`Island Surfing' Mechanism of Electron Acceleration During Magnetic Reconnection

One of the key unresolved problems in the study of space plasmas is to explain the production of energetic electrons as magnetic field lines `reconnect' and release energy in a exposive manner. Recent observations suggest possible roles played by small scale magnetic islands in the reconnection region, but their precise roles and the exact mechanism of electron energization have remained unclear. Here we show that secondary islands generated in the reconnection region are indeed efficient electron accelerators. We found that, when electrons are trapped inside the islands, they are energized continuously by the reconnection electric field prevalent in the reconnection diffusion region. The size and the propagation speed of the secondary islands are similar to those of islands observed in the magnetotail containing energertic electrons.Comment: 5 pages, 4 figures, submitted to J. Geophys. Res

THE EFFECT OF HEALTH EDUCATION AS NON-PHARMACOLOGICAL THERAPY ON PHYSICAL FITNESS, BLOOD CHEMISTRY AND BRAIN FUNCTION AMONG SENIOR CITIZEN IN BOTH RURAL AND URBAN AREAS OF BALI, INDONESIA

Objective: The population of senior citizens has increased and needs more care for the quality of life. Health education is a non-pharmacological therapy to improve physical fitness, blood chemistry and brain function. This research was performed to evaluate the effect of health education on the physical fitness, blood chemistry and brain function of senior citizens in rural and urban Bali. Methods: A total of 60 people aged 67.9±1.2 y were recruited from Tabanan, Indonesia, and 72 people aged 67.3±0.6 y were recruited from Denpasar, Indonesia. The health education program lasted 8 mo, used Japanese-style healthcare modified for the Balinese culture, and measured physical fitness, blood chemistry, and brain function before and after the educational period. Results: The average number of steps in Tabanan was 4247.2±98.9, and those in Denpasar were 4336.1±102.4. The weight and waist circumference were not significantly different between the Tabanan and Denpasar samples. The physical fitness of senior citizens in Tabanan and Denpasar improved significantly. Blood chemistry in the Tabanan sample was not significantly different after the program. In Denpasar, High-Density Lipoprotein and Low-Density Lipoprotein significantly improved. Brain function was significantly improved after the program. Conclusion: Health education using Japanese-style healthcare programs based on Balinese culture as non-pharmacological therapy has beneficial effects on physical fitness, blood chemistry and brain function in senior citizens in both urban and rural areas in Bali, Indonesia. It is suggested that senior citizens should continue our health education program to maintain their health

Geometrical Effects of Baryon Density Inhomogeneities on Primordial Nucleosynthesis

We discuss effects of fluctuation geometry on primordial nucleosynthesis. For the first time we consider condensed cylinder and cylindrical-shell fluctuation geometries in addition to condensed spheres and spherical shells. We find that a cylindrical shell geometry allows for an appreciably higher baryonic contribution to be the closure density (\Omega_b h_{50}^2 \la 0.2) than that allowed in spherical inhomogeneous or standard homogeneous big bang models. This result, which is contrary to some other recent studies, is due to both geometry and recently revised estimates of the uncertainties in the observationally inferred primordial light-element abundances. We also find that inhomogeneous primordial nucleosynthesis in the cylindrical shell geometry can lead to significant Be and B production. In particular, a primordial beryllium abundance as high as [Be] = 12 + log(Be/H) $\approx -3$ is possible while still satisfying all of the light-element abundance constraints.Comment: Latex, 20 pages + 11 figures(not included). Entire ps file with embedded figures available via anonymous ftp at ftp://genova.mtk.nao.ac.jp/pub/prepri/bbgeomet.ps.g

On the Dynamics of Proto-Neutron Star Winds and r-Process Nucleosynthesis

We study here the formation of heavy r-process nuclei in the high-entropy environment of rapidly expanding neutrino-driven winds from compact objects. In particular, we explore the sensitivity of the element creation in the A>130 region to the low-temperature behavior of the outflows. For this purpose we employ a simplified model of the dynamics and thermodynamical evolution for radiation dominated, adiabatic outflows. It consists of a first stage of fast, exponential cooling, followed by a second phase of slower evolution, either assuming constant density and temperature or a power-law decay of these quantities. These cases are supposed to capture the most relevant effects of a strong deceleration or decreasing acceleration of the transsonic outflows, respectively, e.g. in a wind termination shock caused by the collision with the slower, preceding supernova ejecta. We find that not only the transition temperature between the two expansion phases can make a big difference in the formation of the platinum peak, but also the detailed cooling law during the later phase. Unless the transition temperature and corresponding (free neutron) density become too small (T < 2*10^8 K), a lower temperature or faster temperature decline during this phase allow for a stronger appearance of the third abundance peak. Since the nuclear photodisintegration rates between ~2*10^8 K and ~10^9 K are more sensitive to the temperature than the n-capture rates are to the free neutron density, a faster cooling in this temperature regime shifts the r-process path closer to the n-drip line. With low (gamma,n)- but high beta-decay rates, the r-processing then does not proceed through a (gamma,n)-(n,gamma) equilibrium but through a quasi-equilibrium of (n,gamma)-reactions and beta-decays, as recently also pointed out by Wanajo.Comment: 18 pages, 14 figures with 25 eps plots; referee comments included; accepted by Astronomy & Astrophysic

Study of (e, e\u27 α) Reaction on ^9Be(I. Nuclear Physics)

The (e, e\u27 a) cross section has been measured at energy transfers from 10.0 to 28.4 MeV and a momentum transfer of 99 MeV/c, using a 197 MeV continuous electron beam. The cross section rapidly increases with decreasing energy at angles smaller than 25°, while it appears flat at larger angles. The forward-peaked angular distribution was observed below 18 MeV, and the forward peak shrinks at higher energies. An amount of αparticles from decay of ^5He is estimated

The influence of collective neutrino oscillations on a supernova r-process

Recently, it has been demonstrated that neutrinos in a supernova oscillate collectively. This process occurs much deeper than the conventional matter-induced MSW effect and hence may have an impact on nucleosynthesis. In this paper we explore the effects of collective neutrino oscillations on the r-process, using representative late-time neutrino spectra and outflow models. We find that accurate modeling of the collective oscillations is essential for this analysis. As an illustration, the often-used "single-angle" approximation makes grossly inaccurate predictions for the yields in our setup. With the proper multiangle treatment, the effect of the oscillations is found to be less dramatic, but still significant. Since the oscillation patterns are sensitive to the details of the emitted fluxes and the sign of the neutrino mass hierarchy, so are the r-process yields. The magnitude of the effect also depends sensitively on the astrophysical conditions - in particular on the interplay between the time when nuclei begin to exist in significant numbers and the time when the collective oscillation begins. A more definitive understanding of the astrophysical conditions, and accurate modeling of the collective oscillations for those conditions, is necessary.Comment: 27 pages, 10 figure

Rayleigh-Taylor Instabilities in Young Supernova Remnants Undergoing Efficient Particle Acceleration

We employ hydrodynamic simulations to study the effects of high shock compression ratios, as expected for fast shocks with efficient particle acceleration, on the convective instability of driven waves in supernova remnants. We find that the instability itself does not depend significantly on the compression ratio, but because the width of the interaction region between the forward and reverse shocks can shrink significantly with increasing shock compression, we find that convective instabilities can reach all the way to the forward shock front if compression ratios are high enough.Comment: Submitted to The Astrophysical Journa

Large lepton asymmetry from Q-balls

We propose a scenario which can explain large lepton asymmetry and small baryon asymmetry simultaneously. Large lepton asymmetry is generated through Affleck-Dine (AD) mechanism and almost all the produced lepton numbers are absorbed into Q-balls (L-balls). If the lifetime of the L-balls is longer than the onset of electroweak phase transition but shorter than the epoch of big bang nucleosynthesis (BBN), the large lepton asymmetry in the L-balls is protected from sphaleron effects. On the other hand, small (negative) lepton numbers are evaporated from the L-balls due to thermal effects, which are converted into the observed small baryon asymmetry by virtue of sphaleron effects. Large and positive lepton asymmetry of electron type is often requested from BBN. In our scenario, choosing an appropriate flat direction in the minimal supersymmetric standard model (MSSM), we can produce positive lepton asymmetry of electron type but totally negative lepton asymmetry.Comment: 10 pages, 3 figures, ReVTeX

Neutrino physics and the mirror world: how exact parity symmetry explains the solar neutrino deficit, the atmospheric neutrino anomaly and the LSND experiment

Evidence for $\bar \nu_{\mu} \rightarrow \bar \nu_e$ oscillations has been reported at LAMPF using the LSND detector. Further evidence for neutrino mixing comes from the solar neutrino deficit and the atmospheric neutrino anomaly. All of these anomalies require new physics. We show that all of these anomalies can be explained if the standard model is enlarged so that an unbroken parity symmetry can be defined. This explanation holds independently of the actual model for neutrino masses. Thus, we argue that parity symmetry is not only a beautiful candidate for a symmetry beyond the standard model, but it can also explain the known neutrino physics anomalies.Comment: 27 pages, LaTeX, no figures, additional discussion on big bang nucleosynthesis, some additional references, to appear in Phys. Rev.

Broad-band Observations and Modeling of the Shell-Type Supernova Remnant G347.3-0.5

The supernova remnant G347.3--0.5 emits a featureless power-law in X-rays, thought to indicate shock-acceleration of electrons to high energies. We here produce a broad-band spectrum of the bright NW limb of this source by combining radio observations from the Australia Telescope Compact Array (ATCA), X-ray observations from the Advanced Satellite for Cosmology and Astrophysics (ASCA), and TeV gamma-ray observations from the CANGAROO imaging Cerenkov telescope. We assume this emission is produced by an electron population generated by diffusive shock acceleration at the remnant forward shock. The nonlinear aspects of the particle acceleration force a connection between the widely different wavelength bands and between the electrons and the unseen ions, presumably accelerated simultaneously with the electrons. This allows us to infer the relativistic proton spectrum and estimate ambient parameters such as the supernova explosion energy, magnetic field, matter density in the emission region, and efficiency of the shock acceleration process. We find convincing evidence that the shock acceleration is efficient, placing >25% of the shock kinetic energy flux into relativistic ions. Despite this high efficiency, the maximum electron and proton energies, while depending somewhat on assumptions for the compression of the magnetic field in the shock, are well below the observed `knee' at about 10^{15} eV in the Galactic cosmic-ray spectrum.Comment: Submitted to ApJ, 22 pages, 5 figure