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F P Keenan - One of the best experts on this subject based on the ideXlab platform.
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propagating Wave Phenomena detected in observations and simulations of the lower solar atmosphere
The Astrophysical Journal, 2012Co-Authors: D B Jess, Sergiy Shelyag, Mihalis Mathioudakis, Peter H Keys, D J Christian, F P KeenanAbstract:We present high-cadence observations and simulations of the solar photosphere, obtained using the Rapid Oscillations in the Solar Atmosphere imaging system and the MuRAM magnetohydrodynamic (MHD) code, respectively. Each data set demonstrates a wealth of magnetoacoustic oscillatory behavior, visible as periodic intensity fluctuations with periods in the range 110-600 s. Almost no propagating Waves with periods less than 140 s and 110 s are detected in the observational and simulated data sets, respectively. High concentrations of power are found in highly magnetized regions, such as magnetic bright points and intergranular lanes. Radiative diagnostics of the photospheric simulations replicate our observational results, confirming that the current breed of MHD simulations are able to accurately represent the lower solar atmosphere. All observed oscillations are generated as a result of naturally occurring magnetoconvective processes, with no specific input driver present. Using contribution functions extracted from our numerical simulations, we estimate minimum G-band and 4170 A continuum formation heights of 100 km and 25 km, respectively. Detected magnetoacoustic oscillations exhibit a dominant phase delay of –8° between the G-band and 4170 A continuum observations, suggesting the presence of upwardly propagating Waves. More than 73% of MBPs (73% from observations and 96% from simulations) display upwardly propagating Wave Phenomena, suggesting the abundant nature of oscillatory behavior detected higher in the solar atmosphere may be traced back to magnetoconvective processes occurring in the upper layers of the Sun's convection zone.
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propagating Wave Phenomena detected in observations and simulations of the lower solar atmosphere
arXiv: Solar and Stellar Astrophysics, 2012Co-Authors: D B Jess, Sergiy Shelyag, Mihalis Mathioudakis, Peter H Keys, D J Christian, F P KeenanAbstract:We present high-cadence observations and simulations of the solar photosphere, obtained using the Rapid Oscillations in the Solar Atmosphere imaging system and the MuRAM magneto-hydrodynamic code, respectively. Each dataset demonstrates a wealth of magneto-acoustic oscillatory behaviour, visible as periodic intensity fluctuations with periods in the range 110-600 s. Almost no propagating Waves with periods less than 140s and 110s are detected in the observational and simulated datasets, respectively. High concentrations of power are found in highly magnetised regions, such as magnetic bright points and intergranular lanes. Radiative diagnostics of the photospheric simulations replicate our observational results, confirming that the current breed of magneto-hydrodynamic simulations are able to accurately represent the lower solar atmosphere. All observed oscillations are generated as a result of naturally occurring magnetoconvective processes, with no specific input driver present. Using contribution functions extracted from our numerical simulations, we estimate minimum G-band and 4170 Angstrom continuum formation heights of 100 km and 25 km, respectively. Detected magneto-acoustic oscillations exhibit a dominant phase delay of -8 degrees between the G-band and 4170 Angstrom continuum observations, suggesting the presence of upwardly propagating Waves. More than 73% of MBPs (73% from observations, 96% from simulations) display upwardly propagating Wave Phenomena, suggesting the abundant nature of oscillatory behaviour detected higher in the solar atmosphere may be traced back to magnetoconvective processes occurring in the upper layers of the Sun's convection zone.
Kazuyoshi Takayama - One of the best experts on this subject based on the ideXlab platform.
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Laboratory-scale blast Wave Phenomena – optical diagnostics and applications
Shock Waves, 2005Co-Authors: Harald Kleine, E Timofeev, Kazuyoshi TakayamaAbstract:Laboratory-scale experiments with explosive charges in the milligram range are a useful tool to investigate basic blast Wave Phenomena and to replicate, to some extent, large-scale explosions. This paper reviews and discusses the optical diagnostics that can be applied in these experiments and outlines how these techniques can be used to obtain new information about the propagation and interaction of blast Waves. Performance criteria for the required instrumentation are established. Several examples illustrate the potential and the limitations of this approach to blast Wave research.
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laboratory scale blast Wave Phenomena optical diagnostics and applications
Shock Waves, 2005Co-Authors: Harald Kleine, E Timofeev, Kazuyoshi TakayamaAbstract:Laboratory-scale experiments with explosive charges in the milligram range are a useful tool to investigate basic blast Wave Phenomena and to replicate, to some extent, large-scale explosions. This paper reviews and discusses the optical diagnostics that can be applied in these experiments and outlines how these techniques can be used to obtain new information about the propagation and interaction of blast Waves. Performance criteria for the required instrumentation are established. Several examples illustrate the potential and the limitations of this approach to blast Wave research.
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Applications of Shock Wave Phenomena to Interdisciplinary Research
Jsme International Journal Series B-fluids and Thermal Engineering, 2002Co-Authors: Kazuyoshi TakayamaAbstract:Paper briefly describes applications of shock Wave Phenomena to interdisciplinary research, which are in progress in the Interdisciplinary Shock Wave Research Center. This project is funded by the grant-in-aid science research under the COE program entitled the investigation of shock Wave Phenomena in complex media and its interdisciplinary application. Its goal is to extend results of this basic research not only to interdisciplinary research programs and also to establish a new paradigm of shock Wave research.
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Holographic interferometric observation of shock Wave Phenomena
Laser Interferometry IV: Computer-Aided Interferometry, 1992Co-Authors: Masato Watanabe, Akira Abe, R. T. Casey, Kazuyoshi TakayamaAbstract:A holographic interferometric study was made of the structure of a shock Wave discharged from a square cross section shock tube. To visualize the present complex three-dimensional shock Wave Phenomena, two- and three-dimensional holographic interferometry was applied. The results indicated that the vortex which was generated from the shock tube exit changed its configuration from a square shape to a cylindrical shape and that the secondary shock Wave has a complex three-dimensional shape. To compare the experimental results, a numerical simulation using the TVD finite difference scheme was conducted and good agreement was obtained. It is pointed out that quantitative holographic interferometry is particularly useful to validate the CFD code.© (1992) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.
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Visualization of shock Wave Phenomena by using double exposure holographic interferometry
Journal of the Visualization Society of Japan, 1992Co-Authors: Masato Watanabe, Kazuyoshi TakayamaAbstract:Holographic interferometry has been successfully applied quantitatively to visualize shock Wave Phenomena. This paper will demonstrate that this flow visualization technique is more effective in observing three-dimensional shock Wave reflection over cones than other conventional flow visualization techniques.It is well documented that, in a two-dimensional shock Wave reflection over a wedge, regular reflection or Mach reflection occurs according to the shock Mach number and the wedge angle. When a shock Wave reflects at the surface of a cone which has an attack angle, these two reflections can both appear simultaneously because of the difference of incidence angle. Depending on the attack angle of the cone, either regular or Mach reflection occurs. However, very little is known of the three-dimensional shock transition from regular to Mach reflection or vise versa. From a physical point of view, it is important to determine the transitional angle between regular and Mach reflection by using a holographic method. In this paper, a shock Wave reflected from a cone at an angle of attack was visualized quantitatively by using double exposure holographic interferometry and diffuse holographic interferometry.
D B Jess - One of the best experts on this subject based on the ideXlab platform.
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propagating Wave Phenomena detected in observations and simulations of the lower solar atmosphere
The Astrophysical Journal, 2012Co-Authors: D B Jess, Sergiy Shelyag, Mihalis Mathioudakis, Peter H Keys, D J Christian, F P KeenanAbstract:We present high-cadence observations and simulations of the solar photosphere, obtained using the Rapid Oscillations in the Solar Atmosphere imaging system and the MuRAM magnetohydrodynamic (MHD) code, respectively. Each data set demonstrates a wealth of magnetoacoustic oscillatory behavior, visible as periodic intensity fluctuations with periods in the range 110-600 s. Almost no propagating Waves with periods less than 140 s and 110 s are detected in the observational and simulated data sets, respectively. High concentrations of power are found in highly magnetized regions, such as magnetic bright points and intergranular lanes. Radiative diagnostics of the photospheric simulations replicate our observational results, confirming that the current breed of MHD simulations are able to accurately represent the lower solar atmosphere. All observed oscillations are generated as a result of naturally occurring magnetoconvective processes, with no specific input driver present. Using contribution functions extracted from our numerical simulations, we estimate minimum G-band and 4170 A continuum formation heights of 100 km and 25 km, respectively. Detected magnetoacoustic oscillations exhibit a dominant phase delay of –8° between the G-band and 4170 A continuum observations, suggesting the presence of upwardly propagating Waves. More than 73% of MBPs (73% from observations and 96% from simulations) display upwardly propagating Wave Phenomena, suggesting the abundant nature of oscillatory behavior detected higher in the solar atmosphere may be traced back to magnetoconvective processes occurring in the upper layers of the Sun's convection zone.
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propagating Wave Phenomena detected in observations and simulations of the lower solar atmosphere
arXiv: Solar and Stellar Astrophysics, 2012Co-Authors: D B Jess, Sergiy Shelyag, Mihalis Mathioudakis, Peter H Keys, D J Christian, F P KeenanAbstract:We present high-cadence observations and simulations of the solar photosphere, obtained using the Rapid Oscillations in the Solar Atmosphere imaging system and the MuRAM magneto-hydrodynamic code, respectively. Each dataset demonstrates a wealth of magneto-acoustic oscillatory behaviour, visible as periodic intensity fluctuations with periods in the range 110-600 s. Almost no propagating Waves with periods less than 140s and 110s are detected in the observational and simulated datasets, respectively. High concentrations of power are found in highly magnetised regions, such as magnetic bright points and intergranular lanes. Radiative diagnostics of the photospheric simulations replicate our observational results, confirming that the current breed of magneto-hydrodynamic simulations are able to accurately represent the lower solar atmosphere. All observed oscillations are generated as a result of naturally occurring magnetoconvective processes, with no specific input driver present. Using contribution functions extracted from our numerical simulations, we estimate minimum G-band and 4170 Angstrom continuum formation heights of 100 km and 25 km, respectively. Detected magneto-acoustic oscillations exhibit a dominant phase delay of -8 degrees between the G-band and 4170 Angstrom continuum observations, suggesting the presence of upwardly propagating Waves. More than 73% of MBPs (73% from observations, 96% from simulations) display upwardly propagating Wave Phenomena, suggesting the abundant nature of oscillatory behaviour detected higher in the solar atmosphere may be traced back to magnetoconvective processes occurring in the upper layers of the Sun's convection zone.
R. G. Stone - One of the best experts on this subject based on the ideXlab platform.
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Plasma Wave Phenomena observed at interplanetary shocks by the Ulysses URAP experiment.
1992Co-Authors: D. Lengyel-frey, Robert J. Macdowall, R. G. Stone, S. Hoang, F. Pantellini, P. Canu, Nicole Cornilleau-wehrlin, A. Balogh, R. J. ForsythAbstract:Results of a study of 24 interplanetary shocks observed by the Unified Radio and Plasma Wave Experiment (URAP) on the Ulysses spacecraft are presented. These shocks, observed between approximately 1 and 4 AU, display a variety of Wave Phenomena similar to those detected in earlier studies of shocks near 1 AU. The correspondence of the observed low frequency magnetic and electric field Waves with the parallel index of refraction for whistler Waves was investigated. Observed B/E ratios are found to be typically about a factor of 0.7 times the computed index of refraction, supporting the whistler interpretation of these Waves, but also implying a prevalent electrostatic Wave component which may be due to whistlers propagating at an angle to the interplanetary magnetic field. A statistical correlation of the amplitudes of the various types of Waves with shock and solar wind properties is presented.
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Unusual radio and plasma Wave Phenomena observed in March 1991
Geophysical Research Letters, 1992Co-Authors: M. J. Reiner, R. G. Stone, Joseph FainbergAbstract:During the intense solar flare activity in March 1991 a number of unusual radio emission and Langmuir Wave Phenomena were observed by the radio and plasma Wave (URAP) experiment on the Ulysses spacecraft. These Phenomena were associated with unusual conditions in the interplanetary medium (IPM) presumably resulting from intense solar activity. Some of these URAP observations cannot be explained by mechanisms usually attributed to interplanetary (IP) radio emissions and Langmuir Wave activity and require other interpretations.
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Plasma Wave Phenomena at interplanetary shocks observed by the Ulysses URAP experiment
Solar Wind Seven, 1992Co-Authors: D. Lengyel-frey, Robert J. Macdowall, R. G. Stone, S. Hoang, F. Pantellini, C. C. Harvey, Anne Mangeney, Paul J. Kellogg, J. Thiessen, P. CanuAbstract:We present Ulysses URAP observations of plasma Waves at seven interplanetary shocks detected between approximately 1 and 3 AU. The URAP data allows ready correlation of Wave Phenomena from .1 Hz to 1 MHz. Wave Phenomena observed in the shock vicinity include abrupt changes in the quasi-thermal noise continuum, Langmuir Wave activity, ion acoustic noise, whistler Waves and low frequency electrostatic Waves. We focus on the forward/reverse shock pair of May 27, 1991 to demonstrate the characteristics of the URAP data.
T R Akylas - One of the best experts on this subject based on the ideXlab platform.
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Three-Dimensional Long Water-Wave Phenomena
Annual Review of Fluid Mechanics, 1994Co-Authors: T R AkylasAbstract:Water-Wave motion is a fascinating subject of fluid mechanics. Apart from being important in various branches of engineering and applied science, many water-Wave Phenomena are also familiar from everyday experience; obtaining a thorough understanding of the relevant physical mechanisms, however, presents fluid dynamicists with great challenges. Since the early work of Airy and Stokes in the middle of the previous century, it has been recognized that, even under the assumption of potential flow, the water-Wave equations are analytically intractable in general. The main difficulty stems from the nonlinear boundary conditions that apply on the free surface, which itself is unknown and is to be determined as part of the solution. In recent years, considerable progress has been made in illuminating some aspects of water-Wave propagation-most notably the interplay of weak finite-amplitude and dispersive effects-using approximate (model) equations, valid asymptotically in certain limits. Combined with experi mental observations, these asymptotic theories reveal useful insights into the relevant physics. Moreover, in many instances, they have provided the impetus for related computational efforts. Perhaps the most well known model equation for water Waves, first proposed about a century ago [see Miles (1981) for a review including historical details], is the Korteweg-de Vries (KdV) equation (Korteweg & de Vries 1895):
