Japanese Balloon Program

Yoshida, Tetsuya; Akita, Daisuke; Fuke, H.; Kadokura, Akira; Kawada, J.; Ijima, Issei; Izutsu, Naoki; Matsuzaka, Y.; Mizuta, Eiichi; Namiki, Michiyoshi; Nonaka, N.; Ohta, Shigeo; Saito, Yoshitaka; Seo, Motoharu; Tamura, Kouichi; Toriumi, Michihiko; Yamada, Kazuhiko; Yamagami, T.

doi:10.1143/jpsjs.78sa.97

Cited by 3 publications

(4 citation statements)

References 3 publications

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“…This claim is corroborated by the fact that Kawahara & Nakanishi [96] observe anomalous diffusion which means that the evolution of the flow is more complex than it seems. These results have been confirmed recently by Yoshida [98] who showed that the mean square displacements exhibit a universal time dependence [r(t) − r(0)] 2 ∼ t µ with µ = 1.75 ± 0.1. These authors attribute anomalous diffusion to occasional long jumps of the particles convected by long living large vortices.…”

Section: Discussionsupporting

confidence: 74%

“…These inhomogeneities may reduce the timescale of relaxation to the natural timescale Nt D . These "phase-space structures" are indeed present in the simulations of Latora et al [103] and they seem to be responsible for anomalous diffusion in a way similar to what happens in 2D point vortex dynamics [96,98]. Again, this scenario demands to be confirmed but it seems plausible enough to reconcile theory and observations.…”

Section: Discussionmentioning

confidence: 64%

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Kinetic equations for systems with long-range interactions: a unified description

Chavanis¹

2010

J. Stat. Mech.

179

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We complete the existing literature on the kinetic theory of systems with long-range interactions. Starting from the BBGKY hierarchy, or using projection operator technics or a quasilinear theory, a general kinetic equation can be derived when collective effects are neglected. This equation (which is not well-known) applies to possibly spatially inhomogeneous systems, which is specific to systems with long-range interactions. Interestingly, the structure of this kinetic equation bears a clear physical meaning in terms of generalized Kubo relations. Furthermore, this equation takes a very similar form for stellar systems and two-dimensional point vortices providing therefore a unified description of the kinetic theory of these systems. If we assume that the system is spatially homogeneous (or axisymmetric for point vortices), this equation can be simplified and reduces to the Landau equation (or its counterpart for point vortices). Our formalism thus offers a simple derivation of Landau-type equations. We also use this general formalism to derive a kinetic equation, written in angle-action variables, describing spatially inhomogeneous systems with long-range interactions. This new derivation solves the shortcomings of our previous derivation [P.H. Chavanis, Physica A 377, 469 (2007)]. Finally, we consider a test particle approach and derive general expressions for the diffusion and friction (or drift) coefficients of a test particle evolving in a bath of field particles. We make contact with the expressions previously obtained in the literature. As an application of the kinetic theory, we argue that the relaxation time is shorter for inhomogeneous (or high-dimensional) systems than for homogeneous (or low-dimensional) systems because there are potentially more resonances. We compare this prediction with existing numerical results for the HMF model and 2D point vortices. For the HMF model, we argue that the relaxation time scales as N for inhomogeneous distributions and as e N for permanently homogeneous distributions. Phase space structures can reduce the relaxation time by creating some inhomogeneities and resonances. Similar results are expected for 2D point vortices.

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Section: Discussionsupporting

confidence: 74%

Section: Discussionmentioning

confidence: 64%

Kinetic equations for systems with long-range interactions: a unified description

Chavanis¹

2010

J. Stat. Mech.

179

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“…The generalized Lenard-Balescu equation (28) can be viewed as an extension of this equation taking collective effects into account. Note that the Markovian approximation may not be justified in every situation since it has been found numerically that point vortices can exhibit long jumps (Lévy flights) and strong correlations [82,83].…”

Section: Appendix C: General Kinetic Equation Without Collective Effectsmentioning

confidence: 99%

Kinetic theory of Onsager’s vortices in two-dimensional hydrodynamics

Chavanis

2012

Physica A: Statistical Mechanics and its Applications

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Starting from the Liouville equation, and using a BBGKY-like hierarchy, we derive a kinetic equation for the point vortex gas in two-dimensional (2D) hydrodynamics, taking two-body correlations and collective effects into account. This equation is valid at the order 1/N where N ≫ 1 is the number of point vortices in the system (we assume that their individual circulation scales like γ ∼ 1/N ). It gives the first correction, due to graininess and correlation effects, to the 2D Euler equation that is obtained for N → +∞. For axisymmetric distributions, this kinetic equation does not relax towards the Boltzmann distribution of statistical equilibrium. This implies either that (i) the "collisional" (correlational) relaxation time is larger than N tD, where tD is the dynamical time, so that three-body, four-body... correlations must be taken into account in the kinetic theory, or (ii) that the point vortex gas is non-ergodic (or does not mix well) and will never attain statistical equilibrium. Non-axisymmetric distributions may relax towards the Boltzmann distribution on a timescale of the order N tD due to the existence of additional resonances, but this is hard to prove from the kinetic theory. On the other hand, 2D Euler unstable vortex distributions can experience a process of "collisionless" (correlationless) violent relaxation towards a non-Boltzmannian quasistationary state (QSS) on a very short timescale of the order of a few dynamical times. This QSS is possibly described by the Miller-Robert-Sommeria (MRS) statistical theory which is the counterpart, in the context of two-dimensional hydrodynamics, of the Lynden-Bell statistical theory of violent relaxation in stellar dynamics.

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“…We tried to have a one-day engineering flight, in order to verify its day-night performance, but the balloon burst at an altitude of 14.7 km. 7) An image of the on-board high-definition video camera indicates that the initial damage was located around the collar position. Since the film of our super-pressure balloon is hard compared to the polyethylene film and many load ropes run along the balloon surface, the collar or the spooler might have slightly damaged the film.…”

Section: Technical Developments For Ultra-long Duration Flightsmentioning

confidence: 99%

Japanese Contribution for Mid-Latitude Long Duration Balloon Flights

Yoshida

2010

AEROSPACE TECHNOLOGY JAPAN

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Recently, long duration balloon flights are strongly desired by the communities of Astronomy, Astrophysics and Cosmic-ray physics, in order to carry out very precise measurements with high statistics and/or to search for rare phenomena in huge background. Circumnavigation flights over Antarctica give us excellent flight opportunity, but the number of flights in a year is very limited, and the logistics is very hard. Once long duration balloon flights in mid-latitude more than several days can be realized much frequently, scientific ballooning will become much useful for space science experiments. Technical developments for long duration flights in Japan are introduced and the provision for the possible international collaboration will be discussed.

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Japanese Balloon Program

Cited by 3 publications

References 3 publications

Kinetic equations for systems with long-range interactions: a unified description

Kinetic equations for systems with long-range interactions: a unified description

Kinetic theory of Onsager’s vortices in two-dimensional hydrodynamics

Japanese Contribution for Mid-Latitude Long Duration Balloon Flights

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