight. We present detailed wave characteristics and discuss them in terms of Alfven waves and static irregularities that pervade the cusp region at all altitudes.

Ambient temperature and added heat wave effects on hospitalizations in California from 1999 to 2009.

PubMed

Sherbakov, Toki; Malig, Brian; Guirguis, Kristen; Gershunov, Alexander; Basu, Rupa

2018-01-01

Investigators have examined how heat waves or incremental changes in temperature affect health outcomes, but few have examined both simultaneously. We utilized distributed lag nonlinear models (DLNM) to explore temperature associations and evaluate possible added heat wave effects on hospitalizations in 16 climate zones throughout California from May through October 1999-2009. We define heat waves as a period when daily mean temperatures were above the zone- and month-specific 95th percentile for at least two consecutive days. DLNMs were used to estimate climate zone-specific non-linear temperature and heat wave effects, which were then combined using random effects meta-analysis to produce an overall estimate for each. With higher temperatures, admissions for acute renal failure, appendicitis, dehydration, ischemic stroke, mental health, non-infectious enteritis, and primary diabetes were significantly increased, with added effects from heat waves observed for acute renal failure and dehydration. Higher temperatures also predicted statistically significant decreases in hypertension admissions, respiratory admissions, and respiratory diseases with secondary diagnoses of diabetes, though heat waves independently predicted an added increase in risk for both respiratory types. Our findings provide evidence that both heat wave and temperature exposures can exert effects independently. Copyright © 2017 Elsevier Inc. All rights reserved.

Simultaneous Measurements of Harmonic Waves at Fatigue-Cracked Interfaces

NASA Astrophysics Data System (ADS)

Hyunjo, Jeong; Dan, Barnard

2011-08-01

Nonlinear harmonic waves generated at cracked interfaces are investigated theoretically and experimentally. A compact tension specimen is fabricated and the amplitude of the transmitted wave is analyzed as a function of position along the fatigued crack surface. In order to measure as many nonlinear harmonic components as possible, broadband lithium niobate (LiNbO3) transducers are employed together with a calibration technique for making absolute amplitude measurements with fluid-coupled receiving transducers. Cracked interfaces are shown to generate high acoustic nonlinearities, which are manifested as harmonics in the power spectrum of the received signal. The first subharmonic f/2 and the second harmonic 2f waves are found to be dominant nonlinear components for an incident toneburst signal of frequency f. To explain the observed nonlinear behavior, a partially closed crack is modeled by planar half interfaces that can account for crack parameters, such as crack opening displacement and crack surface conditions. The simulation results show reasonable agreement with the experimental results.

Acoustic wave propagation and intensity fluctuations in shallow water 2006 experiment

NASA Astrophysics Data System (ADS)

Luo, Jing

Fluctuations of low frequency sound propagation in the presence of nonlinear internal waves during the Shallow Water 2006 experiment are analyzed. Acoustic waves and environmental data including on-board ship radar images were collected simultaneously before, during, and after a strong internal solitary wave packet passed through a source-receiver acoustic track. Analysis of the acoustic wave signals shows temporal intensity fluctuations. These fluctuations are affected by the passing internal wave and agrees well with the theory of the horizontal refraction of acoustic wave propagation in shallow water. The intensity focusing and defocusing that occurs in a fixed source-receiver configuration while internal wave packet approaches and passes the acoustic track is addressed in this thesis. Acoustic ray-mode theory is used to explain the modal evolution of broadband acoustic waves propagating in a shallow water waveguide in the presence of internal waves. Acoustic modal behavior is obtained from the data through modal decomposition algorithms applied to data collected by a vertical line array of hydrophones. Strong interference patterns are observed in the acoustic data, whose main cause is identified as the horizontal refraction referred to as the horizontal Lloyd mirror effect. To analyze this interference pattern, combined Parabolic Equation model and Vertical-mode horizontal-ray model are utilized. A semi-analytic formula for estimating the horizontal Lloyd mirror effect is developed.

Seismic excitation by space shuttles

USGS Publications Warehouse

Kanamori, H.; Mori, J.; Sturtevant, B.; Anderson, D.L.; Heaton, T.

1992-01-01

Shock waves generated by the space shuttles Columbia (August 13, 1989), Atlantis (April 11, 1991) and Discovery (September 18, 1991) on their return to Edwards Air Force Base, California, were recorded by TERRAscope (Caltech's broadband seismic network), the Caltech-U.S.G.S Southern California Seismic Network (SCSN), and the University of Southern California (USC) Los Angeles Basin Seismic Network. The spatial pattern of the arrival times exhibits hyperbolic shock fronts from which the path, velocity and altitude of the space shuttle could be determined. The shock wave was acoustically coupled to the ground, converted to a seismic wave, and recorded clearly at the broadband TERRAscope stations. The acoustic coupling occurred very differently depending on the conditions of the Earth's surface surrounding the station. For a seismic station located on hard bedrock, the shock wave (N wave) was clearly recorded with little distortion. Aside from the N wave, very little acoustic coupling of the shock wave energy to the ground occurred at these sites. The observed N wave record was used to estimate the overpressure of the shock wave accurately; a pressure change of 0.5 to 2.2 mbars was obtained. For a seismic station located close to the ocean or soft sedimentary basins, a significant amount of shock wave energy was transferred to the ground through acoustic coupling of the shock wave and the oceanic Rayleigh wave. A distinct topography such as a mountain range was found effective to couple the shock wave energy to the ground. Shock wave energy was also coupled to the ground very effectively through large man made structures such as high rise buildings and offshore oil drilling platforms. For the space shuttle Columbia, in particular, a distinct pulse having a period of about 2 to 3 seconds was observed, 12.5 s before the shock wave, with a broadband seismograph in Pasadena. This pulse was probably excited by the high rise buildings in downtown Los Angeles which were simultaneously hit by the space shuttle shock waves. The proximity of the natural periods of the high rise buildings and the modal periods of the Los Angeles basin enabled efficient energy transfer from shock wave to seismic wave. ?? 1992 Springer-Verlag.

Efficient generation of energetic ions in multi-ion plasmas by radio-frequency heating

NASA Astrophysics Data System (ADS)

Kazakov, Ye. O.; Ongena, J.; Wright, J. C.; Wukitch, S. J.; Lerche, E.; Mantsinen, M. J.; van Eester, D.; Craciunescu, T.; Kiptily, V. G.; Lin, Y.; Nocente, M.; Nabais, F.; Nave, M. F. F.; Baranov, Y.; Bielecki, J.; Bilato, R.; Bobkov, V.; Crombé, K.; Czarnecka, A.; Faustin, J. M.; Felton, R.; Fitzgerald, M.; Gallart, D.; Giacomelli, L.; Golfinopoulos, T.; Hubbard, A. E.; Jacquet, Ph.; Johnson, T.; Lennholm, M.; Loarer, T.; Porkolab, M.; Sharapov, S. E.; Valcarcel, D.; van Schoor, M.; Weisen, H.; Marmar, E. S.; Baek, S. G.; Barnard, H.; Bonoli, P.; Brunner, D.; Candy, J.; Canik, J.; Churchill, R. M.; Cziegler, I.; Dekow, G.; Delgado-Aparicio, L.; Diallo, A.; Edlund, E.; Ennever, P.; Faust, I.; Fiore, C.; Gao, Chi; Golfinopoulos, T.; Greenwald, M.; Hartwig, Z. S.; Holland, C.; Hubbard, A. E.; Hughes, J. W.; Hutchinson, I. H.; Irby, J.; Labombard, B.; Lin, Yijun; Lipschultz, B.; Loarte, A.; Mumgaard, R.; Parker, R. R.; Porkolab, M.; Reinke, M. L.; Rice, J. E.; Scott, S.; Shiraiwa, S.; Snyder, P.; Sorbom, B.; Terry, D.; Terry, J. L.; Theiler, C.; Vieira, R.; Walk, J. R.; Wallace, G. M.; White, A.; Whyte, D.; Wolfe, S. M.; Wright, G. M.; Wright, J.; Wukitch, S. J.; Xu, P.; Abduallev, S.; Abhangi, M.; Abreu, P.; Afzal, M.; Aggarwal, K. M.; Ahlgren, T.; Ahn, J. H.; Aho-Mantila, L.; Aiba, N.; Airila, M.; Albanese, R.; Aldred, V.; Alegre, D.; Alessi, E.; Aleynikov, P.; Alfier, A.; Alkseev, A.; Allinson, M.; Alper, B.; Alves, E.; Ambrosino, G.; Ambrosino, R.; Amicucci, L.; Amosov, V.; Sundén, E. Andersson; Angelone, M.; Anghel, M.; Angioni, C.; Appel, L.; Appelbee, C.; Arena, P.; Ariola, M.; Arnichand, H.; Arshad, S.; Ash, A.; Ashikawa, N.; Aslanyan, V.; Asunta, O.; Auriemma, F.; Austin, Y.; Avotina, L.; Axton, M. D.; Ayres, C.; Bacharis, M.; Baciero, A.; Baião, D.; Bailey, S.; Baker, A.; Balboa, I.; Balden, M.; Balshaw, N.; Bament, R.; Banks, J. W.; Baranov, Y. F.; Barnard, M. A.; Barnes, D.; Barnes, M.; Barnsley, R.; Wiechec, A. Baron; Orte, L. Barrera; Baruzzo, M.; Basiuk, V.; Bassan, M.; Bastow, R.; Batista, A.; Batistoni, P.; Baughan, R.; Bauvir, B.; Baylor, L.; Bazylev, B.; Beal, J.; Beaumont, P. S.; Beckers, M.; Beckett, B.; Becoulet, A.; Bekris, N.; Beldishevski, M.; Bell, K.; Belli, F.; Bellinger, M.; Belonohy, É.; Ayed, N. Ben; Benterman, N. A.; Bergsåker, H.; Bernardo, J.; Bernert, M.; Berry, M.; Bertalot, L.; Besliu, C.; Beurskens, M.; Bieg, B.; Bielecki, J.; Biewer, T.; Bigi, M.; Bílková, P.; Binda, F.; Bisoffi, A.; Bizarro, J. P. S.; Björkas, C.; Blackburn, J.; Blackman, K.; Blackman, T. R.; Blanchard, P.; Blatchford, P.; Bobkov, V.; Boboc, A.; Bodnár, G.; Bogar, O.; Bolshakova, I.; Bolzonella, T.; Bonanomi, N.; Bonelli, F.; Boom, J.; Booth, J.; Borba, D.; Borodin, D.; Borodkina, I.; Botrugno, A.; Bottereau, C.; Boulting, P.; Bourdelle, C.; Bowden, M.; Bower, C.; Bowman, C.; Boyce, T.; Boyd, C.; Boyer, H. J.; Bradshaw, J. M. A.; Braic, V.; Bravanec, R.; Breizman, B.; Bremond, S.; Brennan, P. D.; Breton, S.; Brett, A.; Brezinsek, S.; Bright, M. D. J.; Brix, M.; Broeckx, W.; Brombin, M.; Brosławski, A.; Brown, D. P. D.; Brown, M.; Bruno, E.; Bucalossi, J.; Buch, J.; Buchanan, J.; Buckley, M. A.; Budny, R.; Bufferand, H.; Bulman, M.; Bulmer, N.; Bunting, P.; Buratti, P.; Burckhart, A.; Buscarino, A.; Busse, A.; Butler, N. K.; Bykov, I.; Byrne, J.; Cahyna, P.; Calabrò, G.; Calvo, I.; Camenen, Y.; Camp, P.; Campling, D. C.; Cane, J.; Cannas, B.; Capel, A. J.; Card, P. J.; Cardinali, A.; Carman, P.; Carr, M.; Carralero, D.; Carraro, L.; Carvalho, B. B.; Carvalho, I.; Carvalho, P.; Casson, F. J.; Castaldo, C.; Catarino, N.; Caumont, J.; Causa, F.; Cavazzana, R.; Cave-Ayland, K.; Cavinato, M.; Cecconello, M.; Ceccuzzi, S.; Cecil, E.; Cenedese, A.; Cesario, R.; Challis, C. D.; Chandler, M.; Chandra, D.; Chang, C. S.; Chankin, A.; Chapman, I. T.; Chapman, S. C.; Chernyshova, M.; Chitarin, G.; Ciraolo, G.; Ciric, D.; Citrin, J.; Clairet, F.; Clark, E.; Clark, M.; Clarkson, R.; Clatworthy, D.; Clements, C.; Cleverly, M.; Coad, J. P.; Coates, P. A.; Cobalt, A.; Coccorese, V.; Cocilovo, V.; Coda, S.; Coelho, R.; Coenen, J. W.; Coffey, I.; Colas, L.; Collins, S.; Conka, D.; Conroy, S.; Conway, N.; Coombs, D.; Cooper, D.; Cooper, S. R.; Corradino, C.; Corre, Y.; Corrigan, G.; Cortes, S.; Coster, D.; Couchman, A. S.; Cox, M. P.; Craciunescu, T.; Cramp, S.; Craven, R.; Crisanti, F.; Croci, G.; Croft, D.; Crombé, K.; Crowe, R.; Cruz, N.; Cseh, G.; Cufar, A.; Cullen, A.; Curuia, M.; Czarnecka, A.; Dabirikhah, H.; Dalgliesh, P.; Dalley, S.; Dankowski, J.; Darrow, D.; Davies, O.; Davis, W.; Day, C.; Day, I. E.; de Bock, M.; de Castro, A.; de La Cal, E.; de La Luna, E.; Masi, G. De; de Pablos, J. L.; de Temmerman, G.; de Tommasi, G.; de Vries, P.; Deakin, K.; Deane, J.; Agostini, F. Degli; Dejarnac, R.; Delabie, E.; den Harder, N.; Dendy, R. O.; Denis, J.; Denner, P.; Devaux, S.; Devynck, P.; Maio, F. Di; Siena, A. Di; Troia, C. Di; Dinca, P.; D'Inca, R.; Ding, B.; Dittmar, T.; Doerk, H.; Doerner, R. P.; Donné, T.; Dorling, S. E.; Dormido-Canto, S.; Doswon, S.; Douai, D.; Doyle, P. T.; Drenik, A.; Drewelow, P.; Drews, P.; Duckworth, Ph.; Dumont, R.; Dumortier, P.; Dunai, D.; Dunne, M.; Ďuran, I.; Durodié, F.; Dutta, P.; Duval, B. P.; Dux, R.; Dylst, K.; Dzysiuk, N.; Edappala, P. V.; Edmond, J.; Edwards, A. M.; Edwards, J.; Eich, Th.; Ekedahl, A.; El-Jorf, R.; Elsmore, C. G.; Enachescu, M.; Ericsson, G.; Eriksson, F.; Eriksson, J.; Eriksson, L. G.; Esposito, B.; Esquembri, S.; Esser, H. G.; Esteve, D.; Evans, B.; Evans, G. E.; Evison, G.; Ewart, G. D.; Fagan, D.; Faitsch, M.; Falie, D.; Fanni, A.; Fasoli, A.; Faustin, J. M.; Fawlk, N.; Fazendeiro, L.; Fedorczak, N.; Felton, R. C.; Fenton, K.; Fernades, A.; Fernandes, H.; Ferreira, J.; Fessey, J. A.; Février, O.; Ficker, O.; Field, A.; Fietz, S.; Figueiredo, A.; Figueiredo, J.; Fil, A.; Finburg, P.; Firdaouss, M.; Fischer, U.; Fittill, L.; Fitzgerald, M.; Flammini, D.; Flanagan, J.; Fleming, C.; Flinders, K.; Fonnesu, N.; Fontdecaba, J. M.; Formisano, A.; Forsythe, L.; Fortuna, L.; Fortuna-Zalesna, E.; Fortune, M.; Foster, S.; Franke, T.; Franklin, T.; Frasca, M.; Frassinetti, L.; Freisinger, M.; Fresa, R.; Frigione, D.; Fuchs, V.; Fuller, D.; Futatani, S.; Fyvie, J.; Gál, K.; Galassi, D.; Gałązka, K.; Galdon-Quiroga, J.; Gallagher, J.; Gallart, D.; Galvão, R.; Gao, X.; Gao, Y.; Garcia, J.; Garcia-Carrasco, A.; García-Muñoz, M.; Gardarein, J.-L.; Garzotti, L.; Gaudio, P.; Gauthier, E.; Gear, D. F.; Gee, S. J.; Geiger, B.; Gelfusa, M.; Gerasimov, S.; Gervasini, G.; Gethins, M.; Ghani, Z.; Ghate, M.; Gherendi, M.; Giacalone, J. C.; Giacomelli, L.; Gibson, C. S.; Giegerich, T.; Gil, C.; Gil, L.; Gilligan, S.; Gin, D.; Giovannozzi, E.; Girardo, J. B.; Giroud, C.; Giruzzi, G.; Glöggler, S.; Godwin, J.; Goff, J.; Gohil, P.; Goloborod'Ko, V.; Gomes, R.; Gonçalves, B.; Goniche, M.; Goodliffe, M.; Goodyear, A.; Gorini, G.; Gosk, M.; Goulding, R.; Goussarov, A.; Gowland, R.; Graham, B.; Graham, M. E.; Graves, J. P.; Grazier, N.; Grazier, P.; Green, N. R.; Greuner, H.; Grierson, B.; Griph, F. S.; Grisolia, C.; Grist, D.; Groth, M.; Grove, R.; Grundy, C. N.; Grzonka, J.; Guard, D.; Guérard, C.; Guillemaut, C.; Guirlet, R.; Gurl, C.; Utoh, H. H.; Hackett, L. J.; Hacquin, S.; Hagar, A.; Hager, R.; Hakola, A.; Halitovs, M.; Hall, S. J.; Cook, S. P. Hallworth; Hamlyn-Harris, C.; Hammond, K.; Harrington, C.; Harrison, J.; Harting, D.; Hasenbeck, F.; Hatano, Y.; Hatch, D. R.; Haupt, T. D. V.; Hawes, J.; Hawkes, N. C.; Hawkins, J.; Hawkins, P.; Haydon, P. W.; Hayter, N.; Hazel, S.; Heesterman, P. J. L.; Heinola, K.; Hellesen, C.; Hellsten, T.; Helou, W.; Hemming, O. N.; Hender, T. C.; Henderson, M.; Henderson, S. S.; Henriques, R.; Hepple, D.; Hermon, G.; Hertout, P.; Hidalgo, C.; Highcock, E. G.; Hill, M.; Hillairet, J.; Hillesheim, J.; Hillis, D.; Hizanidis, K.; Hjalmarsson, A.; Hobirk, J.; Hodille, E.; Hogben, C. H. A.; Hogeweij, G. M. D.; Hollingsworth, A.; Hollis, S.; Homfray, D. A.; Horáček, J.; Hornung, G.; Horton, A. R.; Horton, L. D.; Horvath, L.; Hotchin, S. P.; Hough, M. R.; Howarth, P. J.; Hubbard, A.; Huber, A.; Huber, V.; Huddleston, T. M.; Hughes, M.; Huijsmans, G. T. A.; Hunter, C. L.; Huynh, P.; Hynes, A. M.; Iglesias, D.; Imazawa, N.; Imbeaux, F.; Imríšek, M.; Incelli, M.; Innocente, P.; Irishkin, M.; Ivanova-Stanik, I.; Jachmich, S.; Jacobsen, A. S.; Jacquet, P.; Jansons, J.; Jardin, A.; Järvinen, A.; Jaulmes, F.; Jednoróg, S.; Jenkins, I.; Jeong, C.; Jepu, I.; Joffrin, E.; Johnson, R.; Johnson, T.; Johnston, Jane; Joita, L.; Jones, G.; Jones, T. T. C.; Hoshino, K. K.; Kallenbach, A.; Kamiya, K.; Kaniewski, J.; Kantor, A.; Kappatou, A.; Karhunen, J.; Karkinsky, D.; Karnowska, I.; Kaufman, M.; Kaveney, G.; Kazakov, Y.; Kazantzidis, V.; Keeling, D. L.; Keenan, T.; Keep, J.; Kempenaars, M.; Kennedy, C.; Kenny, D.; Kent, J.; Kent, O. N.; Khilkevich, E.; Kim, H. T.; Kim, H. S.; Kinch, A.; King, C.; King, D.; King, R. F.; Kinna, D. J.; Kiptily, V.; Kirk, A.; Kirov, K.; Kirschner, A.; Kizane, G.; Klepper, C.; Klix, A.; Knight, P.; Knipe, S. J.; Knott, S.; Kobuchi, T.; Köchl, F.; Kocsis, G.; Kodeli, I.; Kogan, L.; Kogut, D.; Koivuranta, S.; Kominis, Y.; Köppen, M.; Kos, B.; Koskela, T.; Koslowski, H. R.; Koubiti, M.; Kovari, M.; Kowalska-Strzęciwilk, E.; Krasilnikov, A.; Krasilnikov, V.; Krawczyk, N.; Kresina, M.; Krieger, K.; Krivska, A.; Kruezi, U.; Książek, I.; Kukushkin, A.; Kundu, A.; Kurki-Suonio, T.; Kwak, S.; Kwiatkowski, R.; Kwon, O. J.; Laguardia, L.; Lahtinen, A.; Laing, A.; Lam, N.; Lambertz, H. T.; Lane, C.; Lang, P. T.; Lanthaler, S.; Lapins, J.; Lasa, A.; Last, J. R.; Łaszyńska, E.; Lawless, R.; Lawson, A.; Lawson, K. D.; Lazaros, A.; Lazzaro, E.; Leddy, J.; Lee, S.; Lefebvre, X.; Leggate, H. J.; Lehmann, J.; Lehnen, M.; Leichtle, D.; Leichuer, P.; Leipold, F.; Lengar, I.; Lennholm, M.; Lerche, E.; Lescinskis, A.; Lesnoj, S.; Letellier, E.; Leyland, M.; Leysen, W.; Li, L.; Liang, Y.; Likonen, J.; Linke, J.; Linsmeier, Ch.; Lipschultz, B.; Litaudon, X.; Liu, G.; Liu, Y.; Lo Schiavo, V. P.; Loarer, T.; Loarte, A.; Lobel, R. C.; Lomanowski, B.; Lomas, P. J.; Lönnroth, J.; López, J. M.; López-Razola, J.; Lorenzini, R.; Losada, U.; Lovell, J. J.; Loving, A. B.; Lowry, C.; Luce, T.; Lucock, R. M. A.; Lukin, A.; Luna, C.; Lungaroni, M.; Lungu, C. P.; Lungu, M.; Lunniss, A.; Lupelli, I.; Lyssoivan, A.; MacDonald, N.; Macheta, P.; Maczewa, K.; Magesh, B.; Maget, P.; Maggi, C.; Maier, H.; Mailloux, J.; Makkonen, T.; Makwana, R.; Malaquias, A.; Malizia, A.; Manas, P.; Manning, A.; Manso, M. E.; Mantica, P.; Mantsinen, M.; Manzanares, A.; Maquet, Ph.; Marandet, Y.; Marcenko, N.; Marchetto, C.; Marchuk, O.; Marinelli, M.; Marinucci, M.; Markovič, T.; Marocco, D.; Marot, L.; Marren, C. A.; Marshal, R.; Martin, A.; Martin, Y.; Martín de Aguilera, A.; Martínez, F. J.; Martín-Solís, J. R.; Martynova, Y.; Maruyama, S.; Masiello, A.; Maslov, M.; Matejcik, S.; Mattei, M.; Matthews, G. F.; Maviglia, F.; Mayer, M.; Mayoral, M. L.; May-Smith, T.; Mazon, D.; Mazzotta, C.; McAdams, R.; McCarthy, P. J.; McClements, K. G.; McCormack, O.; McCullen, P. A.; McDonald, D.; McIntosh, S.; McKean, R.; McKehon, J.; Meadows, R. C.; Meakins, A.; Medina, F.; Medland, M.; Medley, S.; Meigh, S.; Meigs, A. G.; Meisl, G.; Meitner, S.; Meneses, L.; Menmuir, S.; Mergia, K.; Merrigan, I. R.; Mertens, Ph.; Meshchaninov, S.; Messiaen, A.; Meyer, H.; Mianowski, S.; Michling, R.; Middleton-Gear, D.; Miettunen, J.; Militello, F.; Militello-Asp, E.; Miloshevsky, G.; Mink, F.; Minucci, S.; Miyoshi, Y.; Mlynář, J.; Molina, D.; Monakhov, I.; Moneti, M.; Mooney, R.; Moradi, S.; Mordijck, S.; Moreira, L.; Moreno, R.; Moro, F.; Morris, A. W.; Morris, J.; Moser, L.; Mosher, S.; Moulton, D.; Murari, A.; Muraro, A.; Murphy, S.; Asakura, N. N.; Na, Y. S.; Nabais, F.; Naish, R.; Nakano, T.; Nardon, E.; Naulin, V.; Nave, M. F. F.; Nedzelski, I.; Nemtsev, G.; Nespoli, F.; Neto, A.; Neu, R.; Neverov, V. S.; Newman, M.; Nicholls, K. J.; Nicolas, T.; Nielsen, A. H.; Nielsen, P.; Nilsson, E.; Nishijima, D.; Noble, C.; Nocente, M.; Nodwell, D.; Nordlund, K.; Nordman, H.; Nouailletas, R.; Nunes, I.; Oberkofler, M.; Odupitan, T.; Ogawa, M. T.; O'Gorman, T.; Okabayashi, M.; Olney, R.; Omolayo, O.; O'Mullane, M.; Ongena, J.; Orsitto, F.; Orszagh, J.; Oswuigwe, B. I.; Otin, R.; Owen, A.; Paccagnella, R.; Pace, N.; Pacella, D.; Packer, L. W.; Page, A.; Pajuste, E.; Palazzo, S.; Pamela, S.; Panja, S.; Papp, P.; Paprok, R.; Parail, V.; Park, M.; Diaz, F. Parra; Parsons, M.; Pasqualotto, R.; Patel, A.; Pathak, S.; Paton, D.; Patten, H.; Pau, A.; Pawelec, E.; Soldan, C. Paz; Peackoc, A.; Pearson, I. J.; Pehkonen, S.-P.; Peluso, E.; Penot, C.; Pereira, A.; Pereira, R.; Puglia, P. P. Pereira; von Thun, C. Perez; Peruzzo, S.; Peschanyi, S.; Peterka, M.; Petersson, P.; Petravich, G.; Petre, A.; Petrella, N.; Petržilka, V.; Peysson, Y.; Pfefferlé, D.; Philipps, V.; Pillon, M.; Pintsuk, G.; Piovesan, P.; Dos Reis, A. Pires; Piron, L.; Pironti, A.; Pisano; Pitts, R.; Pizzo, F.; Plyusnin, V.; Pomaro, N.; Pompilian, O. G.; Pool, P. J.; Popovichev, S.; Porfiri, M. T.; Porosnicu, C.; Porton, M.; Possnert, G.; Potzel, S.; Powell, T.; Pozzi, J.; Prajapati, V.; Prakash, R.; Prestopino, G.; Price, D.; Price, M.; Price, R.; Prior, P.; Proudfoot, R.; Pucella, G.; Puglia, P.; Puiatti, M. E.; Pulley, D.; Purahoo, K.; Pütterich, Th.; Rachlew, E.; Rack, M.; Ragona, R.; Rainford, M. S. J.; Rakha, A.; Ramogida, G.; Ranjan, S.; Rapson, C. J.; Rasmussen, J. J.; Rathod, K.; Rattá, G.; Ratynskaia, S.; Ravera, G.; Rayner, C.; Rebai, M.; Reece, D.; Reed, A.; Réfy, D.; Regan, B.; Regaña, J.; Reich, M.; Reid, N.; Reimold, F.; Reinhart, M.; Reinke, M.; Reiser, D.; Rendell, D.; Reux, C.; Cortes, S. D. A. Reyes; Reynolds, S.; Riccardo, V.; Richardson, N.; Riddle, K.; Rigamonti, D.; Rimini, F. G.; Risner, J.; Riva, M.; Roach, C.; Robins, R. J.; Robinson, S. A.; Robinson, T.; Robson, D. W.; Roccella, R.; Rodionov, R.; Rodrigues, P.; Rodriguez, J.; Rohde, V.; Romanelli, F.; Romanelli, M.; Romanelli, S.; Romazanov, J.; Rowe, S.; Rubel, M.; Rubinacci, G.; Rubino, G.; Ruchko, L.; Ruiz, M.; Ruset, C.; Rzadkiewicz, J.; Saarelma, S.; Sabot, R.; Safi, E.; Sagar, P.; Saibene, G.; Saint-Laurent, F.; Salewski, M.; Salmi, A.; Salmon, R.; Salzedas, F.; Samaddar, D.; Samm, U.; Sandiford, D.; Santa, P.; Santala, M. I. K.; Santos, B.; Santucci, A.; Sartori, F.; Sartori, R.; Sauter, O.; Scannell, R.; Schlummer, T.; Schmid, K.; Schmidt, V.; Schmuck, S.; Schneider, M.; Schöpf, K.; Schwörer, D.; Scott, S. D.; Sergienko, G.; Sertoli, M.; Shabbir, A.; Sharapov, S. E.; Shaw, A.; Shaw, R.; Sheikh, H.; Shepherd, A.; Shevelev, A.; Shumack, A.; Sias, G.; Sibbald, M.; Sieglin, B.; Silburn, S.; Silva, A.; Silva, C.; Simmons, P. A.; Simpson, J.; Simpson-Hutchinson, J.; Sinha, A.; Sipilä, S. K.; Sips, A. C. C.; Sirén, P.; Sirinelli, A.; Sjöstrand, H.; Skiba, M.; Skilton, R.; Slabkowska, K.; Slade, B.; Smith, N.; Smith, P. G.; Smith, R.; Smith, T. J.; Smithies, M.; Snoj, L.; Soare, S.; Solano, E. R.; Somers, A.; Sommariva, C.; Sonato, P.; Sopplesa, A.; Sousa, J.; Sozzi, C.; Spagnolo, S.; Spelzini, T.; Spineanu, F.; Stables, G.; Stamatelatos, I.; Stamp, M. F.; Staniec, P.; Stankūnas, G.; Stan-Sion, C.; Stead, M. J.; Stefanikova, E.; Stepanov, I.; Stephen, A. V.; Stephen, M.; Stevens, A.; Stevens, B. D.; Strachan, J.; Strand, P.; Strauss, H. R.; Ström, P.; Stubbs, G.; Studholme, W.; Subba, F.; Summers, H. P.; Svensson, J.; Świderski, Ł.; Szabolics, T.; Szawlowski, M.; Szepesi, G.; Suzuki, T. T.; Tál, B.; Tala, T.; Talbot, A. R.; Talebzadeh, S.; Taliercio, C.; Tamain, P.; Tame, C.; Tang, W.; Tardocchi, M.; Taroni, L.; Taylor, D.; Taylor, K. A.; Tegnered, D.; Telesca, G.; Teplova, N.; Terranova, D.; Testa, D.; Tholerus, E.; Thomas, J.; Thomas, J. D.; Thomas, P.; Thompson, A.; Thompson, C.-A.; Thompson, V. K.; Thorne, L.; Thornton, A.; Thrysøe, A. S.; Tigwell, P. A.; Tipton, N.; Tiseanu, I.; Tojo, H.; Tokitani, M.; Tolias, P.; Tomeš, M.; Tonner, P.; Towndrow, M.; Trimble, P.; Tripsky, M.; Tsalas, M.; Tsavalas, P.; Jun, D. Tskhakaya; Turner, I.; Turner, M. M.; Turnyanskiy, M.; Tvalashvili, G.; Tyrrell, S. G. J.; Uccello, A.; Ul-Abidin, Z.; Uljanovs, J.; Ulyatt, D.; Urano, H.; Uytdenhouwen, I.; Vadgama, A. P.; Valcarcel, D.; Valentinuzzi, M.; Valisa, M.; Olivares, P. Vallejos; Valovic, M.; van de Mortel, M.; van Eester, D.; van Renterghem, W.; van Rooij, G. J.; Varje, J.; Varoutis, S.; Vartanian, S.; Vasava, K.; Vasilopoulou, T.; Vega, J.; Verdoolaege, G.; Verhoeven, R.; Verona, C.; Rinati, G. Verona; Veshchev, E.; Vianello, N.; Vicente, J.; Viezzer, E.; Villari, S.; Villone, F.; Vincenzi, P.; Vinyar, I.; Viola, B.; Vitins, A.; Vizvary, Z.; Vlad, M.; Voitsekhovitch, I.; Vondráček, P.; Vora, N.; Vu, T.; de Sa, W. W. Pires; Wakeling, B.; Waldon, C. W. F.; Walkden, N.; Walker, M.; Walker, R.; Walsh, M.; Wang, E.; Wang, N.; Warder, S.; Warren, R. J.; Waterhouse, J.; Watkins, N. W.; Watts, C.; Wauters, T.; Weckmann, A.; Weiland, J.; Weisen, H.; Weiszflog, M.; Wellstood, C.; West, A. T.; Wheatley, M. R.; Whetham, S.; Whitehead, A. M.; Whitehead, B. D.; Widdowson, A. M.; Wiesen, S.; Wilkinson, J.; Williams, J.; Williams, M.; Wilson, A. R.; Wilson, D. J.; Wilson, H. R.; Wilson, J.; Wischmeier, M.; Withenshaw, G.; Withycombe, A.; Witts, D. M.; Wood, D.; Wood, R.; Woodley, C.; Wray, S.; Wright, J.; Wright, J. C.; Wu, J.; Wukitch, S.; Wynn, A.; Xu, T.; Yadikin, D.; Yanling, W.; Yao, L.; Yavorskij, V.; Yoo, M. G.; Young, C.; Young, D.; Young, I. D.; Young, R.; Zacks, J.; Zagorski, R.; Zaitsev, F. S.; Zanino, R.; Zarins, A.; Zastrow, K. D.; Zerbini, M.; Zhang, W.; Zhou, Y.; Zilli, E.; Zoita, V.; Zoletnik, S.; Zychor, I.

2017-10-01

We describe a new technique for the efficient generation of high-energy ions with electromagnetic ion cyclotron waves in multi-ion plasmas. The discussed `three-ion' scenarios are especially suited for strong wave absorption by a very low number of resonant ions. To observe this effect, the plasma composition has to be properly adjusted, as prescribed by theory. We demonstrate the potential of the method on the world-largest plasma magnetic confinement device, JET (Joint European Torus, Culham, UK), and the high-magnetic-field tokamak Alcator C-Mod (Cambridge, USA). The obtained results demonstrate efficient acceleration of 3He ions to high energies in dedicated hydrogen-deuterium mixtures. Simultaneously, effective plasma heating is observed, as a result of the slowing-down of the fast 3He ions. The developed technique is not only limited to laboratory plasmas, but can also be applied to explain observations of energetic ions in space-plasma environments, in particular, 3He-rich solar flares.

Dynamics in the solar chromosphere as a function of the magnetic field topology

NASA Astrophysics Data System (ADS)

Karlsen, N.; Carlsson, M.

2002-06-01

We have looked at the coupling between the magnetic field and chromospheric dynamics. Observations with the SUMER spectrograph of the continuum radiation at 1319 Å have been correlated with simultaneous MDI magnetograms and dopplergrams in high resolution mode. We have used 7 different observing runs for our analysis, all from 1996. The absolute value of the magnetic field crossing the SUMER slit lies in the range 0-100 gauss. We observe a correlation between continuum intensity and magnetic field strength all the way to the sensitivity limit of MDI (about 2 G as 3σ in the mean value). Relative intensity fluctuations at frequencies corresponding to propagating acoustic waves (>4.5 mHz) have smaller amplitudes with increasing radiation temperature (or magnetic field strength). The absolute intensity fluctuations show an increase with increasing radiation temperature. These findings are consistent with a picture where a basic intensity level is set by a magnetic heating process even in the darkest internetwork areas with superimposed intensity variations caused by acoustic waves.

Observations by GLORIA of stirring and mixing in the UTLS following Rossby wave breaking in winter 2015/2016

NASA Astrophysics Data System (ADS)

Ungermann, Joern; Friedl-Vallon, Felix; Höpfner, Michael; Preusse, Peter; Riese, Martin

2016-04-01

The Gimbaled Limb Observer for Radiance Imaging of the Atmosphere (GLORIA) is an airborne infrared limb-imager combining a 2-D infrared detector with a Fourier transform spectrometer. It was operated aboard the German Gulfstream G550 research aircraft HALO during a series of simultaneous campaigns (POLSTRACC, SALSA, GWLCYCLE, GWEX) during the winter of 2015/2016 over Europe and the Arctic. This poster shows a set of GLORIA observations and analyses of 2-D trace gas cross-sections in the extratropical upper troposphere / lower stratosphere (UTLS). The spatially highly-resolved temperature, H2O, O3 and HNO3 data reveal an intricate layered structure in the extratropical Transition Layer (exTL). This heterogeneous structure was caused by Rossby wave breaking and is similar to the state found during previous measurements in summer 2012 over Europe. This study presents first analyses of the stirring and stratosphere-troposphere-exchange by means of backward-trajectory calculation.

Microrheology: Structural evolution under static and dynamic conditions by simultaneous analysis of confocal microscopy and diffusing wave spectroscopy

NASA Astrophysics Data System (ADS)

Nicolas, Yves; Paques, Marcel; Knaebel, Alexandra; Steyer, Alain; Munch, Jean-Pierre; Blijdenstein, Theo B. J.; van Aken, George A.

2003-08-01

An oscillatory shear configuration was developed to improve understanding of structural evolution during deformation. It combines an inverted confocal scanning laser microscope (CSLM) and a special sample holder that can apply to the sample specific deformation: oscillatory shear or steady strain. In this configuration, a zero-velocity plane is created in the sample by moving two plates in opposite directions, thereby providing stable observation conditions of the structural behavior under deformation. The configuration also includes diffusion wave spectroscopy (DWS) to monitor the network properties via particle mobility under static and dynamic conditions. CSLM and DWS can be performed simultaneously and three-dimensional images can be obtained under static conditions. This configuration is mainly used to study mechanistic phenomena like particle interaction, aggregation, gelation and network disintegration, interactions at interfaces under static and dynamic conditions in semisolid food materials (desserts, dressings, sauces, dairy products) and in nonfood materials (mineral emulsions, etc.). Preliminary data obtained with this new oscillatory shear configuration are described that demonstrate their capabilities and the potential contribution to other areas of application also.

Millimeter- and Submillimeter-Wave Remote Sensing Using Small Satellites

NASA Technical Reports Server (NTRS)

Ehsan, N.; Esper, J.; Piepmeier, J.; Racette, P.; Wu, D.

2014-01-01

Cloud ice properties and processes play fundamental roles in atmospheric radiation and precipitation. Limited knowledge and poor representation of clouds in global climate models have led to large uncertainties about cloud feedback processes under climate change. Ice clouds have been used as a tuning parameter in the models to force agreement with observations of the radiation budget at the top of the atmosphere, and precipitation at the bottom. The lack of ice cloud measurements has left the cloud processes at intermediate altitudes unconstrained. Millimeter (mm) and submillimeter (submm)-wave radiometry is widely recognized for its potential to fill the cloud measurement gap in the middle and upper troposphere. Analyses have shown that channels from 183900 GHz offer good sensitivity to ice cloud scattering and can provide ice water path (IWP) products to an accuracy of 25 by simultaneously retrieving ice particle size (Dme) and IWP. Therefore, it is highly desirable to develop a cost-effective, compact mm/submm-wave instrument for cloud observations that can be deployed on future small satellites.This paper presents a conceptual study for a mm/submm-wave instrument for multispectral measurements of ice clouds. It discusses previous work at these frequencies by NASA Goddard Space Flight Center (GSFC) and the current instrument study, as well as receiver architectures and their anticipated performance. And finally, it describes a microsatellite prototype intended for use with this mm/submm-wave instrument.

Coherent generation of the terrestrial kilometric radiation by nonlinear beatings between electrostatic waves

NASA Technical Reports Server (NTRS)

Roux, A.; Pellat, R.

1978-01-01

The propagation of electrostatic plasma waves in an inhomogeneous and magnetized plasma was studied. These waves, which are driven unstable by auroral beams of electrons, are shown to suffer a further geometrical amplification while they propagate towards resonances. Simultaneously, their group velocities tend to be aligned with the geomagnetic field. It is shown that the electrostatic energy tends to accumulate at, or near omega sub LH and omega sub UH, the local lower and upper hybrid frequencies. Due to this process, large amplitude electrostatic waves with very narrow spectra are observed near these frequencies at any place along the auroral field lines where intense beam driven instability takes place. These intense quasi-monochromatic electrostatic waves are shown to give rise to an intense electromagnetic radiation. Depending upon the ratio omega sub pe/omega sub ce between the electron plasma frequency and the electron gyro-frequency the electromagnetic wave can be radiated in the ordinary mode (at omega sub UH), or in the extraordinary (at 2 omega sub UH). As the ratio omega sub pe/omega sub ce tends to be rather small, it is shown that the most intense radiation should be boserved at 2 omega sub UH in the extraordinary mode.

Cerenkov emissions of ion acoustic-like waves generated by electron beams emitted during TSS 1R

NASA Astrophysics Data System (ADS)

Huang, C. Y.; Burke, W. J.; Hardy, D. A.; Gough, M. P.; Olson, D. G.; Gentile, L. C.; Gilchrist, B. E.; Bonifazi, C.; Raitt, W. J.; Thompson, D. C.

During the Tethered Satellite System reflight the Spacecraft Particle Correlation Experiment detected fluxes of energetic electrons and ions that were simultaneously modulated at low frequencies during firings of both the fast pulsed electron gun (FPEG) and the electron generator assembly (EGA). The modulations have been interpreted as signatures of large-amplitude, ion acoustic-like waves excited in Cerenkov interactions between electron beams and ambient plasmas as the shuttle moved at supersonic speeds across the ionospheric magnetic field. We present examples of particle modulations observed during steady beam emissions. Measurements show that (1) most electron modulations were at frequencies of several hundred Hertz and (2) ions modulated at similar frequencies appeared at spectral energy peaks during shuttle negative charging events. Detection of modulated ion fluxes confirms the Cerenkov emission hypothesis. Observed frequency variations indicate that the EGA beam underwent more spatial spreading than the FPEG beam.

Observation of sum-frequency-generation-induced cascaded four-wave mixing using two crossing femtosecond laser pulses in a 0.1 mm beta-barium-borate crystal.

PubMed

Liu, Weimin; Zhu, Liangdong; Fang, Chong

2012-09-15

We demonstrate the simultaneous generation of multicolor femtosecond laser pulses spanning the wavelength range from UV to near IR in a 0.1 mm Type I beta-barium borate crystal from 800 nm fundamental and weak IR super-continuum white light (SCWL) pulses. The multicolor broadband laser pulses observed are attributed to two concomitant cascaded four-wave mixing (CFWM) processes as corroborated by calculation: (1) directly from the two incident laser pulses; (2) by the sum-frequency generation (SFG) induced CFWM process (SFGFWM). The latter signal arises from the interaction between the frequency-doubled fundamental pulse (400 nm) and the SFG pulse generated in between the fundamental and IR-SCWL pulses. The versatility and simplicity of this spatially dispersed multicolor self-compressed laser pulse generation offer compact and attractive methods to conduct femtosecond stimulated Raman spectroscopy and time-resolved multicolor spectroscopy.

Space-time measurements of oceanic sea states

NASA Astrophysics Data System (ADS)

Fedele, Francesco; Benetazzo, Alvise; Gallego, Guillermo; Shih, Ping-Chang; Yezzi, Anthony; Barbariol, Francesco; Ardhuin, Fabrice

2013-10-01

Stereo video techniques are effective for estimating the space-time wave dynamics over an area of the ocean. Indeed, a stereo camera view allows retrieval of both spatial and temporal data whose statistical content is richer than that of time series data retrieved from point wave probes. We present an application of the Wave Acquisition Stereo System (WASS) for the analysis of offshore video measurements of gravity waves in the Northern Adriatic Sea and near the southern seashore of the Crimean peninsula, in the Black Sea. We use classical epipolar techniques to reconstruct the sea surface from the stereo pairs sequentially in time, viz. a sequence of spatial snapshots. We also present a variational approach that exploits the entire data image set providing a global space-time imaging of the sea surface, viz. simultaneous reconstruction of several spatial snapshots of the surface in order to guarantee continuity of the sea surface both in space and time. Analysis of the WASS measurements show that the sea surface can be accurately estimated in space and time together, yielding associated directional spectra and wave statistics at a point in time that agrees well with probabilistic models. In particular, WASS stereo imaging is able to capture typical features of the wave surface, especially the crest-to-trough asymmetry due to second order nonlinearities, and the observed shape of large waves are fairly described by theoretical models based on the theory of quasi-determinism (Boccotti, 2000). Further, we investigate space-time extremes of the observed stationary sea states, viz. the largest surface wave heights expected over a given area during the sea state duration. The WASS analysis provides the first experimental proof that a space-time extreme is generally larger than that observed in time via point measurements, in agreement with the predictions based on stochastic theories for global maxima of Gaussian fields.

A FAST PROPAGATING EXTREME-ULTRAVIOLET WAVE ASSOCIATED WITH A MINI-FILAMENT ERUPTION

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zheng Ruisheng; Jiang Yunchun; Yang Jiayan

The fast extreme-ultraviolet (EUV) waves (>1000 km s{sup -1}) in the solar corona were very rare in the past. Taking advantage of the high temporal and spatial resolution of the Solar Dynamics Observatory observations, we present a fast EUV wave associated with a mini-filament eruption, a C1.0 flare, and a coronal mass ejection (CME) on 2011 September 30. The event took place at the periphery between two active regions (ARs). The mini-filament rapidly erupted as a blowout jet associated with a flare and a CME. The CME front was likely developed from the large-scale overlying loops. The wave onset wasmore » nearly simultaneous with the start of the jet and the flare. The wave departed far from the flare center and showed a close location relative to the rapid jet. The wave had an initial speed of about 1100 km s{sup -1} and a slight deceleration in the last phase, and the velocity decreased to about 500 km s{sup -1}. The wave propagated in a narrow angle extent, likely to avoid the ARs on both sides. All the results provide evidence that the fast EUV wave was a fast-mode MHD wave. The wave resisted being driven by the CME, because it opened up the large-scale loops and its front likely formed later than the wave. The wave was most likely triggered by the jet, due to their close timing and location relations.« less

Observations of turbulent mixing in a shallow coral reef

NASA Astrophysics Data System (ADS)

Huang, Z. C.

2016-02-01

In situ measurements of waves, currents, and turbulence are presented to study turbulence properties within a depression that is surrounded by multiple coral-reef colonies in a fringing reef in Hobihu, Nan-Wan Bay, southern Taiwan. Turbulence was measured using a dual velocimetry technique, and wave bias contamination in the turbulence is controlled using ogive curve testing of the turbulent shear stress. The observed turbulent dissipation rate is approximately five times greater than simultaneous observations over the nearby sandy bottom site, which indicates stronger mixing within the coral reef than on sandy bottoms. Energetic downward momentum flux exists due to sweeping process; the turbulent kinetic energy is transported downward into the depression through the mechanisms of vertical turbulent transport and advection. The observed turbulent dissipation rate exceeds the shear production rate, which suggests that transport terms or other source terms might be important. The wake flow caused by the resistance force of coral colonies is examined. The form drag coefficient was estimated from the time-averaged alongshore linear momentum between two sites upstream and within the coral reef. The work done due to the form drag, which is termed the wake production, is found to strongly correlate and approximate well to the observed turbulent dissipation rate. The effects of waves and currents on the wake production are discussed. The observed TSS can be described well by classic turbulence closure model when the empirical stability function is adjusted. This study suggests that the complex canopy structure of multiple colonies and the coexistence of the wave-induced and current flows are significant factors for energetic turbulence in the coral reef, which could have positive effects to the health of the coral reefs.

Searching for Correlated Radio Transients & Gravitational Wave Bursts

NASA Astrophysics Data System (ADS)

Kavic, Michael; Shawhan, P. S.; Yancey, C.; Cutchin, S.; Simonetti, J. H.; Bear, B.; Tsai, J.

2013-01-01

We will discuss an ongoing multi-messenger search for transient radio pulses and gravitational wave bursts. This work is being conducted jointly by the Long Wavelength Array (LWA) and the LIGO Scientific Collaboration (LSC). A variety of astrophysical sources can produce simultaneous emission of gravitational waves and coherent low-frequency electromagnetic radiation. The primary common source motivating this work is the merger of neutron star binaries for which the LWA and LSC instruments have comparable sensitivity. Additional common sources include supernovae, long timescale GRBs and cosmic string cusp events. Data taken by both instruments can be compared to search for correlated signals. Identification of correlated signals can be used to increase the sensitivity of both instruments. We will summarize the coincident observations which have already been conducted and outline plans for future work. We will describe the process being used for synthesizing these data set and present preliminary results.

Elastic and anelastic structure of the lowermost mantle beneath the Western Pacific using waveform inversion

NASA Astrophysics Data System (ADS)

Konishi, K.; Deschamps, F.; Fuji, N.

2015-12-01

We investigate quasi-2D elastic and anelastic structure of the lowermost mantle beneath the Western Pacific by inverting S and ScS waveforms. The transverse component data were obtained from F-net for 32 deep sources beneath Tonga and Fiji, filtered between 12.5 and 200 s. We observe a regional variation of S and ScS arrival times and amplitude ratio, according to which we divide our region of interest into four sub-regions and perform 1D waveform inversion for S-wave velocity and Qμ value simultaneously. We find S-shaped structure of S-wave velocity beneath the whole region with sub-regional variation of S-wave velocity peak depths, which can explain regional difference in travel times. Qμ structure varies with sub-regions as well, but the physical interpretation has not yet done.

THz electromagnetic radiation driven by intense relativistic electron beam based on ion focus regime

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zhou, Qing; Xu, Jin; Zhang, Wenchao

The simulation study finds that the relativistic electron beam propagating through the plasma background can produce electromagnetic (EM) radiation. With the propagation of the electron beam, the oscillations of the beam electrons in transverse and longitudinal directions have been observed simultaneously, which provides the basis for the electromagnetic radiation. The simulation results clearly show that the electromagnetic radiation frequency can reach up to terahertz (THz) wave band which may result from the filter-like property of plasma background, and the electromagnetic radiation frequency closely depends on the plasma density. To understand the above simulation results physically, the dispersion relation of themore » beam-plasma system has been derived using the field-matching method, and the dispersion curves show that the slow wave modes can couple with the electron beam effectively in THz wave band, which is an important theoretical evidence of the EM radiation.« less

Design and numerical analysis of a THz square porous-core photonic crystal fiber for low flattened dispersion, ultrahigh birefringence.

PubMed

Luo, Jianfeng; Tian, Fengjun; Qu, Hongkun; Li, Li; Zhang, Jianzhong; Yang, Xinhua; Yuan, Libo

2017-08-20

We propose a kind of square porous-core photonic crystal fiber (PCF) for polarization-maintaining terahertz (THz) wave guidance. An asymmetry is introduced by implementing rectangular array air holes in the porous core of the PCF, and ultrahigh birefringence and low effective material loss (EML) can be achieved simultaneously. The properties of THz wave propagation are analyzed numerically in detail. The numerical results indicate that the proposed fiber offers a high birefringence of 0.063 and a low EML of 0.081  cm -1 at 1 THz. Moreover, a very low flattened dispersion profile is observed over a wide frequency domain of 0.85-1.9 THz. The zero flattened dispersion can be controlled. It is predicted that this PCF would be used potentially in polarization maintaining and dispersion management of THz waves.

DE 1 and Viking observations associated with electron conical distributions

NASA Technical Reports Server (NTRS)

Menietti, J. D.; Weimer, D. R.; Andre, M.; Eliasson, L.

1994-01-01

Data from the electron detectors on board the Swedish Viking satellite launched during a period of low solar activity and from the Dynamic Explorer (DE) 1 satellite launched during active solar coditions have been examined for the occurrence and location of electron conical distributions and several conclusions can be drawn. First, we note that most of the best examples of electron conics observed by the V-3 experiment onboard Viking occurred in the afternoon sector in the range of magneitc local time 14 hours less than Magnetic Local Time (MLT) less than 18 hours, at midaltitudes in the range 10,000 km less than h less than 13,500 km, with few occurring in the nightside auroral region, a region poorly sampled at altitudes greater than 5000 km. For the Viking data there is an association of electron conics with upper hybrid waves. DE 1 observations made by the high-altitude plasma instrument (HAPI) indicate that electron conics were observed in the midmorning sector and the late evening sector, and as has been reported earlier, the correlation with upper hybird waves was good. The HAPI did not sample the afternoon sector. The electon conics observed on both satellites occurred in the presence of at least a modest (several kilovolts) potential difference beneath the satellite with a maximum energy that was usually, but not always, equal to or greater than the maximum energy of the electron conics. Two independent sets of observations by DE 1 suggest two distinct production mechanisms for electron conics. Examiniation of DE 1 electric field measurements from the plasma wave instrument during the observation of electron conics show simultaneous parallel oscillations in the frequency range of 0.2 Hz less than f less than 0.5 Hz during one and perhaps two of four events examined, and upper hybrid waves were observed on all four events. In addition, recent observations of '90-deg' electron conics associated with auroral kilometric radiation source regions suggest a perpendicular heating mechanism produced by wave-particle interaction. Such distributions may be observed as electron conics at higher altitudes. These results suggest more than one possible source mechanism may be responsible for electron conics.

Simultaneous visualization of transonic buffet on a rocket faring model using unsteady PSP measurement and Schlieren method

NASA Astrophysics Data System (ADS)

Nakakita, K.

2017-02-01

Simultaneous visualization technique of the combination of the unsteady Pressure-Sensitive Paint and the Schlieren measurement was introduced. It was applied to a wind tunnel test of a rocket faring model at the JAXA 2mx2m transonic wind tunnel. Quantitative unsteady pressure field was acquired by the unsteady PSP measurement, which consisted of a high-speed camera, high-power laser diode, and so on. Qualitative flow structure was acquired by the Schlieren measurement using a high-speed camera and Xenon lamp with a blue optical filter. Simultaneous visualization was achieved 1.6 kfps frame rate and it gave the detailed structure of unsteady flow fields caused by the unsteady shock wave oscillation due to shock-wave/boundary-layer interaction around the juncture between cone and cylinder on the model. Simultaneous measurement results were merged into a movie including surface pressure distribution on the rocket faring and spatial structure of shock wave system concerning to transonic buffet. Constructed movie gave a timeseries and global information of transonic buffet flow field on the rocket faring model visually.

Topside enhancements of the ionline in response to high-power HF-radio wave pumping at high latitudes

NASA Astrophysics Data System (ADS)

Rexer, Theresa; Gustavsson, Björn; Grydeland, Tom; Rietveld, Mike; Leyser, Thomas; Brändström, Urban; Sergienko, Tima

2017-04-01

A high power, high frequency heating experiment of the polar ionosphere was conducted in Tromsø, Norway in March 2016. The wave-plasma interactions were observed with the European Incoherent SCATer UHF radar co-located with the heating facility. HF pulses in a 3 minute ON 3 minute OFF cycles were transmitted, sweeping frequencies in 10 and 20 kHz steps from just below to just above the 3rd and 4th multiples of the F-region gyro-frequency. Several interesting features have been found in the radar measurements of the backscatter from the heated plasma. In agreement with current theory we observed an enhanced ionline near the HF reflection height on the bottom-side of the F layer. Simultaneously, a less intense, but clearly visible, ionline enhancement was observed approximately 100 km above this bottom-side enhancement for several 3 minute sweep pulses. We present the observations and discuss the top-side enhanced ion-line in relation to Z and L-mode propagation through the F-region peak.

Researche of the Earth's crust structure with powerful vibrational controlled sources

NASA Astrophysics Data System (ADS)

Alekseev, A.; Glinsky, B.; Kovalevsky, V.

2003-04-01

The paper presents the results of experimental researches of the Earth's structure, geodynamic processes and physical phenomena carried out using vibrational sources in Institutes of Siberian Branch RAS. Powerful seismic vibrators are the large mechanical devises and are installed stationary on the vibroseismic test site near Novosibirsk (Russia). The vibro-DSS experiments were carried out on 100 km-long profile from Novosibirsk to Kuzbass region and on 620 km profile between Novosibirsk and Semipalatinsk test site. Specially developed field recording systems based on multichannel three component seismic arrays were used. It allowed us to observe the main crustal waves and waves refracted on Moho boundary. In the experiments on the 620 km profile the comparison of the seismic vibrator and special 100 tons calibration explosion wave fields was made. The possibility to detect small changes of wave velocities by vibroseismic methods were shown in the experiments on the setoff 356 and 430 km, where the relative variations of velocities of seismic waves about 10-5 - 10-6 caused by the Earth's tides deformations of the crust were defined. Some new physical phenomena connected with resonance mechanism of radiation of seismic energy in low-frequency range, the radiation of acoustic waves simultaneously with seismic waves and their interaction on long distances from vibrators were detected.

Considerations for SphygmoCor radial artery pulse wave analysis: side selection and peripheral arterial blood pressure calibration.

PubMed

Martin, Jeffrey S; Borges, Alexandra R; Christy, John B; Beck, Darren T

2015-10-01

Methods employed for pulse wave analysis (PWA) and peripheral blood pressure (PBP) calibration vary. The purpose of this study was to evaluate the agreement of SphygmoCor PWA parameters derived from radial artery tonometry when considering (1) timing (before vs. after tonometry) and side selection (ipsilateral vs. contralateral limb) for PBP calibration and (2) side selection for tonometry (left vs. right arm). In 34 subjects (aged 21.9 ± 2.3 years), bilateral radial artery tonometry was performed simultaneously on three instances. PBP assessment via oscillometric sphygmomanometry in the left arm only and both arms simultaneously occurred following the first and second instances of tonometry, respectively. Significant within arm differences in PWA parameters derived before and after PBP measurement were observed in the right arm only (for example, aortic systolic blood pressure, Δ=0.38 ± 0.64 mm Hg). Simultaneously captured bilateral PWA variables demonstrated significant between arm differences in 88% (14/16) and 56% (9/16) of outcome variables when calibrated to within arm and equivalent PBP, respectively. Moreover, the right arm consistently demonstrated lower values for clinical PWA variables (for example, augmentation index, bias=-2.79%). However, 26% (n=9) of participants presented with clinically significant differences (>10 mm Hg) in bilateral PBP and their exclusion from analysis abolished most between arm differences observed. SphygmoCor PWA in the right radial artery results in greater variability independent of the timing of PBP measurement and magnitude of calibration pressures in young subjects. Moreover, bilateral PBP measurement is imperative to identify subjects in whom a significant difference in bilateral PWA outcomes may exist.

Gravity waves, Tides and Planetary wave characteristics revealed by network of MLT radars over Indian region

NASA Astrophysics Data System (ADS)

Venkat Ratnam, Madineni; Karanam, Kishore Kumar; Sunkara, Eswaraiah; Vijaya Bhaskara Rao, S.; Subrahmanyam, K. V.; Ramanjaneyulu, L.

2016-07-01

Mesosphere and Lower Thermosphere (MLT) mean winds, gravity waves, tidal and planetary wave characteristics are investigated using two years (2013-2015) of advanced meteor radar installed at Tirupathi (13.63oN, 79.4oE), India. The observations reveal the presence of high frequency gravity waves (30-120 minutes), atmospheric tides (diurnal, semi-diurnal and terr-diurnal) along with long period oscillations in both zonal and meridional winds. Background mean zonal winds show clear semi-annual oscillation in the mesosphere, whereas meridional winds are characterized by annual oscillation as expected. Diurnal tide amplitudes are significantly larger (60-80 m/s) than semi-diurnal (10-20 m/s) and terr-diurnal (5-8 m/s) tides and larger in meridional than zonal winds. The measured meridional components are in good agreement with Global Scale Wave Model (GSWM-09) predictions than zonal up to ~90 km in all the seasons, except fall equinox. Diurnal tidal phase matches well than the amplitudes between observations and model predictions. However, no similarity is being found in the semi-diurnal tides between observations and model. The measurements are further compared with nearby Thumba meteor radar (8.5oN, 77oE) observations. Some differences do exist between the measurements from Tirupati and Thumba meteor radar and model outputs at greater heights and the possible reasons are discussed. SVU meteor radar observations clearly showed the dominance of well-known ultra-fast kelvin waves (3.5 days), 5-8 day, 16 day, 27 day, and 30-40 day oscillations. Due to higher meteor count extending up to 110 km, we could investigate the variability of these PWs and oscillations covering wider range (70-110 km) for the first time. Significant change above 100 km is noticed in all the above mentioned PW activity and oscillations. We also used ERA-Interim reanalysis data sets available at 0.125x0.125 degree grids for investigating the characteristics of these PW right from surface to 1 hPa. The presence of these waves and oscillations right from upper troposphere to lower thermosphere simultaneously is noticed. Though these waves are expected to have higher wave number (higher horizontal wave lengths) few important differences are noticed between Tirupati and Thumba, that are separated by only 500 km. The implication of these waves and oscillations on the background atmosphere and vice versa are discussed. Thus, installation of SVU meteor radar made good complementary observations that can be effectively used to investigate vertical and lateral coupling. Role of these tides in modulating the mesopause altitude is further investigated using the Sounding of the Atmosphere using Broadband Emission Radiometry (SABER) on-board Thermosphere Ionosphere Mesosphere Energetics Dynamics (TIMED) satellite. It is found that mesopause altitude is always close to 100 km and is strongly affected by gravity waves, tides and planetary waves.

Simultaneous observations of traveling convection vortices: Ionosphere-thermosphere coupling: M-I-T COUPLING OF TCV

DOE PAGES

Kim, Hyomin; Lessard, Marc R.; Jones, Sarah L.; ...

2017-03-11

We present simultaneous observations of magnetosphere-ionosphere-thermosphere coupling over Svalbard during a traveling convection vortex (TCV) event. Various spaceborne and ground-based instruments made coordinated measurements, including magnetometers, particle detectors, an all-sky camera, European Incoherent Scatter (EISCAT) Svalbard Radar, Super Dual Auroral Radar Network (SuperDARN), and SCANning Doppler Imager (SCANDI). The instruments recorded TCVs associated with a sudden change in solar wind dynamic pressure. The data display typical features of TCVs including vortical ionospheric convection patterns seen by the ground magnetometers and SuperDARN radars and auroral precipitation near the cusp observed by the all-sky camera. Simultaneously, electron and ion temperature enhancements withmore » corresponding density increase from soft precipitation are also observed by the EISCAT Svalbard Radar. The ground magnetometers also detected electromagnetic ion cyclotron waves at the approximate time of the TCV arrival. This implies that they were generated by a temperature anisotropy resulting from a compression on the dayside magnetosphere. SCANDI data show a divergence in thermospheric winds during the TCVs, presumably due to thermospheric heating associated with the current closure linked to a field-aligned current system generated by the TCVs. We conclude that solar wind pressure impulse-related transient phenomena can affect even the upper atmospheric dynamics via current systems established by a magnetosphere-ionosphere-thermosphere coupling process.« less

Simultaneous observations of traveling convection vortices: Ionosphere-thermosphere coupling: M-I-T COUPLING OF TCV

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kim, Hyomin; Lessard, Marc R.; Jones, Sarah L.

We present simultaneous observations of magnetosphere-ionosphere-thermosphere coupling over Svalbard during a traveling convection vortex (TCV) event. Various spaceborne and ground-based instruments made coordinated measurements, including magnetometers, particle detectors, an all-sky camera, European Incoherent Scatter (EISCAT) Svalbard Radar, Super Dual Auroral Radar Network (SuperDARN), and SCANning Doppler Imager (SCANDI). The instruments recorded TCVs associated with a sudden change in solar wind dynamic pressure. The data display typical features of TCVs including vortical ionospheric convection patterns seen by the ground magnetometers and SuperDARN radars and auroral precipitation near the cusp observed by the all-sky camera. Simultaneously, electron and ion temperature enhancements withmore » corresponding density increase from soft precipitation are also observed by the EISCAT Svalbard Radar. The ground magnetometers also detected electromagnetic ion cyclotron waves at the approximate time of the TCV arrival. This implies that they were generated by a temperature anisotropy resulting from a compression on the dayside magnetosphere. SCANDI data show a divergence in thermospheric winds during the TCVs, presumably due to thermospheric heating associated with the current closure linked to a field-aligned current system generated by the TCVs. We conclude that solar wind pressure impulse-related transient phenomena can affect even the upper atmospheric dynamics via current systems established by a magnetosphere-ionosphere-thermosphere coupling process.« less

A novel high-pressure vessel for simultaneous observations of seismic velocity and in situ CO2 distribution in a porous rock using a medical X-ray CT scanner

NASA Astrophysics Data System (ADS)

Jiang, Lanlan; Nishizawa, Osamu; Zhang, Yi; Park, Hyuck; Xue, Ziqiu

2016-12-01

Understanding the relationship between seismic wave velocity or attenuation and CO2 saturation is essential for CO2 storage in deep saline formations. In the present study, we describe a novel upright high-pressure vessel that is designed to keep a rock sample under reservoir conditions and simultaneously image the entire sample using a medical X-ray CT scanner. The pressure vessel is composed of low X-ray absorption materials: a carbon-fibre-enhanced polyetheretherketone (PEEK) cylinder and PEEK vessel closures supported by carbon-fibre-reinforced plastic (CFRP) joists. The temperature was controlled by a carbon-coated film heater and an aramid fibre thermal insulator. The assembled sample cell allows us to obtain high-resolution images of rock samples during CO2 drainage and brine imbibition under reservoir conditions. The rock sample was oriented vertical to the rotation axis of the CT scanner, and seismic wave paths were aligned parallel to the rotation axis to avoid shadows from the acoustic transducers. The reconstructed CO2 distribution images allow us to calculate the CO2 saturation in the first Fresnel zone along the ray path between transducers. A robust relationship between the seismic wave velocity or attenuation and the CO2 saturation in porous rock was obtained from experiments using this pressure vessel.

Response of equatorial and low latitude mesosphere lower thermospheric dynamics to the northern hemispheric sudden stratospheric warming events

NASA Astrophysics Data System (ADS)

Koushik, N.; Kumar, Karanam Kishore; Ramkumar, Geetha; Subrahmanyam, K. V.

2018-04-01

The changes in zonal mean circulation and meridional temperature gradient brought about by Sudden Stratospheric Warming (SSW) events in polar middle atmosphere are found to significantly affect the low latitude counterparts. Several studies have revealed the signatures of SSW events in the low latitude Mesosphere- Lower Thermosphere (MLT) region. Using meteor wind radar observations, the present study investigates the response of semidiurnal oscillations and quasi 2-day waves in the MLT region, simultaneously over low latitude and equatorial stations Thumba (8.5oN, 76.5oE) and Kototabang (0.2oS, 100oE). Unlike many case studies, the present analysis examines the response of low and equatorial latitude MLT region to typical polar stratospheric conditions viz., Quiet winter, Major SSW winter and Minor SSW winter. The present results show that (i) the amplitudes of semidiurnal oscillations and quasi 2-day waves in the equatorial and low latitude MLT region enhance in association with major SSW events, (ii) the semidiurnal oscillations show significant enhancement selectively in the zonal and meridional components over the Northern Hemispheric low latitude and the equatorial stations, respectively (iii) The minor SSW event of January 2012 resulted in anomalously large amplitudes of quasi 2- day waves without any notable increase in the amplitude of semidiurnal oscillations. The significance of the present study lies in comprehensively bringing out the signatures of SSW events in the semidiurnal oscillations and quasi 2-day waves in low latitude and equatorial MLT region, simultaneously for the first time over these latitudes.

Demonstration of uneven distribution of intracranial pulsatility in hydrocephalus patients.

PubMed

Eide, Per K

2008-11-01

Data from intracranial pressure (ICP) recordings in patients with hydrocephalus were reviewed to determine whether intracranial pulsatility within the cerebrospinal fluid (CSF) of cerebral ventricles (ICP(LV)) may differ from that within the brain parenchyma (ICP(PAR)), and whether pulsatility may differ between noncommunicating ventricles. The authors retrieved data from recordings previously obtained in 7 patients with hydrocephalus (noncommunicating in 4 and communicating in 3) and shunt failure who received both an external ventricular drainage (EVD) and an ICP sensor as part of surveillance during intensive care. Simultaneous ICP(LV) and ICP(PAR) signals were available in 6 cases, and simultaneous signals from the lateral and fourth ventricles (ICP(LV) and ICP4V, respectively) were recorded in 1 case. The recordings with both signals were parsed into 6-second time windows. Pulsatility was characterized by the wave amplitude and rise time coefficient, and differences in pulsatility between the ICP(LV) and ICP(PAR) signals (6 cases) or ICP(LV) and ICP4V signals (1 case) were determined. There was uneven distribution of intracranial pulsatility in all 7 patients, shown as significantly elevated pulsatility (that is, higher wave amplitudes and rise time coefficients) within the ventricles (ICP(LV)) than within brain parenchyma (ICP(PAR)) in 6 patients, and significantly higher pulsatility in the fourth (ICP4V) than in the lateral (ICP(LV)) ventricles in 1 patient. Differences > or = 1 mm Hg in ICP wave amplitude were found in 0.5-100% (median 9.4%) of observations in the 7 patients (total number of 6-second time windows, 68,242). The present observations demonstrate uneven distribution of intracranial pulsatility in patients with hydrocephalus, higher pulse pressure amplitudes within the ventricular CSF (ICP(LV)) than within the brain parenchyma (ICP(PAR)). This may be one mechanism behind ventricular enlargement in hydrocephalus.

Simultaneous Airy beam generation for both surface plasmon polaritons and transmitted wave based on metasurface.

PubMed

Wang, Sen; Wang, Xinke; Zhang, Yan

2017-10-02

Based on the amplitude and phase modulation of subwavelength slits, a metasurface which can simultaneously generate Airy beam for surface plasmon polaritons (SPPs) and transmitted wave is presented. Interestingly, by changing the handedness of circularly polarized light, the position of SPPs Airy beam can be switched to the left or right side of the metasurface, while the field distribution and the position of the Airy beam for transmitted wave are not affected. The nondiffracting, self-bending and self-healing properties of the generated Airy beams are analyzed as well. In addition, abruptly autofocusing of SPPs and transmitted wave are demonstrated by interfering two Airy beams. The dual functionality and chirality features of the metasurface can provide more freedoms in the potential applications of Airy beams.

Cup waveguide antenna with integrated polarizer and OMT

NASA Technical Reports Server (NTRS)

Kory, Carol (Inventor); Acosta, Roberto J. (Inventor); Lambert, Kevin M. (Inventor)

2011-01-01

A cup waveguide antenna with integrated polarizer and OMT for simultaneously communicating left and right hand circularly polarized electromagnetic waves is adjustable to obtain efficient propagation and reception of electromagnetic waves. The antenna includes a circular waveguide having an orthomode transducer utilizing first and second pins longitudinally spaced apart and oriented orthogonally with respect to each other. Six radially-oriented adjustable polarizer screws extend from the exterior to the interior of the waveguide. A septum intermediate the first and second pins is aligned with the first pin. Adjustment of the polarizer screws enables maximized propagation of and/or response to left hand circularly polarized electromagnetic waves by the first pin while simultaneously enabling maximized propagation of and/or response to right hand circularly polarized electromagnetic waves by the second pin.

An Investigation in Atmospheric Dynamics and Its Effects on Optical Emissions

DTIC Science & Technology

1991-08-01

waves are as follows: (1) Power spectrum analyses of simultaneous phot01- tric observations 11... of mesospheric and lower thermospheric optical...MAPSTAR Campaign) se-ms to show a surprisingly large number of power peaks with short periods. This would seem to suggest that the higher Fourier...directly aid hame aixrlcw height changes can be est-maed. •idle sawb of ouw results are known qualitatively to G. W. specalists, to ouw ) kowledge there has

Violation of Bell’s inequality: Must the Einstein locality really be abandoned?

NASA Astrophysics Data System (ADS)

Jung, Kurt

2017-08-01

Since John Bell has established his famous inequality and several independent experiments have confirmed the distinct polarization correlation of entangled photons predicted by quantum mechanics it is evident that quantum mechanics cannot be explained by local realistic theories. Actually, the observed polarization correlation can be deduced from wave optical considerations. The correlation has its origin in the phase coupling of the two circularly polarized wave packets leaving the photon source simultaneously. The experimental results violate Bell’s inequality although no non-local interactions have to be assumed. In consequence the principle of locality remains valid in the scope of quantum mechanics. However, the principle of realism has to be replaced by the less stringent principle of contextuality.

Self-accelerating universe in scalar-tensor theories after GW170817

NASA Astrophysics Data System (ADS)

Crisostomi, Marco; Koyama, Kazuya

2018-04-01

The recent simultaneous detection of gravitational waves and a gamma-ray burst from a neutron star merger significantly shrank the space of viable scalar-tensor theories by demanding that the speed of gravity is equal to that of light. The survived theories belong to the class of degenerate higher order scalar-tensor theories. We study whether these theories are suitable as dark energy candidates. We find scaling solutions in the matter dominated universe that lead to de Sitter solutions at late times without the cosmological constant, realizing self-acceleration. We evaluate quasistatic perturbations around self-accelerating solutions and show that the stringent constraints coming from astrophysical objects and gravitational waves can be satisfied, leaving interesting possibilities to test these theories by cosmological observations.

A statistical study of whistler waves observed by Van Allen Probes (RBSP) and lightning detected by WWLLN

NASA Astrophysics Data System (ADS)

Zheng, Hao; Holzworth, Robert H.; Brundell, James B.; Jacobson, Abram R.; Wygant, John R.; Hospodarsky, George B.; Mozer, Forrest S.; Bonnell, John

2016-03-01

Lightning-generated whistler waves are electromagnetic plasma waves in the very low frequency (VLF) band, which play an important role in the dynamics of radiation belt particles. In this paper, we statistically analyze simultaneous waveform data from the Van Allen Probes (Radiation Belt Storm Probes, RBSP) and global lightning data from the World Wide Lightning Location Network (WWLLN). Data were obtained between July to September 2013 and between March and April 2014. For each day during these periods, we predicted the most probable 10 min for which each of the two RBSP satellites would be magnetically conjugate to lightning producing regions. The prediction method uses integrated WWLLN stroke data for that day obtained during the three previous years. Using these predicted times for magnetic conjugacy to lightning activity regions, we recorded high time resolution, burst mode waveform data. Here we show that whistlers are observed by the satellites in more than 80% of downloaded waveform data. About 22.9% of the whistlers observed by RBSP are one-to-one coincident with source lightning strokes detected by WWLLN. About 40.1% more of whistlers are found to be one-to-one coincident with lightning if source regions are extended out 2000 km from the satellites footpoints. Lightning strokes with far-field radiated VLF energy larger than about 100 J are able to generate a detectable whistler wave in the inner magnetosphere. One-to-one coincidences between whistlers observed by RBSP and lightning strokes detected by WWLLN are clearly shown in the L shell range of L = 1-3. Nose whistlers observed in July 2014 show that it may be possible to extend this coincidence to the region of L≥4.

First observations of SPEAR-induced topside and bottomside sporadic E layer heating observed using the EISCAT Svalbard and SuperDARN radars

NASA Astrophysics Data System (ADS)

Baddeley, L. J.; Haggstrøm, I.; Yeoman, T. K.; Rietveld, M.

2012-01-01

We present the first observations of heater-induced simultaneous topside and bottomside sporadic E layer enhancements at very high latitudes (78.15°N) using the Space Plasma Exploration by Active Radar (SPEAR) heating facility and the European Incoherent Scatter (EISCAT) Svalbard Radar. During the experiment the SPEAR heating facility was transmitting with O-mode polarization in a field-aligned direction with a constant effective radiated power of ˜16 MW. Results show distinct heater-induced enhancements in both the ion and plasma line spectra. The plasma line enhancements are observed at the SPEAR heater frequency of 4.45 MHz. The plasma line observations represent the highest spatial resolution data (100 m) obtained of such heater-induced enhancements and indicate simultaneous enhancements at both the topside and bottomside of the layer, respectively (located at ˜107.5 and 109 km altitude, respectively). It is postulated that the results represent evidence of O- to Z-mode conversion of the heater wave occurring at the bottom of the E layer, allowing propagation through the layer resulting in simultaneous topside enhancements. The Z-mode enhancements are observed outside the Spitze angle, which is thought to be a result of field-aligned irregularities causing an increase in angular extent of the observations. Additional data from the Super Dual Auroral Radar Network (SuperDARN) HF Finland radar are also shown, which indicate that upon a thinning of the sporadic E layer, the heater beam propagated into the F region, where it induced artificial field-aligned irregularities.

Correlating Solar Wind Modulation with Ionospheric Variability at Mars from MEX and MAVEN Observations

NASA Astrophysics Data System (ADS)

Kopf, A. J.; Morgan, D. D.; Halekas, J. S.; Ruhunusiri, S.; Gurnett, D. A.; Connerney, J. E. P.

2017-12-01

The synthesis of observations by the Mars Express and Mars Atmosphere and Volatiles Evolution (MAVEN) spacecraft allows for a unique opportunity to study variability in the Martian ionosphere from multiple perspectives. One major source for this variability is the solar wind. Due to its elliptical orbit which precesses over time, MAVEN periodically spends part of its orbit outside the Martian bow shock, allowing for direct measurements of the solar wind impacting the Martian plasma environment. When the Mars Advanced Radar for Subsurface and Ionosphere Sounding (MARSIS) instrument aboard Mars Express is simultaneously sounding the ionosphere, the influence from changes in the solar wind can be observed. Previous studies have suggested a positive correlation, connecting ionospheric density to the solar wind proton flux, but depended on Earth-based measurements for solar wind conditions. More recently, research has indicated that observations of ionospheric variability from these two spacecraft can be connected in special cases, such as shock wave impacts or specific solar wind magnetic field orientations. Here we extend this to more general solar wind conditions and examine how changes in the solar wind properties measured by MAVEN instruments correlate with ionospheric structure and dynamics observed simultaneously in MARSIS remote and local measurements.

Performance evaluation of low-cost airglow cameras for mesospheric gravity wave measurements

NASA Astrophysics Data System (ADS)

Suzuki, S.; Shiokawa, K.

2016-12-01

Atmospheric gravity waves significantly contribute to the wind/thermal balances in the mesosphere and lower thermosphere (MLT) through their vertical transport of horizontal momentum. It has been reported that the gravity wave momentum flux preferentially associated with the scale of the waves; the momentum fluxes of the waves with a horizontal scale of 10-100 km are particularly significant. Airglow imaging is a useful technique to observe two-dimensional structure of small-scale (<100 km) gravity waves in the MLT region and has been used to investigate global behaviour of the waves. Recent studies with simultaneous/multiple airglow cameras have derived spatial extent of the MLT waves. Such network imaging observations are advantageous to ever better understanding of coupling between the lower and upper atmosphere via gravity waves. In this study, we newly developed low-cost airglow cameras to enlarge the airglow imaging network. Each of the cameras has a fish-eye lens with a 185-deg field-of-view and equipped with a CCD video camera (WATEC WAT-910HX) ; the camera is small (W35.5 x H36.0 x D63.5 mm) and inexpensive, much more than the airglow camera used for the existing ground-based network (Optical Mesosphere Thermosphere Imagers (OMTI) operated by Solar-Terrestrial Environmental Laboratory, Nagoya University), and has a CCD sensor with 768 x 494 pixels that is highly sensitive enough to detect the mesospheric OH airglow emission perturbations. In this presentation, we will report some results of performance evaluation of this camera made at Shigaraki (35-deg N, 136-deg E), Japan, where is one of the OMTI station. By summing 15-images (i.e., 1-min composition of the images) we recognised clear gravity wave patterns in the images with comparable quality to the OMTI's image. Outreach and educational activities based on this research will be also reported.

Investigation of sinkhole areas in Germany using 2D shear wave reflection seismics and zero-offset VSP

NASA Astrophysics Data System (ADS)

Tschache, Saskia; Wadas, Sonja; Polom, Ulrich; Krawczyk, Charlotte M.

2017-04-01

Sinkholes pose a serious geohazard for humans and infrastructure in populated areas. The Junior Research Group Subrosion within the Leibniz Institute for Applied Geophysics and the joint project SIMULTAN work on the multi-scale investigation of subrosion processes in the subsurface, which cause natural sinkholes. In two case studies in sinkhole areas of Thuringia in Germany, we applied 2D shear wave reflection seismics using SH-waves with the aim to detect suitable parameters for the characterisation of critical zones. This method has the potential to image near-surface collapse and faulting structures in improved resolution compared to P-wave surveys resulting from the shorter wavelength of shear waves. Additionally, the shear wave velocity field derived by NMO velocity analysis is a basis to calculate further physical parameters, as e.g. the dynamic shear modulus. In both investigation areas, vertical seismic profiles (VSP) were acquired by generating P- and SH-waves (6 component VSP) directly next to a borehole equipped with a 3C downhole sensor. They provide shear and compressional wave velocity profiles, which are used to improve the 2D shear wave velocity field from surface seismics, to perform a depth calibration of the seismic image and to calculate the Vp/Vs ratio. The signals in the VSP data are analysed with respect to changes in polarisation and attenuation with depth and/or azimuth. The VSP data reveal low shear wave velocities of 200-300 m/s in rock layers known to be heavily affected by subrosion and confirm the low velocities calculated from the surface seismic data. A discrepancy of the shear wave velocities is observed in other intervals probably due to unsymmetrical travel paths in the surface seismics. In some VSP data dominant conversion of the direct SH-wave to P-wave is observed that is assumed to be caused by an increased presence of cavities. A potential fault distorting the vertical travel paths was detected by abnormal P-wave first arrivals in the VSP dataset of a borehole located near the city of Bad Frankenhausen. In addition, a strong attenuation of the source signals may indicate areas influenced by subrosion.

Airborne synthetic aperture radar tracking of internal waves in the Strait of Gibraltar

NASA Astrophysics Data System (ADS)

Richez, Claude

As part of the International “Gibraltar Experiment”, we realized, on June 22 and 24, 1986, two surveys of the Strait of Gibraltar, on board an aircraft equipped with a Synthetic Aperture Radar. Our objective was to observe, at Spring tides, and during two twelve-hour tidal cycles, at 24 h interval, the generation of internal wave trains, linked to the hydraulic jump formed west of the sill during the westward phase of the tidal current, and their eastward propagation in the Strait. The speed of propagation of these waves and the effect of the diurnal component of the tide on their generation and propagation could then be determined. Our results suggest that two solitary waves of equal amplitude propagated eastwards in the strait on June 22 (the tidal coefficient being equal to 92), with a speed, relative to the ground, of 2.1 to 2.6 m s -1. 24 h later, during the second survey, on June 24 (tidal coefficient 90), we observed the propagation of a train of non-linear waves, the speed of the leading wave of which being about 1.9 ms -1. Our data show that other waves pass over the Camarinal Sill after the release of the bore, and “secondary” internal wave trains are shown to propagate eastwards from there. Although our SAR data show the appearance of waves west of the northern sill at about 4 h after High Water (HW), the mechanism leading to their generation is not clear. These waves could propagate eastwards, all along the strait, and/or northwestwards along the western Spanish coast. They could be responsible for the solitary-type events observed at the eastern entrance of the strait, at about 7 h after HW, by ZIEGENBEIN (1969, 1970). These events are noticeable in the hydrological parameters time series of ARMI and FARMER (1988) and in the high rate current data (2-min apart) from their April 1986 cruise. Besides these alongstrait waves, our SAR data show the existence of cross-strait waves, and give an idea of their wavelength and speed of propagation. Their presence leads to perturbations in the current, revealed by simultaneous current data, at the Camarinal Sill and north of Cape Cires.

The Relativistic Wave Vector

ERIC Educational Resources Information Center

Houlrik, Jens Madsen

2009-01-01

The Lorentz transformation applies directly to the kinematics of moving particles viewed as geometric points. Wave propagation, on the other hand, involves moving planes which are extended objects defined by simultaneity. By treating a plane wave as a geometric object moving at the phase velocity, novel results are obtained that illustrate the…

Assimilation of Wave Imaging Radar Observations for Real-time Wave-by-Wave Forecasting

DOE Office of Scientific and Technical Information (OSTI.GOV)

Simpson, Alexandra; Haller, Merrick; Walker, David

This project addressed Topic 3: “Wave Measurement Instrumentation for Feed Forward Controls” under the FOA number DE-FOA-0000971. The overall goal of the program was to develop a phase-resolving wave forecasting technique for application to the active control of Wave Energy Conversion (WEC) devices. We have developed an approach that couples a wave imaging marine radar with a phase-resolving linear wave model for real-time wave field reconstruction and forward propagation of the wave field in space and time. The scope of the project was to develop and assess the performance of this novel forecasting system. Specific project goals were as follows:more » Develop and verify a fast, GPU-based (Graphical Processing Unit) wave propagation model suitable for phase-resolved computation of nearshore wave transformation over variable bathymetry; Compare the accuracy and speed of performance of the wave model against a deep water model in their ability to predict wave field transformation in the intermediate water depths (50 to 70 m) typical of planned WEC sites; Develop and implement a variational assimilation algorithm that can ingest wave imaging radar observations and estimate the time-varying wave conditions offshore of the domain of interest such that the observed wave field is best reconstructed throughout the domain and then use this to produce model forecasts for a given WEC location; Collect wave-resolving marine radar data, along with relevant in situ wave data, at a suitable wave energy test site, apply the algorithm to the field data, assess performance, and identify any necessary improvements; and Develop a production cost estimate that addresses the affordability of the wave forecasting technology and include in the Final Report. The developed forecasting algorithm (“Wavecast”) was evaluated for both speed and accuracy against a substantial synthetic dataset. Early in the project, performance tests definitively demonstrated that the system was capable of forecasting in real-time, as the GPU-based wave model backbone was very computationally efficient. The data assimilation algorithm was developed on a polar grid domain in order to match the sampling characteristics of the observation system (wave imaging marine radar). For verification purposes, a substantial set of synthetic wave data (i.e. forward runs of the wave model) were generated to be used as ground truth for comparison to the reconstructions and forecasts produced by Wavecast. For these synthetic cases, Wavecast demonstrated very good accuracy, for example, typical forecast correlation coefficients were between 0.84-0.95 when compared to the input data. Dependencies on shadowing, observational noise, and forecast horizon were also identified. During the second year of the project, a short field deployment was conducted in order to assess forecast accuracy under field conditions. For this, a radar was installed on a fishing vessel and observations were collected at the South Energy Test Site (SETS) off the coast of Newport, OR. At the SETS site, simultaneous in situ wave observations were also available owing to an ongoing field project funded separately. Unfortunately, the position and heading information that was available for the fishing vessel were not of sufficient accuracy in order to validate the forecast in a phase-resolving sense. Instead, a spectral comparison was made between the Wavecast forecast and the data from the in situ wave buoy. Although the wave and wind conditions during the field test were complex, the comparison showed a promising reconstruction of the wave spectral shape, where both peaks in the bimodal spectrum were represented. However, the total reconstructed spectral energy (across all directions and frequencies) was limited to 44% of the observed spectrum. Overall, wave-by-wave forecasting using a data assimilation approach based on wave imaging radar observations and a physics-based wave model shows promise for short-term phase-resolved predictions. Two recommendations for future work are as follows: first, we would recommend additional focused field campaigns for algorithm validation. The field campaign should be long enough to capture a range of wave conditions relevant to the target application and WEC site. In addition, it will be crucial to make sure the vessel of choice has high accuracy position and heading instrumentation (this instrumentation is commercially available but not standard on commercial fishing vessels). The second recommendation is to expand the model physics in the wave model backbone to include some nonlinear effects. Specifically, the third-order correction to the wave speed due to amplitude dispersion would be the next step in order to more accurately represent the phase speeds of large amplitude waves.« less

Energy mode distribution: An analysis of the ratio of anti-Stokes to Stokes amplitudes generated by a pair of counterpropagating Langmuir waves

NASA Astrophysics Data System (ADS)

Simões Júnior, F. J. R.; Alves, M. V.; Rizzato, F. B.

2005-12-01

Results from plasma wave experiments in spacecrafts give support to nonlinear interactions involving Langmuir, electromagnetic, and ion-acoustic waves in association with type III solar radio bursts. Starting from a general form of Zakharov equation (Zakharov, V.E., 1985. Collapse and self-focusing of Langmuir waves. Hand-book of Plasma Physics Cap.2, 81 121) the equations for electric fields and density fluctuations (density gratings) induced by a pair of counterpropagating Langmuir waves are obtained. We consider the coupling of four triplets. Each two triplets have in common the Langmuir pump wave (forward or backward wave) and a pair of independent density gratings. We numerically solve the dispersion relation for the system, extending the work of (Alves, M.V., Chian, A.C.L., Moraes, M.A.E., Abalde, J.R., Rizzato, F.B., 2002. A theory of the fundamental plasma emission of type- III solar radio bursts. Astronomy and Astrophysics 390, 351 357). The ratio of anti-Stokes (AS) (ω0+ω) to Stokes (S) (ω0-ω) electromagnetic mode amplitudes is obtained as a function of the pump wave frequency, wave number, and energy. We notice that the simultaneous excitation of AS and S distinguishable modes, i.e., with Re{ω}=ω≠0, only occurs when the ratio between the pump wave amplitudes, r is ≠1 and the pump wave vector k0 is <(13)W01/2, W0 being the forward pump wave energy. We also observe that the S mode always receives more energy.

Crustal anisotropy across eastern Tibet and surroundings modeled as a depth-dependent tilted hexagonally symmetric medium

NASA Astrophysics Data System (ADS)

Xie, Jiayi; Ritzwoller, Michael H.; Shen, Weisen; Wang, Weitao

2017-04-01

Two types of surface wave anisotropy are observed regularly by seismologists but are only rarely interpreted jointly: apparent radial anisotropy, which is the difference in propagation speed between horizontally and vertically polarized waves inferred from Love and Rayleigh waves, and apparent azimuthal anisotropy, which is the directional dependence of surface wave speeds (usually Rayleigh waves). We show that a new data set of Love and Rayleigh wave isotropic phase speeds and Rayleigh wave azimuthal anisotropy observed within and surrounding eastern Tibet can be explained simultaneously by modeling the crust as a depth-dependent tilted hexagonally symmetric (THS) medium. We specify the THS medium with depth-dependent hexagonally symmetric elastic tensors tilted and rotated through dip and strike angles and estimate these quantities using a Bayesian Monte Carlo inversion to produce a 3-D model of the crust and uppermost mantle on a 0.5° × 0.5° spatial grid. In the interior of eastern Tibet and in the Yunnan-Guizhou plateau, we infer a steeply dipping THS upper crustal medium overlying a shallowly dipping THS medium in the middle-to-lower crust. Such vertical stratification of anisotropy may reflect a brittle to ductile transition in which shallow fractures and faults control upper crustal anisotropy and the crystal-preferred orientation of anisotropic (perhaps micaceous) minerals governs the anisotropy of the deeper crust. In contrast, near the periphery of the Tibetan Plateau the anisotropic medium is steeply dipping throughout the entire crust, which may be caused by the reorientation of the symmetry axes of deeper crustal anisotropic minerals as crustal flows are rotated near the borders of Tibet.

Every slow-wave impulse is associated with motor activity of the human stomach.

PubMed

Hocke, Michael; Schöne, Ulrike; Richert, Hendryk; Görnert, Peter; Keller, Jutta; Layer, Peter; Stallmach, Andreas

2009-04-01

Using a newly developed high-resolution three-dimensional magnetic detector system (3D-MAGMA), we observed periodical movements of a small magnetic marker in the human stomach at the typical gastric slow-wave frequency, that is 3 min(-1). Thus we hypothesized that each gastric slow wave induces a motor response that is not strong enough to be detected by conventional methods. Electrogastrographies (EGG, Medtronic, Minneapolis, MN) for measurement of gastric slow waves and 3D-MAGMA (Innovent, Jena, Germany) measurements were simultaneously performed in 21 healthy volunteers (10 men, 40.4+/-13.6 yr; 11 women, 35.8+/-11.6 yr). The 3D-MAGMA system contains 27 highly sensitive magnetic field sensors that are able to locate a magnetic pill inside a human body with an accuracy of +/-5 mm or less in position and +/-2 degrees in orientation at a frequency of 50 Hz. Gastric transit time of the magnetic marker ranged from 19 to 154 min. The mean dominant EGG frequency while the marker was in the stomach was 2.87+/-0.15 cpm. The mean dominant 3D-MAGMA frequency during this interval was nearly identical; that is, 2.85+/-0.15 movements per minute. We observed a strong linear correlation between individual dominant EGG and 3D-MAGMA frequency (R=0.66, P=0.0011). Our findings suggest that each gastric slow wave induces a minute contraction that is too small to be detected by conventional motility investigations but can be recorded by the 3D-MAGMA system. The present slow-wave theory that assumes that the slow wave is a pure electrical signal should be reconsidered.

Progress Report on the GROWTH (GNSS Reflectometry for Ocean Waves, Tides, and Height) Research Project

NASA Astrophysics Data System (ADS)

Kitazawa, Y.; Ichikawa, K.; Akiyama, H.; Ebinuma, T.; Isoguchi, O.; Kimura, N.; Konda, M.; Kouguchi, N.; Tamura, H.; Tomita, H.; Yoshikawa, Y.; Waseda, T.

2016-12-01

Global Navigation Satellite Systems (GNSS), such as GPS is a system of satellites that provide autonomous geo-spatial positioning with global coverage. It allows small electronic receivers to determine their location to high precision using radio signals transmitted from satellites, GNSS reflectometry (GNSS-R) involves making measurements from the reflections from the Earth of navigation signals from GNSS satellites. Reflected signals from sea surface are considered that those are useful to observe sea state and sea surface height. We have started a research program for GNSS-R applications on oceanographic observations under the contract with MEXT (Ministry of Education Culture, Sports, Science and Technology, JAPAN) and launched a Japanese research consortium, GROWTH (GNSS Reflectometry for Ocean Waves, Tides, and Height). It is aiming to evaluate the capabilities of GNSS-R observations for oceanographic phenomena with different time scales, such as ocean waves (1/10 to tens of seconds), tides (one or half days), and sea surface dynamic height (a few days to years). In situ observations of ocean wave spectrum, wind speed vertical profile, and sea surface height will be quantitatively compared with equivalent estimates from simultaneous GNSS-R measurements. The GROWTH project will utilize different types of observation platforms; marine observation towers (about 20 m height), multi-copters (about 100 to 150 m height), and much higher-altitude CYGNSS data. Cross-platform data, together with in situ oceanographic observations, will be compared after adequate temporal averaging that accounts differences of the footprint sizes and temporal and spatial scales of oceanographic phenomena. This paper will provide overview of the GROWTH project, preliminary test results, obtained by the multi-sensor platform at observation towers, suggest actual footprint sizes and identification of swell. Preparation status of a ground station which will be supplied to receive CYGNSS data at Japan, is also reported. Compatibility tests to CYGNSS data and refurbishment of the ground station were completed.

GW150914: First results from the search for binary black hole coalescence with Advanced LIGO

NASA Astrophysics Data System (ADS)

Abbott, B. P.; Abbott, R.; Abbott, T. D.; Abernathy, M. R.; Acernese, F.; Ackley, K.; Adams, C.; Adams, T.; Addesso, P.; Adhikari, R. X.; Adya, V. B.; Affeldt, C.; Agathos, M.; Agatsuma, K.; Aggarwal, N.; Aguiar, O. D.; Aiello, L.; Ain, A.; Ajith, P.; Allen, B.; Allocca, A.; Altin, P. A.; Anderson, S. B.; Anderson, W. G.; Arai, K.; Araya, M. C.; Arceneaux, C. C.; Areeda, J. S.; Arnaud, N.; Arun, K. G.; Ascenzi, S.; Ashton, G.; Ast, M.; Aston, S. M.; Astone, P.; Aufmuth, P.; Aulbert, C.; Babak, S.; Bacon, P.; Bader, M. K. M.; Baker, P. T.; Baldaccini, F.; Ballardin, G.; Ballmer, S. W.; Barayoga, J. C.; Barclay, S. E.; Barish, B. C.; Barker, D.; Barone, F.; Barr, B.; Barsotti, L.; Barsuglia, M.; Barta, D.; Bartlett, J.; Bartos, I.; Bassiri, R.; Basti, A.; Batch, J. C.; Baune, C.; Bavigadda, V.; Bazzan, M.; Behnke, B.; Bejger, M.; Bell, A. S.; Bell, C. J.; Berger, B. K.; Bergman, J.; Bergmann, G.; Berry, C. P. L.; Bersanetti, D.; Bertolini, A.; Betzwieser, J.; Bhagwat, S.; Bhandare, R.; Bilenko, I. A.; Billingsley, G.; Birch, J.; Birney, R.; Biscans, S.; Bisht, A.; Bitossi, M.; Biwer, C.; Bizouard, M. A.; Blackburn, J. K.; Blair, C. D.; Blair, D. G.; Blair, R. M.; Bloemen, S.; Bock, O.; Bodiya, T. P.; Boer, M.; Bogaert, G.; Bogan, C.; Bohe, A.; Bohémier, K.; Bojtos, P.; Bond, C.; Bondu, F.; Bonnand, R.; Boom, B. A.; Bork, R.; Boschi, V.; Bose, S.; Bouffanais, Y.; Bozzi, A.; Bradaschia, C.; Brady, P. R.; Braginsky, V. B.; Branchesi, M.; Brau, J. E.; Briant, T.; Brillet, A.; Brinkmann, M.; Brisson, V.; Brockill, P.; Brooks, A. F.; Brown, D. A.; Brown, D. D.; Brown, N. M.; Buchanan, C. C.; Buikema, A.; Bulik, T.; Bulten, H. J.; Buonanno, A.; Buskulic, D.; Buy, C.; Byer, R. L.; Cabero, M.; Cadonati, L.; Cagnoli, G.; Cahillane, C.; Calderón Bustillo, J.; Callister, T.; Calloni, E.; Camp, J. B.; Cannon, K. C.; Cao, J.; Capano, C. D.; Capocasa, E.; Carbognani, F.; Caride, S.; Casanueva Diaz, J.; Casentini, C.; Caudill, S.; Cavaglià, M.; Cavalier, F.; Cavalieri, R.; Cella, G.; Cepeda, C. B.; Cerboni Baiardi, L.; Cerretani, G.; Cesarini, E.; Chakraborty, R.; Chalermsongsak, T.; Chamberlin, S. J.; Chan, M.; Chao, S.; Charlton, P.; Chassande-Mottin, E.; Chen, H. Y.; Chen, Y.; Cheng, C.; Chincarini, A.; Chiummo, A.; Cho, H. S.; Cho, M.; Chow, J. H.; Christensen, N.; Chu, Q.; Chua, S.; Chung, S.; Ciani, G.; Clara, F.; Clark, J. A.; Clayton, J. H.; Cleva, F.; Coccia, E.; Cohadon, P.-F.; Cokelaer, T.; Colla, A.; Collette, C. G.; Cominsky, L.; Constancio, M.; Conte, A.; Conti, L.; Cook, D.; Corbitt, T. R.; Cornish, N.; Corsi, A.; Cortese, S.; Costa, C. A.; Coughlin, M. W.; Coughlin, S. B.; Coulon, J.-P.; Countryman, S. T.; Couvares, P.; Cowan, E. E.; Coward, D. M.; Cowart, M. J.; Coyne, D. C.; Coyne, R.; Craig, K.; Creighton, J. D. E.; Creighton, T. D.; Cripe, J.; Crowder, S. G.; Cumming, A.; Cunningham, L.; Cuoco, E.; Dal Canton, T.; Danilishin, S. L.; D'Antonio, S.; Danzmann, K.; Darman, N. S.; Dattilo, V.; Dave, I.; Daveloza, H. P.; Davier, M.; Davies, G. S.; Daw, E. J.; Day, R.; De, S.; DeBra, D.; Debreczeni, G.; Degallaix, J.; De Laurentis, M.; Deléglise, S.; Del Pozzo, W.; Denker, T.; Dent, T.; Dereli, H.; Dergachev, V.; DeRosa, R. T.; De Rosa, R.; DeSalvo, R.; Dhurandhar, S.; Díaz, M. C.; Dietz, A.; Di Fiore, L.; Di Giovanni, M.; Di Lieto, A.; Di Pace, S.; Di Palma, I.; Di Virgilio, A.; Dojcinoski, G.; Dolique, V.; Donovan, F.; Dooley, K. L.; Doravari, S.; Douglas, R.; Downes, T. P.; Drago, M.; Drever, R. W. P.; Driggers, J. C.; Du, Z.; Ducrot, M.; Dwyer, S. E.; Edo, T. B.; Edwards, M. C.; Effler, A.; Eggenstein, H.-B.; Ehrens, P.; Eichholz, J.; Eikenberry, S. S.; Engels, W.; Essick, R. C.; Etzel, T.; Evans, M.; Evans, T. M.; Everett, R.; Factourovich, M.; Fafone, V.; Fair, H.; Fairhurst, S.; Fan, X.; Fang, Q.; Farinon, S.; Farr, B.; Farr, W. M.; Favata, M.; Fays, M.; Fehrmann, H.; Fejer, M. M.; Ferrante, I.; Ferreira, E. C.; Ferrini, F.; Fidecaro, F.; Fiori, I.; Fiorucci, D.; Fisher, R. P.; Flaminio, R.; Fletcher, M.; Fotopoulos, N.; Fournier, J.-D.; Franco, S.; Frasca, S.; Frasconi, F.; Frei, M.; Frei, Z.; Freise, A.; Frey, R.; Frey, V.; Fricke, T. T.; Fritschel, P.; Frolov, V. V.; Fulda, P.; Fyffe, M.; Gabbard, H. A. G.; Gair, J. R.; Gammaitoni, L.; Gaonkar, S. G.; Garufi, F.; Gatto, A.; Gaur, G.; Gehrels, N.; Gemme, G.; Gendre, B.; Genin, E.; Gennai, A.; George, J.; Gergely, L.; Germain, V.; Ghosh, A.; Ghosh, S.; Giaime, J. A.; Giardina, K. D.; Giazotto, A.; Gill, K.; Glaefke, A.; Goetz, E.; Goetz, R.; Goggin, L. M.; Gondan, L.; González, G.; Gonzalez Castro, J. M.; Gopakumar, A.; Gordon, N. A.; Gorodetsky, M. L.; Gossan, S. E.; Gosselin, M.; Gouaty, R.; Graef, C.; Graff, P. B.; Granata, M.; Grant, A.; Gras, S.; Gray, C.; Greco, G.; Green, A. C.; Groot, P.; Grote, H.; Grunewald, S.; Guidi, G. M.; Guo, X.; Gupta, A.; Gupta, M. K.; Gushwa, K. E.; Gustafson, E. K.; Gustafson, R.; Hacker, J. J.; Hall, B. R.; Hall, E. D.; Hammond, G.; Haney, M.; Hanke, M. M.; Hanks, J.; Hanna, C.; Hannam, M. D.; Hanson, J.; Hardwick, T.; Harms, J.; Harry, G. M.; Harry, I. W.; Hart, M. J.; Hartman, M. T.; Haster, C.-J.; Haughian, K.; Heidmann, A.; Heintze, M. C.; Heitmann, H.; Hello, P.; Hemming, G.; Hendry, M.; Heng, I. S.; Hennig, J.; Heptonstall, A. W.; Heurs, M.; Hild, S.; Hoak, D.; Hodge, K. A.; Hofman, D.; Hollitt, S. E.; Holt, K.; Holz, D. E.; Hopkins, P.; Hosken, D. J.; Hough, J.; Houston, E. A.; Howell, E. J.; Hu, Y. M.; Huang, S.; Huerta, E. A.; Huet, D.; Hughey, B.; Husa, S.; Huttner, S. H.; Huynh-Dinh, T.; Idrisy, A.; Indik, N.; Ingram, D. R.; Inta, R.; Isa, H. N.; Isac, J.-M.; Isi, M.; Islas, G.; Isogai, T.; Iyer, B. R.; Izumi, K.; Jacqmin, T.; Jang, H.; Jani, K.; Jaranowski, P.; Jawahar, S.; Jiménez-Forteza, F.; Johnson, W. W.; Jones, D. I.; Jones, G.; Jones, R.; Jonker, R. J. G.; Ju, L.; Haris, K.; Kalaghatgi, C. V.; Kalogera, V.; Kandhasamy, S.; Kang, G.; Kanner, J. B.; Karki, S.; Kasprzack, M.; Katsavounidis, E.; Katzman, W.; Kaufer, S.; Kaur, T.; Kawabe, K.; Kawazoe, F.; Kéfélian, F.; Kehl, M. S.; Keitel, D.; Kelley, D. B.; Kells, W.; Keppel, D. G.; Kennedy, R.; Key, J. S.; Khalaidovski, A.; Khalili, F. Y.; Khan, I.; Khan, S.; Khan, Z.; Khazanov, E. A.; Kijbunchoo, N.; Kim, C.; Kim, J.; Kim, K.; Kim, Nam-Gyu; Kim, Namjun; Kim, Y.-M.; King, E. J.; King, P. J.; Kinzel, D. L.; Kissel, J. S.; Kleybolte, L.; Klimenko, S.; Koehlenbeck, S. M.; Kokeyama, K.; Koley, S.; Kondrashov, V.; Kontos, A.; Korobko, M.; Korth, W. Z.; Kowalska, I.; Kozak, D. B.; Kringel, V.; Krishnan, B.; Królak, A.; Krueger, C.; Kuehn, G.; Kumar, P.; Kuo, L.; Kutynia, A.; Lackey, B. D.; Landry, M.; Lange, J.; Lantz, B.; Lasky, P. D.; Lazzarini, A.; Lazzaro, C.; Leaci, P.; Leavey, S.; Lebigot, E. O.; Lee, C. H.; Lee, H. K.; Lee, H. M.; Lee, K.; Lenon, A.; Leonardi, M.; Leong, J. R.; Leroy, N.; Letendre, N.; Levin, Y.; Levine, B. M.; Li, T. G. F.; Libson, A.; Littenberg, T. B.; Lockerbie, N. A.; Logue, J.; Lombardi, A. L.; Lord, J. E.; Lorenzini, M.; Loriette, V.; Lormand, M.; Losurdo, G.; Lough, J. D.; Lück, H.; Lundgren, A. P.; Luo, J.; Lynch, R.; Ma, Y.; MacDonald, T.; Machenschalk, B.; MacInnis, M.; Macleod, D. M.; Magaña-Sandoval, F.; Magee, R. M.; Mageswaran, M.; Majorana, E.; Maksimovic, I.; Malvezzi, V.; Man, N.; Mandel, I.; Mandic, V.; Mangano, V.; Mansell, G. L.; Manske, M.; Mantovani, M.; Marchesoni, F.; Marion, F.; Márka, S.; Márka, Z.; Markosyan, A. S.; Maros, E.; Martelli, F.; Martellini, L.; Martin, I. W.; Martin, R. M.; Martynov, D. V.; Marx, J. N.; Mason, K.; Masserot, A.; Massinger, T. J.; Masso-Reid, M.; Matichard, F.; Matone, L.; Mavalvala, N.; Mazumder, N.; Mazzolo, G.; McCarthy, R.; McClelland, D. E.; McCormick, S.; McGuire, S. C.; McIntyre, G.; McIver, J.; McKechan, D. J. A.; McManus, D. J.; McWilliams, S. T.; Meacher, D.; Meadors, G. D.; Meidam, J.; Melatos, A.; Mendell, G.; Mendoza-Gandara, D.; Mercer, R. A.; Merilh, E.; Merzougui, M.; Meshkov, S.; Messaritaki, E.; Messenger, C.; Messick, C.; Meyers, P. M.; Mezzani, F.; Miao, H.; Michel, C.; Middleton, H.; Mikhailov, E. E.; Milano, L.; Miller, J.; Millhouse, M.; Minenkov, Y.; Ming, J.; Mirshekari, S.; Mishra, C.; Mitra, S.; Mitrofanov, V. P.; Mitselmakher, G.; Mittleman, R.; Moggi, A.; Mohan, M.; Mohapatra, S. R. P.; Montani, M.; Moore, B. C.; Moore, C. J.; Moraru, D.; Moreno, G.; Morriss, S. R.; Mossavi, K.; Mours, B.; Mow-Lowry, C. M.; Mueller, C. L.; Mueller, G.; Muir, A. W.; Mukherjee, Arunava; Mukherjee, D.; Mukherjee, S.; Mukund, N.; Mullavey, A.; Munch, J.; Murphy, D. J.; Murray, P. G.; Mytidis, A.; Nardecchia, I.; Naticchioni, L.; Nayak, R. K.; Necula, V.; Nedkova, K.; Nelemans, G.; Neri, M.; Neunzert, A.; Newton, G.; Nguyen, T. T.; Nielsen, A. B.; Nissanke, S.; Nitz, A.; Nocera, F.; Nolting, D.; Normandin, M. E.; Nuttall, L. K.; Oberling, J.; Ochsner, E.; O'Dell, J.; Oelker, E.; Ogin, G. H.; Oh, J. J.; Oh, S. H.; Ohme, F.; Oliver, M.; Oppermann, P.; Oram, Richard J.; O'Reilly, B.; O'Shaughnessy, R.; Ottaway, D. J.; Ottens, R. S.; Overmier, H.; Owen, B. J.; Pai, A.; Pai, S. A.; Palamos, J. R.; Palashov, O.; Palomba, C.; Pal-Singh, A.; Pan, H.; Pan, Y.; Pankow, C.; Pannarale, F.; Pant, B. C.; Paoletti, F.; Paoli, A.; Papa, M. A.; Paris, H. R.; Parker, W.; Pascucci, D.; Pasqualetti, A.; Passaquieti, R.; Passuello, D.; Patricelli, B.; Patrick, Z.; Pearlstone, B. L.; Pedraza, M.; Pedurand, R.; Pekowsky, L.; Pele, A.; Penn, S.; Perreca, A.; Phelps, M.; Piccinni, O.; Pichot, M.; Piergiovanni, F.; Pierro, V.; Pillant, G.; Pinard, L.; Pinto, I. M.; Pitkin, M.; Poggiani, R.; Popolizio, P.; Post, A.; Powell, J.; Prasad, J.; Predoi, V.; Premachandra, S. S.; Prestegard, T.; Price, L. R.; Prijatelj, M.; Principe, M.; Privitera, S.; Prodi, G. A.; Prokhorov, L.; Puncken, O.; Punturo, M.; Puppo, P.; Pürrer, M.; Qi, H.; Qin, J.; Quetschke, V.; Quintero, E. A.; Quitzow-James, R.; Raab, F. J.; Rabeling, D. S.; Radkins, H.; Raffai, P.; Raja, S.; Rakhmanov, M.; Rapagnani, P.; Raymond, V.; Razzano, M.; Re, V.; Read, J.; Reed, C. M.; Regimbau, T.; Rei, L.; Reid, S.; Reitze, D. H.; Rew, H.; Reyes, S. D.; Ricci, F.; Riles, K.; Robertson, N. A.; Robie, R.; Robinet, F.; Robinson, C.; Rocchi, A.; Rodriguez, A. C.; Rolland, L.; Rollins, J. G.; Roma, V. J.; Romano, R.; Romanov, G.; Romie, J. H.; Rosińska, D.; Rowan, S.; Rüdiger, A.; Ruggi, P.; Ryan, K.; Sachdev, S.; Sadecki, T.; Sadeghian, L.; Salconi, L.; Saleem, M.; Salemi, F.; Samajdar, A.; Sammut, L.; Sanchez, E. J.; Sandberg, V.; Sandeen, B.; Sanders, J. R.; Santamaría, L.; Sassolas, B.; Sathyaprakash, B. S.; Saulson, P. R.; Sauter, O.; Savage, R. L.; Sawadsky, A.; Schale, P.; Schilling, R.; Schmidt, J.; Schmidt, P.; Schnabel, R.; Schofield, R. M. S.; Schönbeck, A.; Schreiber, E.; Schuette, D.; Schutz, B. F.; Scott, J.; Scott, S. M.; Sellers, D.; Sengupta, A. S.; Sentenac, D.; Sequino, V.; Sergeev, A.; Serna, G.; Setyawati, Y.; Sevigny, A.; Shaddock, D. A.; Shah, S.; Shahriar, M. S.; Shaltev, M.; Shao, Z.; Shapiro, B.; Shawhan, P.; Sheperd, A.; Shoemaker, D. H.; Shoemaker, D. M.; Siellez, K.; Siemens, X.; Sigg, D.; Silva, A. D.; Simakov, D.; Singer, A.; Singer, L. P.; Singh, A.; Singh, R.; Singhal, A.; Sintes, A. M.; Slagmolen, B. J. J.; Smith, J. R.; Smith, N. D.; Smith, R. J. E.; Son, E. J.; Sorazu, B.; Sorrentino, F.; Souradeep, T.; Srivastava, A. K.; Staley, A.; Steinke, M.; Steinlechner, J.; Steinlechner, S.; Steinmeyer, D.; Stephens, B. C.; Stone, R.; Strain, K. A.; Straniero, N.; Stratta, G.; Strauss, N. A.; Strigin, S.; Sturani, R.; Stuver, A. L.; Summerscales, T. Z.; Sun, L.; Sutton, P. J.; Swinkels, B. L.; Szczepańczyk, M. J.; Tacca, M.; Talukder, D.; Tanner, D. B.; Tápai, M.; Tarabrin, S. P.; Taracchini, A.; Taylor, R.; Theeg, T.; Thirugnanasambandam, M. P.; Thomas, E. G.; Thomas, M.; Thomas, P.; Thorne, K. A.; Thorne, K. S.; Thrane, E.; Tiwari, S.; Tiwari, V.; Tokmakov, K. V.; Tomlinson, C.; Tonelli, M.; Torres, C. V.; Torrie, C. I.; Töyrä, D.; Travasso, F.; Traylor, G.; Trifirò, D.; Tringali, M. C.; Trozzo, L.; Tse, M.; Turconi, M.; Tuyenbayev, D.; Ugolini, D.; Unnikrishnan, C. S.; Urban, A. L.; Usman, S. A.; Vahlbruch, H.; Vajente, G.; Valdes, G.; van Bakel, N.; van Beuzekom, M.; van den Brand, J. F. J.; Van Den Broeck, C.; Vander-Hyde, D. C.; van der Schaaf, L.; van Heijningen, J. V.; van Veggel, A. A.; Vardaro, M.; Vass, S.; Vasúth, M.; Vaulin, R.; Vecchio, A.; Vedovato, G.; Veitch, J.; Veitch, P. J.; Venkateswara, K.; Verkindt, D.; Vetrano, F.; Viceré, A.; Vinciguerra, S.; Vine, D. J.; Vinet, J.-Y.; Vitale, S.; Vo, T.; Vocca, H.; Vorvick, C.; Voss, D.; Vousden, W. D.; Vyatchanin, S. P.; Wade, A. R.; Wade, L. E.; Wade, M.; Walker, M.; Wallace, L.; Walsh, S.; Wang, G.; Wang, H.; Wang, M.; Wang, X.; Wang, Y.; Ward, R. L.; Warner, J.; Was, M.; Weaver, B.; Wei, L.-W.; Weinert, M.; Weinstein, A. J.; Weiss, R.; Welborn, T.; Wen, L.; Weßels, P.; West, M.; Westphal, T.; Wette, K.; Whelan, J. T.; White, D. J.; Whiting, B. F.; Wiesner, K.; Williams, R. D.; Williamson, A. R.; Willis, J. L.; Willke, B.; Wimmer, M. H.; Winkler, W.; Wipf, C. C.; Wiseman, A. G.; Wittel, H.; Woan, G.; Worden, J.; Wright, J. L.; Wu, G.; Yablon, J.; Yam, W.; Yamamoto, H.; Yancey, C. C.; Yap, M. J.; Yu, H.; Yvert, M.; ZadroŻny, A.; Zangrando, L.; Zanolin, M.; Zendri, J.-P.; Zevin, M.; Zhang, F.; Zhang, L.; Zhang, M.; Zhang, Y.; Zhao, C.; Zhou, M.; Zhou, Z.; Zhu, X. J.; Zucker, M. E.; Zuraw, S. E.; Zweizig, J.; LIGO Scientific Collaboration; Virgo Collaboration

2016-06-01

On September 14, 2015, at 09∶50:45 UTC the two detectors of the Laser Interferometer Gravitational-Wave Observatory (LIGO) simultaneously observed the binary black hole merger GW150914. We report the results of a matched-filter search using relativistic models of compact-object binaries that recovered GW150914 as the most significant event during the coincident observations between the two LIGO detectors from September 12 to October 20, 2015 GW150914 was observed with a matched-filter signal-to-noise ratio of 24 and a false alarm rate estimated to be less than 1 event per 203000 years, equivalent to a significance greater than 5.1 σ .

GW150914: First Results from the Search for Binary Black Hole Coalescence with Advanced LIGO

NASA Technical Reports Server (NTRS)

Abbott, B. P.; Abbott, R.; Abbott, T. D.; Abernathy, M. R.; Acernese, F.; Ackley, K.; Adams, C.; Adams, T.; Addesso, P.; Adhikari, R. X.;

Dual-laser-beam-induced breakdown spectroscopy of copper using simultaneous continuous wave CO(2) and Q-switched Nd:YAG lasers.

PubMed

Shoursheini, S Z; Parvin, P; Sajad, B; Bassam, M A

2009-04-01

In this work, we investigate the enhancement of Cu emission lines of a micro-plasma induced by a Nd:YAG laser due to the thermal effect of simultaneous irradiation by a continuous wave (CW) CO(2) laser. The enhancement of the emission lines was achieved at a higher temperature with minimal distortion of the target when the focal point of the Nd:YAG laser was located approximately 1 mm away from the sample surface.

RARE/Turbo Spin Echo Imaging with Simultaneous MultiSlice Wave-CAIPI

PubMed Central

Eichner, Cornelius; Bhat, Himanshu; Grant, P. Ellen; Wald, Lawrence L.; Setsompop, Kawin

2014-01-01

Purpose To enable highly accelerated RARE/Turbo Spin Echo (TSE) imaging using Simultaneous MultiSlice (SMS) Wave-CAIPI acquisition with reduced g-factor penalty. Methods SMS Wave-CAIPI incurs slice shifts across simultaneously excited slices while playing sinusoidal gradient waveforms during the readout of each encoding line. This results in an efficient k-space coverage that spreads aliasing in all three dimensions to fully harness the encoding power of coil sensitivities. The novel MultiPINS radiofrequency (RF) pulses dramatically reduce the power deposition of multiband (MB) refocusing pulse, thus allowing high MB factors within the Specific Absorption Rate (SAR) limit. Results Wave-CAIPI acquisition with MultiPINS permits whole brain coverage with 1 mm isotropic resolution in 70 seconds at effective MB factor 13, with maximum and average g-factor penalties of gmax=1.34 and gavg=1.12, and without √R penalty. With blipped-CAIPI, the g-factor performance was degraded to gmax=3.24 and gavg=1.42; a 2.4-fold increase in gmax relative to Wave-CAIPI. At this MB factor, the SAR of the MultiBand and PINS pulses are 4.2 and 1.9 times that of the MultiPINS pulse, while the peak RF power are 19.4 and 3.9 times higher. Conclusion Combination of the two technologies, Wave-CAIPI and MultiPINS pulse, enables highly accelerated RARE/TSE imaging with low SNR penalty at reduced SAR. PMID:25640187

Alfven Waves Underlying Ionospheric Destabilization: Ground-Based Observations

NASA Astrophysics Data System (ADS)

Hirsch, Michael

During geomagnetic storms, terawatts of power in the million mile-per-hour solar wind pierce the Earth's magnetosphere. Geomagnetic storms and substorms create transverse magnetic waves known as Alfven waves. In the auroral acceleration region, Alfven waves accelerate electrons up to one-tenth the speed of light via wave-particle interactions. These inertial Alfven wave (IAW) accelerated electrons are imbued with sub-100 meter structure perpendicular to geomagnetic field B. The IAW electric field parallel to B accelerates electrons up to about 10 keV along B. The IAW dispersion relation quantifies the precipitating electron striation observed with high-speed cameras as spatiotemporally dynamic fine structured aurora. A network of tightly synchronized tomographic auroral observatories using model based iterative reconstruction (MBIR) techniques were developed in this dissertation. The TRANSCAR electron penetration model creates a basis set of monoenergetic electron beam eigenprofiles of auroral volume emission rate for the given location and ionospheric conditions. Each eigenprofile consists of nearly 200 broadband line spectra modulated by atmospheric attenuation, bandstop filter and imager quantum efficiency. The L-BFGS-B minimization routine combined with sub-pixel registered electron multiplying CCD video stream at order 10 ms cadence yields estimates of electron differential number flux at the top of the ionosphere. Our automatic data curation algorithm reduces one terabyte/camera/day into accurate MBIR-processed estimates of IAW-driven electron precipitation microstructure. This computer vision structured auroral discrimination algorithm was developed using a multiscale dual-camera system observing a 175 km and 14 km swath of sky simultaneously. This collective behavior algorithm exploits the "swarm" behavior of aurora, detectable even as video SNR approaches zero. A modified version of the algorithm is applied to topside ionospheric radar at Mars and broadcast FM passive radar. The fusion of data from coherent radar backscatter and optical data at order 10 ms cadence confirms and further quantifies the relation of strong Langmuir turbulence and streaming plasma upflows in the ionosphere with the finest spatiotemporal auroral dynamics associated with IAW acceleration. The software programs developed in this dissertation solve the century-old problem of automatically discriminating finely structured aurora from other forms and pushes the observational wave-particle science frontiers forward.

Multi-arm spectrometer for parallel frequency analysis of radio-wave signals oriented to astronomical observations

NASA Astrophysics Data System (ADS)

Shcherbakov, Alexandre S.; Chavez Dagostino, Miguel; Arellanes, Adan Omar; Tepichin Rodriguez, Eduardo

2017-08-01

We describe a potential prototype of modern spectrometer based on acousto-optical technique with three parallel optical arms for analysis of radio-wave signals specific to astronomical observations. Each optical arm exhibits original performances to provide parallel multi-band observations with different scales simultaneously. Similar multi-band instrument is able to realize measurements within various scenarios from planetary atmospheres to attractive objects in the distant Universe. The arrangement under development has two novelties. First, each optical arm represents an individual spectrum analyzer with its individual performances. Such an approach is conditioned by exploiting various materials for acousto-optical cells operating within various regimes, frequency ranges, and light wavelengths from independent light sources. Individually produced beam shapers give both the needed incident light polarization and the required apodization for light beam to increase the dynamic range of the system as a whole. After parallel acousto-optical processing, a few data flows from these optical arms are united by the joint CCD matrix on the stage of the combined extremely high-bit rate electronic data processing that provides the system performances as well. The other novelty consists in the usage of various materials for designing wide-aperture acousto-optical cells exhibiting the best performances within each of optical arms. Here, one can mention specifically selected cuts of tellurium dioxide, bastron, and lithium niobate, which overlap selected areas within the frequency range from 40 MHz to 2.0 GHz. Thus one yields the united versatile instrument for comprehensive studies of astronomical objects simultaneously with precise synchronization in various frequency ranges.

Small-scale plasma irregularities in the nightside Venus ionosphere

NASA Astrophysics Data System (ADS)

Grebowsky, J. M.; Curtis, S. A.; Brace, L. H.

1991-12-01

The individual volt-ampere curves from the Pioneer Venus Orbiter electron temperature probe showed evidence for small-scale density irregularities, or short-period plasma waves, in regions of the nightside ionosphere where the Orbiter electric field detector observed waves in its 100-Hz channel. A survey of the nightside volt-ampere curves has revealed several hundred examples of such irregularities. The I-V structures correspond to plasma density structure with spatial scale sizes in the range of about 100-2000 m, or alternatively they could be viewed as waves having frequencies extending toward 100 Hz. They are often seen as isolated events, with spatial extent along the orbit frequently less than 80 km. The density irregularities or waves occur in or near prominent gradients in the ambient plasma concentrations both at low altitudes where molecular ions are dominant and at higher altitudes in regions of reduced plasma density where O(+) is the major ion. Electric field 100-Hz bursts occur simultaneously, with the majority of the structured I-V curves providing demonstrative evidence that at least some of the E field signals are produced within the ionosphere.

SUNWARD PROPAGATING ALFVÉN WAVES IN ASSOCIATION WITH SUNWARD DRIFTING PROTON BEAMS IN THE SOLAR WIND

DOE Office of Scientific and Technical Information (OSTI.GOV)

He, Jiansen; Pei, Zhongtian; Wang, Linghua

Using measurements from the WIND spacecraft, here we report the observation of sunward propagating Alfvén waves (AWs) in solar wind that is magnetically disconnected from the Earth's bow shock. In the sunward magnetic field sector, we find a period lasting for more than three days in which there existed (during most time intervals) a negative correlation between the flow velocity and magnetic field fluctuations, thus indicating that the related AWs are mainly propagating sunward. Simultaneous observations of counter-streaming suprathermal electrons suggest that these sunward AWs may not simply be due to the deflection of an open magnetic field line. Moreover,more » no interplanetary coronal mass ejection appears to be associated with the counter-streaming suprathermal electrons. As the scale goes from the magnetohydrodynamic down to the ion kinetic regime, the wave vector of magnetic fluctuations usually becomes more orthogonal to the mean magnetic field direction, and the fluctuations become increasingly compressible, which are both features consistent with quasi-perpendicular kinetic AWs. However, in the case studied here, we find clear signatures of quasi-parallel sunward propagating ion-cyclotron waves. Concurrently, the solar wind proton velocity distribution reveals a sunward field-aligned beam that drifts at about the local Alfvén speed. This beam is found to run in the opposite direction of the normally observed (anti-sunward) proton beam, and is apparently associated with sunward propagating Alfvén/ion-cyclotron waves. The results and conclusions of this study enrich our knowledge of solar wind turbulence and foster our understanding of proton heating and acceleration within a complex magnetic field geometry.« less

Wave Probe - New Instrument For Space Research

NASA Astrophysics Data System (ADS)

Korepanov, V.; Dudkin, F.

2007-12-01

The dispersion relations are very important for the wave activity study in space plasmas. One of the most efficient methods for their analysis is the simultaneous measurements of spatial current density and magnetic field fluctuations during such a wave process. Whereas the measurement of the magnetic field is a routine task realized onboard practically every spacecraft (SC), the direct measurement of spatial current density (SCD) still remains a complicated scientific and technological problem. First attempt to solve it was executed in late 60-ties by a group headed by F. Mozer. They proposed and launched in a rocket experiment the device named "Split Langmuir Probe" (SLP) - two conducting plates separated by a thin insulated split. Unfortunately this experiment failed what diverted the attention of experimenters in space branch from this instrument for many years, practically till now. But the importance to know the SCD stimulated the development of new principles and devices to measure it. A short review of known versions is discussed. The newly evoked interest to this problem caused next attempt to improve the SLP construction and methodology of its application for SCD measurements, which resulted in first successful attempt in 1985: the measured SCD onboard Prognos-10 SC in the bow shock region was in rather good agreement with the calculated value. This attempt was continued onboard Interball-Tail SC (1995-2000) where again a qualitatively good coincidence of measured and calculated values was observed. The obtained experience and further theoretical research allowed developing a new instrument - Wave Probe - which is a combination of induction magnetometer and SLP in one body. Both on-ground tests in plasma chamber and the spatial experiment executed onboard Ukrainian "Sich-1M" SC (2004) showed that the combined in-situ simultaneous measurements of SCD and magnetic field fluctuations allowed obtaining the wave number of the whistler wave. The same wave number was calculated theoretically from dispersion relations of whistler wave using known ionosphere model and the comparison of measured and calculated values of both wave number and SCD gave a good quantitative agreement. The details of theoretical and experimental study are discussed in the report. There is a pleasant duty of the authors to thank Prof. F. Mozer and Prof. S. Klimov for continuous attention and practical support of this work. It was also supported by NSAU contract No 1-02/03.

Observations of tornadoes and wall clouds with a portable FM-CW Doppler radar: 1989--1990 results

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bluestein, H.B.; Unruh, W.P.

1990-01-01

The purpose of this paper is to report on our progress using a portable, 1 W,FM (frequency modulated)-CW (continuous wave) Doppler radar developed at the Los Alamos National Laboratory (LANL), to make measurements of the wind field in tornadoes and wall clouds along with simultaneous visual documentation. Results using a CW version of the radar in 1987--1988 are given in Bluestein and Unruh (1989). 18 refs., 2 figs., 1 tab.

The Simultaneous Combination of Phase Contrast Imaging with In Situ X-ray diffraction from Shock Compressed Matter

NASA Astrophysics Data System (ADS)

McBride, Emma Elizabeth; Seiboth, Frank; Cooper, Leora; Frost, Mungo; Goede, Sebastian; Harmand, Marion; Levitan, Abe; McGonegle, David; Miyanishi, Kohei; Ozaki, Norimasa; Roedel, Melanie; Sun, Peihao; Wark, Justin; Hastings, Jerry; Glenzer, Siegfried; Fletcher, Luke

2017-10-01

Here, we present the simultaneous combination of phase contrast imaging (PCI) techniques with in situ X-ray diffraction to investigate multiple-wave features in laser-driven shock-compressed germanium. Experiments were conducted at the Matter at Extreme Conditions end station at the LCLS, and measurements were made perpendicular to the shock propagation direction. PCI allows one to take femtosecond snapshots of magnified real-space images of shock waves as they progress though matter. X-ray diffraction perpendicular to the shock propagation direction provides the opportunity to isolate and identify different waves and determine the crystal structure unambiguously. Here, we combine these two powerful techniques simultaneously, by using the same Be lens setup to focus the fundamental beam at 8.2 keV to a size of 1.5 mm on target for PCI and the 3rd harmonic at 24.6 keV to a spot size of 2 um on target for diffraction.

Earthquake early warning using P-waves that appear after initial S-waves

NASA Astrophysics Data System (ADS)

Kodera, Y.

2017-12-01

As measures for underprediction for large earthquakes with finite faults and overprediction for multiple simultaneous earthquakes, Hoshiba (2013), Hoshiba and Aoki (2015), and Kodera et al. (2016) proposed earthquake early warning (EEW) methods that directly predict ground motion by computing the wave propagation of observed ground motion. These methods are expected to predict ground motion with a high accuracy even for complicated scenarios because these methods do not need source parameter estimation. On the other hand, there is room for improvement in their rapidity because they predict strong motion prediction mainly based on the observation of S-waves and do not explicitly use P-wave information available before the S-waves. In this research, we propose a real-time P-wave detector to incorporate P-wave information into these wavefield-estimation approaches. P-waves within a few seconds from the P-onsets are commonly used in many existing EEW methods. In addition, we focus on P-waves that may appear in the later part of seismic waves. Kurahashi and Irikura (2013) mentioned that P-waves radiated from strong motion generation areas (SMGAs) were recognizable after S-waves of the initial rupture point in the 2011 off the Pacific coast of Tohoku earthquake (Mw 9.0) (the Tohoku-oki earthquake). Detecting these P-waves would enhance the rapidity of prediction for the peak ground motion generated by SMGAs. We constructed a real-time P-wave detector that uses a polarity analysis. Using acceleration records in boreholes of KiK-net (band-pass filtered around 0.5-10 Hz with site amplification correction), the P-wave detector performed the principal component analysis with a sliding window of 4 s and calculated P-filter values (e.g. Ross and Ben-Zion, 2014). The application to the Tohoku-oki earthquake (Mw 9.0) showed that (1) peaks of P-filter that corresponded to SMGAs appeared in several stations located near SMGAs and (2) real-time seismic intensities (Kunugi et al., 2013) reached the local maximum several seconds after the P-filter peaks appeared. These findings indicate that the proposed P-wave detector allows wavefield-estimation approaches to predict the peak ground motion of SMGAs with a certain lead time.

Storm Time Evolution of Outer Radiation Belt Relativistic Electrons by a Nearly Continuous Distribution of Chorus

NASA Astrophysics Data System (ADS)

Yang, Chang; Xiao, Fuliang; He, Yihua; Liu, Si; Zhou, Qinghua; Guo, Mingyue; Zhao, Wanli

2018-03-01

During the 13-14 November 2012 storm, Van Allen Probe A simultaneously observed a 10 h period of enhanced chorus (including quasi-parallel and oblique propagation components) and relativistic electron fluxes over a broad range of L = 3-6 and magnetic local time = 2-10 within a complete orbit cycle. By adopting a Gaussian fit to the observed wave spectra, we obtain the wave parameters and calculate the bounce-averaged diffusion coefficients. We solve the Fokker-Planck diffusion equation to simulate flux evolutions of relativistic (1.8-4.2 MeV) electrons during two intervals when Probe A passed the location L = 4.3 along its orbit. The simulating results show that chorus with combined quasi-parallel and oblique components can produce a more pronounced flux enhancement in the pitch angle range ˜45°-80°, consistent well with the observation. The current results provide the first evidence on how relativistic electron fluxes vary under the drive of almost continuously distributed chorus with both quasi-parallel and oblique components within a complete orbit of Van Allen Probe.

Voluntary muscle activation and evoked volitional-wave responses as a function of torque.

PubMed

Hight, Robert E; Quarshie, Alwyn T; Black, Christopher D

2018-08-01

This study employed a unique stimulation paradigm which allowed for the simultaneous assessment of voluntary activation levels (VA) via twitch-interpolation, and the evoked V-wave responses of the plantar flexors during submaximal and maximal contractions. Test-retest reliability was also examined. Fourteen participants repeated a stimulation protocol over four visits to assess VA and evoked V-wave amplitude across torque levels ranging from 20% to 100% MVC. MVC torque and EMG amplitude were also measured. VA increased nonlinearly with torque production and plateaued by 80% MVC. V-wave amplitude increased linearly from 20% to 100% MVC. There were no differences in any dependent variable across visits (p > 0.05). VA demonstrated moderate to substantial reliability across all torque levels (ICC = 0.76-0.91) while V-wave amplitude exhibited fair to moderate reliability from 40% to 100% (ICC = 0.48-0.74). We were able to reliably collect VA and the V-wave simultaneously in the plantar flexors. Collection of VA and V-wave during the same contraction provides distinct information regarding the contribution of motor-unit recruitment and descending cortico-spinal drive/excitability to force production. Copyright © 2018 Elsevier Ltd. All rights reserved.

Plasma Pancakes and Deep Cavities Generated by High Power Radio Waves from the Arecibo Observatory

NASA Astrophysics Data System (ADS)

Bernhardt, P. A.; Briczinski, S. J., Jr.; Zawdie, K.; Huba, J.; Siefring, C. L.; Sulzer, M. P.; Nossa, E.; Aponte, N.; Perillat, P.; Jackson-Booth, N.

2017-12-01

Breakdown of the neutral atmosphere at ionospheric altitudes can be achieved with high power HF waves that reflect on the bottomside of the ionosphere. For overdense heating (i.e., wave frequency < maximum plasma frequency in the F-layer), the largest electric fields in the plasma are found just below the reflection altitude. There, electromagnetic waves are converted into electron plasma (Langmir) waves and ion acoustic waves. These waves are measured by scattering of the 430 MHz radar at Arecibo to from an enhanced plasma line. The photo-electron excitation of Langmuir waves yields a weaker plasma-line profile that shows the complete electron profile with the radar. Once HF enhanced Langmuir waves are formed, they can accelerate the photo-electron population to sufficient energies for neutral breakdown and enhanced ionization inside the HF Radio Beam. Plasma pancakes are produced because the breakdown process continues to build up plasma on bottom of the breakdown clouds and recombination occurs on the older breakdown plasma at the top of these clouds. Thus, the plasma pancake falls with altitude from the initial HF wave reflection altitude near 250 km to about 160 km where ion-electron recombination prevents the plasma cloud from being sustained by the high power HF. Experiments in March 2017 have produced plasma pancakes with about 100 Mega-Watts effective radiated power 5.1 MHz with the Arecibo HF Facility. Observations using the 430 MHz radar show falling plasma pancakes that disappear at low altitudes and reform at the F-layer critical reflection altitude. Sometimes the periodic and regular falling motion of the plasma pancakes is influenced by Acoustic Gravity Waves (AGW) propagating through the modified HF region. A rising AGW can cause the plasma pancake to reside at nearly constant altitude for 10 to 20 minutes. Dense cavities are also produced by high power radio waves interacting with the F-Layer. These structures are observed with the Arecibo 430 MHz radar as intense bight-outs in the plasma profile. Multiple cavities are seen simultaneously.

Simultaneous observation of the gamma-ray binary LS I+61 303 with GLAST and Suzaku

DOE Office of Scientific and Technical Information (OSTI.GOV)

Tanaka, Takuya; Fukazawa, Yasushi; Mizuno, Tsunefumi

2007-07-12

The gamma-ray binary LS I+61 303 is a bright gamma-ray source, and thus an attracting object for GLAST. We proposed to observe this object with the X-ray satellite Suzaku (AO-2), simultaneously with GLAST, radio wave, and optical spectro-polarimetry, in order to probe the geometrical state of the binary system emitting the gamma-ray radiation, as a function of the binary orbital phase for the first time. This is essential to understand the mechanism of jet production and gamma-ray emission. The idea is not only to measure the multi-band overall continuum shape, but also to make use of continuous monitoring capability ofmore » GLAST, wide X-ray band of Suzaku, and good accessibility of the Kanata optical/NIR telescope (Hiroshima University) with the sensitive optical spectro-polarimetry. Further collaboration with TeV gamma-ray telescopes is also hoped to constrain the jet constitution.« less

Comparison of different statistical methods for estimation of extreme sea levels with wave set-up contribution

NASA Astrophysics Data System (ADS)

Kergadallan, Xavier; Bernardara, Pietro; Benoit, Michel; Andreewsky, Marc; Weiss, Jérôme

2013-04-01

Estimating the probability of occurrence of extreme sea levels is a central issue for the protection of the coast. Return periods of sea level with wave set-up contribution are estimated here in one site : Cherbourg in France in the English Channel. The methodology follows two steps : the first one is computation of joint probability of simultaneous wave height and still sea level, the second one is interpretation of that joint probabilities to assess a sea level for a given return period. Two different approaches were evaluated to compute joint probability of simultaneous wave height and still sea level : the first one is multivariate extreme values distributions of logistic type in which all components of the variables become large simultaneously, the second one is conditional approach for multivariate extreme values in which only one component of the variables have to be large. Two different methods were applied to estimate sea level with wave set-up contribution for a given return period : Monte-Carlo simulation in which estimation is more accurate but needs higher calculation time and classical ocean engineering design contours of type inverse-FORM in which the method is simpler and allows more complex estimation of wave setup part (wave propagation to the coast for example). We compare results from the two different approaches with the two different methods. To be able to use both Monte-Carlo simulation and design contours methods, wave setup is estimated with an simple empirical formula. We show advantages of the conditional approach compared to the multivariate extreme values approach when extreme sea-level occurs when either surge or wave height is large. We discuss the validity of the ocean engineering design contours method which is an alternative when computation of sea levels is too complex to use Monte-Carlo simulation method.

Conjugate Ground-Spacecraft Observations of VLF Chorus Elements

NASA Astrophysics Data System (ADS)

Demekhov, A. G.; Manninen, J.; Santolík, O.; Titova, E. E.

2017-12-01

We present results of simultaneous observations of VLF chorus elements at the ground-based station Kannuslehto in Northern Finland and on board Van Allen Probe A. Visual inspection and correlation analysis of the data reveal one-to-one correspondence of several (at least 12) chorus elements following each other in a sequence. Poynting flux calculated from electromagnetic fields measured by the Electric and Magnetic Field Instrument Suite and Integrated Science instrument on board Van Allen Probe A shows that the waves propagate at small angles to the geomagnetic field and oppositely to its direction, that is, from northern to southern geographic hemisphere. The spacecraft was located at L≃4.1 at a geomagnetic latitude of -12.4∘ close to the plasmapause and inside a localized density inhomogeneity with about 30% density increase and a transverse size of about 600 km. The time delay between the waves detected on the ground and on the spacecraft is about 1.3 s, with ground-based detection leading spacecraft detection. The measured time delay is consistent with the wave travel time of quasi-parallel whistler-mode waves for a realistic profile of the plasma density distribution along the field line. The results suggest that chorus discrete elements can preserve their spectral shape during a hop from the generation region to the ground followed by reflection from the ionosphere and return to the near-equatorial region.

Force-controlled absorption in a fully-nonlinear numerical wave tank

NASA Astrophysics Data System (ADS)

Spinneken, Johannes; Christou, Marios; Swan, Chris

2014-09-01

An active control methodology for the absorption of water waves in a numerical wave tank is introduced. This methodology is based upon a force-feedback technique which has previously been shown to be very effective in physical wave tanks. Unlike other methods, an a-priori knowledge of the wave conditions in the tank is not required; the absorption controller being designed to automatically respond to a wide range of wave conditions. In comparison to numerical sponge layers, effective wave absorption is achieved on the boundary, thereby minimising the spatial extent of the numerical wave tank. In contrast to the imposition of radiation conditions, the scheme is inherently capable of absorbing irregular waves. Most importantly, simultaneous generation and absorption can be achieved. This is an important advance when considering inclusion of reflective bodies within the numerical wave tank. In designing the absorption controller, an infinite impulse response filter is adopted, thereby eliminating the problem of non-causality in the controller optimisation. Two alternative controllers are considered, both implemented in a fully-nonlinear wave tank based on a multiple-flux boundary element scheme. To simplify the problem under consideration, the present analysis is limited to water waves propagating in a two-dimensional domain. The paper presents an extensive numerical validation which demonstrates the success of the method for a wide range of wave conditions including regular, focused and random waves. The numerical investigation also highlights some of the limitations of the method, particularly in simultaneously generating and absorbing large amplitude or highly-nonlinear waves. The findings of the present numerical study are directly applicable to related fields where optimum absorption is sought; these include physical wavemaking, wave power absorption and a wide range of numerical wave tank schemes.

A Simplified Approach for Simultaneous Measurements of Wavefront Velocity and Curvature in the Heart Using Activation Times.

PubMed

Mazeh, Nachaat; Haines, David E; Kay, Matthew W; Roth, Bradley J

2013-12-01

The velocity and curvature of a wave front are important factors governing the propagation of electrical activity through cardiac tissue, particularly during heart arrhythmias of clinical importance such as fibrillation. Presently, no simple computational model exists to determine these values simultaneously. The proposed model uses the arrival times at four or five sites to determine the wave front speed ( v ), direction (θ), and radius of curvature (ROC) ( r 0 ). If the arrival times are measured, then v , θ, and r 0 can be found from differences in arrival times and the distance between these sites. During isotropic conduction, we found good correlation between measured values of the ROC r 0 and the distance from the unipolar stimulus ( r = 0.9043 and p < 0.0001). The conduction velocity (m/s) was correlated ( r = 0.998, p < 0.0001) using our method (mean = 0.2403, SD = 0.0533) and an empirical method (mean = 0.2352, SD = 0.0560). The model was applied to a condition of anisotropy and a complex case of reentry with a high voltage extra stimulus. Again, results show good correlation between our simplified approach and established methods for multiple wavefront morphologies. In conclusion, insignificant measurement errors were observed between this simplified approach and an approach that was more computationally demanding. Accuracy was maintained when the requirement that ε (ε = b/r 0 , ratio of recording site spacing over wave fronts ROC) was between 0.001 and 0.5. The present simplified model can be applied to a variety of clinical conditions to predict behavior of planar, elliptical, and reentrant wave fronts. It may be used to study the genesis and propagation of rotors in human arrhythmias and could lead to rotor mapping using low density endocardial recording electrodes.

Composition of the Earth's inner core from high-pressure sound velocity measurements in Fe-Ni-Si alloys

NASA Astrophysics Data System (ADS)

Antonangeli, Daniele; Siebert, Julien; Badro, James; Farber, Daniel L.; Fiquet, Guillaume; Morard, Guillaume; Ryerson, Frederick J.

2010-06-01

We performed room-temperature sound velocity and density measurements on a polycrystalline alloy, Fe0.89Ni0.04Si0.07, in the hexagonal close-packed (hcp) phase up to 108 GPa. Over the investigated pressure range the aggregate compressional sound velocity is ∼ 9% higher than in pure iron at the same density. The measured aggregate compressional (VP) and shear (VS) sound velocities, extrapolated to core densities and corrected for anharmonic temperature effects, are compared with seismic profiles. Our results provide constraints on the silicon abundance in the core, suggesting a model that simultaneously matches the primary seismic observables, density, P-wave and S-wave velocities, for an inner core containing 4 to 5 wt.% of Ni and 1 to 2 wt.% of Si.

Seismic evidence for a crustal magma reservoir beneath the upper east rift zoneof Kilauea volcano, Hawaii

USGS Publications Warehouse

Lin, Guoqing; Amelung, Falk; Lavallee, Yan; Okubo, Paul G.

2014-01-01

An anomalous body with low Vp (compressional wave velocity), low Vs (shear wave velocity), and high Vp/Vs anomalies is observed at 8–11 km depth beneath the upper east rift zone of Kilauea volcano in Hawaii by simultaneous inversion of seismic velocity structure and earthquake locations. We interpret this body to be a crustal magma reservoir beneath the volcanic pile, similar to those widely recognized beneath mid-ocean ridge volcanoes. Combined seismic velocity and petrophysical models suggest the presence of 10% melt in a cumulate magma mush. This reservoir could have supplied the magma that intruded into the deep section of the east rift zone and caused its rapid expansion following the 1975 M7.2 Kalapana earthquake.

Hiding the interior region of core-shell nanoparticles with quantum invisible cloaks

NASA Astrophysics Data System (ADS)

Lee, Jeng Yi; Lee, Ray-Kuang

2014-04-01

Based on the scattering cancellation, we provide a method not only making a nanoparticle nearly invisible, but also hiding its interior region from the outside probing matter wave. By applying the interplay among the nodal points of partial waves along with the concept of streamline in fluid dynamics for probability flux, a quantum invisible cloak to the electron transport in a host semiconductor is demonstrated by simultaneously guiding the probability flux outside a hidden region and keeping the total scattering cross section negligible. As the probability flux vanishes in the interior region, one can embed any materials inside a multiple core-shell nanoparticle without affecting physical observables from the outside. Our results reveal the possibility to design a protection shield layer for fragile interior parts from the impact of transport electrons.

Coupling between the lower and middle atmosphere observed during a very severe cyclonic storm 'Madi'

NASA Astrophysics Data System (ADS)

Hima Bindu, H.; Venkat Ratnam, M.; Yesubabu, V.; Narayana Rao, T.; Eswariah, S.; Naidu, C. V.; Vijaya Bhaskara Rao, S.

2018-04-01

Synoptic-scale systems like cyclones can generate broad spectrum of waves, which propagate from its source to the middle atmosphere. Coupling between the lower and middle atmosphere over Tirupati (13.6°N, 79.4°E) is studied during a very severe cyclonic storm 'Madi' (06-13 December 2013) using Weather Research and Forecast (WRF) model assimilated fields and simultaneous meteor radar observations. Since high temporal and spatial measurements are difficult to obtain during these disturbances, WRF model simulations are obtained by assimilating conventional and satellite observations using 3DVAR technique. The obtained outputs are validated for their consistency in predicting cyclone track and vertical structure by comparing them with independent observations. The good agreement between the assimilated outputs and independent observations prompted us to use the model outputs to investigate the gravity waves (GWs) and tides over Tirupati. GWs with the periods 1-5 h are observed with clear downward phase propagation in the lower stratosphere. These upward propagating waves obtained from the model are also noticed in the meteor radar horizontal wind observations in the MLT region (70-110 km). Interestingly, enhancement in the tidal activity in both the zonal and meridional winds in the mesosphere and lower thermosphere (MLT) region is noticed during the peak cyclonic activity except the suppression of semi-diurnal tide in meridional wind. A very good agreement in the tidal activity is also observed in the horizontal winds in the troposphere and lower stratosphere from the WRF model outputs and ERA5. These results thus provide evidence on the vertical coupling of lower and middle atmosphere induced by the tropical cyclone.

Detecting atmospheric normal modes with periods less than 6 h by barometric observations

NASA Astrophysics Data System (ADS)

Ermolenko, S. I.; Shved, G. M.; Jacobi, Ch.

2018-04-01

The theory of atmospheric normal modes (ANMs) predicts the existence of relatively short-period gravity-inertia ANMs. Simultaneous observations of surface air-pressure variations by barometers at distant stations of the Global Geodynamics Project network during an interval of 6 months were used to detect individual gravity-inertia ANMs with periods of ∼2-5 h. Evidence was found for five ANMs with a lifetime of ∼10 days. The data of the stations, which are close in both latitude and longitude, were utilized for deriving the phases of the detected ANMs. The phases revealed wave propagation to the west and increase of zonal wavenumbers with frequency. As all the detected gravity-inertia ANMs are westward propagating, they are suggested to be generated due to the breakdown of migrating solar tides and/or large-scale Rossby waves. The existence of an ANM background will complicate the detection of the translational motions of the Earth's inner core.

Charge density wave order in 1D mirror twin boundaries of single-layer MoSe 2

DOE PAGES

Barja, Sara; Wickenburg, Sebastian; Liu, Zhen-Fei; ...

2016-04-18

Here, We provide direct evidence for the existence of isolated, one-dimensional charge density waves at mirror twin boundaries (MTBs) of single-layer semiconducting MoSe 2. Such MTBs have been previously observed by transmission electron microscopy and have been predicted to be metallic in MoSe 2 and MoS 2. Our low-temperature scanning tunnelling microscopy/spectroscopy measurements revealed a substantial bandgap of 100 meV opening at the Fermi energy in the otherwise metallic one-dimensional structures. We found a periodic modulation in the density of states along the MTB, with a wavelength of approximately three lattice constants. In addition to mapping the energy-dependent densitymore » of states, we determined the atomic structure and bonding of the MTB through simultaneous high-resolution non-contact atomic force microscopy. Density functional theory calculations based on the observed structure reproduced both the gap opening and the spatially resolved density of states.« less

Generalized framework for testing gravity with gravitational-wave propagation. II. Constraints on Horndeski theory

NASA Astrophysics Data System (ADS)

Arai, Shun; Nishizawa, Atsushi

2018-05-01

Gravitational waves (GW) are generally affected by modification of a gravity theory during propagation at cosmological distances. We numerically perform a quantitative analysis on Horndeski theory at the cosmological scale to constrain the Horndeski theory by GW observations in a model-independent way. We formulate a parametrization for a numerical simulation based on the Monte Carlo method and obtain the classification of the models that agrees with cosmic accelerating expansion within observational errors of the Hubble parameter. As a result, we find that a large group of the models in the Horndeski theory that mimic cosmic expansion of the Λ CDM model can be excluded from the simultaneous detection of a GW and its electromagnetic transient counterpart. Based on our result and the latest detection of GW170817 and GRB170817A, we conclude that the subclass of Horndeski theory including arbitrary functions G4 and G5 can hardly explain cosmic accelerating expansion without fine-tuning.

Simultaneous three-wavelength continuous wave laser at 946 nm, 1319 nm and 1064 nm in Nd:YAG

NASA Astrophysics Data System (ADS)

Lü, Yanfei; Zhao, Lianshui; Zhai, Pei; Xia, Jing; Fu, Xihong; Li, Shutao

2013-01-01

A continuous-wave (cw) diode-end-pumped Nd:YAG laser that generates simultaneous laser at the wavelengths 946 nm, 1319 nm and 1064 nm is demonstrated. The optimum oscillation condition for the simultaneous three-wavelength operation has been derived. Using the separation of the three output couplers, we obtained the maximum output powers of 0.24 W at 946 nm, 1.07 W at 1319 nm and 1.88 W at 1064 nm at the absorbed pump power of 11.2 W. A total output power of 3.19 W for the three-wavelength was achieved at the absorbed pump power of 11.2 W with optical conversion efficiency of 28.5%.

Radial anisotropy of the North American upper mantle based on adjoint tomography with USArray

NASA Astrophysics Data System (ADS)

Zhu, Hejun; Komatitsch, Dimitri; Tromp, Jeroen

2017-10-01

We use seismic data from USArray to image the upper mantle underneath the United States based on a so-called `adjoint tomography', an iterative full waveform inversion technique. The inversion uses data from 180 regional earthquakes recorded by 4516 seismographic stations, resulting in 586 185 frequency-dependent measurements. Three-component short-period body waves and long-period surface waves are combined to simultaneously constrain deep and shallow structures. The transversely isotropic model US22 is the result of 22 pre-conditioned conjugate-gradient iterations. Approximate Hessian maps and point-spread function tests demonstrate good illumination of the study region and limited trade-offs among different model parameters. We observe a distinct wave-speed contrast between the stable eastern US and the tectonically active western US. This boundary is well correlated with the Rocky Mountain Front. Stable cratonic regions are characterized by fast anomalies down to 250-300 km, reflecting the thickness of the North American lithosphere. Several fast anomalies are observed beneath the North American lithosphere, suggesting the possibility of lithospheric delamination. Slow wave-speed channels are imaged beneath the lithosphere, which might indicate weak asthenosphere. Beneath the mantle transition zone of the central US, an elongated north-south fast anomaly is observed, which might be the ancient subducted Farallon slab. The tectonically active western US is dominated by prominent slow anomalies with magnitudes greater than -6 per cent down to approximately 250 km. No continuous lower to upper mantle upwellings are observed beneath Yellowstone. In addition, our results confirm previously observed differences between oceans and continents in the anisotropic parameter ξ = (βh/βv)2. A slow wave-speed channel with ξ > 1 is imaged beneath the eastern Pacific at depths from 100 to 200 km, reflecting horizontal shear within the asthenosphere. Underneath continental areas, regions with ξ > 1 are imaged at shallower depths around 100 km. They are characterized by fast shear wave speeds, suggesting different origins of anisotropy underneath oceans and continents. The wave speed and anisotropic signatures of the western Atlantic are similar to continental areas in comparison with the eastern Pacific. Furthermore, we observe regions with ξ < 1 beneath the tectonically active western US at depths between 300 and 400 km, which might reflect vertical flows induced by subduction of the Farallon and Juan de Fuca Plates. Comparing US22 with several previous tomographic models, we observe relatively good correlations for long-wavelength features. However, there are still large discrepancies for small-scale features.

Wave intensity analysis and its application to the coronary circulation

PubMed Central

Davies, JE; Escaned, JE; Hughes, A; Parker, K

Wave intensity analysis (WIA) is a technique developed from the field of gas dynamics that is now being applied to assess cardiovascular physiology. It allows quantification of the forces acting to alter flow and pressure within a fluid system, and as such it is highly insightful in ascribing cause to dynamic blood pressure or velocity changes. When co-incident waves arrive at the same spatial location they exert either counteracting or summative effects on flow and pressure. WIA however allows waves of different origins to be measured uninfluenced by other simultaneously arriving waves. It therefore has found particular applicability within the coronary circulation where both proximal (aortic) and distal (myocardial) ends of the coronary artery can markedly influence blood flow. Using these concepts, a repeating pattern of 6 waves has been consistently identified within the coronary arteries, 3 originating proximally and 3 distally. Each has been associated with a particular part of the cardiac cycle. The most clinically relevant wave to date is the backward decompression wave, which causes the marked increase in coronary flow velocity observed at the start of the diastole. It has been proposed that this wave is generated by the elastic re-expansion of the intra-myocardial blood vessels that are compressed during systolic contraction. Particularly by quantifying this wave, WIA has been used to provide mechanistic and prognostic insight into a number of conditions including aortic stenosis, left ventricular hypertrophy, coronary artery disease and heart failure. It has proven itself to be highly sensitive and as such a number of novel research directions are encouraged where further insights would be beneficial. PMID:28971104

Conjunction of factors triggering waves of seasonal influenza

PubMed Central

Chattopadhyay, Ishanu; Kiciman, Emre; Elliott, Joshua W; Shaman, Jeffrey L

2018-01-01

Using several longitudinal datasets describing putative factors affecting influenza incidence and clinical data on the disease and health status of over 150 million human subjects observed over a decade, we investigated the source and the mechanistic triggers of influenza epidemics. We conclude that the initiation of a pan-continental influenza wave emerges from the simultaneous realization of a complex set of conditions. The strongest predictor groups are as follows, ranked by importance: (1) the host population’s socio- and ethno-demographic properties; (2) weather variables pertaining to specific humidity, temperature, and solar radiation; (3) the virus’ antigenic drift over time; (4) the host population’€™s land-based travel habits, and; (5) recent spatio-temporal dynamics, as reflected in the influenza wave auto-correlation. The models we infer are demonstrably predictive (area under the Receiver Operating Characteristic curve 80%) when tested with out-of-sample data, opening the door to the potential formulation of new population-level intervention and mitigation policies. PMID:29485041

Nonstandard gravitational waves imply gravitational slip: On the difficulty of partially hiding new gravitational degrees of freedom

NASA Astrophysics Data System (ADS)

Sawicki, Ignacy; Saltas, Ippocratis D.; Motta, Mariele; Amendola, Luca; Kunz, Martin

2017-04-01

In many generalized models of gravity, perfect fluids in cosmology give rise to gravitational slip. Simultaneously, in very broad classes of such models, the propagation of gravitational waves is altered. We investigate the extent to which there is a one-to-one relationship between these two properties in three classes of models with one extra degree of freedom: scalar (Horndeski and beyond), vector (Einstein-aether), and tensor (bimetric). We prove that in bimetric gravity and Einstein-aether, it is impossible to dynamically hide the gravitational slip on all scales whenever the propagation of gravitational waves is modified. Horndeski models are much more flexible, but it is nonetheless only possible to hide gravitational slip dynamically when the action for perturbations is tuned to evolve in time toward a divergent kinetic term. These results provide an explicit, theoretical argument for the interpretation of future observations if they disfavored the presence of gravitational slip.

Damage detection and locating using tone burst and continuous excitation modulation method

NASA Astrophysics Data System (ADS)

Li, Zheng; Wang, Zhi; Xiao, Li; Qu, Wenzhong

2014-03-01

Among structural health monitoring techniques, nonlinear ultrasonic spectroscopy methods are found to be effective diagnostic approach to detecting nonlinear damage such as fatigue crack, due to their sensitivity to incipient structural changes. In this paper, a nonlinear ultrasonic modulation method was developed to detect and locate a fatigue crack on an aluminum plate. The method is different with nonlinear wave modulation method which recognizes the modulation of low-frequency vibration and high-frequency ultrasonic wave; it recognizes the modulation of tone burst and high-frequency ultrasonic wave. In the experiment, a Hanning window modulated sinusoidal tone burst and a continuous sinusoidal excitation were simultaneously imposed on the PZT array which was bonded on the surface of an aluminum plate. The modulations of tone burst and continuous sinusoidal excitation was observed in different actuator-sensor paths, indicating the presence and location of fatigue crack. The results of experiments show that the proposed method is capable of detecting and locating the fatigue crack successfully.

Conjunction of factors triggering waves of seasonal influenza.

PubMed

Chattopadhyay, Ishanu; Kiciman, Emre; Elliott, Joshua W; Shaman, Jeffrey L; Rzhetsky, Andrey

2018-02-27

Using several longitudinal datasets describing putative factors affecting influenza incidence and clinical data on the disease and health status of over 150 million human subjects observed over a decade, we investigated the source and the mechanistic triggers of influenza epidemics. We conclude that the initiation of a pan-continental influenza wave emerges from the simultaneous realization of a complex set of conditions. The strongest predictor groups are as follows, ranked by importance: (1) the host population's socio- and ethno-demographic properties; (2) weather variables pertaining to specific humidity, temperature, and solar radiation; (3) the virus' antigenic drift over time; (4) the host population'€™s land-based travel habits, and; (5) recent spatio-temporal dynamics, as reflected in the influenza wave auto-correlation. The models we infer are demonstrably predictive (area under the Receiver Operating Characteristic curve 80%) when tested with out-of-sample data, opening the door to the potential formulation of new population-level intervention and mitigation policies. © 2018, Chattopadhyay et al.

A laboratory investigation of mixing dynamics between biofuels and surface waters

NASA Astrophysics Data System (ADS)

Wang, Xiaoxiang; Cotel, Aline

2017-11-01

Recently, production and usage of ethanol-blend fuels or biofuels have increased dramatically along with increasing risk of spilling into surface waters. Lack of understanding of the environmental impacts and absence of standard clean-up procedures make it crucial to study the mixing behavior between biofuels and water. Biofuels are represented by a solution of ethanol and glycol. A Plexiglas tank in conjunction with a wave generator is used to simulate the mixing of surface waters and biofuels under different natural conditions. In our previous experiments, two distinct mixing regimes were observed. One regime was driven by turbulence and the other by interfacial instabilities. However, under more realistic situations, without wind driven waves, only the first mixing regime was found. After one minute of rapid turbulent mixing, biofuels and water were fully mixed and no interface was formed. During the mixing process, chemical reactions happened simultaneously and influenced mixing dynamics. Current experiments are investigating the effect of waves on the mixing dynamics. Support from NSF CBET 1335878.

High-Speed Photographic Study of Wave Propagation and Impact Damage in Fused Silica and AlON Using the Edge-On Impact (EOI) Method

DOE Office of Scientific and Technical Information (OSTI.GOV)

Strassburger, E.; Patel, P.; McCauley, J. W.

An Edge-on Impact (EOI) technique, developed at the Ernst-Mach-Institute (EMI), coupled with a Cranz-Schardin high-speed camera, has been successfully utilized to visualize dynamic fracture in many brittle materials. In a typical test, the projectile strikes one edge of a specimen and damage formation and fracture propagation is recorded during the first 20 {mu}s after impact. In the present study, stress waves and damage propagation in fused silica and AlON were examined by means of two modified Edge-on Impact arrangements. In one arrangement, fracture propagation was observed simultaneously in side and top views of the specimens by means of two Cranz-Schardinmore » cameras. In another arrangement, the photographic technique was modified by placing the specimen between crossed polarizers and using the photo-elastic effect to visualize the stress waves. Pairs of impact tests at approximately equivalent velocities were carried out in transmitted plane (shadowgraphs) and crossed polarized light.« less

Correlated waves of actin filaments and PIP3 in Dictyostelium cells.

PubMed

Asano, Yukako; Nagasaki, Akira; Uyeda, Taro Q P

2008-12-01

Chemotaxis-deficient amiB-null mutant Dictyostelium cells show two distinct movements: (1) they extend protrusions randomly without net displacements; (2) they migrate persistently and unidirectionally in a keratocyte-like manner. Here, we monitored the intracellular distribution of phosphatidylinositol (3,4,5)-trisphosphate (PIP(3)) to gain insight into roles PIP(3) plays in those spontaneous motilities. In keratocyte-like cells, PIP(3) showed convex distribution over the basal membrane, with no anterior enrichment. In stalled cells, as well as in wild type cells, PIP(3) repeated wave-like changes, including emergence, expansion and disappearance, on the basal membrane. The waves induced lamellipodia when they approached the cell edge, and the advancing speed of the waves was comparable to the migration speed of the keratocyte-like cells. LY294002, an inhibitor of PI3 kinase, abolished PIP(3) waves in stalled cells and stopped keratocyte-like cells. These results together suggested that keratocyte-like cells are "surfing" on the PIP(3) waves by coupling steady lamellipodial protrusions to the PIP(3) waves. Simultaneous live observation of actin filaments and PIP(3) in wild type or stalled amiB(-) cells indicated that the PIP(3) waves were correlated with wave-like distributions of actin filaments. Most notably, PIP(3) waves often followed actin waves, suggesting that PIP(3) induces local depolymerization of actin filaments. Consistent with this idea, cortical accumulation of PIP(3) was often correlated with local retraction of the periphery. We propose that the waves of PIP(3) and actin filaments are loosely coupled with each other and play important roles in generating spontaneous cell polarity. Copyright 2008 Wiley-Liss, Inc.

Diastolic Function in Normal Sinus Rhythm vs. Chronic Atrial Fibrillation: Comparison by Fractionation of E-wave Deceleration Time into Stiffness and Relaxation Components.

PubMed

Mossahebi, Sina; Kovács, Sándor J

2014-01-01

Although the electrophysiologic derangement responsible for atrial fibrillation (AF) has been elucidated, how AF remodels the ventricular chamber and affects diastolic function (DF) has not been fully characterized. The previously validated Parametrized Diastolic Filling (PDF) formalism models suction-initiated filling kinematically and generates error-minimized fits to E-wave contours using unique load (x o ), relaxation (c), and stiffness (k) parameters. It predicts that E-wave deceleration time (DT) is a function of both stiffness and relaxation. Ascribing DT s to stiffness and DTr to relaxation such that DT=DT s +DT r is legitimate because of causality and their predicted and observed high correlation (r=0.82 and r=0.94) with simultaneous (diastatic) chamber stiffness (dP/dV) and isovolumic relaxation (tau), respectively. We analyzed simultaneous echocardiography-cardiac catheterization data and compared 16 age matched, chronic AF subjects to 16, normal sinus rhythm (NSR) subjects (650 beats). All subjects had diastatic intervals. Conventional DF parameters (DT, AT, E peak , E dur , E-VTI, E/E') and E-wave derived PDF parameters (c, k, DT s , DT r ) were compared. Total DT and DT s , DT r in AF were shorter than in NSR (p<0.005), chamber stiffness, (k) in AF was higher than in NSR (p<0.001). For NSR, 75% of DT was due to stiffness and 25% was due to relaxation whereas for AF 81% of DT was due to stiffness and 19% was due to relaxation (p<0.005). We conclude that compared to NSR, increased chamber stiffness is one measurable consequence of chamber remodeling in chronic, rate controlled AF. A larger fraction of E-wave DT in AF is due to stiffness compared to NSR. By trending individual subjects, this method can elucidate and characterize the beneficial or adverse long-term effects on chamber remodeling due to alternative therapies in terms of chamber stiffness and relaxation.

Statistical Study in the mid-altitude cusp region: wave and particle data comparison using a normalized cusp crossing duration

NASA Astrophysics Data System (ADS)

Grison, B.; Escoubet, C. P.; Pitout, F.; Cornilleau-Wehrlin, N.; Dandouras, I.; Lucek, E.

2009-04-01

In the mid altitude cusp region the DC magnetic field presents a diamagnetic cavity due to intense ion earthward flux coming from the magnetosheath. A strong ultra low frequency (ULF) magnetic activity is also commonly observed in this region. Most of the mid altitude cusp statistical studies have focused on the location of the cusp and its dependence and response to solar wind, interplanetary magnetic field, dipole tilt angle parameters. In our study we use the database build by Pitout et al. (2006) in order to study the link of wave power in the ULF range (0.35-10Hz) measured by STAFF SC instrument with the ion plasma properties as measured by CIS (and CODIF) instrument as well as the diamagnetic cavity in the mid-altitude cusp region with FGM data. To compare the different crossings we don`t use the cusp position and dynamics but we use a normalized cusp crossing duration that permits to easily average the properties over a large number of crossings. As usual in the cusp, it is particularly relevant to sort the crossings by the corresponding interplanetary magnetic field (IMF) orientation in order to analyse the results. In particular we try to find out what is the most relevant parameter to link the strong wave activity with. The global statistic confirms previous single case observations that have noticed a simultaneity between ion injections and wave activity enhancements. We will also present results concerning other ion parameters and the diamagnetic cavity observed in the mid altitude cusp region.

Rapid acceleration of outer radiation belt electrons associated with solar wind pressure pulse: Simulation study with Arase and Van Allen Probe observations

NASA Astrophysics Data System (ADS)

Hayashi, M.; Yoshizumi, M.; Saito, S.; Matsumoto, Y.; Kurita, S.; Teramoto, M.; Hori, T.; Matsuda, S.; Shoji, M.; Machida, S.; Amano, T.; Seki, K.; Higashio, N.; Mitani, T.; Takashima, T.; Kasahara, Y.; Kasaba, Y.; Yagitani, S.; Ishisaka, K.; Tsuchiya, F.; Kumamoto, A.; Matsuoka, A.; Shinohara, I.; Blake, J. B.; Fennell, J. F.; Claudepierre, S. G.

2017-12-01

Relativistic electron fluxes of the outer radiation belt rapidly change in response to solar wind variations. One of the shortest acceleration processes of electrons in the outer radiation belt is wave-particle interactions between drifting electrons and fast-mode waves induced by compression of the dayside magnetopause caused by interplanetary shocks. In order to investigate this process by a solar wind pressure pulse, we perform a code-coupling simulation using the GEMSIS-RB test particle simulation (Saito et al., 2010) and the GEMSIS-GM global MHD magnetosphere simulation (Matsumoto et al., 2010). As a case study, an interplanetary pressure pulse with the enhancement of 5 nPa is used as the up-stream condition. In the magnetosphere, the fast mode waves with the azimuthal electric field ( negative 𝐸𝜙 : |𝐸&;#120601;| 10 mV/m, azimuthal mode number : m ≤ 2) propagates from the dayside to nightside, interacting with electrons. From the simulation results, we derived effective acceleration model and condition : The electrons whose drift velocities vd ≥ (π/2)Vfast are accelerated efficiently. On December 20, 2016, the Arase (ERG) satellite was launched , allowing more accurate multi-point simultaneous observation with other satellites. We will compare our simulation results with observations from Arase and Van Allen Probes, and investigate the acceleration condition of relativistic electrons associated with storm sudden commencement (SSC).

Impact compressive and bending behaviour of rocks accompanied by electromagnetic phenomena.

PubMed

Kobayashi, Hidetoshi; Horikawa, Keitaro; Ogawa, Kinya; Watanabe, Keiko

2014-08-28

It is well known that electromagnetic phenomena are often observed preceding earthquakes. However, the mechanism by which these electromagnetic waves are generated during the fracture and deformation of rocks has not been fully identified. Therefore, in order to examine the relationship between the electromagnetic phenomena and the mechanical properties of rocks, uniaxial compression and three-point bending tests for two kinds of rocks with different quartz content, granite and gabbro, have been carried out at quasi-static and dynamic rates. Especially, in the bending tests, pre-cracked specimens of granite were also tested. Using a split Hopkinson pressure bar and a ferrite-core antenna in close proximity to the specimens, both the stress-strain (load-displacement) curve and simultaneous electromagnetic wave magnitude were measured. It was found that the dynamic compressive and bending strengths and the stress increase slope of both rocks were higher than those observed in static tests; therefore, there is a strain-rate dependence in their strength and stress increase rate. It was found from the tests using the pre-cracked bending specimens that the intensity of electromagnetic waves measured during crack extension increased almost proportionally to the increase of the maximum stress intensity factor of specimens. This tendency was observed in both the dynamic and quasi-static three-point bending tests for granite. © 2014 The Author(s) Published by the Royal Society. All rights reserved.

Observations of Munitions Mobility During a Nor'easter at Wallops Island

NASA Astrophysics Data System (ADS)

Swann, C.; Frank, D. P.; Braithwaite, E. F., III; Hagg, R. K.; Calantoni, J.

2017-12-01

Unexploded ordnance (or munitions) may migrate, bury, or become exposed over time, and may pose a hazard to both humans and environment. Understanding the behavior of munitions under various wave and current conditions is central to management and remediation of contaminated underwater sites. We embedded Inertial Measurement Units (IMUs) into inert replicas of large caliber munitions (81 mm - 155 mm), herein referred to as `smart munitions'. Several smart munitions were deployed in the field with IMUs logging at 16 Hz continuously. Simultaneously the local hydrodynamic conditions were monitored to correlate any resulting munitions mobility. Here, we present the response of the smart munitions to wave and current conditions observed during a nor'easter off the coast of Wallops Island, Virginia USA in about 10 m water depth. During the nor'easter, peak significant wave heights of 2.8 m were observed in 10 m water depth. Over a roughly 10-hour period, an 81 mm smart munition migrated approximately 206 ft in a net onshore direction. Displacement and heading of the migrated smart munition were estimated by divers during the recovery. Integration of the trajectory of motion for the smart munition using a custom signal processing algorithm was in good agreement with the diver measurements. Discussion will focus on the relationship of the local sediment type and the potential for munitions mobility.

Propagating Neural Source Revealed by Doppler Shift of Population Spiking Frequency

PubMed Central

Zhang, Mingming; Shivacharan, Rajat S.; Chiang, Chia-Chu; Gonzalez-Reyes, Luis E.

2016-01-01

Electrical activity in the brain during normal and abnormal function is associated with propagating waves of various speeds and directions. It is unclear how both fast and slow traveling waves with sometime opposite directions can coexist in the same neural tissue. By recording population spikes simultaneously throughout the unfolded rodent hippocampus with a penetrating microelectrode array, we have shown that fast and slow waves are causally related, so a slowly moving neural source generates fast-propagating waves at ∼0.12 m/s. The source of the fast population spikes is limited in space and moving at ∼0.016 m/s based on both direct and Doppler measurements among 36 different spiking trains among eight different hippocampi. The fact that the source is itself moving can account for the surprising direction reversal of the wave. Therefore, these results indicate that a small neural focus can move and that this phenomenon could explain the apparent wave reflection at tissue edges or multiple foci observed at different locations in neural tissue. SIGNIFICANCE STATEMENT The use of novel techniques with an unfolded hippocampus and penetrating microelectrode array to record and analyze neural activity has revealed the existence of a source of neural signals that propagates throughout the hippocampus. The source itself is electrically silent, but its location can be inferred by building isochrone maps of population spikes that the source generates. The movement of the source can also be tracked by observing the Doppler frequency shift of these spikes. These results have general implications for how neural signals are generated and propagated in the hippocampus; moreover, they have important implications for the understanding of seizure generation and foci localization. PMID:27013678

Complex behavior and source model of the tremor at Arenal volcano, Costa Rica

NASA Astrophysics Data System (ADS)

Lesage, Philippe; Mora, Mauricio M.; Alvarado, Guillermo E.; Pacheco, Javier; Métaxian, Jean-Philippe

2006-09-01

Typical records of volcanic tremor and explosion quakes at Arenal volcano are analyzed with a high-resolution time-frequency method. The main characteristics of these seismic signals are: (1) numerous regularly spaced spectral peaks including both odd and even overtones; (2) frequency gliding in the range [0.9-2] Hz of the fundamental peak; (3) frequency jumps with either positive or negative increments; (4) tremor episodes with two simultaneous systems of spectral peaks affected by independent frequency gliding; (5) progressive transitions between spasmodic tremor and harmonic tremor; (6) lack of clear and systematic relationship between the occurrence of explosions and tremor. Some examples of alternation between two states of oscillation characterized by different fundamental frequencies are also observed. Some tremor and explosion codas are characterized by acoustic and seismic waves with identical spectral content and frequency gliding, which suggests a common excitation process. We propose a source model for the tremor at Arenal in which intermittent gas flow through fractures produces repetitive pressure pulses. The repeating period of the pulses is stabilized by a feedback mechanism associated with standing or traveling waves in the magmatic conduit. The pressure pulses generate acoustic waves in the atmosphere and act as excitation of the interface waves in the conduit. When the repeating period of the pulses is stable enough, they produce regularly spaced spectral peaks by the Dirac comb effect and hence harmonic tremor. When the period stability is lost, because of failures in the feedback mechanism, the tremor becomes spasmodic. The proposed source model of tremor is similar to the sound emission process of a clarinet. Fractures in the solid or viscous layer capping the lava pool in the crater act as the clarinet reed, and the conduit filled with low velocity bubbly magma is equivalent to the pipe of the musical instrument. The frequency gliding is related to variations of the pressure in the conduit, which modify the gas fraction, the wave velocity and, possibly, the length of the resonator. Moreover, several observations suggest that two seismic sources, associated with two magmatic conduits, are active in Arenal volcano. They could explain in particular the apparent independence of tremor and explosions and the episodes of tremor displaying two simultaneous systems of spectral peaks.

A Unified Directional Spectrum for Long and Short Wind-Driven Waves

NASA Technical Reports Server (NTRS)

Elfouhaily, T.; Chapron, B.; Katsaros, K.; Vandemark, D.

1997-01-01

Review of several recent ocean surface wave models finds that while comprehensive in many regards, these spectral models do not satisfy certain additional, but fundamental, criteria. We propose that these criteria include the ability to properly describe diverse fetch conditions and to provide agreement with in situ observations of Cox and Munk [1954] and Jiihne and Riemer [1990] and Hara et al. [1994] data in the high-wavenumber regime. Moreover, we find numerous analytically undesirable aspects such as discontinuities across wavenumber limits, nonphysical tuning or adjustment parameters, and noncentrosymmetric directional spreading functions. This paper describes a two-dimensional wavenumber spectrum valid over all wavenumbers and analytically amenable to usage in electromagnetic models. The two regime model is formulated based on the Joint North Sea Wave Project (JONSWAP) in the long-wave regime and on the work of Phillips [1985] and Kitaigorodskii [1973] at the high wavenumbers. The omnidirectional and wind-dependent spectrum is constructed to agree with past and recent observations including the criteria mentioned above. The key feature of this model is the similarity of description for the high- and low-wavenumber regimes; both forms are posed to stress that the air-sea interaction process of friction between wind and waves (i.e., generalized wave age, u/c) is occurring at all wavelengths simultaneously. This wave age parameterization is the unifying feature of the spectrum. The spectrum's directional spreading function is symmetric about the wind direction and has both wavenumber and wind speed dependence. A ratio method is described that enables comparison of this spreading function with previous noncentrosymmetric forms. Radar data are purposefully excluded from this spectral development. Finally, a test of the spectrum is made by deriving roughness length using the boundary layer model of Kitaigorodskii. Our inference of drag coefficient versus wind speed and wave age shows encouraging agreement with Humidity Exchange Over the Sea (HEXOS) campaign results.

Temporal correlations between impulsive ultraviolet and hard X-ray bursts in solar flares observed with high time resolution

NASA Technical Reports Server (NTRS)

Cheng, Chung-Chieh; Vanderveen, K.; Orwig, L. E.; Tandberg-Hanssen, E.

1988-01-01

The impulsive phase of solar flares has been simultaneously observed in the ultraviolet O V line, the UV continuum, and hard X-rays with a time resolution of 0.128 s by the SMM satellite. A close time correspondence between the three impulsive components is found, with the best correlation being at the peak of the impulsive phase. Individual bursts or fast features in the O V and the UV continuum are shown to lag behind the corresponding hard X-ray features. None of the considered energy transport mechanisms (thermal conduction, a nonthermal electron beam, electron hole boring, UV radiation, and Alfven waves) are able to consistently account for the observed temporal correlations.

Stereoscopic imaging of gravity waves in the mesosphere over Per.

NASA Astrophysics Data System (ADS)

Moreels, G.; Faivre, M.; Clairemidi, J.; Meriwether, J. W.; Lehmacher, G. A.; Chau, J. L.; Vidal, E.; Veliz, O.

A program of stereo-imaging of the mesospheric near-infrared emissive layer has recently been initiated using two CCD cameras operating in a vis- a -vis observation mode at a separation distance of sim 550 km These images were analyzed using a stereo-correlation method suitable for low contrast objects without discrete contours This approach consists of calculating a normalized cross-correlation parameter for the intensities of matched points Initially the altitude of the layer is chosen to be between 82 and 92 km The computer code calculates the altitude of the centroid of the emissive layer for each observed point and produces surface maps of the layer for 50x50 km 2 areas In addition to results from the Peruvian observations results of simultaneous observations obtained at the Pic du Midi Pyr e n e es and the Ch a teau-Renard Alpes observatories will be presented The surface maps are compared with coded maps of the emission intensity Both types of maps show significant wave structures The vertical amplitude of the waves is found to be typically between 1 and 2 km The Fourier characteristics are measured using a Morlet type wavelet generator function The horizontal wavelengths in the meridional and zonal directions are sim 20-40 km and 100-150 km and the temporal periods are sim 15-30 minutes The same observational program was conducted in the Peruvian Andes in October 2005 The sites were the Cosmos Observatory 12 r 04 S 75 r 34 W altitude 4620m and the Cerro Verde Tellolo mountain 16 r 33 S

Effect of Oblique Electromagnetic Ion Cyclotron Waves on Relativistic Electron Scattering: CRRES Based Calculation

NASA Technical Reports Server (NTRS)

Gamayunov, K. V.; Khazanov, G. V.

2007-01-01

We consider the effect of oblique EMIC waves on relativistic electron scattering in the outer radiation belt using simultaneous observations of plasma and wave parameters from CRRES. The main findings can be s ummarized as follows: 1. In 1comparison with field-aligned waves, int ermediate and highly oblique distributions decrease the range of pitc h-angles subject to diffusion, and reduce the local scattering rate b y an order of magnitude at pitch-angles where the principle absolute value of n = 1 resonances operate. Oblique waves allow the absolute va lue of n > 1 resonances to operate, extending the range of local pitc h-angle diffusion down to the loss cone, and increasing the diffusion at lower pitch angles by orders of magnitude; 2. The local diffusion coefficients derived from CRRES data are qualitatively similar to the local results obtained for prescribed plasma/wave parameters. Conseq uently, it is likely that the bounce-averaged diffusion coefficients, if estimated from concurrent data, will exhibit the dependencies similar to those we found for model calculations; 3. In comparison with f ield-aligned waves, intermediate and highly oblique waves decrease th e bounce-averaged scattering rate near the edge of the equatorial lo ss cone by orders of magnitude if the electron energy does not excee d a threshold (approximately equal to 2 - 5 MeV) depending on specified plasma and/or wave parameters; 4. For greater electron energies_ ob lique waves operating the absolute value of n > 1 resonances are more effective and provide the same bounce_averaged diffusion rate near the loss cone as fiel_aligned waves do.

Autonomous Vehicles for Wave Energy Site Characterisation and monitoring in the Atlantic areas: North Scotland and Portugal

NASA Astrophysics Data System (ADS)

McIlvenny, J.; Campuzano, F.; Goddijn-Murphy, L.

2016-02-01

Surface autonomous marine robots allow the collection of environmental data for weeks or months at a time in difficult to reach or extreme oceanic environments. Wave glider technology has improved in recent years and is now capable of carrying instruments from different manufacturers1, such as ADCP, wave modules, and acoustic sensors2. Here we investigate the suitability of surface based robotic platforms for the collection of environmental data for the renewable energy industry. The Waveglider robotic platform was chosen for this study, representing one of the most advanced platforms in its class. Two sites were chosen: Farr point in North Scotland and Nazare in Portugal. Both study sites are potential locations for wave energy development. We present the results of two simultaneous field campaigns using Waveglider technology. Of particular importance to the study were data integrity and accuracy, platform ability, performance and durability and risk. The project's main aims were to test the platform's capabilities and collect wave data from two wave energy lease sites. The wave data from the Waveglider are compared to nearshore wave height and period data from simultaneous overhead passes by the altimeter satellite AltiKa3. In addition, Waverider buoys were also deployed and recording wave characteristics at both sites visited by the Waveglider. We present the preliminary inter-comparison between the three wave datasets at both sites and assess the performance of the Waveglider technology.

Optical coating on a corrugated surface to align the polarization of an unpolarized wave without loss

NASA Astrophysics Data System (ADS)

Jen, Yi Jun

2017-12-01

A multilayer comprising birefringent thin films is devised to present to function as a polarization beam splitter and waveplate simultaneously. By arranging such a multilayer on a right triangle-shaped corrugated surface, a polarizer is realized to align the randomly oscillating electric field of an unpolarized wave into a linear polarized wave without loss.

Observations with the ROWS instrument during the Grand Banks calibration/validation experiments

NASA Technical Reports Server (NTRS)

Vandemark, D.; Chapron, B.

1994-01-01

As part of a global program to validate the ocean surface sensors on board ERS-1, a joint experiment on the Grand Banks of Newfoundland was carried out in Nov. 1991. The principal objective was to provide a field validation of ERS-1 Synthetic Aperture Radar (SAR) measurement of ocean surface structure. The NASA-P3 aircraft measurements made during this experiment provide independent measurements of the ocean surface along the validation swath. The Radar Ocean Wave Spectrometer (ROWS) is a radar sensor designed to measure direction of the long wave components using spectral analysis of the tilt induced radar backscatter modulation. This technique greatly differs from SAR and thus, provides a unique set of measurements for use in evaluating SAR performance. Also, an altimeter channel in the ROWS gives simultaneous information on the surface wave height and radar mean square slope parameter. The sets of geophysical parameters (wind speed, significant wave height, directional spectrum) are used to study the SAR's ability to accurately measure ocean gravity waves. The known distortion imposed on the true directional spectrum by the SAR imaging mechanism is discussed in light of the direct comparisons between ERS-1 SAR, airborne Canadian Center for Remote Sensing (CCRS) SAR, and ROWS spectra and the use of the nonlinear ocean SAR transform.

Simultaneous teleseismic and geodetic observations of the stick-slip motion of an Antarctic ice stream.

PubMed

Wiens, Douglas A; Anandakrishnan, Sridhar; Winberry, J Paul; King, Matt A

2008-06-05

Long-period seismic sources associated with glacier motion have been recently discovered, and an increase in ice flow over the past decade has been suggested on the basis of secular changes in such measurements. Their significance, however, remains uncertain, as a relationship to ice flow has not been confirmed by direct observation. Here we combine long-period surface-wave observations with simultaneous Global Positioning System measurements of ice displacement to study the tidally modulated stick-slip motion of the Whillans Ice Stream in West Antarctica. The seismic origin time corresponds to slip nucleation at a region of the bed of the Whillans Ice Stream that is likely stronger than in surrounding regions and, thus, acts like an 'asperity' in traditional fault models. In addition to the initial pulse, two seismic arrivals occurring 10-23 minutes later represent stopping phases as the slip terminates at the ice stream edge and the grounding line. Seismic amplitude and average rupture velocity are correlated with tidal amplitude for the different slip events during the spring-to-neap tidal cycle. Although the total seismic moment calculated from ice rigidity, slip displacement, and rupture area is equivalent to an earthquake of moment magnitude seven (M(w) 7), seismic amplitudes are modest (M(s) 3.6-4.2), owing to the source duration of 20-30 minutes. Seismic radiation from ice movement is proportional to the derivative of the moment rate function at periods of 25-100 seconds and very long-period radiation is not detected, owing to the source geometry. Long-period seismic waves are thus useful for detecting and studying sudden ice movements but are insensitive to the total amount of slip.

MACS, An Instrument and a Methodology for Simultaneous and Global Measurements of the Coronal Electron Temperature and the Solar Wind Velocity on the Solar Corona

NASA Technical Reports Server (NTRS)

Reginald, Nelson L.

2000-01-01

In Cram's theory for the formation of the K-coronal spectrum he observed the existence of temperature sensitive anti-nodes, which were separated by temperature insensitive nodes, at certain wave-lengths in the K-coronal spectrum. Cram also showed these properties were remarkably independent of altitude above the solar limb. In this thesis Cram's theory has been extended to incorporate the role of the solar wind in the formation of the K-corona, and we have identified both temperature and wind sensitive intensity ratios. The instrument, MACS, for Multi Aperture Coronal Spectrometer, a fiber optic based spectrograph, was designed for global and simultaneous measurements of the thermal electron temperature and the solar wind velocity in the solar corona. The first ever experiment of this nature was conducted in conjunction with the total solar eclipse of 11 August 1999 in Elazig, Turkey. Here twenty fiber optic tips were positioned in the focal plane of the telescope to observe simultaneously at many different latitudes and two different radial distances in the solar corona. The other ends were vertically stacked and placed at the primary focus of the spectrograph. By isolating the K-coronal spectrum from each fiber the temperature and the wind sensitive intensity ratios were calculated.

PROTON HEATING IN SOLAR WIND COMPRESSIBLE TURBULENCE WITH COLLISIONS BETWEEN COUNTER-PROPAGATING WAVES

DOE Office of Scientific and Technical Information (OSTI.GOV)

He, Jiansen; Tu, Chuanyi; Wang, Linghua

Magnetohydronamic turbulence is believed to play a crucial role in heating laboratory, space, and astrophysical plasmas. However, the precise connection between the turbulent fluctuations and the particle kinetics has not yet been established. Here we present clear evidence of plasma turbulence heating based on diagnosed wave features and proton velocity distributions from solar wind measurements by the Wind spacecraft. For the first time, we can report the simultaneous observation of counter-propagating magnetohydrodynamic waves in the solar wind turbulence. As opposed to the traditional paradigm with counter-propagating Alfvén waves (AWs), anti-sunward AWs are encountered by sunward slow magnetosonic waves (SMWs) inmore » this new type of solar wind compressible turbulence. The counter-propagating AWs and SWs correspond, respectively, to the dominant and sub-dominant populations of the imbalanced Elsässer variables. Nonlinear interactions between the AWs and SMWs are inferred from the non-orthogonality between the possible oscillation direction of one wave and the possible propagation direction of the other. The associated protons are revealed to exhibit bi-directional asymmetric beams in their velocity distributions: sunward beams appear in short, narrow patterns and anti-sunward in broad extended tails. It is suggested that multiple types of wave–particle interactions, i.e., cyclotron and Landau resonances with AWs and SMWs at kinetic scales, are taking place to jointly heat the protons perpendicular and in parallel.« less

Capability of simultaneous Rayleigh LiDAR and O2 airglow measurements in exploring the short period wave characteristics

NASA Astrophysics Data System (ADS)

Taori, Alok; Raghunath, Karnam; Jayaraman, Achuthan

We use combination of simultaneous measurements made with Rayleigh lidar and O2 airglow monitoring to improve lidar investigation capability to cover a higher altitude range. We feed instantaneous O2 airglow temperatures instead the model values at the top altitude for subsequent integration method of temperature retrieval using Rayleigh lidar back scattered signals. Using this method, errors in the lidar temperature estimates converges at higher altitudes indicating better altitude coverage compared to regular methods where model temperatures are used instead of real-time measurements. This improvement enables the measurements of short period waves at upper mesospheric altitudes (~90 km). With two case studies, we show that above 60 km the few short period wave amplitude drastically increases while, some of the short period wave show either damping or saturation. We claim that by using such combined measurements, a significant and cost effective progress can be made in the understanding of short period wave processes which are important for the coupling across the different atmospheric regions.

ELF/VLF wave propagation at subauroral latitudes: Conjugate observation between the ground and Van Allen Probes A

NASA Astrophysics Data System (ADS)

Martinez-Calderon, Claudia; Shiokawa, Kazuo; Miyoshi, Yoshizumi; Keika, Kunihiro; Ozaki, Mitsunori; Schofield, Ian; Connors, Martin; Kletzing, Craig; Hanzelka, Miroslav; Santolik, Ondrej; Kurth, William S.

2016-06-01

We report simultaneous observation of ELF/VLF emissions, showing similar spectral and frequency features, between a VLF receiver at Athabasca (ATH), Canada, (L = 4.3) and Van Allen Probes A (Radiation Belt Storm Probes (RBSP) A). Using a statistical database from 1 November 2012 to 31 October 2013, we compared a total of 347 emissions observed on the ground with observations made by RBSP in the magnetosphere. On 25 February 2013, from 12:46 to 13:39 UT in the dawn sector (04-06 magnetic local time (MLT)), we observed a quasiperiodic (QP) emission centered at 4 kHz, and an accompanying short pulse lasting less than a second at 4.8 kHz in the dawn sector (04-06 MLT). RBSP A wave data showed both emissions as right-hand polarized with their Poynting vector earthward to the Northern Hemisphere. Using cross-correlation analysis, we did, for the first time, time delay analysis of a conjugate ELF/VLF event between ground and space, finding +2 to +4 s (ATH first) for the QP and -3 s (RBSP A first) for the pulse. Using backward tracing from ATH to the geomagnetic equator and forward tracing from the equator to RBSP A, based on plasmaspheric density observed by the spacecraft, we validate a possible propagation path for the QP emission which is consistent with the observed time delay.

A generalized invariant imbedding for wave propagation

NASA Astrophysics Data System (ADS)

Ayoubi, I. S.; Nelson, P.

1984-04-01

The initial-value problems for reflection and transmission coefficients (imbeddings) obtained by Bellman and Wing are critically reviewed. It is shown in detail how the two reduce to a common form when both are valid. A simultaneous generalization of these two imbeddings is obtained. The generalized imbedding involves incidence onto an intermediate region of continuous wave number, from a region of smooth wave number, but with no requirement concerning the manner in which the wave numbers join at the interface.

Initial Steps Toward Next-Generation, Waveform-Based, Three-Dimensional Models and Metrics to Improve Nuclear Explosion Monitoring in the Middle East

DTIC Science & Technology

2008-09-30

propagation effects by splitting apart the longer period surface waves from the shorter period, depth-sensitive Pnl waves. Problematic, or high-error... Pnl waves. Problematic, or high-error, stations and paths were further analyzed to identify systematic errors with unknown sensor responses and...frequency Pnl components and slower, longer period surface waves. All cut windows are fit simultaneously, allowing equal weighting of phases that may be

Continuous two-wave lasing in microchip Nd : YAG lasers

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ievlev, Ivan V; Koryukin, Igor' V; Lebedeva, Yu S

2011-08-31

Simultaneous two-wave lasing was obtained in microchip end-pumped Nd:YAG lasers at the wavelengths of 1061.5 and 1064.17 nm at room temperature. Laser wave intensities were studied as functions of crystal temperature and pump power. The ranges of parameters were determined in which the two-wave lasing occurs and the reasons for such lasing were established. A model is suggested, which adequately describes the experimental results obtained. (control of radiation parameters)

VHF radar measurements during MAP/WINE

NASA Technical Reports Server (NTRS)

Czechowsky, P.; Klostermeyer, J.; Ruster, R.; Schmidt, G.; Rottger, J.

1983-01-01

Sensitive Doppler radars which operate in the very high frequency (VHF) band, usually near 50 MHz can measure profiles of background winds, tides, atmospheric gravity waves and turbulence at tropospheric, stratospheric and mesospheric heights. Their ability to observe simultaneously large and small-scale processes makes them unique instruments for studying not only each process separately but also their nonlinear interactions. The mobile VHF radar to be used during the MAP/WINE campaign on Andoya is a modified version of the SOUSY VHF radar being in operation for six years in the Harz Mountains.

Brillouin Optomechanics in Coupled Silicon Microcavities

NASA Astrophysics Data System (ADS)

Espinel, Y. A. V.; Santos, F. G. S.; Luiz, G. O.; Alegre, T. P. Mayer; Wiederhecker, G. S.

2017-03-01

The simultaneous control of optical and mechanical waves has enabled a range of fundamental and technological breakthroughs, from the demonstration of ultra-stable frequency reference devices, to the exploration of the quantum-classical boundaries in optomechanical laser-cooling experiments. More recently, such an optomechanical interaction has been observed in integrated nano-waveguides and microcavities in the Brillouin regime, where short-wavelength mechanical modes scatter light at several GHz. Here we engineer coupled optical microcavities to enable a low threshold excitation of mechanical travelling-wave modes through backward stimulated Brillouin scattering. Exploring the backward scattering we propose silicon microcavity designs based on laterally coupled single and double-layer cavities, the proposed structures enable optomechanical coupling with very high frequency modes (11 to 25 GHz) and large optomechanical coupling rates (g0/2π) from 50 kHz to 90 kHz.

The Detached Auroras Induced by the Solar Wind Pressure Enhancement in Both Hemispheres From Imaging and In Situ Particle Observations

NASA Astrophysics Data System (ADS)

Zhou, Su; Luan, Xiaoli; Søraas, Finn; Østgaard, Nikolai; Raita, Tero

2018-04-01

This paper presents simultaneous detached proton auroras that appeared in both hemispheres at 11:06 UT, 08 March 2012, just 2 min after a sudden solar wind pressure enhancement ( 11:04 UT) hit the Earth. They were observed under northward interplanetary magnetic field Bz condition and during the recovery phase of a moderate geomagnetic storm. In the Northern Hemisphere, Defense Meteorological Satellite Program/Special Sensor Ultraviolet Spectrographic Imager observed that the detached arc occurred within 60°-65° magnetic latitude and covered a few magnetic local time (MLT) hours ranging from 0530 to 0830 MLT with a possible extension toward noon. At the same time (11:06 UT), Polar Orbiting Environment Satellites 19 detected a detached proton aurora around 1300 MLT in the Southern Hemisphere, centering 62° magnetic latitude, which was at the same latitudes as the northern detached arc. This southern aurora was most probably a part of a dayside detached arc that was conjugate to the northern one. In situ particle observations indicated that the detached auroras were dominated by protons/ions with energies ranging from around 20 keV to several hundreds of keV, without obvious electron precipitations. These detached arcs persisted for less than 6 min, consistent with the impact from pressure enhancement and the observed electromagnetic ion cyclotron (EMIC) waves. It is suggested that the increasing solar wind pressure pushed the hot ions in the ring current closer to Earth where the steep gradient of cold plasma favored EMIC wave growth. By losing energy to EMIC waves the energetic protons (>20 keV) were scattered into the loss cone and produced the observed detached proton auroras.

WASP family members and formin proteins coordinate regulation of cell protrusions in carcinoma cells

PubMed Central

Sarmiento, Corina; Wang, Weigang; Dovas, Athanassios; Yamaguchi, Hideki; Sidani, Mazen; El-Sibai, Mirvat; DesMarais, Vera; Holman, Holly A.; Kitchen, Susan; Backer, Jonathan M.; Alberts, Art; Condeelis, John

2008-01-01

We examined the role of the actin nucleation promoters neural Wiskott-Aldrich syndrome protein (N-WASP) and WAVE2 in cell protrusion in response to epidermal growth factor (EGF), a key regulator in carcinoma cell invasion. We found that WAVE2 knockdown (KD) suppresses lamellipod formation and increases filopod formation, whereas N-WASP KD has no effect. However, simultaneous KD of both proteins results in the formation of large jagged protrusions with lamellar properties and increased filopod formation. This suggests that another actin nucleation activity is at work in carcinoma cells in response to EGF. A mammalian Diaphanous–related formin, mDia1, localizes at the jagged protrusions in double KD cells. Constitutively active mDia1 recapitulated the phenotype, whereas inhibition of mDia1 blocked the formation of these protrusions. Increased RhoA activity, which stimulates mDia1 nucleation, was observed in the N-WASP/WAVE2 KD cells and was shown to be required for the N-WASP/WAVE2 KD phenotype. These data show that coordinate regulation between the WASP family and mDia proteins controls the balance between lamellar and lamellipodial protrusion activity. PMID:18362183

Direct imaging of delayed magneto-dynamic modes induced by surface acoustic waves.

PubMed

Foerster, Michael; Macià, Ferran; Statuto, Nahuel; Finizio, Simone; Hernández-Mínguez, Alberto; Lendínez, Sergi; Santos, Paulo V; Fontcuberta, Josep; Hernàndez, Joan Manel; Kläui, Mathias; Aballe, Lucia

2017-09-01

The magnetoelastic effect-the change of magnetic properties caused by the elastic deformation of a magnetic material-has been proposed as an alternative approach to magnetic fields for the low-power control of magnetization states of nanoelements since it avoids charge currents, which entail ohmic losses. Here, we have studied the effect of dynamic strain accompanying a surface acoustic wave on magnetic nanostructures in thermal equilibrium. We have developed an experimental technique based on stroboscopic X-ray microscopy that provides a pathway to the quantitative study of strain waves and magnetization at the nanoscale. We have simultaneously imaged the evolution of both strain and magnetization dynamics of nanostructures at the picosecond time scale and found that magnetization modes have a delayed response to the strain modes, adjustable by the magnetic domain configuration. Our results provide fundamental insight into magnetoelastic coupling in nanostructures and have implications for the design of strain-controlled magnetostrictive nano-devices.Understanding the effects of local dynamic strain on magnetization may help the development of magnetic devices. Foerster et al. demonstrate stroboscopic imaging that allows the observation of both strain and magnetization dynamics in nickel when surface acoustic waves are driven in the substrate.

WASP family members and formin proteins coordinate regulation of cell protrusions in carcinoma cells.

PubMed

Sarmiento, Corina; Wang, Weigang; Dovas, Athanassios; Yamaguchi, Hideki; Sidani, Mazen; El-Sibai, Mirvat; Desmarais, Vera; Holman, Holly A; Kitchen, Susan; Backer, Jonathan M; Alberts, Art; Condeelis, John

2008-03-24

We examined the role of the actin nucleation promoters neural Wiskott-Aldrich syndrome protein (N-WASP) and WAVE2 in cell protrusion in response to epidermal growth factor (EGF), a key regulator in carcinoma cell invasion. We found that WAVE2 knockdown (KD) suppresses lamellipod formation and increases filopod formation, whereas N-WASP KD has no effect. However, simultaneous KD of both proteins results in the formation of large jagged protrusions with lamellar properties and increased filopod formation. This suggests that another actin nucleation activity is at work in carcinoma cells in response to EGF. A mammalian Diaphanous-related formin, mDia1, localizes at the jagged protrusions in double KD cells. Constitutively active mDia1 recapitulated the phenotype, whereas inhibition of mDia1 blocked the formation of these protrusions. Increased RhoA activity, which stimulates mDia1 nucleation, was observed in the N-WASP/WAVE2 KD cells and was shown to be required for the N-WASP/WAVE2 KD phenotype. These data show that coordinate regulation between the WASP family and mDia proteins controls the balance between lamellar and lamellipodial protrusion activity.

Statistical Downscaling in Multi-dimensional Wave Climate Forecast

NASA Astrophysics Data System (ADS)

Camus, P.; Méndez, F. J.; Medina, R.; Losada, I. J.; Cofiño, A. S.; Gutiérrez, J. M.

2009-04-01

Wave climate at a particular site is defined by the statistical distribution of sea state parameters, such as significant wave height, mean wave period, mean wave direction, wind velocity, wind direction and storm surge. Nowadays, long-term time series of these parameters are available from reanalysis databases obtained by numerical models. The Self-Organizing Map (SOM) technique is applied to characterize multi-dimensional wave climate, obtaining the relevant "wave types" spanning the historical variability. This technique summarizes multi-dimension of wave climate in terms of a set of clusters projected in low-dimensional lattice with a spatial organization, providing Probability Density Functions (PDFs) on the lattice. On the other hand, wind and storm surge depend on instantaneous local large-scale sea level pressure (SLP) fields while waves depend on the recent history of these fields (say, 1 to 5 days). Thus, these variables are associated with large-scale atmospheric circulation patterns. In this work, a nearest-neighbors analog method is used to predict monthly multi-dimensional wave climate. This method establishes relationships between the large-scale atmospheric circulation patterns from numerical models (SLP fields as predictors) with local wave databases of observations (monthly wave climate SOM PDFs as predictand) to set up statistical models. A wave reanalysis database, developed by Puertos del Estado (Ministerio de Fomento), is considered as historical time series of local variables. The simultaneous SLP fields calculated by NCEP atmospheric reanalysis are used as predictors. Several applications with different size of sea level pressure grid and with different temporal domain resolution are compared to obtain the optimal statistical model that better represents the monthly wave climate at a particular site. In this work we examine the potential skill of this downscaling approach considering perfect-model conditions, but we will also analyze the suitability of this methodology to be used for seasonal forecast and for long-term climate change scenario projection of wave climate.

The Frequency-dependent Damping of Slow Magnetoacoustic Waves in a Sunspot Umbral Atmosphere

DOE Office of Scientific and Technical Information (OSTI.GOV)

Prasad, S. Krishna; Jess, D. B.; Doorsselaere, T. Van

High spatial and temporal resolution images of a sunspot, obtained simultaneously in multiple optical and UV wavelengths, are employed to study the propagation and damping characteristics of slow magnetoacoustic waves up to transition region heights. Power spectra are generated from intensity oscillations in sunspot umbra, across multiple atmospheric heights, for frequencies up to a few hundred mHz. It is observed that the power spectra display a power-law dependence over the entire frequency range, with a significant enhancement around 5.5 mHz found for the chromospheric channels. The phase difference spectra reveal a cutoff frequency near 3 mHz, up to which themore » oscillations are evanescent, while those with higher frequencies propagate upward. The power-law index appears to increase with atmospheric height. Also, shorter damping lengths are observed for oscillations with higher frequencies suggesting frequency-dependent damping. Using the relative amplitudes of the 5.5 mHz (3 minute) oscillations, we estimate the energy flux at different heights, which seems to decay gradually from the photosphere, in agreement with recent numerical simulations. Furthermore, a comparison of power spectra across the umbral radius highlights an enhancement of high-frequency waves near the umbral center, which does not seem to be related to magnetic field inclination angle effects.« less

Astrophysical Model Selection in Gravitational Wave Astronomy

NASA Technical Reports Server (NTRS)

Adams, Matthew R.; Cornish, Neil J.; Littenberg, Tyson B.

2012-01-01

Theoretical studies in gravitational wave astronomy have mostly focused on the information that can be extracted from individual detections, such as the mass of a binary system and its location in space. Here we consider how the information from multiple detections can be used to constrain astrophysical population models. This seemingly simple problem is made challenging by the high dimensionality and high degree of correlation in the parameter spaces that describe the signals, and by the complexity of the astrophysical models, which can also depend on a large number of parameters, some of which might not be directly constrained by the observations. We present a method for constraining population models using a hierarchical Bayesian modeling approach which simultaneously infers the source parameters and population model and provides the joint probability distributions for both. We illustrate this approach by considering the constraints that can be placed on population models for galactic white dwarf binaries using a future space-based gravitational wave detector. We find that a mission that is able to resolve approximately 5000 of the shortest period binaries will be able to constrain the population model parameters, including the chirp mass distribution and a characteristic galaxy disk radius to within a few percent. This compares favorably to existing bounds, where electromagnetic observations of stars in the galaxy constrain disk radii to within 20%.

Nanoscale steady-state temperature gradients within polymer nanocomposites undergoing continuous-wave photothermal heating from gold nanorods.

PubMed

Maity, Somsubhra; Wu, Wei-Chen; Tracy, Joseph B; Clarke, Laura I; Bochinski, Jason R

2017-08-17

Anisotropically-shaped metal nanoparticles act as nanoscale heaters via excitation of a localized surface plasmon resonance, utilizing a photothermal effect which converts the optical energy into local heat. Steady-state temperatures within a polymer matrix embedded with gold nanorods undergoing photothermal heating using continuous-wave excitation are measured in the immediate spatial vicinity of the nanoparticle (referred to as the local temperature) from observing the rate of physical rotation of the asymmetric nanoparticles within the locally created polymer melt. Average temperatures across the entire (mostly solid) sample (referred to as the global temperature) are simultaneously observed using a fluorescence method from randomly dispersed molecular emitters. Comparing these two independent measurements in films having varying concentrations of nanorods reveals the interplay between the local and global temperatures, clearly demonstrating the capability of these material samples to sustain large steady-state spatial temperature gradients when experiencing continuous-wave excitation photothermal heating. These results are discussed quantitatively. Illustrative imaging studies of nanofibers under photothermal heating also support the presence of a large temperature gradient. Photothermal heating in this manner has potential utility in creating unique thermal processing conditions for outcomes such as driving chemical reactions, inducing crystallinity changes, or enhancing degradation processes in a manner unachievable by conventional heating methods.

Structure of the Lithosphere and Asthenosphere beneath the Western US from Simultaneous Multi-Parameter Inversion

NASA Astrophysics Data System (ADS)

Steck, L.; Maceira, M.; Ammon, C. J.; Herrmann, R. B.

2013-12-01

Joint inversion of multiple datasets should produce more realistic images of Earth structure. Here we simultaneously invert surface wave dispersion, receiver functions, and gravity to determine structure of the crust and upper mantle of the western United States. Our target region is comprised of a one-degree grid that spans latitudes from 30 to 50 degrees North and longitudes from 95 to 125 degrees West. Receiver functions come from the Earthscope Automated Receiver system, and are stacked to produce an average model for each cell. Rayleigh and Love dispersion data come from multiple filter analysis of regional earthquakes, while the gravity observations are extracted from the EGM2008 model. Our starting model is comprised of an oceanic PREM model west of the Pacific coast, a western US model between that and the eastern front of the Rocky Mountains, and a continental PREM model east of the Rocky Mountain Front. Several different velocity/density relationships have been tested and all result in very similar models. Our inversion reduces RMS surface wave residuals by 58% and receiver function misfits by about 18%. Gravity residuals are reduced by more than 90%. While the reduction in residuals for receiver functions is not as profound as for surface waves or gravity, they are meaningful and produce sharper boundaries for the observed crustal anomalies. The addition of gravity produces subtle changes to the final model. Our final results are consistent with numerous previous studies in the region. In general, the craton exhibits higher velocities than the tectonically active regions to its west. We see high mid-crustal velocities under the Snake River Plain and the Colorado Plateau. In the lower crust we observe lowest velocities in the western Basin and Range and under the Colorado Mineral Belt. At 80km depth we see broad low velocities fanning out from the Snake River Plain associated with the mantle plume feeding Yellowstone Caldera. Additionally we see high and low velocity anomalies along the west coast that reflect ongoing subduction processes beneath the western US, including the subducting slab and slab window.

Quantifying the Uncertainties and Multi-parameter Trade-offs in Joint Inversion of Receiver Functions and Surface Wave Velocity and Ellipticity

NASA Astrophysics Data System (ADS)

Gao, C.; Lekic, V.

2016-12-01

When constraining the structure of the Earth's continental lithosphere, multiple seismic observables are often combined due to their complementary sensitivities.The transdimensional Bayesian (TB) approach in seismic inversion allows model parameter uncertainties and trade-offs to be quantified with few assumptions. TB sampling yields an adaptive parameterization that enables simultaneous inversion for different model parameters (Vp, Vs, density, radial anisotropy), without the need for strong prior information or regularization. We use a reversible jump Markov chain Monte Carlo (rjMcMC) algorithm to incorporate different seismic observables - surface wave dispersion (SWD), Rayleigh wave ellipticity (ZH ratio), and receiver functions - into the inversion for the profiles of shear velocity (Vs), compressional velocity (Vp), density (ρ), and radial anisotropy (ξ) beneath a seismic station. By analyzing all three data types individually and together, we show that TB sampling can eliminate the need for a fixed parameterization based on prior information, and reduce trade-offs in model estimates. We then explore the effect of different types of misfit functions for receiver function inversion, which is a highly non-unique problem. We compare the synthetic inversion results using the L2 norm, cross-correlation type and integral type misfit function by their convergence rates and retrieved seismic structures. In inversions in which only one type of model parameter (Vs for the case of SWD) is inverted, assumed scaling relationships are often applied to account for sensitivity to other model parameters (e.g. Vp, ρ, ξ). Here we show that under a TB framework, we can eliminate scaling assumptions, while simultaneously constraining multiple model parameters to varying degrees. Furthermore, we compare the performance of TB inversion when different types of model parameters either share the same or use independent parameterizations. We show that different parameterizations can lead to differences in retrieved model parameters, consistent with limited data constraints. We then quantitatively examine the model parameter trade-offs and find that trade-offs between Vp and radial anisotropy might limit our ability to constrain shallow-layer radial anisotropy using current seismic observables.

Facilitation of cytosolic calcium wave propagation by local calcium uptake into the sarcoplasmic reticulum in cardiac myocytes.

PubMed

Maxwell, Joshua T; Blatter, Lothar A

2012-12-01

The widely accepted paradigm for cytosolic Ca(2+) wave propagation postulates a 'fire-diffuse-fire' mechanism where local Ca(2+)-induced Ca(2+) release (CICR) from the sarcoplasmic reticulum (SR) via ryanodine receptor (RyR) Ca(2+) release channels diffuses towards and activates neighbouring release sites, resulting in a propagating Ca(2+) wave. A recent challenge to this paradigm proposed the requirement for an intra-SR 'sensitization' Ca(2+) wave that precedes the cytosolic Ca(2+) wave and primes RyRs from the luminal side to CICR. Here, we tested this hypothesis experimentally with direct simultaneous measurements of cytosolic ([Ca(2+)](i); rhod-2) and intra-SR ([Ca(2+)](SR); fluo-5N) calcium signals during wave propagation in rabbit ventricular myocytes, using high resolution fluorescence confocal imaging. The increase in [Ca(2+)](i) at the wave front preceded depletion of the SR at each point along the calcium wave front, while during this latency period a transient increase of [Ca(2+)](SR) was observed. This transient elevation of [Ca(2+)](SR) could be identified at individual release junctions and depended on the activity of the sarco-endoplasmic reticulum Ca(2+)-ATPase (SERCA). Increased SERCA activity (β-adrenergic stimulation with 1 μM isoproterenol (isoprenaline)) decreased the latency period and increased the amplitude of the transient elevation of [Ca(2+)](SR), whereas inhibition of SERCA (3 μM cyclopiazonic acid) had the opposite effect. In conclusion, the data provide experimental evidence that local Ca(2+) uptake by SERCA into the SR facilitates the propagation of cytosolic Ca(2+) waves via luminal sensitization of the RyR, and supports a novel paradigm of a 'fire-diffuse-uptake-fire' mechanism for Ca(2+) wave propagation in cardiac myocytes.

Quantitative shear wave optical coherence elastography (SW-OCE) with acoustic radiation force impulses (ARFI) induced by phase array transducer

NASA Astrophysics Data System (ADS)

Song, Shaozhen; Le, Nhan Minh; Wang, Ruikang K.; Huang, Zhihong

2015-03-01

Shear Wave Optical Coherence Elastography (SW-OCE) uses the speed of propagating shear waves to provide a quantitative measurement of localized shear modulus, making it a valuable technique for the elasticity characterization of tissues such as skin and ocular tissue. One of the main challenges in shear wave elastography is to induce a reliable source of shear wave; most of nowadays techniques use external vibrators which have several drawbacks such as limited wave propagation range and/or difficulties in non-invasive scans requiring precisions, accuracy. Thus, we propose linear phase array ultrasound transducer as a remote wave source, combined with the high-speed, 47,000-frame-per-second Shear-wave visualization provided by phase-sensitive OCT. In this study, we observed for the first time shear waves induced by a 128 element linear array ultrasound imaging transducer, while the ultrasound and OCT images (within the OCE detection range) were triggered simultaneously. Acoustic radiation force impulses are induced by emitting 10 MHz tone-bursts of sub-millisecond durations (between 50 μm - 100 μm). Ultrasound beam steering is achieved by programming appropriate phase delay, covering a lateral range of 10 mm and full OCT axial (depth) range in the imaging sample. Tissue-mimicking phantoms with agarose concentration of 0.5% and 1% was used in the SW-OCE measurements as the only imaging samples. The results show extensive improvements over the range of SW-OCE elasticity map; such improvements can also be seen over shear wave velocities in softer and stiffer phantoms, as well as determining the boundary of multiple inclusions with different stiffness. This approach opens up the feasibility to combine medical ultrasound imaging and SW-OCE for high-resolution localized quantitative measurement of tissue biomechanical property.

Facilitation of cytosolic calcium wave propagation by local calcium uptake into the sarcoplasmic reticulum in cardiac myocytes

PubMed Central

Maxwell, Joshua T; Blatter, Lothar A

2012-01-01

The widely accepted paradigm for cytosolic Ca2+ wave propagation postulates a ‘fire-diffuse-fire’ mechanism where local Ca2+-induced Ca2+ release (CICR) from the sarcoplasmic reticulum (SR) via ryanodine receptor (RyR) Ca2+ release channels diffuses towards and activates neighbouring release sites, resulting in a propagating Ca2+ wave. A recent challenge to this paradigm proposed the requirement for an intra-SR ‘sensitization’ Ca2+ wave that precedes the cytosolic Ca2+ wave and primes RyRs from the luminal side to CICR. Here, we tested this hypothesis experimentally with direct simultaneous measurements of cytosolic ([Ca2+]i; rhod-2) and intra-SR ([Ca2+]SR; fluo-5N) calcium signals during wave propagation in rabbit ventricular myocytes, using high resolution fluorescence confocal imaging. The increase in [Ca2+]i at the wave front preceded depletion of the SR at each point along the calcium wave front, while during this latency period a transient increase of [Ca2+]SR was observed. This transient elevation of [Ca2+]SR could be identified at individual release junctions and depended on the activity of the sarco-endoplasmic reticulum Ca2+-ATPase (SERCA). Increased SERCA activity (β-adrenergic stimulation with 1 μm isoproterenol (isoprenaline)) decreased the latency period and increased the amplitude of the transient elevation of [Ca2+]SR, whereas inhibition of SERCA (3 μm cyclopiazonic acid) had the opposite effect. In conclusion, the data provide experimental evidence that local Ca2+ uptake by SERCA into the SR facilitates the propagation of cytosolic Ca2+ waves via luminal sensitization of the RyR, and supports a novel paradigm of a ‘fire-diffuse-uptake-fire’ mechanism for Ca2+ wave propagation in cardiac myocytes. PMID:22988145

Plasma phenomena observed in the MAP/WINE campaign

NASA Technical Reports Server (NTRS)

Friedrich, M.

1989-01-01

The wealth of plasma data gathered in the MAP/WINE campaign allows insight into the generation of electron densities on a large, and the nature of the ions on a small scale. The associated measurements of winds and charged particles help to understand the morphology of the midlatitude ionization which turns out to correlate poorly with geomagnetic activity, but at least slightly with the prevailing winds. A somewhat clearer connection seems to exist between stratospheric warmings and radio wave absorption minima. On the local scale the interpretation of the rocket measurements of positive ions was helped by simultaneous observations of temperatures and atomic oxygen. The relevance of the description winter anomaly for high latitude electron density profiles are examined.

Alternating current scanning electrochemical microscopy with simultaneous fast-scan cyclic voltammetry.

PubMed

Koch, Jason A; Baur, Melinda B; Woodall, Erica L; Baur, John E

2012-11-06

Fast-scan cyclic voltammetry (FSCV) is combined with alternating current scanning electrochemical microscopy (AC-SECM) for simultaneous measurements of impedance and faradaic current. Scan rates of 10-1000 V s(-1) were used for voltammetry, while a high-frequency (100 kHz), low-amplitude (10 mV rms) sine wave was added to the voltammetric waveform for the ac measurement. Both a lock-in amplifier and an analog circuit were used to measure the amplitude of the resultant ac signal. The effect of the added sine wave on the voltammetry at a carbon fiber electrode was investigated and found to have negligible effect. The combined FSCV and ac measurements were used to provide simultaneous chemical and topographical information about a substrate using a single carbon fiber probe. The technique is demonstrated in living cell culture, where cellular respiration and topography were simultaneously imaged without the addition of a redox mediator. This approach promises to be useful for the topographical and multidimensional chemical imaging of substrates.

C/NOFS Satellite Electric Field and Plasma Density Observations of Plasma Instabilities Below the Equatorial F-Peak -- Evidence for Approximately 500 km-Scale Spread-F "Precursor" Waves Driven by Zonal Shear Flow and km-Scale, Narrow-Banded Irregularities

NASA Technical Reports Server (NTRS)

Pfaff, R.; Freudenreich, H.; Klenzing, J.; Liebrecht, C.; Valladares, C.

2011-01-01

As solar activity has increased, the ionosphere F-peak has been elevated on numerous occasions above the C/NOFS satellite perigee of 400km. In particular, during the month of April, 2011, the satellite consistently journeyed below the F-peak whenever the orbit was in the region of the South Atlantic anomaly after sunset. During these passes, data from the electric field and plasma density probes on the satellite have revealed two types of instabilities which had not previously been observed in the C/NOFS data set (to our knowledge): The first is evidence for 400-500km-scale bottomside "undulations" that appear in the density and electric field data. In one case, these large scale waves are associated with a strong shear in the zonal E x B flow, as evidenced by variations in the meridional (outward) electric fields observed above and below the F-peak. These undulations are devoid of smaller scale structures in the early evening, yet appear at later local times along the same orbit associated with fully-developed spread-F with smaller scale structures. This suggests that they may be precursor waves for spread-F, driven by a collisional shear instability, following ideas advanced previously by researchers using data from the Jicamarca radar. A second new result (for C/NOFS) is the appearance of km-scale irregularities that are a common feature in the electric field and plasma density data that also appear when the satellite is below the F -peak at night. The vector electric field instrument on C/NOFS clearly shows that the electric field component of these waves is strongest in the zonal direction. These waves are strongly correlated with simultaneous observations of plasma density oscillations and appear both with, and without, evidence of larger-scale spread-F depletions. These km-scale, quasi-coherent waves strongly resemble the bottomside, sinusoidal irregularities reported in the Atmosphere Explorer satellite data set by Valladares et al. [JGR, 88, 8025, 1983]. We interpret these new observations in terms of fundamental plasma instabilities associated with the unstable, nighttime equatorial ionosphere.

The evolution of the X-ray afterglow emission of GW 170817/ GRB 170817A in XMM-Newton observations

NASA Astrophysics Data System (ADS)

D'Avanzo, P.; Campana, S.; Salafia, O. S.; Ghirlanda, G.; Ghisellini, G.; Melandri, A.; Bernardini, M. G.; Branchesi, M.; Chassande-Mottin, E.; Covino, S.; D'Elia, V.; Nava, L.; Salvaterra, R.; Tagliaferri, G.; Vergani, S. D.

2018-05-01

We report our observation of the short gamma-ray burst (GRB) GRB 170817A, associated to the binary neutron star merger gravitational wave (GW) event GW 170817, performed in the X-ray band with XMM-Newton 135 d after the event (on 29 December, 2017). We find evidence for a flattening of the X-ray light curve with respect to the previously observed brightening. This is also supported by a nearly simultaneous optical Hubble Space Telescope observation and successive X-ray Chandra and low-frequency radio observations recently reported in the literature. Since the optical-to-X-ray spectral slope did not change with respect to previous observations, we exclude that the change in the temporal evolution of the light curve is due to the passage of the cooling frequency: its origin must be geometric or dynamical. We interpret all the existing afterglow data with two models: i) a structured jet and ii) a jet-less isotropic fireball with some stratification in its radial velocity structure. Both models fit the data and predict that the radio flux must decrease simultaneously with the optical and X-ray emission, making it difficult to distinguish between them at the present stage. Polarimetric measurements and the rate of short GRB-GW associations in future LIGO/Virgo runs will be key to disentangle these two geometrically different scenarios.

Ultrasonic monitoring of spontaneous imbibition experiments: Precursory moisture diffusion effects ahead of water front

NASA Astrophysics Data System (ADS)

David, Christian; Sarout, Joël.; Dautriat, Jérémie; Pimienta, Lucas; Michée, Marie; Desrues, Mathilde; Barnes, Christophe

2017-07-01

Fluid substitution processes have been investigated in the laboratory on 14 carbonate and siliciclastic reservoir rock analogues through spontaneous imbibition experiments on vertical cylindrical specimens with simultaneous ultrasonic monitoring and imaging. The motivation of our study was to identify the seismic attributes of fluid substitution in reservoir rocks and to link them to physical processes. It is shown that (i) the P wave velocity either decreases or increases when the capillary front reaches the Fresnel clearance zone, (ii) the P wave amplitude is systematically impacted earlier than the velocity is, (iii) this precursory amplitude decrease occurs when the imbibition front is located outside of the Fresnel zone, and (iv) the relative variation of the P wave amplitude is always much larger than that of the P wave velocity. These results suggest that moisture diffuses into the pore space ahead of the water front. This postulate is further supported by a quantitative analysis of the time evolution of the observed P wave amplitudes. In a sense, P wave amplitude acts as a precursor of the arrival of the capillary front. This phenomenon is used to estimate the effective diffusivity of moisture in the tested rocks. The effective moisture diffusivity estimated from the ultrasonic data is strongly correlated with permeability: a power law with exponent 0.96 predicts permeability from ultrasonic monitoring within a factor 3 without noticeable bias. When the effective diffusivity is high, moisture diffusion affects ultrasonic P wave attributes even before the imbibition starts and impacts the P wave reflectivity as evidenced by the variations recorded in the waveform coda.

A twofold quantum delayed-choice experiment in a superconducting circuit

PubMed Central

Liu, Ke; Xu, Yuan; Wang, Weiting; Zheng, Shi-Biao; Roy, Tanay; Kundu, Suman; Chand, Madhavi; Ranadive, Arpit; Vijay, Rajamani; Song, Yipu; Duan, Luming; Sun, Luyan

2017-01-01

Wave-particle complementarity lies at the heart of quantum mechanics. To illustrate this mysterious feature, Wheeler proposed the delayed-choice experiment, where a quantum system manifests the wave- or particle-like attribute, depending on the experimental arrangement, which is made after the system has entered the interferometer. In recent quantum delayed-choice experiments, these two complementary behaviors were simultaneously observed with a quantum interferometer in a superposition of being closed and open. We suggest and implement a conceptually different quantum delayed-choice experiment by introducing a which-path detector (WPD) that can simultaneously record and neglect the system’s path information, but where the interferometer itself is classical. Our experiment is realized with a superconducting circuit, where a cavity acts as the WPD for an interfering qubit. Using this setup, we implement the first twofold delayed-choice experiment, which demonstrates that the system’s behavior depends not only on the measuring device’s configuration that can be chosen even after the system has been detected but also on whether we a posteriori erase or mark the which-path information, the latter of which cannot be revealed by previous quantum delayed-choice experiments. Our results represent the first demonstration of both counterintuitive features with the same experimental setup, significantly extending the concept of quantum delayed-choice experiment. PMID:28508079

A twofold quantum delayed-choice experiment in a superconducting circuit.

PubMed

Liu, Ke; Xu, Yuan; Wang, Weiting; Zheng, Shi-Biao; Roy, Tanay; Kundu, Suman; Chand, Madhavi; Ranadive, Arpit; Vijay, Rajamani; Song, Yipu; Duan, Luming; Sun, Luyan

2017-05-01

Wave-particle complementarity lies at the heart of quantum mechanics. To illustrate this mysterious feature, Wheeler proposed the delayed-choice experiment, where a quantum system manifests the wave- or particle-like attribute, depending on the experimental arrangement, which is made after the system has entered the interferometer. In recent quantum delayed-choice experiments, these two complementary behaviors were simultaneously observed with a quantum interferometer in a superposition of being closed and open. We suggest and implement a conceptually different quantum delayed-choice experiment by introducing a which-path detector (WPD) that can simultaneously record and neglect the system's path information, but where the interferometer itself is classical. Our experiment is realized with a superconducting circuit, where a cavity acts as the WPD for an interfering qubit. Using this setup, we implement the first twofold delayed-choice experiment, which demonstrates that the system's behavior depends not only on the measuring device's configuration that can be chosen even after the system has been detected but also on whether we a posteriori erase or mark the which-path information, the latter of which cannot be revealed by previous quantum delayed-choice experiments. Our results represent the first demonstration of both counterintuitive features with the same experimental setup, significantly extending the concept of quantum delayed-choice experiment.

On traveling-wave field-effect flow control for simultaneous induced-charge electroosmotic pumping and mixing in microfluidics: physical perspectives and theoretical analysis

NASA Astrophysics Data System (ADS)

Liu, Weiyu; Ren, Yukun; Tao, Ye; Li, Yanbo; Wu, Qisheng

2018-05-01

Since its first proposition at the end of the last century (Schasfoort et al 1999 Science 286 942-5), field-effect flow control at micrometer dimensions has attracted tremendous attention from the microfluidic community. Most previous research on this subject has mainly focused on enhancing the electroosmotic pump flow rate by introducing an additional in-phase counterionic charge across the diffusing screening cloud with external gate electrodes of static DC voltages. However, there is a flaw, namely that AC fields, which suppress undesirable electrochemical reactions, result in zero time-averaged flow. Starting from this point, we present herein a brand new approach to traveling-wave field-effect electroosmosis control from a theoretical point of view, in the context of a smart manipulation tool for the stratified liquid content of miniaturization systems. In the configuration of a traveling-wave flow field-effect transistor (TW-FFET), the field-induced out-of-phase Debye screening charge within the thin double layer originates from the forward propagation of a traveling potential wave along a discrete arrangement of external gating electrode arrays, which interacts actively with the horizontal standing-wave electric field imposed across the source-drain terminal. Since the voltage waves and induced free charge are all sinusoidal functions of the observation time, the net ICEO flow component can survive in a broad frequency range. Due to the action of the background AC electric field on the inhomogeneous counterionic charge induced at the solution/sidewall interface, asymmetric ICEO vortex patterns appear above the traveling-wave gate arrays, giving rise to simultaneous induced-charge electroosmotic pumping and mixing of fluidic samples. A mathematical model is then developed to numerically investigate the feasibility of TW-FFETs in electrokinetic microflow manipulation. A prototyping paradigm of fully electrokinetics-driven microfabricated fluidic networks in a cross shape is theoretically erected, with four sets of gating traveling-fields in perpendicular orientations, from which the resulting liquid mixture is obtainable at any one of the three outlet ports. Supported by mathematical analysis, our physical demonstration of the TW-FFET shows it has great potential to advance fully automated electroconvective sample treatment in modern micro total analytical systems.

Measuring the accelerating effect of the planetary-scale waves on Venus observed with UVI/AKATSUKI and ground-based telescopes

NASA Astrophysics Data System (ADS)

Imai, M.; Kouyama, T.; Takahashi, Y.; Watanabe, S.; Yamazaki, A.; Yamada, M.; Nakamura, M.; Satoh, T.; Imamura, T.; Nakaoka, T.; Kawabata, M.; Yamanaka, M.; Kawabata, K. S.

2017-12-01

Venus has a global cloud layer, and the atmosphere rotates with the speed over 100 m/s. The scattering of solar radiance and absorber in clouds cause the strong dark and bright contrast in 365 nm unknown absorption bands. The Japanese Venus orbiter AKATSUKI and the onboard instrument UVI capture 100 km mesoscale cloud features over the entire visible dayside area. In contrast, planetary-scale features are observed when the orbiter is at the moderate distance from Venus and when the Sun-Venus-orbiter phase angle is smaller than 45 deg. Cloud top wind velocity was measured with the mesoscale cloud tracking technique, however, observations of the propagation velocity and its variation of the planetary-scale feature are not well conducted because of the limitation of the observable area. The purpose of the study is measuring the effect of wind acceleration by planetary-scale waves. Each cloud motion can be represented as the wind and phase velocity of the planetary-scale waves, respectively. We conducted simultaneous observations of the zonal motion of both mesoscale and planetary-scale feature using UVI/AKATSUKI and ground-based Pirka and Kanata telescopes in Japan. Our previous ground-based observation revealed the periodicity change of planetary-scale waves with a time scale of a couple of months. For the initial analysis of UVI images, we used the time-consecutive images taken in the orbit #32. During this orbit (from Nov. 13 to 20, 2016), 7 images were obtained with 2 hr time-interval in a day whose spatial resolution ranged from 10-35 km. To investigate the typical mesoscale cloud motion, the Gaussian-filters with sigma = 3 deg. were used to smooth geometrically mapped images with 0.25 deg. resolution. Then the amount of zonal shift for each 5 deg. latitudinal bands between the pairs of two time-consecutive images were estimated by searching the 2D cross-correlation maximum. The final wind velocity (or rotation period) for mesoscale features were determined with a small error about +/- 0.1-day period in equatorial region (Figure 2). The same method will be applied for planetary-scale features captured by UVI, and ground-based observations compensate the discontinuity in UVI data. At the presentation, the variability in winds and wave propagation velocity with the time scale of a couple of months will be shown.

High-resolution observations of core and suprathermal ions in the auroral ionosphere: Techniques and results from the GEODESIC sounding rocket

NASA Astrophysics Data System (ADS)

Burchill, Johnathan Kerr

Low-energy (Ek ˜ 10-1--10 1 eV) ions comprise the bulk of Earth's ionosphere, and represent the initial stages of ion heating and outflow from Earth's auroral regions. The suprathermal ion imager (SII) is a fast (˜93 images/sec), compact, two-dimensional ion energy (0 < Ek < 20 eV) and direction-of-arrival analyzer designed to observe the energy distributions of these ions in detail, with emphasis on exploring small-scale (˜10--100 m) structure in the ionosphere. The SII was flown into an auroral substorm on the GEODESIC sounding rocket from Poker Flat, Alaska, on 26 February 2000. The technical element of this thesis deals with the development of a computer model of the SII, and techniques for extracting and interpreting physical quantities from the SII observations. Laboratory and in-flight calibrations demonstrate that the analyzer imaging capability departs from the ideal model. Nevertheless, the SII represents a technological step forward, and has yielded new scientific results. The scientific element of this thesis focuses on simultaneous observations of ion energy distributions and low-frequency plasma waves in the topside (500--1000 km) auroral ionosphere. GEODESIC encountered three types of plasma wave which have previously been associated with ion heating. However, heated ions were only observed in association with localized density depletions and wave enhancements known as lower-hybrid solitary structures (LHSS). Approximately 90% of the LHSS ion number density is comprised of the ambient isotropic sub-eV core population. The remaining 10% corresponds to transverse acceleration of ions (TAI) to within 5° transverse to the geomagnetic field and to mean energies up to 5--10 eV, consistent with previous findings. Contrary to previously published observations, the GEODESIC TAI is consistent with localized bulk heating of some of the ambient core. Ion heating was not observed in association with large-scale (>1 km) broadband extremely low frequency (BB ELF) wave enhancements. Similarly, no ion heating was detected in the presence of large amplitude, short perpendicular wavelength Alfven waves. Differences between low-frequency ion flow fluctuations and convection drift fluctuations can be explained only partially by ion polarization drift physics.

Timing the state of light with anomalous dispersion and a gradient echo memory

NASA Astrophysics Data System (ADS)

Clark, Jeremy B.

We study the effects of anomalous dispersion on the continuous-variable entanglement of EPR states (generated using four-wave mixing in 85 Rb) by sending one part of the state through a fast-light medium and measuring the state's quantum mutual information. We observe an advance in the maximum of the quantum mutual information between modes. In contrast, due to uncorrelated noise added by a small phase-insensitive gain, we do not observe any statistically significant advance in the leading edge of the mutual information. We also study the storage and retrieval of multiplexed optical signals in a Gradient Echo Memory (GEM) at relevant four-wave mixing frequencies in 85Rb. Temporal multiplexing capabilities are demonstrated by storing multiple classical images in the memory simultaneously and observing the expected first-in last-out order of recall without obvious cross-talk. We also develop a technique wherein selected portions of an image written into the memory can be spatially targeted for readout and erasure on demand. The effect of diffusion on the quality of the recalled images is characterized. Our results indicate that Raman-based atomic memories may serve as a flexible platform for the storage and retrieval of multiplexed optical signals.

Investigating the Role of Gravity Wave on Equatorial Ionospheric Irregularities using SABER and C/NOFS Satellites Observations

NASA Astrophysics Data System (ADS)

Nigussie, M.; Damtie, B.; Moldwin, M.; Yizengaw, E.; Tesema, F.; Tebabal, A.

2017-12-01

Theoretical simulations have shown that gravity wave (GW) seeded perturbations amplified by Rayleigh-Taylor Instability (RTI) results in ESF (equatorial spread F); however, there have been limited observational studies using simultaneous observations of GW and ionospheric parameters. In this paper, for the fist time, simultaneous atmospheric temperature perturbation profiles that are due to GWs obtained from Sounding of the Atmosphere using Broadband Emission Radiometry (SABER) on-board the TIMED satellite and equatorial in -situ ion density and vertical plasma drift velocity observations with and without ESF activity obtained from C/NOFS satellites are used to investigate the effect of GW on the generation of ESF. The horizontal and vertical wavelengths of ionospheric oscillations and GWs respectively have been estimated applying wavelet transforms. Cross wavelet analysis has also been applied between two closely observed profiles of temperature perturbations to estimate the horizontal wavelength of the GWs. Moreover, vertically propagating GWs that dissipate energy at the upper atmosphere have been investigated using spectral analysis compared with theoretical results. The analysis show that when the ion density shows strong post sunset irregularity between 20 and 24 LT, vertically upward drift velocities increase between 17 and 19 LT, but it becomes vertically downward when the ion density shows smooth variation. The horizontal wavelengths estimated from C/NOFS and SABER observations show excellent agreement when ion density observations show strong fluctuations; otherwise, they have poor agreement. It is also found that altitude profiles of potential energy of GW increases up to 90 km and then decreases significantly. It is found that the vertical wavelength of GW, corresponding to the dominant spectral power, ranges from about 7 km to 20 km regardless of the situation of the ionosphere; however, GWs with vertical wavelengths between 100 m to 1 km are found to be saturated between 90 and 110 km whether the ionosphere exhibits irregularity or not. The above results imply that ESF is due to the amplification of perturbations as a result of energy dissipation from GW with vertical wavelength 100 m to 1 km by the RTI that is mainly controlled by Pre-Reversal Enhancement of the zonal electric field.

Bifunctional metamaterials with simultaneous and independent manipulation of thermal and electric fields.

PubMed

Lan, Chuwen; Bi, Ke; Fu, Xiaojian; Li, Bo; Zhou, Ji

2016-10-03

Metamaterials offer a powerful way to manipulate a variety of physical fields ranging from wave fields (electromagnetic field, acoustic field, elastic wave, etc.), static fields (static magnetic field, static electric field) to diffusive fields (thermal field, diffusive mass). However, the relevant reports and studies are usually limited to a single physical field or functionality. In this study, we proposed and experimentally demonstrated a bifunctional metamaterial which could manipulate thermal and electric fields simultaneously and independently. Specifically, a composite with independently controllable thermal and electric conductivity was introduced, on the basis of which a bifunctional device capable of shielding thermal flux and concentrating electric current simultaneously was designed, fabricated and characterized. This work provides an encouraging example of metamaterials transcending their natural limitations, which offers a promising future in building a broad platform for the manipulation of multi-physics fields.

Multi-wavelength and High-resolution Observations of Solar Eruptive Activities

NASA Astrophysics Data System (ADS)

Shen, Y. D.

2014-09-01

In recent years, various solar eruptive activities have been observed in the solar atmosphere, such as solar flares, filament eruptions, jets, coronal mass ejections (CMEs), and magnetohydrodynamics (MHD) waves. Previous observations have indicated that solar magnetic field plays a dominant role in the processes of all kinds of solar activities. Since many large-scale solar eruptive activities can cause significant effects on the space environment of the Earth as well as the human life, studying and forecasting the solar activities are urgent tasks for us. In addition, the Sun is the nearest star to the Earth, so that people can directly observe and study it in detail. Hence, studying the Sun can also provide a reference to study other stars in the universe. This thesis focuses on the multi-wavelength and high-resolution observations of three types of solar eruptive activities: filament eruptions, coronal jets, and coronal MHD waves. By analyzing various observations taken by ground-based and space-borne instruments, we try to understand the inherent physical mechanisms, and construct models to interpret different kinds of solar eruptive activities. The triggering mechanism and the cause of a failed filament eruption are studied in Chapter 3, which indicates that the energy released in the flare is a key factor to the fate of the filament. Two successive filament eruptions are studied in Chapter 4, which indicates that the magnetic implosion could be the physical linkage between them, and the structures of coronal magnetic fields are important for producing sympathetic eruptions. A magnetic unwinding jet and a blowout jet are studied in Chapters 5 and 6, respectively. The former exhibits obvious radial expansion, which undergoes three distinct phases: the slow expansion phase, the fast expansion phase, and the steady phase. In addition, calculation indicates that the non-potential magnetic field in the jet can supply sufficient energy for producing the unwinding jet. The latter is associated with a simultaneous bubble-like and a jet-like CME. It is found that the jet-like CME is driven by the reconnection between the closed field and the ambient open field, while the bubble-like CME is associated with the mini-filament confined by the closed field. In Chapter 7, a quasi-periodic fast propagating (QFP) magnetosonic wave and the associated flare are studied. It is found that the wave and the flare have the same periods, suggesting their common origin. In addition, the leakage of photospheric p-mode oscillation to the corona is also an important source of QFP waves. Large-scale coronal waves are studied in Chapters 8 and 9. It is found that coronal waves can be observed in the low solar atmosphere like the top of the photosphere. Based on the analysis, we propose that large-scale coronal waves are fast magnetosonic or shock waves, which are driven by the expanding flanks of the associated CMEs. A short summary and unsolved problems are given in Chapter 10. Along with the fast development of many new solar telescopes, high quality observations will certainly help us to reveal the true physics behind various solar eruptive activities.

Neutral wind and density perturbations in the thermosphere created by gravity waves observed by the TIDDBIT sounder

NASA Astrophysics Data System (ADS)

Vadas, Sharon L.; Crowley, Geoff

2017-06-01

In this paper, we study the 10 traveling ionospheric disturbances (TIDs) observed at zobs˜283 km by the TIDDBIT ionospheric sounder on 30 October 2007 at 0400-0700 UT near Wallops Island, USA. These TIDs propagated northwest/northward and were previously found to be secondary gravity waves (GWs) from tropical storm Noel. An instrumented sounding rocket simultaneously measured a large neutral wind peak uH' with a similar azimuth at z ˜ 325 km. Using the measured TID amplitudes and wave vectors from the TIDDBIT system, together with ion-neutral theory, GW dissipative polarization relations and ray tracing, we determine the GW neutral horizontal wind and density perturbations as a function of altitude from 220 to 380 km. We find that there is a serious discrepancy between the GW dissipative theory and the observations unless the molecular viscosity, μ, decreases with altitude in the middle to upper thermosphere. Assuming that μ∝ρ¯q, where ρ¯ is the density, we find using GW dissipative theory that the GWs could have been observed at zobs and that one or more of the GWs could have caused the uH' wind peak at z≃325 km if q ˜ 0.67 for z≥220 km. This implies that the kinematic viscosity, ν=μ/ρ¯, increases less rapidly with altitude for z≥220 km: ν∝1/ρ¯0.33. This dependence makes sense because as ρ¯→0, the distance between molecules goes to infinity, which implies no molecular collisions and therefore no molecular viscosity μ.

Biomedical imaging with THz waves

NASA Astrophysics Data System (ADS)

Nguyen, Andrew

2010-03-01

We discuss biomedical imaging using radio waves operating in the terahertz (THz) range between 300 GHz to 3 THz. Particularly, we present the concept for two THz imaging systems. One system employs single antenna, transmitter and receiver operating over multi-THz-frequency simultaneously for sensing and imaging small areas of the human body or biological samples. Another system consists of multiple antennas, a transmitter, and multiple receivers operating over multi-THz-frequency capable of sensing and imaging simultaneously the whole body or large biological samples. Using THz waves for biomedical imaging promises unique and substantial medical benefits including extremely small medical devices, extraordinarily fine spatial resolution, and excellent contrast between images of diseased and healthy tissues. THz imaging is extremely attractive for detection of cancer in the early stages, sensing and imaging of tissues near the skin, and study of disease and its growth versus time.

Simultaneous determination of hydroquinone and catechol at gold nanoparticles mesoporous silica modified carbon paste electrode.

PubMed

Tashkhourian, J; Daneshi, M; Nami-Ana, F; Behbahani, M; Bagheri, A

2016-11-15

A new electrochemical sensor based on gold nanoparticles mesoporous silica modified carbon paste electrode (AuNPs-MPS) was developed for simultaneous determination of hydroquinone and catechol. Morphology and structure of the AuNPs-MPS were characterized by transmission electron microscopy, X-ray diffraction and Fourier transform infrared spectroscopy. The electrochemical behavior of hydroquinone and catechol were investigated using square wave voltammetry and the results indicate that the electrochemical responses are improved significantly at the modified electrode. The observed oxidative peaks separation of about 120mV made possible the simultaneous determination of hydroquinone and catechol in their binary-mixture. Under the optimized condition, a linear dynamic range of 10.0μM-1.0mM range for hydroquinone with the detection limit of 1.2μM and from 30.0μM-1.0mM for catechol with the detection limit of 1.1μM were obtained. The applicability of the method was demonstrated by the recovery studies of hydroquinone and catechol in spiked tap water samples. Copyright © 2016 Elsevier B.V. All rights reserved.

Diffuse esophageal spasm: has the term lost its relevance? Analysis of 217 cases.

PubMed

Tsuboi, K; Mittal, S K

2011-07-01

Diffuse esophageal spasm (DES) has been reported as a potential cause of dysphagia or chest pain; however, the patho-physiology of DES is unclear. The aim of this study was to examine the manometric correlates of dysphagia and chest pain in this patient population. All patients undergoing manometry at our institution are entered into a prospectively maintained database. After institutional review board approval, the database was queried to identify patients meeting criteria for DES (≥20% simultaneous waves with greater than 30 mm Hg pressure in the distal esophagus). The patient-reported symptoms and manometric data, along with the results of a 24-hour pH study (if done), were extracted for further analysis. Out of 4923 patients, 240 (4.9%) met the manometric criteria for DES. Of these, 217 patients had complete manometry data along with at least one reported symptom. Of the patients with DES, 159 (73.3%) had dysphagia or chest pain as a reported symptom. Patients reporting either dysphagia or chest pain had significantly higher lower esophageal sphincter (LES) pressure than patients without these symptoms (P= 0.007). Significant association was noted between reported dysphagia and percentage of simultaneous waves. Chest pain did not correlate with percent of simultaneous waves, mean amplitude of peristalsis, or 24-hour pH score. The origin of reported chest pain in patients with DES is not clear but may be related to higher LES pressure. Simultaneous waves were associated with reported dysphagia. Using current diagnostic criteria, the term DES has no clinical relevance. © 2010 Copyright the Authors. Journal compilation © 2010, Wiley Periodicals, Inc. and the International Society for Diseases of the Esophagus.

MHD oscillations observed in the solar photosphere with the Michelson Doppler Imager

NASA Astrophysics Data System (ADS)

Norton, A.; Ulrich, R. K.; Bogart, R. S.; Bush, R. I.; Hoeksema, J. T.

Magnetohydrodynamic oscillations are observed in the solar photosphere with the Michelson Doppler Imager (MDI). Images of solar surface velocity and magnetic field strength with 4'' spatial resolution and a 60 second temporal resolution are analyzed. A two dimensional gaussian aperture with a FWHM of 10'' is applied to the data in regions of sunspot, plage and quiet sun and the resulting averaged signal is returned each minute. Significant power is observed in the magnetic field oscillations with periods of five minutes. The effect of misregistration between MDI's left circularly polarized (LCP) and right circularly polarized (RCP) images has been investigated and is found not to be the cause of the observed magnetic oscillations. It is assumed that the large amplitude acoustic waves with 5 minute periods are the driving mechanism behind the magnetic oscillations. The nature of the magnetohydrodynamic oscillations are characterized by their phase relations with simultaneously observed solar surface velocity oscillations.

Influence of Pore-Fluid Pressure on Elastic Wave Velocity and Electrical Conductivity in Water-Saturated Rocks

NASA Astrophysics Data System (ADS)

Higuchi, A.; Watanabe, T.

2013-12-01

Pore-fluid pressure in seismogenic zones can play a key role in the occurrence of earthquakes (e.g., Sibson, 2009). Its evaluation via geophysical observations can lead to a good understanding of seismic activities. The evaluation requires a thorough understanding of the influence of the pore-fluid pressure on geophysical observables like seismic velocity and electrical conductivity. We have studied the influence of pore-fluid pressure on elastic wave velocity and electrical conductivity in water-saturated rocks. Fine grained (100-500μm) biotite granite (Aji, Kagawa pref., Japan) was used as rock samples. The density is 2.658-2.668 g/cm3, and the porosity 0.68-0.87%. The sample is composed of 52.8% plagioclase, 36.0% Quartz, 3.0% K-feldspar, 8.2% biotite. SEM images show that a lot of grain boundaries are open. Few intracrystalline cracks were observed. Following the method proposed by David and Zimmerman (2012), the distribution function of crack aspect ratio was evaluated from the pressure dependence of compressional and shear wave velocities in a dry sample. Cylindrical sample has dimensions of 25 mm in diameter and 30 mm in length, and saturated with 0.01 mol/l KCl aqueous solution. Compressional and shear wave velocities were measured with the pulse transmission technique (PZT transducers, f=2 MHz), and electrical conductivity the two-electrode method (Ag-AgCl electrodes, f=1 Hz-100 kHz). Simultaneous measurements of velocities and conductivity were made using a 200 MPa hydrostatic pressure vessel, in which confining and pore-fluid pressures can be separately controlled. The pore-fluid is electrically insulated from the metal work of the pressure vessel by using a newly designed plastic device (Watanabe and Higuchi, 2013). The confining pressure was progressively increased up to 25 MPa, while the pore-fluid pressure was kept at 0.1 MPa. It took five days or longer for the electrical conductivity to become stationary after increasing the confining pressure. Elastic wave velocities and electrical conductivity showed reproducibly contrasting changes for a small increase in the confining pressure. The elastic wave velocities increased only by 5% as the confining pressure increased from 0.1 MPa to 25 MPa, while the electrical conductivity decreased by an order of magnitude. Based on the SEM examinations, open grain boundaries work as cracks. The changes in elastic wave velocities and electrical conductivity must be caused by the closure of open grain boundaries. Most (˜80%) of the decrease in electrical conductivity occurred below the confining pressure of 5 MPa. As the confining pressure increased from 0.1 MPa to 5 MPa, cracks with the aspect ratio smaller than 7.5×10-5 were closed. The decrease in porosity was only 0.0005%. Such a small change in porosity caused a large change in electrical conductivity. The connectivity of fluid was maintained at the confining pressure of 25 MPa by cracks with the aspect ratio larger than 3.7×10-4. Simultaneous measurements have provided us a lot of information on the microstructure of fluid-bearing rocks.

Simultaneous anterior and posterior serosal mapping of gastric slow-wave dysrhythmias induced by vasopressin.

PubMed

Du, Peng; O'Grady, Gregory; Paskaranandavadivel, Niranchan; Tang, Shou-Jiang; Abell, Thomas; Cheng, Leo K

2016-06-06

What is the central question of this study? This study aimed to provide the first comparison of simultaneous high-resolution mapping of anterior and posterior gastric serosa over sustained periods. What is the main finding and its importance? Episodes of spontaneous gastric slow-wave dysrhythmias increased significantly following intravenous infusion of vasopressin compared with the baseline state. A number of persistent dysrhythmias were defined, including ectopic activation, conduction block, rotor, retrograde and collision/merger of wavefronts. Slow-wave dysrhythmias could occur either simultaneously or independently on the anterior and posterior gastric serosa, and interacted depending on activation-repolarization and frequency dynamics. High-resolution mapping enables mechanistic insights into gastric slow-wave dysrhythmias and is now achieving clinical translation. However, previous studies have focused mainly on dysrhythmias occurring on the anterior gastric wall. The present study simultaneously mapped the anterior and posterior gastric serosa during episodes of dysrhythmias induced by vasopressin to aid understanding of dysrhythmia initiation, maintenance and termination. High-resolution mapping (8 × 16 electrodes on each serosa; 20-74 cm 2 ) was performed in anaesthetized dogs. Baseline recordings (21 ± 8 min) were followed by intravenous infusion of vasopressin (0.1-0.5 IU ml -1 at 60-190 ml h -1 ) and further recordings (22 ± 13 min). Slow-wave activation maps, amplitudes, velocity, interval and frequency were calculated, and differences compared between baseline and postinfusion. All dogs demonstrated an increased prevalence of dysrhythmic events following infusion of vasopressin (17 versus 51%). Both amplitude and velocity demonstrated significant differences (baseline versus postinfusion: 3.6 versus 2.2 mV; 7.7 versus 6.5 mm s -1 ; P < 0.05 for both). Dysrhythmias occurred simultaneously or independently on the anterior and posterior serosa, and then interacted according to frequency dynamics. A number of persistent dysrhythmias were compared, including the following: ectopic activation (n = 2 animals), conduction block (n = 1), rotor (n = 2), retrograde (n = 3) and collision/merger of wavefronts (n = 2). We conclude that infusion of vasopressin induces gastric dysrhythmias, which occur across a heterogeneous range of frequencies and patterns. The results demonstrate that different classes of gastric dysrhythmias may arise simultaneously or independently in one or both surfaces of the serosa, then interact according to their relative frequencies. These results will help to inform interpretation of clinical dysrhythmia. © 2016 The Authors. Experimental Physiology © 2016 The Physiological Society.

Spiral wave classification using normalized compression distance: Towards atrial tissue spatiotemporal electrophysiological behavior characterization.

PubMed

Alagoz, Celal; Guez, Allon; Cohen, Andrew; Bullinga, John R

2015-08-01

Analysis of electrical activation patterns such as re-entries during atrial fibrillation (Afib) is crucial in understanding arrhythmic mechanisms and assessment of diagnostic measures. Spiral waves are a phenomena that provide intuitive basis for re-entries occurring in cardiac tissue. Distinct spiral wave behaviors such as stable spiral waves, meandering spiral waves, and spiral wave break-up may have distinct electrogram manifestations on a mapping catheter. Hence, it is desirable to have an automated classification of spiral wave behavior based on catheter recordings for a qualitative characterization of spatiotemporal electrophysiological activity on atrial tissue. In this study, we propose a method for classification of spatiotemporal characteristics of simulated atrial activation patterns in terms of distinct spiral wave behaviors during Afib using two different techniques: normalized compressed distance (NCD) and normalized FFT (NFFTD). We use a phenomenological model for cardiac electrical propagation to produce various simulated spiral wave behaviors on a 2D grid and labeled them as stable, meandering, or breakup. By mimicking commonly used catheter types, a star shaped and a circular shaped both of which do the local readings from atrial wall, monopolar and bipolar intracardiac electrograms are simulated. Virtual catheters are positioned at different locations on the grid. The classification performance for different catheter locations, types and for monopolar or bipolar readings were also compared. We observed that the performance for each case differed slightly. However, we found that NCD performance is superior to NFFTD. Through the simulation study, we showed the theoretical validation of the proposed method. Our findings suggest that a qualitative wavefront activation pattern can be assessed during Afib without the need for highly invasive mapping techniques such as multisite simultaneous electrogram recordings.

Selections from 2016: Primordial Black Holes as Dark Matter

NASA Astrophysics Data System (ADS)

Kohler, Susanna

2016-12-01

Editors note:In these last two weeks of 2016, well be looking at a few selections that we havent yet discussed on AAS Nova from among the most-downloaded paperspublished in AAS journals this year. The usual posting schedule will resume after the AAS winter meeting.LIGO Gravitational Wave Detection, Primordial Black Holes, and the Near-IR Cosmic Infrared Background AnisotropiesPublished May2016Main takeaway:A study by Alexander Kashlinsky (NASA Goddard SFC) proposes that the cold dark matter that makes up the majority of the universes matter may be made of black holes. These black holes, Kashlinsky suggests, are primordial: they collapsed directly from dense regions of the universe soon after the Big Bang.Why its interesting:This model would simultaneously explain several observations. In particular, we see similarities in patterns between the cosmic infrared and X-ray backgrounds. This would make sense if accretion onto primordial black holes in halos produced the X-ray background in the same regions where the first stars also formed, producing the infrared background.What this means for current events:In Kashlinskys model, primordial black holes would occasionally form binary pairs and eventually spiral in and merge. The release of energy from such an event would then be observable by gravitational-wave detectors. Could the gravitational-wave signal that LIGO detected last year have been two primordial black holes merging? More observations will be needed to find out.CitationA. Kashlinsky 2016 ApJL 823 L25. doi:10.3847/2041-8205/823/2/L25

The lower ionosphere response to its disturbances by powerful radio waves

NASA Astrophysics Data System (ADS)

Bakhmetieva, N. V.; Frolov, V. L.; Vyakhirev, V. D.; Kalinina, E. E.; Akchurin, A. D.; Zykov, E. Yu.

2018-04-01

The paper presents data from some campaigns at Sura heating facility in 2011-1016. The experiments on probing of the artificial disturbed region of the lower ionosphere were carried out at two observation sites. One of them was located near Vasil'sursk 1 km from Sura facility (56.1°N; 46.1°E) and the other site was located at the Observatory (55.85°N; 48.8°E) of Kazan State University, 170 km to the East. Investigation of the features of the disturbed region of the lower ionosphere based on its diagnostics by the methods of the vertical sounding and oblique backscattering is the main goal of this paper. Ionosphere disturbance was fulfilled by the effect of the powerful radio wave of the ordinary or extraordinary polarization emitted by transmitters of the Sura facility with effective radiated power ERP = 50-120 MW at the frequency of 4.3, 4.7 and 5.6 MHz. Pumping waves were emitted with period from 30 s to 15 min. The disturbed region of the ionosphere in Vasil'sursk was probed by the vertical sounding technique using the partial reflexion radar at the frequency of 2.95 and 4.7 MHz. For the oblique sounding of the disturbed region the modified ionosonde Cyclon-M, operating at ten frequencies from 2.01 to 6.51 MHz was used at the Observatory site. On many heating sessions simultaneous variations of the probing partial reflection signals in Vasil'sursk and backscattered signals in Observatory were observed at the height at 40-100 km below the reflection height of the pumping wave. These observations were correlated with the pumping periods of the Sura facility. Possible mechanisms of the appearance of the disturbance in the lower ionosphere and its effect on the probing radio waves are discussed.

Transverse Oscillations of Coronal Loops

NASA Astrophysics Data System (ADS)

Ruderman, Michael S.; Erdélyi, Robert

2009-12-01

On 14 July 1998 TRACE observed transverse oscillations of a coronal loop generated by an external disturbance most probably caused by a solar flare. These oscillations were interpreted as standing fast kink waves in a magnetic flux tube. Firstly, in this review we embark on the discussion of the theory of waves and oscillations in a homogeneous straight magnetic cylinder with the particular emphasis on fast kink waves. Next, we consider the effects of stratification, loop expansion, loop curvature, non-circular cross-section, loop shape and magnetic twist. An important property of observed transverse coronal loop oscillations is their fast damping. We briefly review the different mechanisms suggested for explaining the rapid damping phenomenon. After that we concentrate on damping due to resonant absorption. We describe the latest analytical results obtained with the use of thin transition layer approximation, and then compare these results with numerical findings obtained for arbitrary density variation inside the flux tube. Very often collective oscillations of an array of coronal magnetic loops are observed. It is natural to start studying this phenomenon from the system of two coronal loops. We describe very recent analytical and numerical results of studying collective oscillations of two parallel homogeneous coronal loops. The implication of the theoretical results for coronal seismology is briefly discussed. We describe the estimates of magnetic field magnitude obtained from the observed fundamental frequency of oscillations, and the estimates of the coronal scale height obtained using the simultaneous observations of the fundamental frequency and the frequency of the first overtone of kink oscillations. In the last part of the review we summarise the most outstanding and acute problems in the theory of the coronal loop transverse oscillations.

Testing the effectiveness of monolayers under wind and wave conditions.

PubMed

Palada, C; Schouten, P; Lemckert, C

2012-01-01

Monolayers are highly desirable for their evaporation reducing capabilities due to their relatively minimal cost and ease of application. Despite these positive attributes, monolayers have consistently failed to perform effectively due to the harsh wind and wave conditions prevalent across real-world water reserves. An exhaustive and consistent study testing the influence of wind and wave combinations on monolayer performance has yet to be presented in the literature. To remedy this, the effect of simultaneous wind and wave conditions on a benchmark high-performance monolayer (octadecanol suspension, CH(3)(CH(2))(16)CH(2)OH) has been analysed. Subjected only to waves, the monolayer remained intact due to its innate ability to compress and expand. However, the constant simultaneous application of wind and waves caused the monolayer to break up and gather down-wind where it volatilised over time. At wind speeds above 1.3 m s(-1) the monolayer was completely ineffective. For wind speeds below this threshold, the monolayer had an influence on the evaporation rate dependent on wind speed. From these results a series of application protocols can now be developed for the optimised deployment of monolayers in real-world water reserves. This will be of interest to private, commercial and government organisations involved in the storage and management of water resources.

Location of γ-ray Flare Emission in the Jet of the BL Lacertae Object OJ287 More than 14 pc from the Central Engine

NASA Astrophysics Data System (ADS)

Agudo, Iván; Jorstad, Svetlana G.; Marscher, Alan P.; Larionov, Valeri M.; Gómez, José L.; Lähteenmäki, Anne; Gurwell, Mark; Smith, Paul S.; Wiesemeyer, Helmut; Thum, Clemens; Heidt, Jochen; Blinov, Dmitriy A.; D'Arcangelo, Francesca D.; Hagen-Thorn, Vladimir A.; Morozova, Daria A.; Nieppola, Elina; Roca-Sogorb, Mar; Schmidt, Gary D.; Taylor, Brian; Tornikoski, Merja; Troitsky, Ivan S.

2011-01-01

We combine time-dependent multi-waveband flux and linear polarization observations with submilliarcsecond-scale polarimetric images at λ = 7 mm of the BL Lacertae type blazar OJ287 to locate the γ-ray emission in prominent flares in the jet of the source >14 pc from the central engine. We demonstrate a highly significant correlation between the strongest γ-ray and millimeter-wave flares through Monte Carlo simulations. The two reported γ-ray peaks occurred near the beginning of two major millimeter-wave outbursts, each of which is associated with a linear polarization maximum at millimeter wavelengths. Our very long baseline array observations indicate that the two millimeter-wave flares originated in the second of two features in the jet that are separated by >14 pc. The simultaneity of the peak of the higher-amplitude γ-ray flare and the maximum in polarization of the second jet feature implies that the γ-ray and millimeter-wave flares are cospatial and occur >14 pc from the central engine. We also associate two optical flares, accompanied by sharp polarization peaks, with the two γ-ray events. The multi-waveband behavior is most easily explained if the γ-rays arise from synchrotron self-Compton scattering of optical photons from the flares. We propose that flares are triggered by interaction of moving plasma blobs with a standing shock. The γ-ray and optical emission is quenched by inverse Compton losses as synchrotron photons from the newly shocked plasma cross the emission region. The millimeter-wave polarization is high at the onset of a flare, but decreases as the electrons emitting at these wavelengths penetrate less polarized regions.

Solitary waves in dusty plasmas with weak relativistic effects in electrons and ions

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kalita, B. C., E-mail: bckalita123@gmail.com; Choudhury, M., E-mail: choudhurymamani@gmail.com

2016-10-15

Two distinct classes of dust ion acoustic (DIA) solitary waves based on relativistic ions and electrons, dust charge Z{sub d} and ion-to-dust mass ratio Q’ = m{sub i}/m{sub d} are established in this model of multicomponent plasmas. At the increase of mass ratio Q’ due to increase of relativistic ion mass and accumulation of more negative dust charges into the plasma causing decrease of dust mass, relativistic DIA solitons of negative potentials are abundantly observed. Of course, relativistic compressive DIA solitons are also found to exist simultaneously. Further, the decrease of temperature inherent in the speed of light c causesmore » the nonlinear term to be more active that increases the amplitude of the rarefactive solitons and dampens the growth of compressive solitons for relatively low and high mass ratio Q’, respectively. The impact of higher initial streaming of the massive ions is observed to identify the point of maximum dust density N{sub d} to yield rarefactive relativistic solitons of maximum amplitude.« less

Observations of enhanced ion line frequency spectrum during Arecibo ionospheric modification experiment

NASA Technical Reports Server (NTRS)

Hagfors, T.; Zamlutti, C. J.

1974-01-01

The Arecibo 430 MHz incoherent scatter radar (ISR) was used to monitor the effects of modifying the ionosphere by a high power HF transmitter feeding the 305 m reflector antenna. When in the ordinary magnetoionic mode parametric instabilities develop in the ionosphere near the reflection level. Manifestations of these instabilities are the strong enhancement of Langmuir oscillations in the direction of the ISR beam at a wavelength of 35 cm and the simultaneous much weaker enhancement of ion oscillations in that direction. The spectral analysis of the enhanced peak with a height resolution of 2.4 km shows that the ionic mode enhancement most often has a double humped frequency spectrum corresponding to up- and down-going ion acoustic waves. The shape of the frequency spectrum is interpreted in terms of a stable oscillation which is driven by a secondary electrostatic field caused by nonlinear interaction of Langmuir waves within a cone centered on the magnetic field and by the scattering of the pump field on stable Langmuir waves travelling along the direction of the ISR.

Theory of finite disturbances in a centrifugal compression system with a vaneless radial diffuser

NASA Technical Reports Server (NTRS)

Moore, F. K.

1990-01-01

A previous small perturbation analysis of circumferential waves in circumferential compression systems, assuming inviscid flow, is shown to be consistent with observations that narrow diffusers are more stable than wide ones, when boundary layer displacement effect is included. The Moore-Greitzer analysis for finite strength transients containing both surge and rotating stall in axial machines is adapted for a centrifugal compression system. Under certain assumptions, and except for a new second order swirl, the diffuser velocity field, including resonant singularities, can be carried over from the previous inviscid linear analysis. Nonlinear transient equations are derived and applied in a simple example to show that throttling through a resonant value of flow coefficient must occur in a sudden surge-like drop, accompanied by a transient rotating wave. This inner solution is superseded by an outer surge response on a longer time scale. Surge may occur purely as result of circumferential wave resonance. Numerical results are shown for various parametric choices relating to throttle schedule and the characteristic slope. A number of circumferential modes considered simultaneously is briefly discussed.

Tracking silica in Earth's upper mantle using new sound velocity data for coesite to 5.8 GPa and 1073 K

NASA Astrophysics Data System (ADS)

Chen, Ting; Liebermann, Robert C.; Zou, Yongtao; Li, Ying; Qi, Xintong; Li, Baosheng

2017-08-01

The compressional and shear wave velocities for coesite have been measured simultaneously up to 5.8 GPa and 1073 K by ultrasonic interferometry for the first time. The shear wave velocity decreases with pressure along all isotherms. The resulting contrasts between coesite and stishovite reach 34% and 45% for P and S wave velocities, respectively, and 64% and 75% for their impedance at mantle conditions. The large velocity and impedance contrasts across coesite-stishovite transition imply that to generate the velocity and impedance contrasts observed at the X-discontinuity, only a small amount of silica would be required. The velocity jump dependences on silica, d(lnVP)/d(SiO2) = 0.38 (wt %)-1 and d(lnVS)/d(SiO2) = 0.52 (wt %)-1, are utilized to place constraints on the amount of silica in the upper mantle and provide a geophysical approach to track mantle eclogite materials and ancient subducted oceanic slabs.

Tracking silica in Earth's upper mantle using new sound velocity data for coesite to 5.8 GPa and 1073 K: Tracking Silica in Earth's Upper Mantle

DOE Office of Scientific and Technical Information (OSTI.GOV)

Chen, Ting; Liebermann, Robert C.; Zou, Yongtao

The compressional and shear wave velocities for coesite have been measured simultaneously up to 5.8 GPa and 1073 K by ultrasonic interferometry for the first time. The shear wave velocity decreases with pressure along all isotherms. The resulting contrasts between coesite and stishovite reach ~34% and ~45% for P and S wave velocities, respectively, and ~64% and ~75% for their impedance at mantle conditions. The large velocity and impedance contrasts across coesite-stishovite transition imply that to generate the velocity and impedance contrasts observed at the X-discontinuity, only a small amount of silica would be required. The velocity jump dependences onmore » silica, d(lnVP)/d(SiO2) = 0.38 (wt %)-1 and d(lnVS)/d(SiO2) = 0.52 (wt %)-1, are utilized to place constraints on the amount of silica in the upper mantle and provide a geophysical approach to track mantle eclogite materials and ancient subducted oceanic slabs.« less

Full-wave and half-wave rectification in second-order motion perception

NASA Technical Reports Server (NTRS)

Solomon, J. A.; Sperling, G.

1994-01-01

Microbalanced stimuli are dynamic displays which do not stimulate motion mechanisms that apply standard (Fourier-energy or autocorrelational) motion analysis directly to the visual signal. In order to extract motion information from microbalanced stimuli, Chubb and Sperling [(1988) Journal of the Optical Society of America, 5, 1986-2006] proposed that the human visual system performs a rectifying transformation on the visual signal prior to standard motion analysis. The current research employs two novel types of microbalanced stimuli: half-wave stimuli preserve motion information following half-wave rectification (with a threshold) but lose motion information following full-wave rectification; full-wave stimuli preserve motion information following full-wave rectification but lose motion information following half-wave rectification. Additionally, Fourier stimuli, ordinary square-wave gratings, were used to stimulate standard motion mechanisms. Psychometric functions (direction discrimination vs stimulus contrast) were obtained for each type of stimulus when presented alone, and when masked by each of the other stimuli (presented as moving masks and also as nonmoving, counterphase-flickering masks). RESULTS: given sufficient contrast, all three types of stimulus convey motion. However, only one-third of the population can perceive the motion of the half-wave stimulus. Observers are able to process the motion information contained in the Fourier stimulus slightly more efficiently than the information in the full-wave stimulus but are much less efficient in processing half-wave motion information. Moving masks are more effective than counterphase masks at hampering direction discrimination, indicating that some of the masking effect is interference between motion mechanisms, and some occurs at earlier stages. When either full-wave and Fourier or half-wave and Fourier gratings are presented simultaneously, there is a wide range of relative contrasts within which the motion directions of both gratings are easily determinable. Conversely, when half-wave and full-wave gratings are combined, the direction of only one of these gratings can be determined with high accuracy. CONCLUSIONS: the results indicate that three motion computations are carried out, any two in parallel: one standard ("first order") and two non-Fourier ("second-order") computations that employ full-wave and half-wave rectification.

Sedimentary structures formed under water surface waves: examples from a sediment-laden flash flood observed by remote camer

NASA Astrophysics Data System (ADS)

Froude, Melanie; Alexander, Jan; Cole, Paul; Barclay, Jenni

2014-05-01

On 13-14 October 2012, Tropical Storm Rafael triggered sediment-laden flash floods in the Belham Valley on Montserrat, West Indies. Rainfall was continuous for ~38 hours and intensity peaked at 48 mm/hr. Flow was strongly unsteady, turbulent with sediment concentrations varying up to hyperconcentrated. Time-lapse images captured at >1 frame per second by remote camera overlooking a surveyed valley section show the development of trains of water surface waves at multiple channel locations during different flow stages. Waves grew and diminished in height and remained stationary or migrated upstream. Trains of waves persisted for <5 minutes, until a single wave broke, sometimes initiating the breaking of adjacent waves within the train. Channel-wide surges (bores) propagating downstream with distinct turbulent flow fronts, were observed at irregular intervals during and up to 7 hours after peak stage. These bores are mechanically similar to breaking front tidal bores and arid flood bores, and resulted in a sudden increase in flow depth and velocity. When a bore front came into close proximity (within ~10 m) upstream of a train of water surface waves, the waves appeared to break simultaneously generating a localised surge of water upstream, that was covered by the bore travelling downstream. Those trains in which waves did not break during the passage of a bore temporarily reduced in height. In both cases, water surface waves reformed immediately after the surge in the same location. Deposits from the event, were examined in <4 m deep trenches ~0.5 km downstream of the remote camera. These contained laterally extensive lenticular and sheet-like units comprised of varying admixtures of sand and gravel that are attributed to antidunes, and associated transitions from upper-stage-plane-beds. Some of the structures are organised within concave upward sequences which contain downflow shifts between foreset and backset laminae; interpreted as trough fills from chute-and-pools or water surface wave breaking. At least 90% of the deposit is interpreted upper flow regime origin. The sequence, geometry and lamina-scale texture of the sedimentary structures will be discussed with reference to remote camera images of rapidly varying, unsteady and pulsatory flow behaviour.

Characteristics of medium- and large-scale TIDs over Japan derived from OI 630-nm nightglow observation

NASA Astrophysics Data System (ADS)

Kubota, M.; Fukunishi, H.; Okano, S.

2001-07-01

A new optical instrument for studying upper atmospheric dynamics, called the Multicolor All-sky Imaging System (MAIS), has been developed. The MAIS can obtain all-sky images of airglow emission at two different wavelengths simultaneously with a time resolution of several minutes. Since December 1991, imaging observations with the MAIS have been conducted at the Zao observatory (38.09°N, 140.56°E). From these observations, two interesting events with wave structures have been detected in OI 630-nm nightglow images. The first event was observed on the night of June 2/3, 1992 during a geomagnetically quiet period. Simultaneous data of ionospheric parameters showed that they are caused by propagation of the medium-scale traveling ionospheric disturbance (TID). Phase velocity and horizontal wavelength determined from the image data are 45-100 m/s and ~280 km, and the propagation direction is south-westward. The second event was observed on the night of February 27/28, 1992 during a geomagnetic storm. It is found that a large enhancement of OI 630-nm emission is caused by a propagation of the large-scale TID. Meridional components of phase velocities and wavelengths determined from ionospheric data are 305-695 m/s (southward) and 930-5250 km. The source of this large-scale TID appears to be auroral processes at high latitudes.

Human seizures couple across spatial scales through travelling wave dynamics

NASA Astrophysics Data System (ADS)

Martinet, L.-E.; Fiddyment, G.; Madsen, J. R.; Eskandar, E. N.; Truccolo, W.; Eden, U. T.; Cash, S. S.; Kramer, M. A.

2017-04-01

Epilepsy--the propensity toward recurrent, unprovoked seizures--is a devastating disease affecting 65 million people worldwide. Understanding and treating this disease remains a challenge, as seizures manifest through mechanisms and features that span spatial and temporal scales. Here we address this challenge through the analysis and modelling of human brain voltage activity recorded simultaneously across microscopic and macroscopic spatial scales. We show that during seizure large-scale neural populations spanning centimetres of cortex coordinate with small neural groups spanning cortical columns, and provide evidence that rapidly propagating waves of activity underlie this increased inter-scale coupling. We develop a corresponding computational model to propose specific mechanisms--namely, the effects of an increased extracellular potassium concentration diffusing in space--that support the observed spatiotemporal dynamics. Understanding the multi-scale, spatiotemporal dynamics of human seizures--and connecting these dynamics to specific biological mechanisms--promises new insights to treat this devastating disease.

Coherence properties of spontaneous parametric down-conversion pumped by a multi-mode cw diode laser.

PubMed

Kwon, Osung; Ra, Young-Sik; Kim, Yoon-Ho

2009-07-20

Coherence properties of the photon pair generated via spontaneous parametric down-conversion pumped by a multi-mode cw diode laser are studied with a Mach-Zehnder interferometer. Each photon of the pair enters a different input port of the interferometer and the biphoton coherence properties are studied with a two-photon detector placed at one output port. When the photon pair simultaneously enters the interferometer, periodic recurrence of the biphoton de Broglie wave packet is observed, closely resembling the coherence properties of the pump diode laser. With non-zero delays between the photons at the input ports, biphoton interference exhibits the same periodic recurrence but the wave packet shapes are shown to be dependent on both the input delay as well as the interferometer delay. These properties could be useful for building engineered entangled photon sources based on diode laser-pumped spontaneous parametric down-conversion.

High-order Stokes generation in a KTP Raman laser pumped by a passively Q-switched ND:YLF laser

NASA Astrophysics Data System (ADS)

Wang, Maorong; Zhong, Kai; Mei, Jialin; Guo, Shibei; Xu, Degang; Yao, Jianquan

2015-12-01

High-order Stokes wave was observed in an x-cut KTP crystal based on stimulated Raman scattering (SRS) pumped by a passively Q-switched Nd:YLF laser with a Cr4+:YAG saturable absorber. Output spectra including the fundamental wave at 1047 nm and six Stokes wavelengths at 1077 nm, 1110 nm, 1130 nm, 1143 nm, 1164 nm, 1180 nm based on two Raman frequency shift at 267.4 cm-1 and 693.0 cm-1 were obtained simultaneously. We also detected green light generation with output power of 12 mW from self frequency mixing in the KTP crystal. The maximum total output power reached 452 mW at the repetition frequency of 8.1 kHz, corresponding to the optical-to-optical conversion efficiency of 4.61% and pump-to-Raman conversion efficiency of 3.6%.

Wide-Band Heterodyne Submillimetre Wave Spectrometer for Planetary Atmospheres

NASA Technical Reports Server (NTRS)

Schlecht, Erich

2010-01-01

We present calculations and measurements on a passive submillimetre wave spectroscopic sounder to gather data on the thermal structure, dynamics and composition of the upper atmosphere of a planet, e.g. the stratosphere of Jupiter, or the entire thickness of the atmosphere of Mars. The instrument will be capable of measuring wind speeds, temperature, pressure, and key constituent concentrations in the stratosphere of the target planet. This instrument consists of a Schottky diode based front end and a digital back-end spectrometer. It differs from previous space-based spectrometers in its combination of wide tunability (520-590 GHz), and rapid frequency switching between widely spaced lines within that range. This will enable near simultaneous observation of multiple lines, which is critical to the reconstruction of atmospheric pressure and density versus altitude profiles. At the same time frequency accuracy must be high to enable wind speeds to be determined directly by measurement of the line's Doppler shift.

LASE Observations of Interactions Between African Easterly Waves and the Saharan Air Layer

NASA Technical Reports Server (NTRS)

Ismail, Syed; Ferrare, Richard; Browell, Edward; Kooi, Susan; Biswas, Mrinal; Krishnamurti, T. N.; Notari, Anthony; Heymsfield, Andrew; Butler, Carolyn; Burton, Sharon;

Further evaluation of waves and turbulence encountered by the Galileo Probe during descent in Jupiter's atmosphere

NASA Astrophysics Data System (ADS)

Seiff, Alvin; Kirk, Donn B.; Mihalov, John; Knight, Tony C. D.

Data from the Galileo Probe in Jupiter descent indicated descent velocity oscillations as large as ±5 m/s on a height scale of a few km, which suggested gravity waves in the atmosphere between 4 and 20 bars (Seiff et al., 1998), an important observation for atmospheric stability and dynamics. But we now find these velocity fluctuations to be inconsistent with simultaneous measurements of mean accelerations, which were relatively steady. This conflict is resolved in favor of the accelerometers. The velocity fluctuations can be explained from digital uncertainties in the slow rate of pressure rise. However, the accelerometers did record higher frequency perturbations of up to 0.1g. Attributed to turbulence, these imply turbulent velocities from 0.3 to 5 m/s at scales of 10 to 40 m. However, they were at least partly a result of unsteady parachute aerodynamics.

Measurements of vector fields with diode array

NASA Technical Reports Server (NTRS)

Wiehr, E. J.; Scholiers, W.

1985-01-01

A polarimeter was designed for high spatial and spectral resolution. It consists of a quarter-wave plate alternately operating in two positions for Stoke-V measurements and an additional quarter-wave plate for Stokes-U and -Q measurements. The spatial range covers 75 arcsec, the spectral window of about 1.8 a allows the simultaneous observations of neighboring lines. The block diagram of the data processing and acquisition system consists of five memories each one having a capacity of 10 to the 4th power 16-bit words. The total time to acquire profiles of Stokes parameters can be chosen by selecting the number of successive measurements added in the memories, each individual measurement corresponding to an integration time of 0.5 sec. Typical values range between 2 and 60 sec depending on the brightness of the structure, the amount of polarization and a compromise between desired signal-to-noise ratio and spatial resolution.

All-optical simultaneous multichannel quadrature phase shift keying signal regeneration based on phase-sensitive amplification

NASA Astrophysics Data System (ADS)

Wang, Hongxiang; Wang, Qi; Bai, Lin; Ji, Yuefeng

2018-01-01

A scheme is proposed to realize the all-optical phase regeneration of four-channel quadrature phase shift keying (QPSK) signal based on phase-sensitive amplification. By utilizing conjugate pump and common pump in a highly nonlinear optical fiber, degenerate four-wave mixing process is observed, and QPSK signals are regenerated. The number of waves is reduced to decrease the cross talk caused by undesired nonlinear interaction during the coherent superposition process. In addition, to avoid the effect of overlapping frequency, frequency spans between pumps and signals are set to be nonintegral multiples. Optical signal-to-noise ratio improvement is validated by bit error rate measurements. Compared with single-channel regeneration, multichannel regeneration brings 0.4-dB OSNR penalty when the value of BER is 10-3, which shows the cross talk in regeneration process is negligible.

The TolTEC Camera for the LMT Telescope

NASA Astrophysics Data System (ADS)

Bryan, Sean

2018-01-01

TolTEC is a new camera being built for the 50-meter Large Millimeter-wave Telescope (LMT) on Sierra Negra in Puebla, Mexico. The instrument will discover and characterize distant galaxies by detecting the thermal emission of dust heated by starlight. The polarimetric capabilities of the camera will measure magnetic fields in star-forming regions in the Milky Way. The optical design of the camera uses mirrors, lenses, and dichroics to simultaneously couple a 4 arcminute diameter field of view onto three single-band focal planes at 150, 220, and 280 GHz. The 7000 polarization-selective detectors are single-band horn-coupled LEKID detectors fabricated at NIST. A rotating half wave plate operates at ambient temperature to modulate the polarized signal. In addition to the galactic and extragalactic surveys already planned, TolTEC installed at the LMT will provide open observing time to the community.

The Impact of a Deepwater Wave on a Wall with Finite Vertical Extent

NASA Astrophysics Data System (ADS)

Wang, An; Duncan, James H.

2016-11-01

The impact of a dispersively focused 2D plunging breaker (average wave frequency 1.15 Hz) on a 2D wall that is 45 cm high and 30 cm thick is studied experimentally. The temporal evolution of the water surface profile upstream of the wall is measured with a cinematic LIF technique using frame rates up to 4,500 Hz. Impact pressures on the wall are measured simultaneously at sample rates up to 900 kHz. The wall is located horizontally 6.41 m from the wave maker in all cases and the submergence of the bottom surface of the wall is varied. It is found that the impact behavior varies dramatically with the wall submergence. When the bottom is submerged by 13.3 cm, a flip-through impact occurs. In this case, the impact evolves without wave breaking and a vertical jet is formed. When the wall is submerged by less than 4.5 cm, small-amplitude components in the wave packet interact with the bottom of the wall before the main crest arrives. Ripples reflected during this interaction modify the behavior of the incoming breaker significantly. When the bottom of the wall is located sufficiently high above the mean water level, the first interaction occurs when the undisturbed wave crest collides with the wall. The highest pressures are observed in this case. The support of the Office of Naval Research is gratefully acknowledged.

Radiation from an electron beam in magnetized plasma: excitation of a whistler mode wave packet by interacting, higher-frequency, electrostatic-wave eigenmodes

NASA Astrophysics Data System (ADS)

Brenning, N.; Axnäs, I.; Koepke, M.; Raadu, M. A.; Tennfors, E.

2017-12-01

Infrequent, bursty, electromagnetic, whistler-mode wave packets, excited spontaneously in the laboratory by an electron beam from a hot cathode, appear transiently, each with a time duration τ around ∼1 μs. The wave packets have a center frequency f W that is broadly distributed in the range 7 MHz < f W < 40 MHz. They are excited in a region with separate electrostatic (es) plasma oscillations at values of f hf, 200 MHz < f hf < 500 MHz, that are hypothesized to match eigenmode frequencies of an axially localized hf es field in a well-defined region attached to the cathode. Features of these es-eigenmodes that are studied include: the mode competition at times of transitions from one dominating es-eigenmode to another, the amplitude and spectral distribution of simultaneously occurring es-eigenmodes that do not lead to a transition, and the correlation of these features with the excitation of whistler mode waves. It is concluded that transient coupling of es-eigenmode pairs at f hf such that | {{{f}}}1,{{h}{{f}}}-{{{f}}}2,{{h}{{f}}}| = {f}{{W}}< {f}{{g}{{e}}} can explain both the transient lifetime and the frequency spectra of the whistler-mode wave packets (f W) as observed in lab. The generalization of the results to bursty whistler-mode excitation in space from electron beams, created on the high potential side of double layers, is discussed.

Electromechanical vortex filaments during cardiac fibrillation

NASA Astrophysics Data System (ADS)

Christoph, J.; Chebbok, M.; Richter, C.; Schröder-Schetelig, J.; Bittihn, P.; Stein, S.; Uzelac, I.; Fenton, F. H.; Hasenfuß, G.; Gilmour, R. F., Jr.; Luther, S.

2018-03-01

The self-organized dynamics of vortex-like rotating waves, which are also known as scroll waves, are the basis of the formation of complex spatiotemporal patterns in many excitable chemical and biological systems. In the heart, filament-like phase singularities that are associated with three-dimensional scroll waves are considered to be the organizing centres of life-threatening cardiac arrhythmias. The mechanisms that underlie the onset, maintenance and control of electromechanical turbulence in the heart are inherently three-dimensional phenomena. However, it has not previously been possible to visualize the three-dimensional spatiotemporal dynamics of scroll waves inside cardiac tissues. Here we show that three-dimensional mechanical scroll waves and filament-like phase singularities can be observed deep inside the contracting heart wall using high-resolution four-dimensional ultrasound-based strain imaging. We found that mechanical phase singularities co-exist with electrical phase singularities during cardiac fibrillation. We investigated the dynamics of electrical and mechanical phase singularities by simultaneously measuring the membrane potential, intracellular calcium concentration and mechanical contractions of the heart. We show that cardiac fibrillation can be characterized using the three-dimensional spatiotemporal dynamics of mechanical phase singularities, which arise inside the fibrillating contracting ventricular wall. We demonstrate that electrical and mechanical phase singularities show complex interactions and we characterize their dynamics in terms of trajectories, topological charge and lifetime. We anticipate that our findings will provide novel perspectives for non-invasive diagnostic imaging and therapeutic applications.

Ion absorption of the high harmonic fast wave in the National Spherical Torus Experiment

NASA Astrophysics Data System (ADS)

Rosenberg, Adam Lewis

Ion absorption of the high harmonic fast wave in a spherical torus is of critical importance to assessing the viability of the wave as a means of heating and driving current. Analysis of recent NSTX shots has revealed that under some conditions when neutral beam and RF power are injected into the plasma simultaneously, a fast ion population with energy above the beam injection energy is sustained by the wave. In agreement with modeling, these experiments find the RF-induced fast ion tail strength and neutron rate at lower B-fields to be less enhanced, likely due to a larger β profile, which promotes greater off-axis absorption where the fast ion population is small. Ion loss codes find the increased loss fraction with decreased B insufficient to account for the changes in tail strength, providing further evidence that this is an RF interaction effect. Though greater ion absorption is predicted with lower k∥, surprisingly little variation in the tail was observed, along with a neutron rate enhancement with higher k∥. Data from the neutral particle analyzer, neutron detectors, x-ray crystal spectrometer, and Thomson scattering is presented, along with results from the TRANSP transport analysis code, ray-tracing codes HPRT and CURRAY, full-wave code and AORSA, quasilinear code CQL3D, and ion loss codes EIGOL and CONBEAM.

Failure Wave in DEDF and Soda-Lime Glass during Rod Impact

DOE Office of Scientific and Technical Information (OSTI.GOV)

Orphal, D. L.; Behner, Th.; Hohler, V.

2006-07-28

Investigations of glass by planar, and classical and symmetric Taylor impact experiments reveal that failure wave velocity vF depends on impact velocity, geometry, and type of glass. vF typically increases with impact velocity vP to between cS and cL or to {radical}2cS (shear and longitudinal wave velocity). This paper reports initial results of an investigation of failure waves associated with gold rod impact on high-density (DEDF) glass and soda-lime glass. Data are obtained by visualizing simultaneously the failure propagation in the glass with a high-speed camera and the rod penetration velocity u with flash radiography. Results for DEDF glass aremore » reported for vP between 1.2 and 2.0 km/s, those for soda-lime glass with vP {approx_equal}1.3 km/s. It is shown that vF > u, and that in the case of DEDF glass vF/u decreases from ; 1.38 to 1.13 with increasing vp. In addition, several Taylor tests were performed. For both DEDF and soda-lime glass the vF-values, found here as well as vF- data reported in the literature, reveal that--for equal pressures--the failure wave velocities determined from Taylor tests or planar-impact tests are distinctly greater than those observed during steady-state rod penetration.« less

{Interball-1 Plasma, Magnetic Field, and Energetic Particle Observations}

NASA Technical Reports Server (NTRS)

Sibeck, David G.

1998-01-01

Funding from NASA was received in two installments. The first installment supported research using Russian/Czech/Slovak/French Interball-1 plasma, magnetic field, and energetic particles observations in the vicinity of the magnetopause. The second installment provided salary support to review unsolicited proposals to NASA for data recovery and archiving, and also to survey ISTP data provision efforts. Two papers were published under the auspices of the grant. Sibeck et al. reported Interball-1 observations of a wave on the magnetopause with an amplitude in excess of 5 R(sub E), the largest ever reported to date. They attributed the wave to a hot flow anomaly striking the magnetopause and suggested that the hot flow anomaly itself formed during the interaction of an IMF discontinuity with the bow shock. Nemecek et al. used Interball-1's VDP Faraday cup to identify large transient increases in the magnetosheath density. They noted large variations in simultaneous Wind observations of the IMF cone angle, but were unable to establish any relationship between the cone angle variations at Wind and the density variations at Interball-1. Funds from the second installment were used to review over 20 proposals from various researchers in the scientific community who sought NASA support to restore or archive past observations. It also supported a survey of ISTP data provisions which was used as input to a Senior Review of ongoing NASA ISTP programs.

Explosive plane-wave lens

DOEpatents

Marsh, Stanley P.

1988-01-01

An explosive plane-wave air lens which enables a spherical wave form to be converted to a planar wave without the need to specially machine or shape explosive materials is described. A disc-shaped impactor having a greater thickness at its center than around its periphery is used to convert the spherical wave into a plane wave. When the wave reaches the impactor, the center of the impactor moves first because the spherical wave reaches the center of the impactor first. The wave strikes the impactor later in time as one moves radially along the impactor. Because the impactor is thinner as one moves radially outward, the velocity of the impactor is greater at the periphery than at the center. An acceptor explosive is positioned so that the impactor strikes the acceptor simultaneously. Consequently, a plane detonation wave is propagated through the acceptor explosive.

A Guided Wave Sensor Enabling Simultaneous Wavenumber-Frequency Analysis for Both Lamb and Shear-Horizontal Waves.

PubMed

Ren, Baiyang; Cho, Hwanjeong; Lissenden, Cliff J

2017-03-01

Guided waves in plate-like structures have been widely investigated for structural health monitoring. Lamb waves and shear horizontal (SH) waves, two commonly used types of waves in plates, provide different benefits for the detection of various types of defects and material degradation. However, there are few sensors that can detect both Lamb and SH waves and also resolve their modal content, namely the wavenumber-frequency spectrum. A sensor that can detect both waves is desirable to take full advantage of both types of waves in order to improve sensitivity to different discontinuity geometries. We demonstrate that polyvinylidene difluoride (PVDF) film provides the basis for a multi-element array sensor that detects both Lamb and SH waves and also measures their modal content, i.e., the wavenumber-frequency spectrum.

Explosive plane-wave lens

DOEpatents

Marsh, S.P.

1988-03-08

An explosive plane-wave air lens which enables a spherical wave form to be converted to a planar wave without the need to specially machine or shape explosive materials is described. A disc-shaped impactor having a greater thickness at its center than around its periphery is used to convert the spherical wave into a plane wave. When the wave reaches the impactor, the center of the impactor moves first because the spherical wave reaches the center of the impactor first. The wave strikes the impactor later in time as one moves radially along the impactor. Because the impactor is thinner as one moves radially outward, the velocity of the impactor is greater at the periphery than at the center. An acceptor explosive is positioned so that the impactor strikes the acceptor simultaneously. Consequently, a plane detonation wave is propagated through the acceptor explosive. 4 figs.

Simultaneous wavelength conversion of ASK and DPSK signals based on four-wave-mixing in dispersion engineered silicon waveguides.

PubMed

Xu, Lin; Ophir, Noam; Menard, Michael; Lau, Ryan Kin Wah; Turner-Foster, Amy C; Foster, Mark A; Lipson, Michal; Gaeta, Alexander L; Bergman, Keren

2011-06-20

We experimentally demonstrate four-wave-mixing (FWM)-based continuous wavelength conversion of optical differential-phase-shift-keyed (DPSK) signals with large wavelength conversion ranges as well as simultaneous wavelength conversion of dual-wavelength channels with mixed modulation formats in 1.1-cm-long dispersion-engineered silicon waveguides. We first validate up to 100-nm wavelength conversion range for 10-Gb/s DPSK signals, showcasing the capability to perform phase-preserving operations at high bit rates in chip-scale devices over wide conversion ranges. We further validate the wavelength conversion of dual-wavelength channels modulated with 10-Gb/s packetized phase-shift-keyed (PSK) and amplitude-shift-keyed (ASK) signals; demonstrate simultaneous operation on multiple channels with mixed formats in chip-scale devices. For both configurations, we measure the spectral and temporal responses and evaluate the performances using bit-error-rate (BER) measurements.

Assessment of fine-scale parameterizations of turbulent dissipation rates in the Southern Ocean

NASA Astrophysics Data System (ADS)

Takahashi, A.; Hibiya, T.

2016-12-01

To sustain the global overturning circulation, more mixing is required in the ocean than has been observed. The most likely candidates for this missing mixing are breaking of wind-induced near-inertial waves and bottom-generated internal lee waves in the sparsely observed Southern Ocean. Nevertheless, there is a paucity of direct microstructure measurements in the Southern Ocean where energy dissipation rates have been estimated mostly using fine-scale parameterizations. In this study, we assess the validity of the existing fine-scale parameterizations in the Antarctic Circumpolar Current (ACC) region using the data obtained from simultaneous full-depth measurements of micro-scale turbulence and fine-scale shear/strain carried out south of Australia during January 17 to February 2, 2016. Although the fine-scale shear/strain ratio (Rω) is close to the Garrett-Munk (GM) value at the station north of Subtropical Front, the values of Rω at the stations south of Subantarctic Front well exceed the GM value, suggesting that the local internal wave spectra are significantly biased to lower frequencies. We find that not all of the observed energy dissipation rates at these locations are well predicted using Gregg-Henyey-Polzin (GHP; Gregg et al., 2003) and Ijichi-Hibiya (IH; Ijichi and Hibiya, 2015) parameterizations, both of which take into account the spectral distortion in terms of Rω; energy dissipation rates at some locations are obviously overestimated by GHP and IH, although only the strain-based Wijesekera (Wijesekera et al., 1993) parameterization yields fairly good predictions. One possible explanation for this result is that a significant portion of the observed shear variance at these locations might be attributed to kinetic-energy-dominant small-scale eddies associated with the ACC, so that fine-scale strain rather than Rω becomes a more appropriate parameter to characterize the actual internal wave field.

Combined ocular and cervical vestibular evoked myogenic potential in individuals with vestibular hyporeflexia and in patients with Ménière's disease.

PubMed

Silva, Tatiana Rocha; de Resende, Luciana Macedo; Santos, Marco Aurélio Rocha

The vestibular evoked myogenic potential is a potential of mean latency that measures the muscle response to auditory stimulation. This potential can be generated from the contraction of the sternocleidomastoid muscle and also from the contraction of extraocular muscles in response to high-intensity sounds. This study presents a combined or simultaneous technique of cervical and ocular vestibular evoked myogenic potential in individuals with changes in the vestibular system, for use in otoneurologic diagnosis. To characterize the records and analyze the results of combined cervical and ocular VEMP in individuals with vestibular hyporeflexia and in those with Ménière's disease. The study included 120 subjects: 30 subjects with vestibular hyporeflexia, 30 with Ménière's disease, and 60 individuals with normal hearing. Data collection was performed by simultaneously recording the cervical and ocular vestibular evoked myogenic potential. There were differences between the study groups (individuals with vestibular hyporeflexia and individuals with Ménière's disease) and the control group for most of wave parameters in combined cervical and ocular vestibular evoked myogenic potential. For cervical vestibular evoked myogenic potential, it was observed that the prolongation of latency of the P13 and N23 waves was the most frequent finding in the group with vestibular hyporeflexia and in the group with Ménière's disease. For ocular vestibular evoked myogenic potential, prolonged latency of N10 and P15 waves was the most frequent finding in the study groups. Combined cervical and ocular vestibular evoked myogenic potential presented relevant results for individuals with vestibular hyporeflexia and for those with Ménière's disease. There were differences between the study groups and the control group for most of the wave parameters in combined cervical and ocular vestibular evoked myogenic potential. Copyright © 2016 Associação Brasileira de Otorrinolaringologia e Cirurgia Cérvico-Facial. Published by Elsevier Editora Ltda. All rights reserved.

Guided Acoustic and Optical Waves in Silicon-on-Insulator for Brillouin Scattering and Optomechanics

DTIC Science & Technology

2016-08-01

APL PHOTONICS 1, 071301 (2016) Guided acoustic and optical waves in silicon-on- insulator for Brillouin scattering and optomechanics Christopher J...is possible to simultaneously guide optical and acoustic waves in the technologically important silicon on insulator (SOI) material system. Thin...mechanism on which to base on-chip nonlinear optical devices compatible with a rapidly growing silicon photonics toolbox.3–9 While silicon on insulator

Compressional and shear wave velocities in granular materials to 2.5 kilobars

NASA Technical Reports Server (NTRS)

Talwani, P.; Nur, A.; Kovach, R. L.

1973-01-01

The velocities of seismic compressional waves and, for the first time, shear wave velocities in silica sand, volcanic ash, and basalt powder were determined under hydrostatic confining pressures to 2.5 kb. Simultaneously, the porosity of these materials was obtained as a function of confining pressure. The presented results have important implications for the self-compaction hypothesis that has been postulated to explain the lunar near-surface seismic velocity variation.

Realization of multiple orbital angular momentum modes simultaneously through four-dimensional antenna arrays.

PubMed

Sun, Chao; Yang, Shiwen; Chen, Yikai; Guo, Jixin; Qu, Shiwei

2018-01-09

Electromagnetic waves carrying orbital angular momentum (OAM) in radio frequency range have drawn great attention owing to its potential applications in increasing communication capacity. In this paper, both single-pole single-throw (SPST) switches and single-pole double-throw (SPDT) switches are designed and implemented. Optimal time sequence allows four-dimensional (4-D) circular antenna array to generate multiple OAM-carrying waves as well as enhance the field intensity of each OAM-carrying wave. A novel experimental platform is developed to measure the phase distribution when the transmitting antenna and the receiving antenna operate at different frequencies. The good agreement between the measurement and simulation results demonstrate that 4-D circular antenna array is able to generate multiple OAM modes simultaneously. Furthermore, the superiority of the 4-D circular antenna array in receiving and demodulating multiple OAM-carrying signals is validated through the filter and bit error rate (BER) simulations.

Simultaneous imaging of strain waves and induced magnetization dynamics at the nanometer scale

NASA Astrophysics Data System (ADS)

Macia, Ferran; Foerster, Michael; Statuto, Nahuel; Finizio, Simone; Hernandez-Minguez, Alberto; Lendinez, Sergi; Santos, Paulo V.; Fontcuberta, Josep; Hernandez, Joan Manel; Klaui, Mathias; Aballe, Lucia

The magnetoelastic effect or inverse magnetostriction-the change of magnetic properties by elastic deformation or strain-is often a key coupling mechanism in multiferroic heterostructures and nanocomposites. It has lately attracted considerable interest as a possible approach for controlling magnetization by electric fields (instead of current) in future devices with low power consumption. However, many experiments addressing the magnetoelastic effect are performed at slow speeds, often using materials and conditions which are impractical or too expensive for device integration. Here, we have studied the effect of the dynamic strain accompanying a surface acoustic wave on magnetic nanostructures. We have simultaneously imaged the temporal evolution of both strain waves and magnetization dynamics of nanostructures at the picosecond timescale. Our experimental technique, based on X-ray microscopy, is versatile and provides a pathway to the study of strain-induced effects at the nanoscale.

Acousto-optical interaction of surface acoustic and optical waves in a two-dimensional phoxonic crystal hetero-structure cavity.

PubMed

Ma, Tian-Xue; Zou, Kui; Wang, Yue-Sheng; Zhang, Chuanzeng; Su, Xiao-Xing

2014-11-17

Phoxonic crystal is a promising material for manipulating sound and light simultaneously. In this paper, we theoretically demonstrate the propagation of acoustic and optical waves along the truncated surface of a two-dimensional square-latticed phoxonic crystal. Further, a phoxonic crystal hetero-structure cavity is proposed, which can simultaneously confine surface acoustic and optical waves. The interface motion and photoelastic effects are taken into account in the acousto-optical coupling. The results show obvious shifts in eigenfrequencies of the photonic cavity modes induced by different phononic cavity modes. The symmetry of the phononic cavity modes plays a more important role in the single-phonon exchange process than in the case of the multi-phonon exchange. Under the same deformation, the frequency shift of the photonic transverse electric mode is larger than that of the transverse magnetic mode.

Elastic metamaterials with simultaneously negative effective shear modulus and mass density.

PubMed

Wu, Ying; Lai, Yun; Zhang, Zhao-Qing

2011-09-02

We propose a type of elastic metamaterial comprising fluid-solid composite inclusions which can possess a negative shear modulus and negative mass density over a large frequency region. Such a material has the unique property that only transverse waves can propagate with a negative dispersion while longitudinal waves are forbidden. This leads to many interesting phenomena such as negative refraction, which is demonstrated by using a wedge sample and a significant amount of mode conversion from transverse waves to longitudinal waves that cannot occur on the interface of two natural solids.

Observations of LHR noise with banded structure by the sounding rocket S29 barium-GEOS

NASA Technical Reports Server (NTRS)

Koskinen, H. E. J.; Holmgren, G.; Kintner, P. M.

1983-01-01

The measurement of electrostatic noise near the lower hybrid frequency made by the sounding rocket S29 barium-GEOS is reported. The noise is related to the spin of the rocket and reaches well below the local lower hybrid resonance frequency. Above the altitude of 300 km the noise shows banded structure roughly organized by the hydrogen cyclotron frequency. Simultaneously with the banded structure a signal near the hydrogen cyclotron frequency is detected. This signal is also spin modulated. The character of the noise strongly suggests that it is locally generated by the rocket payload disturbing the plasma. If this interpretation is correct, plasma wave experiments on other spacecrafts are expected to observe similar phenomena.

Study of solar photospheric MHD oscillations: Observations with MDI, ASP and MWO

NASA Astrophysics Data System (ADS)

Norton, Aimee Ann

Magnetodydrodynamical waves are expected to be an important energy transport mechanism in the solar atmosphere. This thesis uses data from a spectro-polarimeter and longitudinal magnetographs to study characteristics of magneto-hydrodynamical oscillations at photospheric heights. Significant oscillatory magnetic power is observed with the Michelson Doppler Imager in three frequency regimes: 0.5--1.0, 3.0--3.5 and 5.5--6.0 mHz corresponding to timescales of magnetic evolution, p-modes and the three minute resonant sunspot oscillation. Spatial distribution of magnetogram oscillatory power exhibits the same general features in numerous datasets. Low frequency magnetogram power is found in rings with filamentary structure surrounding sunspots. Five minute power peaks in extended regions of plage. Three minute oscillations are observed in sunspot umbra. Phase angles between velocity and magnetic fluctuations are found to be approximately -90°, a signature of magnetoacoustic waves, in disk-center active region data. Phase dependence upon observation angle is established through sunspot values decreasing from -100° at disk-center towards -31° at the limb, confirming greater Alfen wave visibility at the limb. Consistent propagation direction or field-aligned velocities explain an unexpected phase jump from negative to positive values for divergent sunspot fields observed away from disk-center. Simultaneously obtained Stokes profiles and longitudinal magnetogram maps of a positive plage region provide time series which could be compared. The velocity signals are in excellent agreement. Magnetic flux correlates best with fluctuations in filling factor, not inclination angle or field strength, implying the responsible physical mechanism is internally unperturbed flux tubes being buffeted by external pressure fluctuations. Sampling signals from different heights of formation provides slight phase shifts and large propagation speeds for velocity, indicative of modified standing waves. Phase speeds associated with magnetic signals are characteristic of photospheric Alfven speeds for plage fields. The phase speed increase with height agrees with the altitude dependence of the Alfven speed. Observed fluctuations, phase angles and phase lags are interpreted as a superposition of signatures from the horizontal component of the driving mechanism sweeping the field lines in/out of the resolution area and the magnetic response of the flux tube to this buffeting.

Coherent Detector Arrays for Continuum and Spectral Line Applications

NASA Technical Reports Server (NTRS)

Gaier, Todd C.

2006-01-01

This viewgraph presentation reviews the requirements for improved coherent detector arrays for use in continuum and spectral line applications. With detectors approaching fundamental limits, large arrays offer the only path to sensitivity improvement. Monolithic Microwave Integrated Circuit (MMIC) technology offers a straightforward path to massive focal plane millimeter wave arrays: The technology will readily support continuum imagers, polarimeters and spectral line receivers from 30-110 GHz. Science programs, particularly large field blind surveys will benefit from simultaneous observations of hundreds or thousands of pixels 1000 element array is competitive with a cost less than $2M.

Criterion for Bose-Einstein condensation in a harmonic trap in the case with attractive interactions

DOE Office of Scientific and Technical Information (OSTI.GOV)

Gajda, Mariusz

2006-02-15

Using a model many-body wave function I analyze the standard criterion for Bose-Einstein condensation and its relation to coherence properties of the system. I pay special attention to an attractive condensate under such a condition that a characteristic length scale of the spatial extension of its center of mass differs significantly from length scales of relative coordinates. I show that although no interference fringes are produced in the two-slit Young interference experiment performed on this system, fringes of a high visibility can be observed in a conditional simultaneous detection of two particles.

Hurricane Directional Wave Spectrum Spatial Variation in the Open Ocean

NASA Technical Reports Server (NTRS)

Wright, C. W.; Walsh, E. J.; Vandemark, D.; Krabill, W. B.; Garcia, A. W.

1999-01-01

The sea surface directional wave spectrum was measured for the first time in all quadrants of a hurricane in open water using the NASA airborne scanning radar altimeter (SRA) carried aboard one of the NOAA WP-3D hurricane hunter aircraft at 1.5 km height. The SRA measures the energetic portion of the directional wave spectrum by generating a topographic map of the sea surface. At 8 Hz, the SRA sweeps a radar beam of 1 deg half-power width (two-way) across the aircraft ground track over a swath equal to 0. 8 of the aircraft height, simultaneously measuring the backscattered power at its 36 GHz (8.3 mm) operating frequency and the range to the sea surface at 64 positions. These slant ranges are multiplied by the cosine of the incidence angles to determine the vertical distances from the aircraft to the sea surface. Subtracting these distances from the aircraft height produces the sea surface elevation map. The sea surface topography is interpolated to a uniform grid, transformed by a two-dimensional FFT, and Doppler corrected. The data presented were acquired on 24 August 1998 when hurricane Bonnie was east of the Bahamas and moving slowly to the north. Wave heights up to 18 m were observed and the spatial variation of the wave field was dramatic. The dominant waves generally propagated at significant angles to the downwind direction and at times there were wave fields traveling at right angles to each other. The NOAA aircraft spent over five hours within 180 km of the hurricane Bonnie eye, and made five eye penetrations. A 2-minute animation of the directional wave spectrum spatial variation over this period will be shown.

Using graphene nano-particle embedded in photonic crystal fiber for evanescent wave mode-locking of fiber laser.

PubMed

Lin, Yung-Hsiang; Yang, Chun-Yu; Liou, Jia-Hong; Yu, Chin-Ping; Lin, Gong-Ru

2013-07-15

A photonic crystal fiber (PCF) with high-quality graphene nano-particles uniformly dispersed in the hole cladding are demonstrated to passively mode-lock the erbium-doped fiber laser (EDFL) by evanescent-wave interaction. The few-layer graphene nano-particles are obtained by a stabilized electrochemical exfoliation at a threshold bias. These slowly and softly exfoliated graphene nano-particle exhibits an intense 2D band and an almost disappeared D band in the Raman scattering spectrum. The saturable phenomena of the extinction coefficient β in the cladding provides a loss modulation for the intracavity photon intensity by the evanescent-wave interaction. The evanescent-wave mode-locking scheme effectively enlarges the interaction length of saturable absorption with graphene nano-particle to provide an increasing transmittance ΔT of 5% and modulation depth of 13%. By comparing the core-wave and evanescent-wave mode-locking under the same linear transmittance, the transmittance of the graphene nano-particles on the end-face of SMF only enlarges from 0.54 to 0.578 with ΔT = 3.8% and the modulation depth of 10.8%. The evanescent wave interaction is found to be better than the traditional approach which confines the graphene nano-particles at the interface of two SMF patchcords. When enlarging the intra-cavity gain by simultaneously increasing the pumping current of 980-nm and 1480-nm pumping laser diodes (LDs) to 900 mA, the passively mode-locked EDFL shortens its pulsewidth to 650 fs and broadens its spectral linewidth to 3.92 nm. An extremely low carrier amplitude jitter (CAJ) of 1.2-1.6% is observed to confirm the stable EDFL pulse-train with the cladding graphene nano-particle based evanescent-wave mode-locking.

Simultaneous Observations of Lower Band Chorus Emissions at the Equator and Microburst Precipitating Electrons in the Ionosphere

NASA Astrophysics Data System (ADS)

Mozer, F. S.; Agapitov, O. V.; Blake, J. B.; Vasko, I. Y.

2018-01-01

On 11 December 2016 at 00:12:30 UT, Van Allen Probe-B, at the equator and near midnight, and AC6-B, in the ionosphere, were on magnetic field lines whose 100 km altitude foot points were separated by 600 km. Van Allen Probe-B observed a 30 s burst of lower band chorus waves (with maximum amplitudes >1 nT) at the same time that AC6-B observed intense microburst electrons in the loss cone. One second averaged variations of the chorus intensity and the microburst electron flux were well correlated. The low-altitude electron flux expected from quasi-linear diffusion of the equatorial electrons by the equatorial chorus is in excellent agreement with the observed, 1 s averaged, low-altitude electron flux. However, the large-amplitude, <0.5 s duration, low-altitude electron pulses require nonlinear processes for their explanation.

From Loschmidt daemons to time-reversed waves.

PubMed

Fink, Mathias

2016-06-13

Time-reversal invariance can be exploited in wave physics to control wave propagation in complex media. Because time and space play a similar role in wave propagation, time-reversed waves can be obtained by manipulating spatial boundaries or by manipulating time boundaries. The two dual approaches will be discussed in this paper. The first approach uses 'time-reversal mirrors' with a wave manipulation along a spatial boundary sampled by a finite number of antennas. Related to this method, the role of the spatio-temporal degrees of freedom of the wavefield will be emphasized. In a second approach, waves are manipulated from a time boundary and we show that 'instantaneous time mirrors', mimicking the Loschmidt point of view, simultaneously acting in the entire space at once can also radiate time-reversed waves. © 2016 The Author(s).

Seismic triplication used to reveal slab subduction that had disappeared in the late Mesozoic beneath the northeastern South China Sea

NASA Astrophysics Data System (ADS)

Wang, Xiaoran; Li, Qiusheng; Li, Guohui; Zhou, Yuanze; Ye, Zhuo; Zhang, Hongshuang

2018-03-01

We provided a new study of the seismic velocity structure of the mantle transition zone (MTZ) beneath the northeastern South China Sea using P-wave triplications from two earthquakes at the central Philippines recorded by the Chinese Digital Seismic Network. Through fitting the observed and theoretical triplications modeled by the dynamic ray tracing method for traveltimes, and the reflectivity method for synthetic waveforms using grid-searching method, best-fit velocity models based on IASP91 were obtained to constrain the P-wave velocity structure of the MTZ. The models show that a high-velocity anomaly (HVA) resides at the bottom of MTZ. The HVA is 215 km to 225 km thick, with a P-wave velocity increment of 1.0% between 450 km and 665 km or 675 km transition and increase by 2.5-3.5% at 665 km or 675 km depth. The P-wave velocity increment ranges from approximately 0.3% to 0.8% below the 665 km or 675 km. We proposed that the HVA in the MTZ was caused by the broken fragments of a diving oceanic plate falling into the MTZ at a high angle, and/or by unstable thick continental lithosphere dropping into the MTZ sequentially or almost simultaneously.

Quantitative Mapping of Pore Fraction Variations in Silicon Nitride Using an Ultrasonic Contact Scan Technique

NASA Technical Reports Server (NTRS)

Roth, Don J.; Kiser, James D.; Swickard, Suzanne M.; Szatmary, Steven A.; Kerwin, David P.

1993-01-01

An ultrasonic scan procedure using the pulse-echo contact configuration was employed to obtain maps of pore fraction variations in sintered silicon nitride samples in terms of ultrasonic material properties. Ultrasonic velocity, attenuation coefficient, and reflection coefficient images were obtained simultaneously over a broad band of frequencies (e.g., 30 to 110 MHz) by using spectroscopic analysis. Liquid and membrane (dry) coupling techniques and longitudinal and shear-wave energies were used. The major results include the following: Ultrasonic velocity (longitudinal and shear wave) images revealed and correlated with the extent of average through-thickness pore fraction variations in the silicon nitride disks. Attenuation coefficient images revealed pore fraction nonuniformity due to the scattering that occurred at boundaries between regions of high and low pore fraction. Velocity and attenuation coefficient images were each nearly identical for machined and polished disks, making the method readily applicable to machined materials. Velocity images were similar for wet and membrane coupling. Maps of apparent Poisson's ratio constructed from longitudinal and shear-wave velocities quantified Poisson's ratio variations across a silicon nitride disk. Thermal wave images of a disk indicated transient thermal behavior variations that correlated with observed variations in pore fraction and velocity and attenuation coefficients.

An atomic gravitational wave interferometric sensor in low earth orbit (AGIS-LEO)

NASA Astrophysics Data System (ADS)

Hogan, Jason M.; Johnson, David M. S.; Dickerson, Susannah; Kovachy, Tim; Sugarbaker, Alex; Chiow, Sheng-Wey; Graham, Peter W.; Kasevich, Mark A.; Saif, Babak; Rajendran, Surjeet; Bouyer, Philippe; Seery, Bernard D.; Feinberg, Lee; Keski-Kuha, Ritva

2011-07-01

We propose an atom interferometer gravitational wave detector in low Earth orbit (AGIS-LEO). Gravitational waves can be observed by comparing a pair of atom interferometers separated by a 30 km baseline. In the proposed configuration, one or three of these interferometer pairs are simultaneously operated through the use of two or three satellites in formation flight. The three satellite configuration allows for the increased suppression of multiple noise sources and for the detection of stochastic gravitational wave signals. The mission will offer a strain sensitivity of {<10^{-18}/sqrt{Hz}} in the 50mHz-10Hz frequency range, providing access to a rich scientific region with substantial discovery potential. This band is not currently addressed with the LIGO, VIRGO, or LISA instruments. We analyze systematic backgrounds that are relevant to the mission and discuss how they can be mitigated at the required levels. Some of these effects do not appear to have been considered previously in the context of atom interferometry, and we therefore expect that our analysis will be broadly relevant to atom interferometric precision measurements. Finally, we present a brief conceptual overview of shorter-baseline ({lesssim100 m}) atom interferometer configurations that could be deployed as proof-of-principle instruments on the International Space Station (AGIS-ISS) or an independent satellite.

Probe Oscillation Shear Elastography (PROSE): A High Frame-Rate Method for Two-Dimensional Ultrasound Shear Wave Elastography.

PubMed

Mellema, Daniel C; Song, Pengfei; Kinnick, Randall R; Urban, Matthew W; Greenleaf, James F; Manduca, Armando; Chen, Shigao

2016-09-01

Ultrasound shear wave elastography (SWE) utilizes the propagation of induced shear waves to characterize the shear modulus of soft tissue. Many methods rely on an acoustic radiation force (ARF) "push beam" to generate shear waves. However, specialized hardware is required to generate the push beams, and the thermal stress that is placed upon the ultrasound system, transducer, and tissue by the push beams currently limits the frame-rate to about 1 Hz. These constraints have limited the implementation of ARF to high-end clinical systems. This paper presents Probe Oscillation Shear Elastography (PROSE) as an alternative method to measure tissue elasticity. PROSE generates shear waves using a harmonic mechanical vibration of an ultrasound transducer, while simultaneously detecting motion with the same transducer under pulse-echo mode. Motion of the transducer during detection produces a "strain-like" compression artifact that is coupled with the observed shear waves. A novel symmetric sampling scheme is proposed such that pulse-echo detection events are acquired when the ultrasound transducer returns to the same physical position, allowing the shear waves to be decoupled from the compression artifact. Full field-of-view (FOV) two-dimensional (2D) shear wave speed images were obtained by applying a local frequency estimation (LFE) technique, capable of generating a 2D map from a single frame of shear wave motion. The shear wave imaging frame rate of PROSE is comparable to the vibration frequency, which can be an order of magnitude higher than ARF based techniques. PROSE was able to produce smooth and accurate shear wave images from three homogeneous phantoms with different moduli, with an effective frame rate of 300 Hz. An inclusion phantom study showed that increased vibration frequencies improved the accuracy of inclusion imaging, and allowed targets as small as 6.5 mm to be resolved with good contrast (contrast-to-noise ratio ≥ 19 dB) between the target and background.

Probe Oscillation Shear Elastography (PROSE): A High Frame-Rate Method for Two-Dimensional Ultrasound Shear Wave Elastography

PubMed Central

Mellema, Daniel C.; Song, Pengfei; Kinnick, Randall R.; Urban, Matthew W.; Greenleaf, James F.; Manduca, Armando; Chen, Shigao

2017-01-01

Ultrasound shear wave elastography (SWE) utilizes the propagation of induced shear waves to characterize the shear modulus of soft tissue. Many methods rely on an acoustic radiation force (ARF) “push beam” to generate shear waves. However, specialized hardware is required to generate the push beams, and the thermal stress that is placed upon the ultrasound system, transducer, and tissue by the push beams currently limits the frame-rate to about 1 Hz. These constraints have limited the implementation of ARF to high-end clinical systems. This paper presents Probe Oscillation Shear Elastography (PROSE) as an alternative method to measure tissue elasticity. PROSE generates shear waves using a harmonic mechanical vibration of an ultrasound transducer, while simultaneously detecting motion with the same transducer under pulse-echo mode. Motion of the transducer during detection produces a “strain-like” compression artifact that is coupled with the observed shear waves. A novel symmetric sampling scheme is proposed such that pulse-echo detection events are acquired when the ultrasound transducer returns to the same physical position, allowing the shear waves to be decoupled from the compression artifact. Full field-of-view (FOV) two-dimensional (2D) shear wave speed images were obtained by applying a local frequency estimation (LFE) technique, capable of generating a 2D map from a single frame of shear wave motion. The shear wave imaging frame rate of PROSE is comparable to the vibration frequency, which can be an order of magnitude higher than ARF based techniques. PROSE was able to produce smooth and accurate shear wave images from three homogeneous phantoms with different moduli, with an effective frame rate of 300Hz. An inclusion phantom study showed that increased vibration frequencies improved the accuracy of inclusion imaging, and allowed targets as small as 6.5 mm to be resolved with good contrast (contrast-to-noise ratio ≥19 dB) between the target and background. PMID:27076352

A parametric study of the linear growth of magnetospheric EMIC waves in a hot plasma

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wang, Qi; Cao, Xing; Gu, Xudong, E-mail: guxudong@whu.edu.cn, E-mail: bbni@whu.edu.cn

2016-06-15

Since electromagnetic ion cyclotron (EMIC) waves in the terrestrial magnetosphere play a crucial role in the dynamic losses of relativistic electrons and energetic protons and in the ion heating, it is important to pursue a comprehensive understanding of the EMIC wave dispersion relation under realistic circumstances, which can shed significant light on the generation, amplification, and propagation of magnetospheric EMIC waves. The full kinetic linear dispersion relation is implemented in the present study to evaluate the linear growth of EMIC waves in a multi-ion (H{sup +}, He{sup +}, and O{sup +}) magnetospheric plasma that also consists of hot ring currentmore » protons. Introduction of anisotropic hot protons strongly modifies the EMIC wave dispersion surface and can result in the simultaneous growth of H{sup +}-, He{sup +}-, and O{sup +}-band EMIC emissions. Our parametric analysis demonstrates that an increase in the hot proton concentration can produce the generation of H{sup +}- and He{sup +}-band EMIC waves with higher possibility. While the excitation of H{sup +}-band emissions requires relatively larger temperature anisotropy of hot protons, He{sup +}-band emissions are more likely to be triggered in the plasmasphere or plasmaspheric plume where the background plasma is denser. In addition, the generation of He{sup +}-band waves is more sensitive to the variation of proton temperature than H{sup +}-band waves. Increase of cold heavy ion (He{sup +} and O{sup +}) density increases the H{sup +} cutoff frequency and therefore widens the frequency coverage of the stop band above the He{sup +} gyrofrequency, leading to a significant damping of H{sup +}-band EMIC waves. In contrast, O{sup +}-band EMIC waves characteristically exhibit the temporal growth much weaker than the other two bands, regardless of all considered variables, suggesting that O{sup +}-band emissions occur at a rate much lower than H{sup +}- and He{sup +}-band emissions, which is consistent with the observations.« less

Direct measurement of nonlinear dispersion relation for water surface waves

NASA Astrophysics Data System (ADS)

Magnus Arnesen Taklo, Tore; Trulsen, Karsten; Elias Krogstad, Harald; Gramstad, Odin; Nieto Borge, José Carlos; Jensen, Atle

2013-04-01

The linear dispersion relation for water surface waves is often taken for granted for the interpretation of wave measurements. High-resolution spatiotemporal measurements suitable for direct validation of the linear dispersion relation are on the other hand rarely available. While the imaging of the ocean surface with nautical radar does provide the desired spatiotemporal coverage, the interpretation of the radar images currently depends on the linear dispersion relation as a prerequisite, (Nieto Borge et al., 2004). Krogstad & Trulsen (2010) carried out numerical simulations with the nonlinear Schrödinger equation and its generalizations demonstrating that the nonlinear evolution of wave fields may render the linear dispersion relation inadequate for proper interpretation of observations, the reason being that the necessary domain of simultaneous coverage in space and time would allow significant nonlinear evolution. They found that components above the spectral peak can have larger phase and group velocities than anticipated by linear theory, and that the spectrum does not maintain a thin dispersion surface. We have run laboratory experiments and accurate numerical simulations designed to have sufficient resolution in space and time to deduce the dispersion relation directly. For a JONSWAP spectrum we find that the linear dispersion relation can be appropriate for the interpretation of spatiotemporal measurements. For a Gaussian spectrum with narrower bandwidth we find that the dynamic nonlinear evolution in space and time causes the directly measured dispersion relation to deviate from the linear dispersion surface in good agreement with our previous numerical predictions. This work has been supported by RCN grant 214556/F20. Krogstad, H. E. & Trulsen, K. (2010) Interpretations and observations of ocean wave spectra. Ocean Dynamics 60:973-991. Nieto Borge, J. C., Rodríguez, G., Hessner, K., Izquierdo, P. (2004) Inversion of marine radar images for surface wave analysis. J. Atmos. Ocean. Tech. 21:1291-1300.

GYROSURFING ACCELERATION OF IONS IN FRONT OF EARTH's QUASI-PARALLEL BOW SHOCK

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kis, Arpad; Lemperger, Istvan; Wesztergom, Viktor

2013-07-01

It is well known that shocks in space plasmas can accelerate particles to high energies. However, many details of the shock acceleration mechanism are still unknown. A critical element of shock acceleration is the injection problem; i.e., the presence of the so called seed particle population that is needed for the acceleration to work efficiently. In our case study, we present for the first time observational evidence of gyroresonant surfing acceleration in front of Earth's quasi-parallel bow shock resulting in the appearance of the long-suspected seed particle population. For our analysis, we use simultaneous multi-spacecraft measurements provided by the Clustermore » spacecraft ion (CIS), magnetic (FGM), and electric field and wave instrument (EFW) during a time period of large inter-spacecraft separation distance. The spacecraft were moving toward the bow shock and were situated in the foreshock region. The results show that the gyroresonance surfing acceleration takes place as a consequence of interaction between circularly polarized monochromatic (or quasi-monochromatic) transversal electromagnetic plasma waves and short large amplitude magnetic structures (SLAMSs). The magnetic mirror force of the SLAMS provides the resonant conditions for the ions trapped by the waves and results in the acceleration of ions. Since wave packets with circular polarization and different kinds of magnetic structures are very commonly observed in front of Earth's quasi-parallel bow shock, the gyroresonant surfing acceleration proves to be an important particle injection mechanism. We also show that seed ions are accelerated directly from the solar wind ion population.« less

An investigation of mechanisms other than lightning to explain certain wideband plasma wave bursts detected in the Venusian nightside ionosphere

NASA Technical Reports Server (NTRS)

Carpenter, D. L.

1992-01-01

Several related topics are briefly discussed. Reviewed here is work on an investigation of plasma wave phenomena associated with the question of lightning on Venus. The work supported the contention that lightning is at least a candidate explanation for many of the 100 Hz-only Pioneer Venus orbital electric field detector (OEFD) signals. A review of the work on the investigation of mechanisms other than lightning to explain certain wideband plasma wave bursts detected in the Venusian nightside ionosphere is given. A summary is given of our analysis of data from 23 OEFD observing periods as well as a discussion of the properties of specifically multifrequency events. Our opportunity to work on this topic was not sufficient to draw any firm conclusions about the origins of the multifrequency bursts, but we call attention to what we consider to be several candidate sources. Also discussed are case studies to test for evidence of whistler mode propagation from subionospheric sources, results of a search for dispersive effects in the OEFD data, the results for a search for simultaneous 100 Hz and 730 Hz observations at altitudes below 150 km, changes with altitude in dispersive broadening effects in the time signatures of 100 Hz bursts, and a survey of activity at altitudes above 1000 km.

Radio triangulation - mapping the 3D position of the solar radio emission

NASA Astrophysics Data System (ADS)

Magdalenic, Jasmina

2016-04-01

Understanding the relative position of the sources of the radio emission and the associated solar eruptive phenomena (CME and the associated shock wave) has always been a challenge. While ground-based radio interferometer observations provide us with the 2D position information for the radio emission originating from the low corona (up to 2.5 Ro), this is not the case for the radio emission originating at larger heights. The radio triangulation measurements (also referred to as direction-finding or goniopolarimetric measurements) from two or more widely separated spacecraft can provide information on the 3D positions of the sources of the radio emission. This type of interplanetary radio observations are currently performed by STEREO WAVES and WIND WAVES instruments, providing a unique possibility for up to three simultaneous radio triangulations (using up to three different pairs of spacecraft). The recent results of the radio triangulation studies bring new insight into the causal relationship of the solar radio emission and CMEs. In this presentation I will discuss some of the most intriguing results on the source positions of: a) type III radio bursts indicating propagation of the fast electrons accelerated along the open field lines, b) type II radio bursts indicating interaction of the CME-driven shocks and other coronal structures e.g. streamers and c) type IV-like radio bursts possibly associated with CME-CME interaction.

Electromagnetic Waves and Bursty Electron Acceleration: Implications from Freja

NASA Technical Reports Server (NTRS)

Andersson, Laila; Ivchenko, N.; Wahlund, J.-E.; Clemmons, J.; Gustavsson, B.; Eliasson, L.

2000-01-01

Dispersive Alfven wave activity is identified in four dayside auroral oval events measured by the Freja satellite. The events are characterized by ion injection, bursty electron precipitation below about I keV, transverse ion heating and broadband extremely low frequency (ELF) emissions below the lower hybrid cutoff frequency (a few kHz). The broadband emissions are observed to become more electrostatic towards higher frequencies. Large-scale density depletions/cavities, as determined by the Langmuir probe measurements, and strong electrostatic emissions are often observed simultaneously. A correlation study has been carried out between the E- and B-field fluctuations below 64 Hz (the dc instrument's upper threshold) and the characteristics of the precipitating electrons. This study revealed that the energization of electrons is indeed related to the broadband ELF emissions and that the electrostatic component plays a predominant role during very active magnetospheric conditions. Furthermore, the effect of the ELF electromagnetic emissions on the larger scale field-aligned current systems has been investigated, and it is found that such an effect cannot be detected. Instead, the Alfvenic activity creates a local region of field-aligned currents. It is suggested that dispersive Alfven waves set up these local field-aligned current regions and in turn trigger more electrostatic emissions during certain conditions. In these regions ions are transversely heated, and large-scale density depletions/cavities may be created during especially active periods.

Improved Pulse Wave Velocity Estimation Using an Arterial Tube-Load Model

PubMed Central

Gao, Mingwu; Zhang, Guanqun; Olivier, N. Bari; Mukkamala, Ramakrishna

2015-01-01

Pulse wave velocity (PWV) is the most important index of arterial stiffness. It is conventionally estimated by non-invasively measuring central and peripheral blood pressure (BP) and/or velocity (BV) waveforms and then detecting the foot-to-foot time delay between the waveforms wherein wave reflection is presumed absent. We developed techniques for improved estimation of PWV from the same waveforms. The techniques effectively estimate PWV from the entire waveforms, rather than just their feet, by mathematically eliminating the reflected wave via an arterial tube-load model. In this way, the techniques may be more robust to artifact while revealing the true PWV in absence of wave reflection. We applied the techniques to estimate aortic PWV from simultaneously and sequentially measured central and peripheral BP waveforms and simultaneously measured central BV and peripheral BP waveforms from 17 anesthetized animals during diverse interventions that perturbed BP widely. Since BP is the major acute determinant of aortic PWV, especially under anesthesia wherein vasomotor tone changes are minimal, we evaluated the techniques in terms of the ability of their PWV estimates to track the acute BP changes in each subject. Overall, the PWV estimates of the techniques tracked the BP changes better than those of the conventional technique (e.g., diastolic BP root-mean-squared-errors of 3.4 vs. 5.2 mmHg for the simultaneous BP waveforms and 7.0 vs. 12.2 mmHg for the BV and BP waveforms (p < 0.02)). With further testing, the arterial tube-load model-based PWV estimation techniques may afford more accurate arterial stiffness monitoring in hypertensive and other patients. PMID:24263016

Jupiter's magnetosphere and aurorae observed by the Juno spacecraft during its first polar orbits.

PubMed

Connerney, J E P; Adriani, A; Allegrini, F; Bagenal, F; Bolton, S J; Bonfond, B; Cowley, S W H; Gerard, J-C; Gladstone, G R; Grodent, D; Hospodarsky, G; Jorgensen, J L; Kurth, W S; Levin, S M; Mauk, B; McComas, D J; Mura, A; Paranicas, C; Smith, E J; Thorne, R M; Valek, P; Waite, J

2017-05-26

The Juno spacecraft acquired direct observations of the jovian magnetosphere and auroral emissions from a vantage point above the poles. Juno's capture orbit spanned the jovian magnetosphere from bow shock to the planet, providing magnetic field, charged particle, and wave phenomena context for Juno's passage over the poles and traverse of Jupiter's hazardous inner radiation belts. Juno's energetic particle and plasma detectors measured electrons precipitating in the polar regions, exciting intense aurorae, observed simultaneously by the ultraviolet and infrared imaging spectrographs. Juno transited beneath the most intense parts of the radiation belts, passed about 4000 kilometers above the cloud tops at closest approach, well inside the jovian rings, and recorded the electrical signatures of high-velocity impacts with small particles as it traversed the equator. Copyright © 2017, American Association for the Advancement of Science.

Jupiter’s magnetosphere and aurorae observed by the Juno spacecraft during its first polar orbits

NASA Astrophysics Data System (ADS)

Connerney, J. E. P.; Adriani, A.; Allegrini, F.; Bagenal, F.; Bolton, S. J.; Bonfond, B.; Cowley, S. W. H.; Gerard, J.-C.; Gladstone, G. R.; Grodent, D.; Hospodarsky, G.; Jorgensen, J. L.; Kurth, W. S.; Levin, S. M.; Mauk, B.; McComas, D. J.; Mura, A.; Paranicas, C.; Smith, E. J.; Thorne, R. M.; Valek, P.; Waite, J.

2017-05-01

The Juno spacecraft acquired direct observations of the jovian magnetosphere and auroral emissions from a vantage point above the poles. Juno’s capture orbit spanned the jovian magnetosphere from bow shock to the planet, providing magnetic field, charged particle, and wave phenomena context for Juno’s passage over the poles and traverse of Jupiter’s hazardous inner radiation belts. Juno’s energetic particle and plasma detectors measured electrons precipitating in the polar regions, exciting intense aurorae, observed simultaneously by the ultraviolet and infrared imaging spectrographs. Juno transited beneath the most intense parts of the radiation belts, passed about 4000 kilometers above the cloud tops at closest approach, well inside the jovian rings, and recorded the electrical signatures of high-velocity impacts with small particles as it traversed the equator.

Mutual transformation of light waves by reflection holograms in photorefractive crystals of the 4-bar 3m symmetry

DOE Office of Scientific and Technical Information (OSTI.GOV)

Naunyka, V. N.; Shepelevich, V. V., E-mail: vasshep@inbox.ru

2011-05-15

The mutual transformation of light waves in the case of their simultaneous diffraction from a bulk reflection phase hologram, which was formed in a cubic photorefractive crystal of the 4-bar 3m symmetry class, has been studied. The indicator surfaces of the polarization-optimized values of the relative intensity of the object wave, which make it possible to determine the amplification of this wave for any crystal cut, are constructed. The linear polarization azimuths at which the energy exchange between the light waves reaches a maximum are found numerically for crystals of different cuts.

Augmented shock wave fracture/severance of materials

NASA Technical Reports Server (NTRS)

Schimmel, Morry L. (Inventor); Bement, Laurence J. (Inventor)

1995-01-01

The present invention related generally to severing materials, and more particularly to severing or weakening materials through explosively induced, augmented shock waves. Explosive cords are placed in grooves on the upper surface of the material to be severed or weakened. The explosive cords are initiated simultaneously to introduce explosive shock waves into the material. These shock waves progress toward the centerline between the explosive cords and the lower surface of the material. Intersecting and reflected waves produce a rarefaction zone on the centerline to fail the material in tension. A groove may also be cut in the lower surface of the material to aid in severing or weakening the material.

Global Intracellular Slow-Wave Dynamics of the Thalamocortical System

PubMed Central

Sheroziya, Maxim

2014-01-01

It is widely accepted that corticothalamic neurons recruit the thalamus in slow oscillation, but global slow-wave thalamocortical dynamics have never been experimentally shown. We analyzed intracellular activities of neurons either from different cortical areas or from a variety of specific and nonspecific thalamic nuclei in relation to the phase of global EEG signal in ketamine-xylazine anesthetized mice. We found that, on average, slow-wave active states started off within frontal cortical areas as well as higher-order and intralaminar thalamus (posterior and parafascicular nuclei) simultaneously. Then, the leading edge of active states propagated in the anteroposterior/lateral direction over the cortex at ∼40 mm/s. The latest structure we recorded within the slow-wave cycle was the anterior thalamus, which followed active states of the retrosplenial cortex. Active states from different cortical areas tended to terminate simultaneously. Sensory thalamic ventral posterior medial and lateral geniculate nuclei followed cortical active states with major inhibitory and weak tonic-like “modulator” EPSPs. In these nuclei, sharp-rising, large-amplitude EPSPs (“drivers”) were not modulated by cortical slow waves, suggesting their origin in ascending pathways. The thalamic active states in other investigated nuclei were composed of depolarization: some revealing “driver”- and “modulator”-like EPSPs, others showing “modulator”-like EPSPs only. We conclude that sensory thalamic nuclei follow the propagating cortical waves, whereas neurons from higher-order thalamic nuclei display “hub dynamics” and thus may contribute to the generation of cortical slow waves. PMID:24966387

New advanced tools for combined ULF wave analysis of multipoint space-borne and ground observations: application to single event and statistical studies

NASA Astrophysics Data System (ADS)

Balasis, G.; Papadimitriou, C.; Daglis, I. A.; Georgiou, M.; Giamini, S. A.

2013-12-01

In the past decade, a critical mass of high-quality scientific data on the electric and magnetic fields in the Earth's magnetosphere and topside ionosphere has been progressively collected. This data pool will be further enriched by the measurements of the upcoming ESA/Swarm mission, a constellation of three satellites in three different polar orbits between 400 and 550 km altitude, which is expected to be launched in November 2013. New analysis tools that can cope with measurements of various spacecraft at various regions of the magnetosphere and in the topside ionosphere as well as ground stations will effectively enhance the scientific exploitation of the accumulated data. Here, we report on a new suite of algorithms based on a combination of wavelet spectral methods and artificial neural network techniques and demonstrate the applicability of our recently developed analysis tools both for individual case studies and statistical studies of ultra-low frequency (ULF) waves. First, we provide evidence for a rare simultaneous observation of a ULF wave event in the Earth's magnetosphere, topside ionosphere and surface: we have found a specific time interval during the Halloween 2003 magnetic storm, when the Cluster and CHAMP spacecraft were in good local time (LT) conjunction, and have examined the ULF wave activity in the Pc3 (22-100 mHz) and Pc4-5 (1-22 mHz) bands using data from the Geotail, Cluster and CHAMP missions, as well as the CARISMA and GIMA magnetometer networks. Then, we perform a statistical study of Pc3 wave events observed by CHAMP for the full decade (2001-2010) of the satellite vector magnetic data: the creation of a database of such events enabled us to derive valuable statistics for many important physical properties relating to the spatio-temporal location of these waves, the wave power and frequency, as well as other parameters and their correlation with solar wind conditions, magnetospheric indices, electron density data, ring current decay and radiation belt enhancements. The work leading to this paper has received funding from the European Union's Seventh Framework Programme (FP7-SPACE-2011-1) under grant agreement no. 284520 for the MAARBLE (Monitoring, Analyzing and Assessing Radiation Belt Energization and Loss) collaborative research project.

A guided wave sensor enabling simultaneous wavenumber-frequency analysis for both lamb and shear-horizontal waves

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ren, Baiyang; Cho, Hwanjeong; Lissenden, Cliff J.

Guided waves in plate-like structures have been widely investigated for structural health monitoring. Lamb waves and shear horizontal (SH) waves, two commonly used types of waves in plates, provide different benefits for the detection of various types of defects and material degradation. However, there are few sensors that can detect both Lamb and SH waves and also resolve their modal content, namely the wavenumber-frequency spectrum. A sensor that can detect both waves is desirable to take full advantage of both types of waves in order to improve sensitivity to different discontinuity geometries. As a result, we demonstrate that polyvinylidene difluoridemore » (PVDF) film provides the basis for a multi-element array sensor that detects both Lamb and SH waves and also measures their modal content, i.e., the wavenumber-frequency spectrum.« less

On Hokusai's Great wave off Kanagawa: localization, linearity and a rogue wave in sub-Antarctic waters.

PubMed

Dudley, J M; Sarano, V; Dias, F

2013-06-20

The Hokusai woodcut entitled The great wave off Kanagawa has been interpreted as an unusually large storm wave, likely to be classed as a rogue wave, and possibly generated from nonlinear wave dynamics (J. H. E. Cartwright and H. Nakamura, Notes Rec. R. Soc. 63 , 119-135 (2009)). In this paper, we present a complementary discussion of this hypothesis, discussing in particular how linear and nonlinear mechanisms can both contribute to the emergence of rogue wave events. By making reference to the Great wave 's simultaneous transverse and longitudinal localization, we show that the purely linear mechanism of directional focusing also predicts characteristics consistent with those of the Great wave . In addition, we discuss the properties of a particular rogue wave photographed on the open ocean in sub-Antarctic waters, which shows two-dimensional localization and breaking dynamics remarkably similar to Hokusai's depiction in the woodcut.

On Hokusai's Great wave off Kanagawa: localization, linearity and a rogue wave in sub-Antarctic waters

PubMed Central

Dudley, J. M.; Sarano, V.; Dias, F.

2013-01-01

The Hokusai woodcut entitled The great wave off Kanagawa has been interpreted as an unusually large storm wave, likely to be classed as a rogue wave, and possibly generated from nonlinear wave dynamics (J. H. E. Cartwright and H. Nakamura, Notes Rec. R. Soc. 63, 119–135 (2009)). In this paper, we present a complementary discussion of this hypothesis, discussing in particular how linear and nonlinear mechanisms can both contribute to the emergence of rogue wave events. By making reference to the Great wave's simultaneous transverse and longitudinal localization, we show that the purely linear mechanism of directional focusing also predicts characteristics consistent with those of the Great wave. In addition, we discuss the properties of a particular rogue wave photographed on the open ocean in sub-Antarctic waters, which shows two-dimensional localization and breaking dynamics remarkably similar to Hokusai's depiction in the woodcut. PMID:24687148

A guided wave sensor enabling simultaneous wavenumber-frequency analysis for both lamb and shear-horizontal waves

DOE PAGES

Ren, Baiyang; Cho, Hwanjeong; Lissenden, Cliff J.

2017-03-01

Guided waves in plate-like structures have been widely investigated for structural health monitoring. Lamb waves and shear horizontal (SH) waves, two commonly used types of waves in plates, provide different benefits for the detection of various types of defects and material degradation. However, there are few sensors that can detect both Lamb and SH waves and also resolve their modal content, namely the wavenumber-frequency spectrum. A sensor that can detect both waves is desirable to take full advantage of both types of waves in order to improve sensitivity to different discontinuity geometries. As a result, we demonstrate that polyvinylidene difluoridemore » (PVDF) film provides the basis for a multi-element array sensor that detects both Lamb and SH waves and also measures their modal content, i.e., the wavenumber-frequency spectrum.« less

Explosive plane-wave lens

DOEpatents

Marsh, S.P.

1987-03-12

An explosive plane-wave air lens which enables a spherical wave form to be converted to a planar wave without the need to specially machine or shape explosive materials is described. A disc-shaped impactor having a greater thickness at its center than around its periphery is used to convert the spherical wave into a plane wave. When the wave reaches the impactor, the center of the impactor moves first because the spherical wave reaches the center of the impactor first. The wave strikes the impactor later in time as one moves radially along the impactor. Because the impactor is thinner as one moves radially outward, the velocity of the impactor is greater at the periphery than at the center. An acceptor explosive is positioned so that the impactor strikes the acceptor simultaneously. Consequently, a plane detonation wave is propagated through the acceptor explosive. 3 figs., 3 tabs.

Generation of uniform large-area very high frequency plasmas by launching two specific standing waves simultaneously

DOE Office of Scientific and Technical Information (OSTI.GOV)

Chen, Hsin-Liang, E-mail: hlchen@iner.gov.tw; Tu, Yen-Cheng; Hsieh, Cheng-Chang

2014-09-14

With the characteristics of higher electron density and lower ion bombardment energy, large-area VHF (very high frequency) plasma enhanced chemical vapor deposition has become an essential manufacturing equipment to improve the production throughput and efficiency of thin film silicon solar cell. However, the combination of high frequency and large electrodes leads to the so-called standing wave effect causing a serious problem for the deposition uniformity of silicon thin film. In order to address this issue, a technique based on the idea of simultaneously launching two standing waves that possess similar amplitudes and are out of phase by 90° in timemore » and space is proposed in this study. A linear plasma reactor with discharge length of 54 cm is tested with two different frequencies including 60 and 80 MHz. The experimental results show that the proposed technique could effectively improve the non-uniformity of VHF plasmas from >±60% when only one standing wave is applied to <±10% once two specific standing waves are launched at the same time. Moreover, in terms of the reactor configuration adopted in this study, in which the standing wave effect along the much shorter dimension can be ignored, the proposed technique is applicable to different frequencies without the need to alter the number and arrangement of power feeding points.« less

Advanced Multivariate Inversion Techniques for High Resolution 3D Geophysical Modeling (Invited)

NASA Astrophysics Data System (ADS)

Maceira, M.; Zhang, H.; Rowe, C. A.

2009-12-01

We focus on the development and application of advanced multivariate inversion techniques to generate a realistic, comprehensive, and high-resolution 3D model of the seismic structure of the crust and upper mantle that satisfies several independent geophysical datasets. Building on previous efforts of joint invesion using surface wave dispersion measurements, gravity data, and receiver functions, we have added a fourth dataset, seismic body wave P and S travel times, to the simultaneous joint inversion method. We present a 3D seismic velocity model of the crust and upper mantle of northwest China resulting from the simultaneous, joint inversion of these four data types. Surface wave dispersion measurements are primarily sensitive to seismic shear-wave velocities, but at shallow depths it is difficult to obtain high-resolution velocities and to constrain the structure due to the depth-averaging of the more easily-modeled, longer-period surface waves. Gravity inversions have the greatest resolving power at shallow depths, and they provide constraints on rock density variations. Moreover, while surface wave dispersion measurements are primarily sensitive to vertical shear-wave velocity averages, body wave receiver functions are sensitive to shear-wave velocity contrasts and vertical travel-times. Addition of the fourth dataset, consisting of seismic travel-time data, helps to constrain the shear wave velocities both vertically and horizontally in the model cells crossed by the ray paths. Incorporation of both P and S body wave travel times allows us to invert for both P and S velocity structure, capitalizing on empirical relationships between both wave types’ seismic velocities with rock densities, thus eliminating the need for ad hoc assumptions regarding the Poisson ratios. Our new tomography algorithm is a modification of the Maceira and Ammon joint inversion code, in combination with the Zhang and Thurber TomoDD (double-difference tomography) program.

Viscosity in the thermosphere: Evidence from gravity wave, neutral wind and direct lab measurements that the standard viscosity coefficients are too large in the thermosphere; and implication for gravity wave propagation in the thermosphere

NASA Astrophysics Data System (ADS)

Vadas, Sharon; Crowley, Geoff

2017-04-01

In this paper, we review measurements of 1) gravity waves (GWs) observed as traveling ionospheric disturbances (TIDs) at z 283 km by the TIDDBIT sounder on 30 October 2007, and 2) simultaneous rockets measurements of in-situ neutral winds at z 320-385 km. The neutral wind contains a 100 m/s peak at z 325 km in the same direction as the GWs, but oppositely-directed to the diurnal tides. We hypothesize that several of the TIDDBIT GWs propagated upwards and created this neutral wind peak. Using an anelastic GW ray trace model which includes thermospheric dissipation from molecular viscosity and thermal conductivity with mu proportional to the temperature to the power of 0.7, we forward ray trace the GWs from z_i=220 km. Surprisingly, the GWs dissipate below z 260 km, well below the altitude they were observed. Furthermore, none of the GWs could have propagated high-enough to create the neutral wind peak. In our opinion, this constitutes a significant discrepancy between observations and GW dissipative theory. We perform sensitivity experiments to rule out background temperature and wind effects as being the cause. We propose a modification to the formula for mu, and show that this yields ray trace results that agree reasonably well with the observations. We examine papers and reports for laboratory experiments which measured mu at low pressures, and find similar results. We conclude that the standard formulas for mu routinely used in thermospheric models must be modified in the thermosphere to account for this important effect. We also show preliminary GW ray trace results using this modified formula for mu, and compare with previous theoretical results.

Simultaneous measurement of the de Haas-van Alphen and the Shubnikov-de Haas effect in a two-dimensional electron system

NASA Astrophysics Data System (ADS)

Ruhe, N.; Springborn, J. I.; Heyn, Ch.; Wilde, M. A.; Grundler, D.

2006-12-01

In a simultaneous experiment we studied the de Haas-van Alphen (dHvA) and the Shubnikov-de Haas (SdH) effects in a two-dimensional electron system (2DES) in a modulation-doped GaAs/AlxGa1-xAs heterostructure. For this, a gated 2DES mesa was monolithically integrated with a micromechnical cantilever with an interferometric fiber-optics readout. In situ measurement of the dHvA and SdH oscillations at 300mK in a magnetic field B allowed us to directly compare the variation of the ground state energy and the nonequilibrium transport behavior, respectively. This was done on a 2DES of a small carrier density ns ranging from 5×1010to33×1010cm-2 . The wave forms of the dHvA oscillations were nonsinusoidal down to a magnetic field as small as 1.45T . At the same time the zero-field mobility was as low as μe=105cm2/Vs . We found that at fixed B the observed dHvA wave form and amplitude were independent of ns and μe . This was unexpected and in contrast to the established picture in the literature. To understand the dHvA effect quantitatively in a disordered 2DES our data suggest that energetic details of the disorder potentials have to be considered.

Coherent perfect absorber and laser modes in purely imaginary metamaterials

NASA Astrophysics Data System (ADS)

Fu, Yangyang; Cao, Yanyan; Cummer, Steven A.; Xu, Yadong; Chen, Huanyang

2017-10-01

Conjugate metamaterials, in which the permittivity and the permeability are complex conjugates of each other, possess the elements of loss and gain simultaneously. By employing a conjugate metamaterial with a purely imaginary form, we propose a mechanism for realizing both coherent perfect absorber (CPA) and laser modes. Moreover, the general conditions for obtaining CPA and laser modes, including obtaining them simultaneously, are revealed by analyzing the wave scattering properties of a slab made of purely imaginary metamaterials (PIMs). Specifically, in a PIM slab with a subunity effective refractive index, the CPA mode can be simplified as a perfect absorption mode and the incident wave from one side could be perfectly absorbed.

An investigation of turbulent scatter from the mesosphere as observed by coherent-scatter radar

NASA Technical Reports Server (NTRS)

Gibbs, K. P.; Bowhill, S. A.

1983-01-01

Turbulent scatter from he mesosphere is observed using the Urbana coherent-scatter radar. The variation in signal-to-noise ratio as a function of time-of-day is examined. The origin of scattering regions is investigated by comparing the variations in scattered power and Doppler velocity. Nighttime echoes are shown for periods of enhanced electron concentration. The spectrum of the returned signal is studied with a resolution of ten seconds. Spectral information is used to increase altitude resolution and observe the motion of scatterers. The expected variation in signal-to-noise ratio with solar flux is observed. It is found that variations in the scattered power generally do not correspond to the gravity waves which are simultaneously observed. Turbulent layers are observed at altitudes with high shear in the horizontal velocity and at altitudes with low shear. The ten-second resolution is necessary to distinguish meteor echoes from echoes produced by the advection of a scattering layer through the radar beam.

Coherent observations of gravitational radiation with LISA and gLISA

NASA Astrophysics Data System (ADS)

Tinto, Massimo; de Araujo, José C. N.

2016-10-01

The geosynchronous Laser Interferometer Space Antenna (gLISA) is a space-based gravitational wave (GW) mission that, for the past 5 years, has been under joint study at the Jet Propulsion Laboratory; Stanford University; the National Institute for Space Research (I.N.P.E., Brazil); and Space Systems Loral. If flown at the same time as the LISA mission, the two arrays will deliver a joint sensitivity that accounts for the best performance of both missions in their respective parts of the millihertz band. This simultaneous operation will result in an optimally combined sensitivity curve that is "white" from about 3 ×10-3 Hz to 1 Hz, making the two antennas capable of detecting, with high signal-to-noise ratios (SNRs), coalescing black-hole binaries (BHBs) with masses in the range (10 -1 08)M⊙ . Their ability of jointly tracking, with enhanced SNR, signals similar to that observed by the Advanced Laser Interferometer Gravitational Wave Observatory (aLIGO) on September 14, 2015 (the GW150914 event) will result in a larger number of observable small-mass binary black holes and an improved precision of the parameters characterizing these sources. Together, LISA, gLISA and aLIGO will cover, with good sensitivity, the (10-4-1 03) Hz frequency band.

Radiation Transport of Heliospheric Lyman-alpha from Combined Cassini and Voyager Data Sets

NASA Technical Reports Server (NTRS)

Pryor, W.; Gangopadhyay, P.; Sandel, B.; Forrester, T.; Quemerais, E.; Moebius, E.; Esposito, L.; Stewart, I.; McClintock, W.; Jouchoux, A.;

Diastolic Backward-Traveling Decompression (Suction) Wave Correlates With Simultaneously Acquired Indices of Diastolic Function and Is Reduced in Left Ventricular Stunning.

PubMed

Ladwiniec, Andrew; White, Paul A; Nijjer, Sukhjinder S; O'Sullivan, Michael; West, Nick E J; Davies, Justin E; Hoole, Stephen P

2016-09-01

Wave intensity analysis can distinguish proximal (propulsion) and distal (suction) influences on coronary blood flow and is purported to reflect myocardial performance and microvascular function. Quantifying the amplitude of the peak, backwards expansion wave (BEW) may have clinical utility. However, simultaneously acquired wave intensity analysis and left ventricular (LV) pressure-volume loop data, confirming the origin and effect of myocardial function on the BEW in humans, have not been previously reported. Patients with single-vessel left anterior descending coronary disease and normal ventricular function (n=13) were recruited prospectively. We simultaneously measured LV function with a conductance catheter and derived wave intensity analysis using a pressure-low velocity guidewire at baseline and again 30 minutes after a 1-minute coronary balloon occlusion. The peak BEW correlated with the indices of diastolic LV function: LV dP/dtmin (rs=-0.59; P=0.002) and τ (rs=-0.59; P=0.002), but not with systolic function. In 12 patients with paired measurements 30 minutes post balloon occlusion, LV dP/dtmax decreased from 1437.1±163.9 to 1299.4±152.9 mm Hg/s (median difference, -110.4 [-183.3 to -70.4]; P=0.015) and τ increased from 48.3±7.4 to 52.4±7.9 ms (difference, 4.1 [1.3-6.9]; P=0.01), but basal average peak coronary flow velocity was unchanged, indicating LV stunning post balloon occlusion. However, the peak BEW amplitude decreased from -9.95±5.45 W·m(-2)/s(2)×10(5) to -7.52±5.00 W·m(-2)/s(2)×10(5) (difference 2.43×10(5) [0.20×10(5) to 4.67×10(5); P=0.04]). Peak BEW assessed by coronary wave intensity analysis correlates with invasive indices of LV diastolic function and mirrors changes in LV diastolic function confirming the origin of the suction wave. This may have implications for physiological lesion assessment after percutaneous coronary intervention. URL: http://www.isrctn.org. Unique identifier: ISRCTN42864201. © 2016 American Heart Association, Inc.

Refrigeration system having standing wave compressor

DOEpatents

Lucas, Timothy S.

1992-01-01

A compression-evaporation refrigeration system, wherein gaseous compression of the refrigerant is provided by a standing wave compressor. The standing wave compressor is modified so as to provide a separate subcooling system for the refrigerant, so that efficiency losses due to flashing are reduced. Subcooling occurs when heat exchange is provided between the refrigerant and a heat pumping surface, which is exposed to the standing acoustic wave within the standing wave compressor. A variable capacity and variable discharge pressure for the standing wave compressor is provided. A control circuit simultaneously varies the capacity and discharge pressure in response to changing operating conditions, thereby maintaining the minimum discharge pressure needed for condensation to occur at any time. Thus, the power consumption of the standing wave compressor is reduced and system efficiency is improved.

Observations of a solar storm from the stratosphere: The BARREL Mission

NASA Astrophysics Data System (ADS)

Halford, Alexa

2016-07-01

During the Balloon Array for Radiation belt Relativistic Electron Losses (BARREL) second campaign, BARREL observed with a single primary instrument, a 3"x3" NaI spectrometer measuring 20 keV - 10 MeV X-rays [Woodger et al 2015 JGR], portions of an entire solar storm. This very small event, in terms of geomagnetic activity, or one of the largest of the current solar cycle, in terms of solar energetic particle events, has given us a very clear set of observations of the response of the day side magnetosphere to the arrival of an interplanetary coronal mass ejection shock. The BARREL mission of opportunity working in tandem with the Van Allen Probes was designed to study the loss of radiation belt electrons to the ionosphere and upper atmosphere. However BARREL is able to see X-rays from a multitude of sources. During the second campaign, the Sun produced, and BARREL observed, an X-class flare [McGregor et al in prep.]. This was followed by BARREL observations of X-rays, gamma-rays, and directly injected protons from the solar energetic particle (SEP) event associated with the eruption from the Sun while simultaneously the Van Allen Probes observed the SEP protons in the inner magnetosphere [Halford et al 2016 submitted JGR]. Two days later the shock generated by the interplanetary coronal mass ejection (ICME-shock) hit the Earth while BARREL was in conjunction with the Van Allen Probes and GOES [Halford et al 2015 JGR]. Although this was a Mars directed CME and the Earth only received a glancing blow [Möstl et al 2015 Nat. Commun., Mays et al 2015 ApJ], the modest compression led to the formation of ultra low frequency (ULF) waves, electromagnetic ion cyclotron (EMIC) waves, and very low frequency (VLF) whistler mode waves [Halford and Mann 2016 submitted to JGR]. The combination of these waves and the enhancement of the local particle population led to precipitation of electrons remotely observed by BARREL. This was not a Halloween, Bastille Day, or one of the now many St. Patricks Day storms. In fact it's unlikely that it will ever get it's own Holliday nickname. But unlike those larger geomagnetic events, the 7 - 10 January 2014 event was less complicated allowing us to directly test the relative importance of multiple loss mechanisms, see how waves are generated, and by and large gain a more complete understanding of how the system interacts as well as how quiet times can affect radiation belt dynamics.

Investigating flow patterns and related dynamics in multi-instability turbulent plasmas using a three-point cross-phase time delay estimation velocimetry scheme

NASA Astrophysics Data System (ADS)

Brandt, C.; Thakur, S. C.; Tynan, G. R.

2016-04-01

Complexities of flow patterns in the azimuthal cross-section of a cylindrical magnetized helicon plasma and the corresponding plasma dynamics are investigated by means of a novel scheme for time delay estimation velocimetry. The advantage of this introduced method is the capability of calculating the time-averaged 2D velocity fields of propagating wave-like structures and patterns in complex spatiotemporal data. It is able to distinguish and visualize the details of simultaneously present superimposed entangled dynamics and it can be applied to fluid-like systems exhibiting frequently repeating patterns (e.g., waves in plasmas, waves in fluids, dynamics in planetary atmospheres, etc.). The velocity calculations are based on time delay estimation obtained from cross-phase analysis of time series. Each velocity vector is unambiguously calculated from three time series measured at three different non-collinear spatial points. This method, when applied to fast imaging, has been crucial to understand the rich plasma dynamics in the azimuthal cross-section of a cylindrical linear magnetized helicon plasma. The capabilities and the limitations of this velocimetry method are discussed and demonstrated for two completely different plasma regimes, i.e., for quasi-coherent wave dynamics and for complex broadband wave dynamics involving simultaneously present multiple instabilities.

Investigating flow patterns and related dynamics in multi-instability turbulent plasmas using a three-point cross-phase time delay estimation velocimetry scheme

DOE Office of Scientific and Technical Information (OSTI.GOV)

Brandt, C.; Max-Planck-Institute for Plasma Physics, Wendelsteinstr. 1, D-17491 Greifswald; Thakur, S. C.

2016-04-15

Complexities of flow patterns in the azimuthal cross-section of a cylindrical magnetized helicon plasma and the corresponding plasma dynamics are investigated by means of a novel scheme for time delay estimation velocimetry. The advantage of this introduced method is the capability of calculating the time-averaged 2D velocity fields of propagating wave-like structures and patterns in complex spatiotemporal data. It is able to distinguish and visualize the details of simultaneously present superimposed entangled dynamics and it can be applied to fluid-like systems exhibiting frequently repeating patterns (e.g., waves in plasmas, waves in fluids, dynamics in planetary atmospheres, etc.). The velocity calculationsmore » are based on time delay estimation obtained from cross-phase analysis of time series. Each velocity vector is unambiguously calculated from three time series measured at three different non-collinear spatial points. This method, when applied to fast imaging, has been crucial to understand the rich plasma dynamics in the azimuthal cross-section of a cylindrical linear magnetized helicon plasma. The capabilities and the limitations of this velocimetry method are discussed and demonstrated for two completely different plasma regimes, i.e., for quasi-coherent wave dynamics and for complex broadband wave dynamics involving simultaneously present multiple instabilities.« less

DIRECT SOLUTIONS OF THE MAXWELL EQUATIONS EXPLAIN OPPOSITION PHENOMENA OBSERVED FOR HIGH-ALBEDO SOLAR SYSTEM OBJECTS

DOE Office of Scientific and Technical Information (OSTI.GOV)

Mishchenko, Michael I.; Liu Li; Dlugach, Janna M.

2009-11-10

Several spectacular backscattering effects observed for particulate planetary surfaces have been interpreted in terms of the effect of weak localization (WL) of electromagnetic waves. However, the interference concept of WL explicitly relies on the notion of phase of an electromagnetic wave and is strictly applicable only when particles forming the surface are widely separated. Therefore, one needs a definitive quantitative proof of the WL nature of specific optical effects observed for densely packed particulate media. We use numerically exact computer solutions of the Maxwell equations to simulate electromagnetic scattering by realistic models consisting of large numbers of randomly positioned, denselymore » packed particles. By increasing the particle packing density from zero to approx40%, we track the onset and evolution of the full suite of backscattering optical effects predicted by the low-density theory of WL, including the brightness and polarization opposition effects (BOE and POE). We find that all manifestations of WL, except the circular polarization ratio and POE, are remarkably immune to packing-density effects. Even POE can survive packing densities typical of planetary regolith surfaces. Our numerical data coupled with the results of unique observations at near-backscattering geometries demonstrate that the BOE and POE detected simultaneously for high-albedo solar system objects are caused by the effect of WL.« less

Dynamics of Endo- and Epicardial Focal Fibrillation Waves at the Right Atrium in a Patient With Advanced Atrial Remodelling.

PubMed

van der Does, Lisette J M E; Kik, Charles; Bogers, Ad J J C; Allessie, Maurits A; de Groot, Natasja M S

2016-10-01

Focal waves appear frequently at the epicardium during persistent atrial fibrillation (AF), however, the origin of these waves is under debate. We performed simultaneous endo-epicardial mapping of the right atrial wall during longstanding persistent AF in a patient undergoing cardiac surgery. During 10 seconds 53 and 59 focal waves appeared at random at respectively the endocardium and epicardium. Repetitive focal activity did not last longer than 3 cycles. Transmural asynchrony and conduction might be the origin of focal waves. Asynchronous propagation of fibrillation waves in 3 dimensions would stabilize the arrhythmia and could explain the limited success of persistent AF ablation. Copyright © 2016 Canadian Cardiovascular Society. Published by Elsevier Inc. All rights reserved.

Note: A novel method for generating multichannel quasi-square-wave pulses.

PubMed

Mao, C; Zou, X; Wang, X

2015-08-01

A 21-channel quasi-square-wave nanosecond pulse generator was constructed. The generator consists of a high-voltage square-wave pulser and a channel divider. Using an electromagnetic relay as a switch and a 50-Ω polyethylene cable as a pulse forming line, the high-voltage pulser produces a 10-ns square-wave pulse of 1070 V. With a specially designed resistor-cable network, the channel divider divides the high-voltage square-wave pulse into 21 identical 10-ns quasi-square-wave pulses of 51 V, exactly equal to 1070 V/21. The generator can operate not only in a simultaneous mode but also in a delay mode if the cables in the channel divider are different in length.

Dissipation of ionospheric irregularities by wave-particle and collisional interactions

NASA Technical Reports Server (NTRS)

Bernhardt, P. A.; Pongratz, M. B.; Gray, S. P.; Thomsen, M. F.

1982-01-01

The nonlinear dissipation of plasma irregularities aligned parallel to an ambient magnetic field is studied numerically using a model which employs both wave-particle and collisional diffusion. A wave-particle diffusion coefficient derived from a local theory of the universal drift instability is used. This coefficient is effective in regions of nonzero plasma gradients and produces triangular-shaped irregularities with spectra which vary as f to the -4th, where f is the spatial frequency. Collisional diffusion acts rapidly on the vertices of the irregularities to reduce their amplitude. The simultaneous action of the two dissipative processes is more efficient than collisions acting alone. In this model, wave-particle diffusion mimics the forward cascade process of wave-wave coupling.

Simultaneous excitation system for efficient guided wave structural health monitoring

NASA Astrophysics Data System (ADS)

Hua, Jiadong; Michaels, Jennifer E.; Chen, Xin; Lin, Jing

2017-10-01

Many structural health monitoring systems utilize guided wave transducer arrays for defect detection and localization. Signals are usually acquired using the ;pitch-catch; method whereby each transducer is excited in turn and the response is received by the remaining transducers. When extensive signal averaging is performed, the data acquisition process can be quite time-consuming, especially for metallic components that require a low repetition rate to allow signals to die out. Such a long data acquisition time is particularly problematic if environmental and operational conditions are changing while data are being acquired. To reduce the total data acquisition time, proposed here is a methodology whereby multiple transmitters are simultaneously triggered, and each transmitter is driven with a unique excitation. The simultaneously transmitted waves are captured by one or more receivers, and their responses are processed by dispersion-compensated filtering to extract the response from each individual transmitter. The excitation sequences are constructed by concatenating a series of chirps whose start and stop frequencies are randomly selected from a specified range. The process is optimized using a Monte-Carlo approach to select sequences with impulse-like autocorrelations and relatively flat cross-correlations. The efficacy of the proposed methodology is evaluated by several metrics and is experimentally demonstrated with sparse array imaging of simulated damage.

Dynamic Neurovascular Coupling and Uncoupling during Ictal Onset, Propagation, and Termination Revealed by Simultaneous In Vivo Optical Imaging of Neural Activity and Local Blood Volume

PubMed Central

Zhao, Mingrui; Schwartz, Theodore H.

2013-01-01

Traditional models of ictal propagation involve the concept of an initiation site and a progressive outward march of activation. The process of neurovascular coupling, whereby the brain supplies oxygenated blood to metabolically active neurons presumably results in a similar outward cascade of hyperemia. However, ictal neurovascular coupling has never been assessed in vivo using simultaneous measurements of membrane potential change and hyperemia with wide spatial sampling. In an acute rat ictal model, using simultaneous intrinsic optical signal (IOS) and voltage-sensitive dye (VSD) imaging of cerebral blood volume and membrane potential changes, we demonstrate that seizures consist of multiple dynamic multidirectional waves of membrane potential change with variable onset sites that spread through a widespread network. Local blood volume evolves on a much slower spatiotemporal scale. At seizure onset, the VSD waves extend beyond the IOS signal. During evolution, spatial correlation with hemodynamic signal only exists briefly at the maximal spread of the VSD signal. At termination, the IOS signal extends spatially and temporally beyond the VSD waves. Hence, vascular reactivity evolves in a separate but parallel fashion to membrane potential changes resulting in a mechanism of neurovascular coupling and uncoupling, which is as dynamic as the seizure itself. PMID:22499798

New GOES High-Resolution Magnetic Measurements and their Contribution to Understanding Magnetospheric Particle Dynamics

NASA Astrophysics Data System (ADS)

Redmon, R. J.; Loto'aniu, P. T. M.; Boudouridis, A.; Chi, P. J.; Singer, H. J.; Kress, B. T.; Rodriguez, J. V.; Abdelqader, A.; Tilton, M.

2017-12-01

The era of NOAA observations of the geomagnetic field started with SMS-1 in May 1974 and continues to this day with GOES-13-16 (on-orbit). We describe the development of a new 20+ year archive of science-quality, high-cadence geostationary measurements of the magnetic field from eight NOAA spacecraft (GOES-8 through GOES-15), the status of GOES-16 and new scientific results using these data. GOES magnetic observations provide an early warning of impending space weather, are the core geostationary data set used for the construction of magnetospheric magnetic models, and can be used to estimate electromagnetic wave power in frequency bands important for plasma processes. Many science grade improvements are being made across the GOES archive to unify the format and content from GOES-8 through the new GOES-R series (with the first of that series launched on November 19, 2016). A majority of the 2-Hz magnetic observations from GOES-8-12 have never before been publicly accessible due to processing constraints. Now, a NOAA Big Earth Data Initiative project is underway to process these measurements starting from original telemetry records. Overall the new archive will include vector measurements in geophysically relevant coordinates (EPN, GSM, and VDH), comprehensive documentation, highest temporal cadence, best calibration parameters, recomputed means, updated quality flagging, full spacecraft ephemeris information, a unified standard format and public access. We are also developing spectral characterization tools for estimating power in standard frequency bands (up to 1 Hz for G8-15), and detecting ULF waves related to field-line resonances. We present the project status and findings, including in-situ statistical and extreme ULF event properties, and case studies where the ULF oscillations along the same field line were observed simultaneously by GOES near the equator in the magnetosphere, the ST-5 satellites at low altitudes, and ground magnetometer stations. For event studies, we find that the wave amplitude of poloidal oscillations is amplified at low altitudes but attenuated on the ground, confirming the theoretical predictions of wave propagation from the magnetosphere to the ground. We include examples of GOES-16 particle flux and magnetic field observations illustrating complex particle dynamics.

Preliminary analysis of seismic anisotropy in the uppermost mantle beneath NW Pacific reveled by the Normal Oceanic Mantle project

NASA Astrophysics Data System (ADS)

Takeo, A.; Isse, T.; Nishida, K.; Kawakatsu, H.; Shiobara, H.; Sugioka, H.; Ito, A.; Utada, H.

2013-12-01

Seismic structure including anisotropy in the oceanic uppermost mantle is essential for understanding deformation related to plate tectonics. Recent reports of a sharp discontinuity between the high velocity LID and the low velocity zone (LVZ) especially emphasize the importance of observation in oceanic basins apart from ridges and hotspots for determining the structure including LID and LVZ. In this study, we analyzed records of four broadband ocean bottom seismometers (BBOBSs) deployed in the northwest of Shatsky Rise by the pilot observation of the Normal Oceanic Mantle (NOMan) project in 2010-2011. We first measured average phase velocities of surface waves at periods of 5-30 s by the ambient-noise cross correlation method. Based on the method of Takeo et al. (in prep. GJI), we analyzed fundamental- and first higher- mode Rayleigh waves and fundamental-mode Love wave simultaneously by waveform fitting after the correction of clock delay. At periods of 25-100 s, we measured phase velocities of fundamental-mode surface waves by the array analysis of teleseismic waveforms. We then determined one-dimensional radially anisotropic structure beneath the array by the method of Takeo et al. (2013, JGR). The obtained structure shows transition from LID to LVZ at depths of 50-80km, which is marginally consistent with the depth of ~80 km estimated by a receiver function analysis at WP2 station situated at east of the studies area (Kawakatsu et al., 2009). The velocity gradient in the LID is almost zero and inconsistent with the simple cooling model of homogeneous oceanic plate. The average intensity of S-wave radial anisotropy at depths of ~10-220 km is ~3% (VSH>VSV). We further estimated S-wave azimuthal anisotropy at depths of ~30-100 km by analyzing teleseismic fundamental-mode Rayleigh waves at periods of 25-50 s. The intensity of anisotropy is 2-3%. The fastest direction is about N35W, close to that of Sn-wave velocity around WP2 station obtained by a refraction survey (Shinohara et al., 2008), and indicates the presence of past mantle flow almost perpendicular to the ancient mid ocean ridge or the presence of current mantle flow parallel to the plate motion at depths of 30-100 km. We will further analyze new records after the recovery of 13 BBOBSs in August 2013 and will present more detailed structure around Shatsky Rise. BBOBS stations of pilot observation of NOMan project (white crosses), WP2 station (circle), isochrons (white lines). Black bars show the fastest directions of Rayleigh wave at periods of 25-50 s and the fastest direction of Sn-wave velocity (Shinohara et al. 2008).

Wave-CAIPI ViSTa: highly accelerated whole-brain direct myelin water imaging with zero-padding reconstruction.

PubMed

Wu, Zhe; Bilgic, Berkin; He, Hongjian; Tong, Qiqi; Sun, Yi; Du, Yiping; Setsompop, Kawin; Zhong, Jianhui

2018-09-01

This study introduces a highly accelerated whole-brain direct visualization of short transverse relaxation time component (ViSTa) imaging using a wave controlled aliasing in parallel imaging (CAIPI) technique, for acquisition within a clinically acceptable scan time, with the preservation of high image quality and sufficient spatial resolution, and reduced residual point spread function artifacts. Double inversion RF pulses were applied to preserve the signal from short T 1 components for directly extracting myelin water signal in ViSTa imaging. A 2D simultaneous multislice and a 3D acquisition of ViSTa images incorporating wave-encoding were used for data acquisition. Improvements brought by a zero-padding method in wave-CAIPI reconstruction were also investigated. The zero-padding method in wave-CAIPI reconstruction reduced the root-mean-square errors between the wave-encoded and Cartesian gradient echoes for all wave gradient configurations in simulation, and reduced the side-main lobe intensity ratio from 34.5 to 16% in the thin-slab in vivo ViSTa images. In a 4 × acceleration simultaneous-multislice scenario, wave-CAIPI ViSTa achieved negligible g-factors (g mean /g max  = 1.03/1.10), while retaining minimal interslice artifacts. An 8 × accelerated acquisition of 3D wave-CAIPI ViSTa imaging covering the whole brain with 1.1 × 1.1 × 3 mm 3 voxel size was achieved within 15 minutes, and only incurred a small g-factor penalty (g mean /g max  = 1.05/1.16). Whole-brain ViSTa images were obtained within 15 minutes with negligible g-factor penalty by using wave-CAIPI acquisition and zero-padding reconstruction. The proposed zero-padding method was shown to be effective in reducing residual point spread function for wave-encoded images, particularly for ViSTa. © 2018 International Society for Magnetic Resonance in Medicine.

The Seasat SAR Wind and Ocean Wave Monitoring Capabilities: A case study for pass 1339m

NASA Technical Reports Server (NTRS)

Beal, R. C.

1980-01-01

A well organized low energy 11 sec. swell system off the East Coast of the U.S. was detected with the Seasat Synthetic Aperture Radar and successfully tracked from deep water, across the continental shelf, and into shallow water. In addition, a less organized 7 sec. system was tentatively identified in the imagery. Both systems were independently confirmed with simultaneous wave spectral measurements from a research pier, aircraft laser profilometer data, and Fleet Numerical Spectral Ocean Wave Models.