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Masaru Sugiyama - One of the best experts on this subject based on the ideXlab platform.
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overshoot of the non equilibrium temperature in the shock wave structure of a rarefied polyatomic gas subject to the Dynamic Pressure
2016Co-Authors: Shigeru Taniguchi, Tommaso Ruggeri, Takashi Arima, Masaru SugiyamaAbstract:Abstract The shock wave structure in a rarefied polyatomic gas is analyzed on the basis of non-linear extended thermoDynamics with 6 independent fields (ET6); the mass density, the velocity, the temperature and the Dynamic Pressure, which permits us to study the shock profile also for large Mach numbers. The first result of this paper is that the shock wave structure is substantially the same as that obtained previously from the linear theory for small or moderately large Mach numbers. Only for very large Mach numbers there exist some differences in the relaxation part of the profile between the model with a non-linear production term and the one with a linear production term. The mathematical reason of this behavior is due to the fact that the non-linear differential system has the same principal part of the linear one. The classical Meixner theory of relaxation processes with one internal variable is fully compatible with the ET6 theory and this fact gives us the explicit expressions of the internal variable and the non-equilibrium temperature in the Meixner theory in terms of the 6 fields, especially, of the Dynamic Pressure. By using the correspondence relation, the shock wave structure described by the ET6 theory is converted into the variables described by the Meixner theory. It is shown that the non-equilibrium Meixner temperature overshoots in a shock wave in contrast to the kinetic temperature. This implies that the temperature overshoot is a matter of definition of the non-equilibrium temperature.
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the role of the Dynamic Pressure in stationary heat conduction of a rarefied polyatomic gas
2014Co-Authors: Takashi Arima, Elvira Barbera, Francesca Brini, Masaru SugiyamaAbstract:Abstract The effect of the Dynamic Pressure (non-equilibrium Pressure) on stationary heat conduction in a rarefied polyatomic gas at rest is elucidated by the theory of extended thermoDynamics. It is shown that this effect is observable in a non-polytropic gas. Numerical studies are presented for a para-hydrogen gas as a typical example.
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effect of the Dynamic Pressure on the shock wave structure in a rarefied polyatomic gas
2014Co-Authors: Shigeru Taniguchi, Tommaso Ruggeri, Takashi Arima, Masaru SugiyamaAbstract:We study the shock wave structure in a rarefied polyatomic gas based on a simplified model of extended thermoDynamics in which the dissipation is due only to the Dynamic Pressure. In this case the differential system is very simple because it is a variant of Euler system with a new scalar equation for the Dynamic Pressure [T. Arima, S. Taniguchi, T. Ruggeri, and M. Sugiyama, Phys. Lett. A 376, 2799–2803 (2012)]. It is shown that this theory is able to describe the three types of the shock wave structure observed in experiments: the nearly symmetric shock wave structure (Type A, small Mach number), the asymmetric structure (Type B, moderate Mach number), and the structure composed of thin and thick layers (Type C, large Mach number).
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extended thermoDynamics of real gases with Dynamic Pressure an extension of meixnerʼs theory
2012Co-Authors: Takashi Arima, Tommaso Ruggeri, Shigeru Taniguchi, Masaru SugiyamaAbstract:Abstract Basing on the recent theory of extended thermoDynamics of dense gases, we study a thermoDynamic theory of gases with the energy transfer from molecular translational mode to internal modes as an extension of Meixnerʼs theory. We focus our attention on the simplest case with only one dissipative process due to the Dynamic Pressure. The dispersion relation for sound derived from the present theory is compared with that from Meixnerʼs theory. Kinetic theoretical basis of the present approach is also discussed.
L R Lyons - One of the best experts on this subject based on the ideXlab platform.
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enhanced solar wind geoeffectiveness after a sudden increase in Dynamic Pressure during southward imf orientation
2005Co-Authors: A Boudouridis, E Zesta, L R Lyons, P C Anderson, D LummerzheimAbstract:[1] It is well known that a persistent southward Interplanetary Magnetic Field (IMF) produces increased geomagnetic activity. It has recently been shown that a sudden increase in solar wind Pressure results in poleward expansion of the auroral oval and closing of the polar cap over a wide range of MLTs, and this effect is more pronounced under southward IMF orientation. We show that southward IMF conditions combined with high solar wind Dynamic Pressure immediately after a Pressure front impact lead to enhanced coupling between the solar wind and the terrestrial magnetosphere, significantly increasing the geoeffectiveness of the solar wind. We evaluate geoeffectiveness by the coupling efficiency, defined as the ratio of the cross-polar-cap potential measured by Defense Meteorological Satellite Program (DMSP) spacecraft to the cross-magnetospheric potential calculated using solar wind parameters. We examine changes in the size of the polar cap and the coupling efficiency for a number of solar wind Pressure enhancements under southward IMF configuration. We confirm the previously observed closing of the polar cap and show that there is a simultaneous increase of the coupling efficiency. This increase is measured for all cases, despite the fact that the magnetosphere is greatly compressed, and the increase is measured even when the solar wind electric field is reduced.
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sawtooth oscillations directly driven by solar wind Dynamic Pressure enhancements
2004Co-Authors: Dabin Lee, L R Lyons, K YumotoAbstract:[1] We have examined four well-defined events of sawtooth oscillations in energetic particle flux and magnetic field at geosynchronous orbit. During all four events, nearly simultaneous energetic particle flux enhancements and magnetic field variations occurred at all MLTs for each sawtooth cycle. Geomagnetic H component data at low to middle latitude also show a global H increase simultaneously with the geosynchronous responses at all MLTs, and the northern and southern PC indices generally show increases at each sawtooth cycle. All these are what is expected if solar wind Pressure enhancements impacted the magnetosphere at times appropriate to have caused the onset of each sawtooth cycle. By directly checking the solar wind data, we find that there indeed exists a series of solar wind Dynamic Pressure enhancements for each sawtooth event. In identifying these Pressure enhancements, we have found that the relative change in the Dynamic Pressure is important, particularly when the magnitude of the Dynamic Pressure is small and that even a modest Dynamic Pressure enhancement can result in significant changes in the magnetosphere when the IMF stays strongly southward for a long interval. We show that each cycle of the sawtooth oscillation can be reasonably associated in timing with a corresponding solar wind Dynamic Pressure enhancement. On the basis of this association and the global, simultaneous geosynchronous and ground responses, we suggest that the sawtooth oscillations studied in this paper are directly driven by series of solar wind Pressure enhancements and are not a repetitive internal magnetospheric response to sustained enhanced solar wind energy input.
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geosynchronous magnetic field response to solar wind Dynamic Pressure pulse
2004Co-Authors: L R LyonsAbstract:The present study examines the morning-afternoon asymmetry of the geosynchronous magnetic field strength on the dayside (magnetic local time [MLT] = 06:00~18:00) using observations by the Geostationary Operational Environmental Satellites (GOES) over a period of 9 years from February 1998 to January 2007. During geomagnetically quiet time (Kp < 3), we observed that a peak of the magnetic field strength is skewed toward the earlier local times (11:07~11:37 MLT) with respect to local noon and that the geosynchronous field strength is larger in the morning sector than in the afternoon sector. That is, there is the morning-afternoon asymmetry of the geosynchronous magnetic field strength. Using solar wind data, it is confirmed that the morning-afternoon asymmetry is not associated with the aberration effect due to the orbital motion of the Earth about the Sun. We found that the peak location of the magnetic field strength is shifted to ward the earlier local times as the ratio of the magnetic field strength at MLT = 18 (B-dusk) to the magnetic field strength at MLT = 06 (B-dawn) is decreasing. It is also found that the dawn-dusk magnetic field median ratio, B-dusk/B-dawn, is decreasing as the solar wind Dynamic Pressure is increasing. The morning-afternoon asymmetry of the magnetic field strength appears in Tsyganenko geomagnetic field model (TS-04 model) when the partial ring current is included in TS04 model. Unlike our observations, however, TS-04 model shows that the peak location of the magnetic field strength is shifted toward local noon as the solar wind Dynamic Pressure grows in magnitude. This may be due to that the symmetric magnetic field associated with the magnetopause current, strongly affected by the solar wind Dynamic Pressure, increases. However, the partial ring current is not affected as much as the magnetopause current by the solar wind Dynamic Pressure in TS-04 model. Thus, our observations suggest that the contribution of the partial ring current at geosynchronous orbit is much larger than that expected from TS-04 model as the solar wind Dynamic Pressure increases.
C T Russell - One of the best experts on this subject based on the ideXlab platform.
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martian ionospheric responses to Dynamic Pressure enhancements in the solar wind
2014Co-Authors: Xiaohua Fang, C T Russell, A F Nagy, G TothAbstract:As a weakly magnetized planet, Mars ionosphere/atmosphere interacts directly with the shocked solar wind plasma flow. Even though many numerical studies have been successful in reproducing numerous features of the interaction process, these earlier studies focused mainly on interaction under steady solar wind conditions. Recent observations suggest that plasma escape fluxes are significantly enhanced in response to solar wind Dynamic Pressure pulses. In this study, we focus on the response of the ionosphere to Pressure enhancements in the solar wind. Through modeling of two idealized events using a magnetohydroDynamics model, we find that the upper ionosphere of Mars responds almost instantaneously to solar wind Pressure enhancements, while the collision dominated lower ionosphere (below ~150 km) does not have noticeable changes in density. We also find that ionospheric perturbations in density, magnetic field, and velocity can last more than an hour after the solar wind returns to the quiet conditions. The topside ionosphere forms complicated transient shapes in response, which may explain unexpected ionospheric behaviors in recent observations. We also find that ionospheric escape fluxes do not correlate directly with simultaneous solar wind Dynamic Pressure. Rather, their intensities also depend on the earlier solar wind conditions. It takes a few hours for the ionospheric/atmospheric system to reach a new quasi-equilibrium state.
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modeling the size and shape of saturn s magnetopause with variable Dynamic Pressure
2006Co-Authors: Chris S. Arridge, KK Kamal K Khurana, NA Achilleos, M. K. Dougherty, C T RussellAbstract:[1] The location and shape of a planetary magnetopause is principally determined by the Dynamic Pressure, Dp, of the solar wind, the orientation of the planet's magnetic dipole with respect to the solar wind flow, and by the distribution of stresses inside the magnetosphere. The magnetospheres of Saturn and Jupiter have strong internal plasma sources compared to the solar wind source and also rotate rapidly, causing an equatorial inflation of the magnetosphere and consequently the magnetopause. Empirical studies using Voyager and Pioneer data concluded that the kronian magnetopause was Earth-like in terms of its Dynamics (Slavin et al., 1985) as revealed by how the position of the magnetopause varies with Dynamic Pressure. In this paper we present a new Pressure-dependent model of Saturn's magnetopause, using the functional form proposed by Shue et al. (1997). To establish the Pressure-dependence, we also use a new technique for fitting a Pressure-dependent model in the absence of simultaneous upstream Pressure measurements. Using a Newtonian form of the Pressure balance across the magnetopause boundary and using model rather than minimum variance normals, we estimate the solar wind Dynamic Pressure at each crossing. By iteratively fitting our model to magnetopause crossings observed by the Cassini and Voyager spacecraft, in parallel with the Pressure balance, we obtain a model which is self-consistent with the Dynamic Pressure estimates obtained. We find a model whose size varies as ∼Dp−1/4.3 and whose flaring decreases with increasing Dynamic Pressure. This is interpreted in terms of a different distribution of fields and particles stresses which has more in common with the jovian magnetosphere compared with the terrestrial situation. We compare our model with the existing models of the magnetopause and highlight the very different geometries. We find our results are consistent with recent MHD modeling of Saturn's magnetosphere (Hansen et al., 2005).
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geomagnetic field response along the polar orbit to rapid changes in the solar wind Dynamic Pressure
2001Co-Authors: G J Fowler, C T RussellAbstract:Magnetometer observations on board the Polar spacecraft have been used to measure the magnetospheric response to rapid changes in the Dynamic Pressure of the solar wind. Over much of the magnetosphere the magnetic field increases when the solar wind Dynamic Pressure increases, roughly in proportion to the square root of the change of the solar wind Dynamic Pressure with a proportionality similar to that seen in ground-based data. Nevertheless, Dynamic Pressure increases can lead to reductions in the magnitude of the magnetic field. These reductions occur on the dayside polar field lines, where the magnetospheric field points southward while the perturbation field due to the magnetopause current is northward. Throughout most of the magnetosphere these changes occur slowly over - 5-10 min as the interplanetary shock envelopes the dayside magnetosphere and near tail. Compressions of the magnetosphere generally lead to increases in the intensity of the ULF waves along the field lines, but in one case the wave intensity decreased upon compression of the field. This decrease occurred in the predawn sector while the increases occurred in the noon to postdusk sector.
X C Shen - One of the best experts on this subject based on the ideXlab platform.
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magnetospheric ulf waves with increasing amplitude related to solar wind Dynamic Pressure changes the time history of events and macroscale interactions during substorms themis observations
2015Co-Authors: Anmin Tian, Quanqi Shi, X C Shen, Q G Zong, W J Sun, Yu Wang, X Z Zhou, M D HartingerAbstract:Ultralow frequency (ULF) waves play an important role in transferring energy by buffeting the magnetosphere with solar wind Pressure impulses. The amplitudes of magnetospheric ULF waves, which are induced by solar wind Dynamic Pressure enhancements or shocks, are thought to damp in one half a wave cycle or an entire wave cycle. We report in situ observations of solar wind Dynamic Pressure impulse-induced magnetospheric ULF waves with increasing amplitudes. We found six ULF wave events induced by solar wind Dynamic Pressure enhancements with slow but clear wave amplitude increase. During three or four wave cycles, the amplitudes of ion velocities and electric field of these waves increased continuously by 1.3–4.4 times. Two significant events were selected to further study the characteristics of these ULF waves. We found that the wave amplitude growth is mainly contributed by the toroidal mode wave. Three possible mechanisms of causing the wave amplitude increase are discussed. First, solar wind Dynamic Pressure perturbations, which are observed in a duration of 20–30 min, might transfer energy to the magnetospheric ULF waves continually. Second, the wave amplitude increase in the radial electric field may be caused by superposition of two wave modes, a standing wave excited by the solar wind Dynamic impulse and a propagating compressional wave directly induced by solar wind oscillations. When superposed, the two wave modes fit observations as does a calculation that superposes electric fields from two wave sources. Third, the normal of the solar wind discontinuity is at an angle to the Sun-Earth line. Thus, the discontinuity will affect the dayside magnetopause continuously for a long time.
Jinke Han - One of the best experts on this subject based on the ideXlab platform.
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leakage monitoring research and design for natural gas pipelines based on Dynamic Pressure waves
2017Co-Authors: Cuiwei Liu, Liping Fang, Jinke HanAbstract:Abstract Many types of gases, such as natural gas, hydrogen, and so on, are transported via pipelines using a chemical process, though leakages in these pipelines create waste and pose hazards and risks to industries, the environment and people. To monitor gas pipelines, a new leak detection and location method based on the amplitude attenuation model of Dynamic Pressure waves was designed and researched by experiments, compared with traditional method based on the propagation velocity and time differences as determined by the waveforms of the upstream and downstream signals. Both methods are achieved based on the propagation law of the Dynamic Pressure waves in the fluid flow. First, the fundamentals of the newly proposed method are clarified by considering the influence of gas flow on the waves. The experiments are then conducted in gas pipelines with 42 mm internal diameters. Finally, the results of the experiments are discussed and analyzed. The results indicate that all leakages can be detected by both methods but that the largest location error of the traditional method is −0.780%, whereas the largest location errors with respect to the new method are 0.054% with the experimental attenuation coefficients and 2.055% with the theoretical attenuation coefficients. It is further determined that the influence of the gas flow effects cannot be ignored by either method. Accordingly, the conclusions drawn suggest that the proposed methods can be applied to monitor gas pipelines.
