Coupled Map Modeling for Cloud Dynamics

A coupled map model for cloud dynamics is proposed, which consists of the successive operations of the physical processes; buoyancy, diffusion, viscosity, adiabatic expansion, fall of a droplet by gravity, descent flow dragged by the falling droplet, and advection. Through extensive simulations, the phases corresponding to stratus, cumulus, stratocumulus and cumulonimbus are found, with the change of the ground temperature and the moisture of the air. They are characterized by order parameters such as the cluster number, perimeter-to-area ratio of a cloud, and Kolmogorov-Sinai entropy.Comment: 9 pages, 4 figure, LaTeX, mpeg simulations available at http://aurora.elsip.hokudai.ac.jp

Slow relaxation to equipartition in spring-chain systems

In this study, one-dimensional systems of masses connected by springs, i.e., spring-chain systems, are investigated numerically. The average kinetic energy of chain-end particles of these systems is larger than that of other particles, which is similar to the behavior observed for systems made of masses connected by rigid links. The energetic motion of the end particles is, however, transient, and the system relaxes to thermal equilibrium after a while, where the average kinetic energy of each particle is the same, that is, equipartition of energy is achieved. This is in contrast to the case of systems made of masses connected by rigid links, where the energetic motion of the end particles is observed in equilibrium. The timescale of relaxation estimated by simulation increases rapidly with increasing spring constant. The timescale is also estimated using the Boltzmann-Jeans theory and is found to be in quite good agreement with that obtained by the simulation

Design of Easily Synchronizable Oscillator Networks Using the Monte Carlo Optimization Method

Starting with an initial random network of oscillators with a heterogeneous frequency distribution, its autonomous synchronization ability can be largely improved by appropriately rewiring the links between the elements. Ensembles of synchronization-optimized networks with different connectivities are generated and their statistical properties are studied

Chaotic pulses for discrete reaction diffusion systems

Existence and dynamics of chaotic pulses on a one-dimensional lattice are discussed. Traveling pulses arise typically in reaction diffusion systems like the FitzHugh-Nagumo equations. Such pulses annihilate when they collide with each other. A new type of traveling pulse has been found recently in many systems where pulses bounce off like elastic balls. We consider the behavior of such a localized pattern on one-dimensional lattice, i.e., an infinite system of ODEs with nearest interaction of diffusive type. Besides the usual standing and traveling pulses, a new type of localized pattern, which moves chaotically on a lattice, is found numerically. Employing the strength of diffusive interaction as a bifurcation parameter, it is found that the route from standing pulse to chaotic pulse is of intermittent type. If two chaotic pulses collide with appropriate timing, they form a periodic oscillating pulse called a molecular pulse. Interaction among many chaotic pulses is also studied numerically

Simulating Cherenkov Telescope Array observation of RX J1713.7-3946

We perform simulations of Cherenkov Telescope Array (CTA) observations of a young supernova remnant RX J1713.7-3946. This target is not only one of the brightest sources ever discovered in very high-energy gamma rays but also well observed in other wavebands. In X-rays, the emission is dominated by synchrotron radiation, which links directly to the existence of high-energy electrons. Radio observations of CO and HI gas have revealed a highly inhomogeneous medium surrounding the SNR, such as clumpy molecular clouds. Therefore gamma rays from hadronic interactions are naturally expected. However, the spectrum in GeV energy range measured by Fermi/LAT indicates more typical of leptonic emission from accelerated electrons. Despite lots of multi-wavelength information, the competing interpretations have led to much uncertainty in the quest of unraveling the true origin of the gamma-ray emission from RX~J1713.7--3946. CTA will achieve highest performance ever in sensitivity, angular resolution, and energy resolution. We estimate CTA capability to examine the emission mechanisms of the gamma rays through simulated spatial distribution, spectra, and their time variation.Comment: 8 pages, 3 figures. In Proceedings of the 34th International Cosmic Ray Conference (ICRC2015), The Hague, The Netherlands. All CTA contributions at arXiv:1508.0589

TeV Gamma Ray Emission from Southern Sky Objects and CANGAROO Project

We report recent results of the CANGAROO Collaboration on very high energy gamma ray emission from pulsars, their nebulae, SNR and AGN in the southern sky. Observations are made in South Australia using the imaging technique of detecting atmospheric Cerenkov light from gamma rays higher than about 1 TeV. The detected gamma rays are most likely produced by the inverse Compton process by electrons which also radiate synchrotron X-rays. Together with information from longer wavelengths, our results can be used to infer the strength of magnetic field in the emission region of gamma rays as well as the energy of the progenitor electrons. A description of the CANGAROO project is also given, as well as details of the new telescope of 7 m diameter which is scheduled to be in operation within two years.Comment: 5 pages, 1 figure, LaTeX 2.09 with aipproc.sty & epsfig.sty, to appear in proceedings of the 4th Compton Symposium, Williamsburg, 199

Evidence for TeV gamma-ray emission from the shell type SNR RXJ1713.7-3946

We report the results of TeV gamma-ray observations of the shell type SNR RXJ1713.7-3946 (G347.3-0.5). The discovery of strong non-thermal X-ray emission from the northwest part of the remnant strongly suggests the existence of electrons with energies up to 100 TeV in the remnant, making the SNR a good candidate TeV gamma-ray source. We observed RXJ1713.7-3946 from May to August 1998 with the CANGAROO 3.8m atmospheric imaging Cerenkov telescope and obtained evidence for TeV gamma-ray emission from the NW rim of the remnant with the significance of 5.6 sigma. The observed TeV gamma-ray flux from the NW rim region was estimated to be (5.3 +/- 0.9[statistical] +/- 1.6[systematic]) * 10^{-12} photons cm^{-2} s^{-1} at energies >= 1.8 +/- 0.9 TeV. The data indicate that the emitting region is much broader than the point spread function of our telescope. The extent of the emission is consistent with that of hard X-rays observed by ASCA. This TeV gamma-ray emission can be attributed to the Inverse Compton scattering of the Cosmic Microwave Background Radiation by shock accelerated ultra-relativistic electrons. Under this assumption, a rather low magnetic field of 11 micro gauss is deduced for the remnant from our observation.Comment: Accepted for publication by Astronomy and Astrophysics (5 pages, 2 figures