Showing papers by "Japan Aerospace Exploration Agency published in 2010"

The AKARI/IRC mid-infrared all-sky survey

Abstract: Context. AKARI is the first Japanese astronomical satellite dedicated to infrared astronomy. One of the main purposes of AKARI is the all-sky survey performed with six infrared bands between 9 μ m and 200 μ m during the period from 2006 May 6 to 2007 August 28. In this paper, we present the mid-infrared part (9 μ m and 18 μ m bands) of the survey carried out with one of the on-board instruments, the infrared camera (IRC).Aims. We present unprecedented observational results of the 9 μ m and 18 μ m AKARI all-sky survey and detail the operation and data processing leading to the point source detection and measurements.Methods. The raw data are processed to produce small images for every scan, and the point sources candidates are derived above the 5σ noise level per single scan. The celestial coordinates and fluxes of the events are determined statistically and the reliability of their detections is secured through multiple detections of the same source within milli-seconds, hours, and months from each other.Results. The sky coverage is more than 90% for both bands. A total of 877 091 sources (851 189 for 9 μ m, 195 893 for 18 μ m) are confirmed and included in the current release of the point source catalog. The detection limit for point sources is 50 mJy and 90 mJy for the 9 μ m and 18 μ m bands, respectively. The position accuracy is estimated to be better than 2'' . Uncertainties in the in-flight absolute flux calibration are estimated to be 3% for the 9 μ m band and 4% for the 18 μ m band. The coordinates and fluxes of detected sources in this survey are also compared with those of the IRAS survey and are found to be statistically consistent.

Outflow Feedback Regulated Massive Star Formation in Parsec-Scale Cluster-Forming Clumps

Abstract: We investigate massive star formation in turbulent, magnetized, parsec-scale clumps of molecular clouds including protostellar outflow feedback using three dimensional numerical simulations of effective resolution 2048{sup 3}. The calculations are carried out using a block structured adaptive mesh refinement code that solves the ideal MHD equations including self-gravity and implements accreting sink particles. We find that, in the absence of regulation by magnetic fields and outflow feedback, massive stars form readily in a turbulent, moderately condensed clump of {approx} 1,600 M{sub {circle_dot}} (containing {approx} 10{sup 2} initial Jeans masses), along with a cluster of hundreds of lower mass stars. The massive stars are fed at high rates by (1) transient dense filaments produced by large-scale turbulent compression at early times, and (2) by the clump-wide global collapse resulting from turbulence decay at late times. In both cases, the bulk of the massive star's mass is supplied from outside a 0.1 pc-sized 'core' that surrounds the star. In our simulation, the massive star is clump-fed rather than core-fed. The need for large-scale feeding makes the massive star formation prone to regulation by outflow feedback, which directly opposes the feeding processes. The outflows reduce the mass accretion rates onto the massive stars by breaking up the dense filaments that feed the massive star formation at early times, and by collectively slowing down the global collapse that fuel the massive star formation at late times. The latter is aided by a moderate magnetic field of strength in the observed range (corresponding to a dimensionless clump mass-to-flux ratio {lambda} {approx} a few); the field allows the outflow momenta to be deposited more efficiently inside the clump. We conclude that the massive star formation in our simulated turbulent, magnetized, parsec-scale clump is outflow-regulated and clump-fed (ORCF for short). An important implication is that the formation of low-mass stars in a dense clump can affect the formation of massive stars in the same clump, through their outflow feedback on the clump dynamics. In a companion paper, we discuss the properties of the lower mass cluster members formed along with the massive stars, including their mass distribution and spatial clustering.

The Detection of a Population of Submillimeter-Bright, Strongly Lensed Galaxies

Abstract: Gravitational lensing is a powerful astrophysical and cosmological probe and is particularly valuable at submillimeter wavelengths for the study of the statistical and individual properties of dusty star-forming galaxies. However, the identification of gravitational lenses is often time-intensive, involving the sifting of large volumes of imaging or spectroscopic data to find few candidates. We used early data from the Herschel Astrophysical Terahertz Large Area Survey to demonstrate that wide-area submillimeter surveys can simply and easily detect strong gravitational lensing events, with close to 100% efficiency.

Gamma-ray emission from the shell of supernova remnant W44 revealed by the Fermi LAT

Abstract: Recent observations of supernova remnants (SNRs) hint that they accelerate cosmic rays to energies close to ~1015 electron volts. However, the nature of the particles that produce the emission remains ambiguous. We report observations of SNR W44 with the Fermi Large Area Telescope at energies between 2 × 108 electron volts and 3 × 1011 electron volts. The detection of a source with a morphology corresponding to the SNR shell implies that the emission is produced by particles accelerated there. The gamma-ray spectrum is well modeled with emission from protons and nuclei. Its steepening above ~109 electron volts provides a probe with which to study how particle acceleration responds to environmental effects such as shock propagation in dense clouds and how accelerated particles are released into interstellar space.

Flight status of IKAROS deep space solar sail demonstrator

Abstract: JAXA launched the world's first deep space solar sail demonstration spacecraft “IKAROS” on May 21, 2010. IKAROS was injected to an Earth–Venus trajectory to demonstrate several key technologies for solar sail utilizing the deep space flight environment. IKAROS succeeded in deploying a 20 m-span solar sail on June 9, and is now flying towards the Venus with the assist of solar photon acceleration. This paper describes the mission design, system design, solar sail deployment operation and current flight status of IKAROS.

Coupled thermal–electrical analysis for carbon fiber/epoxy composites exposed to simulated lightning current

Abstract: A coupled thermal–electrical analysis of carbon fiber reinforced polymer composites (CFRP) exposed to simulated lightning current was conducted in order to elucidate the damage behavior caused by a lightning strike with the numerical results being compared to experimental results. Based on the experimental results and a preliminary analysis, the specific mechanism of electrical conduction through the thickness direction of CFRP following thermal decomposition was revealed to be a key parameter for accurate numerical simulation. In particular, assuming the electrical conductivity in the thickness direction to be linear with respect to temperature in the range from the epoxy decomposition temperature to carbon sublimation temperature produced reasonable numerical results. The delamination area and damage depth were estimated from numerical results and thermal decomposition behavior of CFRP with the estimated damage area agreeing qualitatively with the experimental results. Numerical results suggest that Joule heat generation significantly influences lightning strike damage.

Electron acceleration by multi-island coalescence

Abstract: Energetic electrons of up to tens of MeV are created during explosive phenomena in the solar corona. While many theoretical models consider magnetic reconnection as a possible way of generating energetic electrons, the precise roles of magnetic reconnection during acceleration and heating of electrons still remain unclear. Here, we show from two-dimensional particle-in-cell simulations that coalescence of magnetic islands that naturally form as a consequence of tearing mode instability and associated magnetic reconnection leads to efficient energization of electrons. The key process is the secondary magnetic reconnection at the merging points, or the "anti-reconnection," which is, in a sense, driven by the converging outflows from the initial magnetic reconnection regions. By following the trajectories of the most energetic electrons, we found a variety of different acceleration mechanisms but the energization at the anti-reconnection is found to be the most important process. We discuss possible applications to the energetic electrons observed in the solar flares. We anticipate our results to be a starting point for more sophisticated models of particle acceleration during the explosive energy release phenomena.

Quiescent prominence dynamics observed with the hinode solar optical telescope. i. turbulent upflow plumes

Abstract: Hinode/Solar Optical Telescope (SOT) observations reveal two new dynamic modes in quiescent solar prominences: large-scale (20-50 Mm) 'arches' or 'bubbles' that 'inflate' from below into prominences, and smaller-scale (2-6 Mm) dark turbulent upflows. These novel dynamics are related in that they are always dark in visible-light spectral bands, they rise through the bright prominence emission with approximately constant speeds, and the small-scale upflows are sometimes observed to emanate from the top of the larger bubbles. Here we present detailed kinematic measurements of the small-scale turbulent upflows seen in several prominences in the SOT database. The dark upflows typically initiate vertically from 5 to 10 Mm wide dark cavities between the bottom of the prominence and the top of the chromospheric spicule layer. Small perturbations on the order of 1 Mm or less in size grow on the upper boundaries of cavities to generate plumes up to 4-6 Mm across at their largest widths. All plumes develop highly turbulent profiles, including occasional Kelvin-Helmholtz vortex 'roll-up' of the leading edge. The flows typically rise 10-15 Mm before decelerating to equilibrium. We measure the flowfield characteristics with a manual tracing method and with the Nonlinear Affine Velocity Estimator (NAVE) 'optical flow' code tomore » derive velocity, acceleration, lifetime, and height data for several representative plumes. Maximum initial speeds are in the range of 20-30 km s{sup -1}, which is supersonic for a {approx}10,000 K plasma. The plumes decelerate in the final few Mm of their trajectories resulting in mean ascent speeds of 13-17 km s{sup -1}. Typical lifetimes range from 300 to 1000 s ({approx}5-15 minutes). The area growth rate of the plumes (observed as two-dimensional objects in the plane of the sky) is initially linear and ranges from 20,000 to 30,000 km{sup 2} s{sup -1} reaching maximum projected areas from 2 to 15 Mm{sup 2}. Maximum contrast of the dark flows relative to the bright prominence plasma in SOT images is negative and ranges from -10% for smaller flows to -50% for larger flows. Passive scalar 'cork movies' derived from NAVE measurements show that prominence plasma is entrained by the upflows, helping to counter the ubiquitous downflow streams in the prominence. Plume formation shows no clear temporal periodicity. However, it is common to find 'active cavities' beneath prominences that can spawn many upflows in succession before going dormant. The mean flow recurrence time in these active locations is roughly 300-500 s (5-8 minutes). Locations remain active on timescales of tens of minutes up to several hours. Using a column density ratio measurement and reasonable assumptions on plume and prominence geometries, we estimate that the mass density in the dark cavities is at most 20% of the visible prominence density, implying that a single large plume could supply up to 1% of the mass of a typical quiescent prominence. We hypothesize that the plumes are generated from a Rayleigh-Taylor instability taking place on the boundary between the buoyant cavities and the overlying prominence. Characteristics, such as plume size and frequency, may be modulated by the strength and direction of the cavity magnetic field relative to the prominence magnetic field. We conclude that buoyant plumes are a source of quiescent prominence mass as well as a mechanism by which prominence plasma is advected upward, countering constant gravitational drainage.« less

Artificial lightning testing on graphite/epoxy composite laminate

Abstract: This study examines the evolution of damage in graphite/epoxy composite laminates due to lightning strikes To clarify the influence of lightning parameters and specimen size, artificial lightning testing was performed on a series of laminated composite specimens Damage was assessed using visual inspection, ultrasonic testing, micro X-ray inspection, and sectional observation The results showed that the damage modes can be categorized into fiber damage, resin deterioration, and internal delamination modes Damage progression is governed by the strong electrical orthotropic properties of the laminates, and the lightning parameters defining impulse waveform show strong relationship with certain damage modes, though specimen size and thickness variation barely affect damage size

Summary of the Fourth AIAA CFD Drag Prediction Workshop

Abstract: Results from the Fourth AIAA Drag Prediction Workshop (DPW-IV) are summarized. The workshop focused on the prediction of both absolute and differential drag levels for wing-body and wing-body-horizontal-tail configurations that are representative of transonic transport air- craft. Numerical calculations are performed using industry-relevant test cases that include lift- specific flight conditions, trimmed drag polars, downwash variations, dragrises and Reynolds- number effects. Drag, lift and pitching moment predictions from numerous Reynolds-Averaged Navier-Stokes computational fluid dynamics methods are presented. Solutions are performed on structured, unstructured and hybrid grid systems. The structured-grid sets include point- matched multi-block meshes and over-set grid systems. The unstructured and hybrid grid sets are comprised of tetrahedral, pyramid, prismatic, and hexahedral elements. Effort is made to provide a high-quality and parametrically consistent family of grids for each grid type about each configuration under study. The wing-body-horizontal families are comprised of a coarse, medium and fine grid; an optional extra-fine grid augments several of the grid families. These mesh sequences are utilized to determine asymptotic grid-convergence characteristics of the solution sets, and to estimate grid-converged absolute drag levels of the wing-body-horizontal configuration using Richardson extrapolation.

Tensile fatigue behaviour of FRP and hybrid FRP sheets

Abstract: This paper presents the fatigue behaviour of various fibre reinforced polymer (FRP) composites, namely, carbon, glass, polyparaphenylenl benzobisoxazole (PBO), and basalt fibres, including the effect of hybrid applications such as carbon/glass and carbon/basalt composites. A coupon test was conducted to examine the mechanical characteristics of the FRP composites subjected to monotonic and cyclic loads. Test parameters included the applied load range and different types of hybridization. Study results show that (1) the mechanical properties of the emerging PBO and basalt fibres are comparable to those of the conventional carbon and glass fibres; (2) the tensile modulus of the fibres influences the failure mode of the composite coupons; (3) the progressive damage propagation causes fatigue failure of the composites; (4) the hybrid composites of carbon/basalt significantly improves the fatigue resistance in comparison to the homogeneous basalt composite, whereas the resistance of the carbon/glass hybrid composites does not provide such effects.

Possible mantle origin of olivine around lunar impact basins detected by SELENE

Abstract: The composition, structure and evolution of the Moon’s mantle is poorly constrained. A global survey of the Moon’s surface, using the spectral profiler onboard the lunar explorer SELENE/Kaguya, identifies a number of exposures of olivine in concentric regions around lunar craters, with a possible mantle origin. The composition, structure and evolution of the Moon’s mantle is poorly constrained. The mineral olivine, one of the main constituents of Earth’s mantle, has been identified by Earth-based telescopic observations at two craters on the near side of the Moon, Aristarchus and Copernicus1,2,3. Global reflectance spectra in five discrete spectral bands produced by the spacecraft Clementine4,5,6 suggested several possible olivine-bearing sites, but one of the candidate occurrences of olivine was later re-classified, on the basis of continuous reflectance spectra over the entire 1 μm band, as a mixture of plagioclase and pyroxene7. Here we present a global survey of the lunar surface using the Spectral Profiler onboard the lunar explorer SELENE/Kaguya7,8. We found many exposures of olivine on the Moon, located in concentric regions around the South Pole-Aitken, Imbrium and Moscoviense impact basins where the crust is relatively thin. We propose that these exposures of olivine can be attributed either to an excavation of the lunar mantle at the time of the impacts that formed the basins3, or to magnesium-rich pluton in the Moon’s lower crust. On the basis of radiative transfer modelling4,8,9,10, we suggest that at least some of the olivine detected near impact basins originates from upper mantle of the Moon.

Breakdown of kennicutt–schmidt law at giant molecular cloud scales in m33

Abstract: We have mapped the northern area (30' ? 20') of a Local Group spiral galaxy M33 in 12CO(J = 1-0) line with the 45 m telescope at the Nobeyama Radio Observatory. Along with H? and Spitzer 24 ?m data, we have investigated the relationship between the surface density of molecular gas mass and that of star formation rate (SFR) in an external galaxy (Kennicutt-Schmidt law) with the highest spatial resolution (~80 pc) to date, which is comparable to scales of giant molecular clouds (GMCs). At positions where CO is significantly detected, the SFR surface density exhibits a wide range of over four orders of magnitude, from ?SFR 10?10 to ~10?6 M ? yr?1 pc?2, whereas the values are mostly within 10-40 M ? pc?2. The surface density of gas and that of SFR correlate well at an ~1 kpc resolution, but the correlation becomes looser with higher resolution and breaks down at GMC scales. The scatter of the ?SFR- relationship in the ~80?pc resolution results from the variety of star-forming activity among GMCs, which is attributed to the various evolutionary stages of GMCs and to the drift of young clusters from their parent GMCs. This result shows that the Kennicutt-Schmidt law is valid only in scales larger than that of GMCs, when we average the spatial offset between GMCs and star-forming regions, and their various evolutionary stages.

Effects of Low-Intensity Cycle Training with Restricted Leg Blood Flow on Thigh Muscle Volume and VO2MAX in Young Men

Abstract: Concurrent improvements in aerobic capacity and muscle hypertrophy in response to a single mode of training have not been reported. We examined the effects of low-intensity cycle exercise training with and without blood flow restriction (BFR) on muscle size and maximum oxygen uptake (VO2max). A group of 19 young men (mean age ± SD: 23.0 ± 1.7 years) were allocated randomly into either a BFR-training group (n=9, BFR-training) or a non-BFR control training group (n=10, CON-training), both of which trained 3 days/wk for 8 wk. Training intensity and duration were 40% of VO2max and 15 min for the BFR-training group and 40% of VO2max and 45 min for the CON-training group. MRI-measured thigh and quadriceps muscle cross-sectional area and muscle volume increased by 3.4-5.1% (P < 0.01) and isometric knee extension strength tended to increase by 7.7% (p < 0.10) in the BFR-training group. There was no change in muscle size (~0.6%) and strength (~1.4%) in the CON-training group. Significant improvements in VO2max (6.4%) and exercise time until exhaustion (15.4%) were observed in the BFR-training group (p < 0.05) but not in the CON-training group (-0.1 and 3. 9%, respectively). The results suggest that low-intensity, short-duration cycling exercise combined with BFR improves both muscle hypertrophy and aerobic capacity concurrently in young men. Key points Concurrent improvements in aerobic capacity and muscle hypertrophy in response to a single mode of training have not been reported. In the present study, low-intensity (40% of VO2max) cycle training with BFR can elicit concurrent improvement in muscle hypertrophy and aerobic capacity.

The ASTRO-H mission

Abstract: The joint JAXA/NASA ASTRO-H mission is the sixth in a series of highly successful X-ray missions initiated by the Institute of Space and Astronautical Science (ISAS). ASTRO-H will investigate the physics of the high-energy universe by performing high-resolution, high-throughput spectroscopy with moderate angular resolution. ASTRO-H covers very wide energy range from 0.3 keV to 600 keV. ASTRO-H allows a combination of wide band X-ray spectroscopy (5-80 keV) provided by multilayer coating, focusing hard X-ray mirrors and hard X-ray imaging detectors, and high energy-resolution soft X-ray spectroscopy (0.3-12 keV) provided by thin-foil X-ray optics and a micro-calorimeter array. The mission will also carry an X-ray CCD camera as a focal plane detector for a soft X-ray telescope (0.4-12 keV) and a non-focusing soft gamma-ray detector (40-600 keV) . The micro-calorimeter system is developed by an international collaboration led by ISAS/JAXA and NASA. The simultaneous broad bandpass, coupled with high spectral resolution of ΔE ~7 eV provided by the micro-calorimeter will enable a wide variety of important science themes to be pursued.

X-Ray Temperature and Mass Measurements to the Virial Radius of Abell 1413 with Suzaku

Abstract: We present X-ray observations of the northern outskirts of the relaxed galaxy cluster A 1413 with Suzaku, whose XIS instrument has the low intrinsic background needed to make measurements of these low surface brightness regions. We excised 15 point sources superimposed on the image above a flux of 1 10 erg cm 2 s 1 (2–10 keV) using XMM-Newton and Suzaku images of the cluster. We quantified all known systematic errors as part of our analysis, and showed that our statistical errors encompass them for the most part. Our results extend previous measurements with Chandra and XMM-Newton, and show a significant temperature drop to about 3 keV at the virial radius, r200. Our entropy profile in the outer region (>0.5r200) joins smoothly onto that of XMM-Newton, and shows a flatter slope compared with simple models, similar to a few other clusters observed at the virial radius. The integrated mass of the cluster at the virial radius is approximately 7.5 10Mˇ, and varies by about 30%, depending on the particular method used to measure it.

Design of a Concentration Solar Thermoelectric Generator

Abstract: Thermoelectric technology can be another direct way to convert solar radiation into electricity, using the Seebeck effect. Herein, a prototype concentration solar thermoelectric generator (CTG) and a discrete numerical model for the evaluation of the whole system are presented. The model takes into account the temperature dependence of the thermoelectric material properties by dividing the thermoelectric leg into finite elements and is proved to be more accurate for calculation of the conversion efficiency of the thermoelectric modules when large temperature gradients occur in the CTG system. Based on the best available properties of various bulk thermoelectric materials reported in the literature, the best possible performance of the CTG system is predicted, and the CTG system design, including the selection of the concentration ratio and the cooling method for different thermoelectric materials, are discussed in detail.

AKARI IRC INFRARED 2.5-5 μm SPECTROSCOPY OF A LARGE SAMPLE OF LUMINOUS INFRARED GALAXIES

Abstract: We present the results of our systematic infrared 2.5-5 μm spectroscopy of 60 luminous infrared galaxies (LIRGs) with infrared luminosities L IR = 1011-1012 L ☉ and 54 ultraluminous infrared galaxies (ULIRGs) with L IR ≥ 1012 L ☉, using the AKARI Infrared Camera (IRC). AKARI IRC slit-less spectroscopy allows us to probe the full range of emission from these galaxies, including spatially extended components. The 3.3 μm polycyclic aromatic hydrocarbon (PAH) emission features, hydrogen recombination emission lines, and various absorption features are detected and used to investigate the properties of these galaxies. Because of the relatively small effect of dust extinction in the infrared range, quantitative discussion of these dusty galaxy populations is possible. For sources with clearly detectable Brβ (2.63 μm) and Brα (4.05 μm) emission lines, the flux ratios are found to be similar to those predicted by case B theory. Starburst luminosities are estimated from both 3.3 μm PAH and Brα emission, which roughly agree with each other. In addition to the detected starburst activity, a significant fraction of the observed sources display signatures of obscured active galactic nuclei (AGNs), such as low PAH equivalent widths, large optical depths of dust absorption features, and red continuum emission. The energetic importance of optically elusive buried AGNs in optically non-Seyfert galaxies tends to increase with increasing galaxy infrared luminosity, from LIRGs to ULIRGs.

In-flight Performance and Initial Results of Plasma Energy Angle and Composition Experiment (PACE) on SELENE (Kaguya)

Abstract: MAP-PACE (MAgnetic field and Plasma experiment—Plasma energy Angle and Composition Experiment) on SELENE (Kaguya) has completed its ∼1.5-year observation of low-energy charged particles around the Moon. MAP-PACE consists of 4 sensors: ESA (Electron Spectrum Analyzer)-S1, ESA-S2, IMA (Ion Mass Analyzer), and IEA (Ion Energy Analyzer). ESA-S1 and S2 measured the distribution function of low-energy electrons in the energy range 6 eV–9 keV and 9 eV–16 keV, respectively. IMA and IEA measured the distribution function of low-energy ions in the energy ranges 7 eV/q–28 keV/q and 7 eV/q–29 keV/q. All the sensors performed quite well as expected from the laboratory experiment carried out before launch. Since each sensor has a hemispherical field of view, two electron sensors and two ion sensors installed on the spacecraft panels opposite each other could cover the full 3-dimensional phase space of low-energy electrons and ions. One of the ion sensors IMA is an energy mass spectrometer. IMA measured mass-specific ion energy spectra that have never before been obtained at a 100 km altitude polar orbit around the Moon. The newly observed data show characteristic ion populations around the Moon. Besides the solar wind, MAP-PACE-IMA found four clearly distinguishable ion populations on the dayside of the Moon: (1) Solar wind protons backscattered at the lunar surface, (2) Solar wind protons reflected by magnetic anomalies on the lunar surface, (3) Reflected/backscattered protons picked-up by the solar wind, and (4) Ions originating from the lunar surface/lunar exosphere.

Overview and early results of the Superconducting Submillimeter‐Wave Limb‐Emission Sounder (SMILES)

Abstract: [1] The Superconducting Submillimeter-Wave Limb-Emission Sounder (SMILES) was successfully launched and attached to the Japanese Experiment Module (JEM) on the International Space Station (ISS) on 25 September 2009. It has been making atmospheric observations since 12 October 2009 with the aid of a 4 K mechanical cooler and superconducting mixers for submillimeter limb-emission sounding in the frequency bands of 624.32–626.32 GHz and 649.12–650.32 GHz . On the basis of the observed spectra, the data processing has been retrieving vertical profiles for the atmospheric minor constituents in the middle atmosphere, such as O3 with isotopes, HCl, ClO, HO2, BrO, and HNO3. Results from SMILES have demonstrated its high potential to observe atmospheric minor constituents in the middle atmosphere. Unfortunately, SMILES observations have been suspended since 21 April 2010 owing to the failure of a critical component.

Observations of Slow Electron Holes at a Magnetic Reconnection Site

Abstract: We report in situ observations of high-frequency electrostatic waves in the vicinity of a reconnection site in the Earth's magnetotail. Two different types of waves are observed inside an ion-scale magnetic flux rope embedded in a reconnecting current sheet. Electron holes (weak double layers) produced by the Buneman instability are observed in the density minimum in the center of the flux rope. Higher frequency broadband electrostatic waves with frequencies extending up to f(pe) are driven by the electron beam and are observed in the denser part of the rope. Our observations demonstrate multiscale coupling during the reconnection: Electron-scale physics is induced by the dynamics of an ion-scale flux rope embedded in a yet larger-scale magnetic reconnection process.

In Situ Observation of Dendrite Growth of Electrodeposited Li Metal

Abstract: The dendrite growth behavior of Li metal galvanostatically electrodeposited on Ni substrate in a LiClO 4 -propylene carbonate electrolyte solution was in situ observed by a laser scanning confocal microscope with a metallographic microscope. A Li dendrite precursor is stochastically evolved on Ni substrate probably through a solid electrolyte interphase layer produced by the surface chemical reaction between a reduced Li metal and an organic electrolyte. The measured length of randomly growing Li dendrite arms was statistically analyzed. The initiation period of the dendrite precursor becomes shorter with increasing current density and decreasing LiClO 4 concentration. Once it has been initiated, the ionic mass transfer rate starts to govern the growth process of the dendrite arm length, exceeding over the surface chemistry controlling step. The dendrite arm length averaged over the substrate surface grows linearly proportional to the square root of time. The lower the concentration of LiClO 4 , the steeper the inclination of the line at 5 mA cm -2 , whereas the concentration dependence of inclination is not evident at 0.5 mA cm -2 .

EXPANSION VELOCITY OF EJECTA IN TYCHO's SUPERNOVA REMNANT MEASURED BY DOPPLER BROADENED X-RAY LINE EMISSION

Abstract: We show that the expansion of ejecta in Tycho's supernova remnant (SNR) is consistent with a spherically symmetric shell, based on Suzaku measurements of the Doppler broadened X-ray emission lines. All of the strong Kα line emissions show broader widths at the center than at the rim, while the centroid energies are constant across the remnant (except for Ca). This is the pattern expected for Doppler broadening due to expansion of the SNR ejecta in a spherical shell. To determine the expansion velocities of the ejecta, we applied a model for each emission-line feature having two Gaussian components separately representing red- and blueshifted gas, and inferred the Doppler velocity difference between these two components directly from the fitted centroid energy difference. Taking into account the effect of projecting a three-dimensional shell to the plane of the detector, we derived average spherical expansion velocities independently for the Kα emission of Si, S, Ar, and Fe, and Kβ of Si. We found that the expansion velocities of Si, S, and Ar ejecta of 4700 ± 100 km s–1 are distinctly higher than that obtained from Fe Kα emission, 4000 ± 300 km s–1, which is consistent with segregation of the Fe in the inner ejecta. Combining the observed ejecta velocities with the ejecta proper-motion measurements by Chandra, we derived a distance to Tycho's SNR of 4 ± 1 kpc.

Evaluation of GSMaP Precipitation Estimates over the Contiguous United States

Abstract: Precipitation estimates from the Global Satellite Mapping of Precipitation (GSMaP) project are evaluated over the contiguous United States (CONUS) for the period of 2005–06. GSMaP combines precipitation retrievals from the Tropical Rainfall Measuring Mission satellite and other polar-orbiting satellites, and interpolates them with cloud motion vectors derived from infrared images from geostationary satellites, to produce a high-resolution dataset. Four other satellite-based datasets are also evaluated concurrently with GSMaP, to provide a better perspective. The new Climate Prediction Center (CPC) unified gauge analysis is used as the reference data. The evaluation shows that GSMaP does well in capturing the spatial patterns of precipitation, especially for summer, and that it has better estimation of precipitation amount over the eastern than over the western CONUS. Meanwhile, GSMaP shares many of the challenges common to other satellite-based products, including that it underestimates in winter...

An improved lunar gravity field model from SELENE and historical tracking data: Revealing the farside gravity features

Abstract: [1] A new spherical harmonic solution of the lunar gravity field to degree and order 100, called SGM100h, has been developed using historical tracking data and 14.2 months of SELENE tracking data (from 20 October 2007 to 26 December 2008 plus 30 January 2009). The latter includes all usable 4-way Doppler data collected which allowed direct observations of the farside gravity field for the first time. The new model successfully reveals farside features in free-air gravity anomalies which are characterized by ring-shaped structures for large impact basins and negative spots for large craters. SGM100h produces a correlation with SELENE-derived topography as high as about 0.9, through degree 70. Comparison between SGM100h and LP100K (one of the pre-SELENE models) shows that the large gravity errors which existed in LP100K are drastically reduced and the asymmetric error distribution between the nearside and the farside almost disappears. The gravity anomaly errors predicted from the error covariance, through degree and order 100, are 26 mGal and 35 mGal for the nearside and the farside, respectively. Owing to the 4-way Doppler measurements the gravity coefficients below degree and order 70 are now determined by real observations with contribution factors larger than 80 percent. With the SELENE farside data coverage, it is possible to estimate the gravity field to degree and order 70 without applying any a priori constraint or regularization. SGM100h can be used for global geophysical interpretation through degree and order 70.

The 2010 Maule, Chile earthquake: Downdip rupture limit revealed by space geodesy

Abstract: Radar interferometry from the ALOS satellite captured the coseismic ground deformation associated with the 2010 Mw 8.8 Maule, Chile earthquake. The ALOS interferograms reveal a sharp transition in fringe pattern at ~150 km from the trench axis that is diagnostic of the downdip rupture limit of the Maule earthquake. An elastic dislocation model based on ascending and descending ALOS interferograms and 13 near-field 3-component GPS measurements reveals that the coseismic slip decreases more or less linearly from a maximum of 17 m (along-strike average of 6.5 m) at 18 km depth to near zero at 43–48 km depth, quantitatively indicating the downdip limit of the seismogenic zone. The depth at which slip drops to near zero appears to be at the intersection of the subducting plate with the continental Moho. Our model also suggests that the depth where coseismic slip vanishes is nearly uniform along the strike direction for a rupture length of ~600 km. The average coseismic slip vector and the interseismic velocity vector are not parallel, which can be interpreted as a deficit in strike-slip moment release.

Evaluation of Euler Fluxes for Hypersonic Heating Computations

Abstract: In hypersonic flow computations, it is a key issue to predict surface heating accurately, though this is still challenging because there always are possibilities of resulting in anomalous solutions. In this paper, three properties for flux functions are proposed: 1) shock stability/robustness, 2) conservation of total enthalpy, and 3) resolving boundary layer. Then, numerical experiments are performed for widely used or recently developed flux functions, and these fluxes are categorized into five major groups based on how they satisfy the three properties. These tests reveal that no flux function investigated here possesses all the three properties. In particular, the first one is not satisfied by any flux functions, including flux-vector-splittings. Finally, contributions of those properties are compared inatwo-dimensional, viscous, hypersonicblunt-bodyproblem. Results showedthatthe firstandthe third properties are crucial, and the second one is preferred to predict hypersonic heating. A group of flux functions that best satisfies these properties is suggested, and they are recommended either to be used or designed for hypersonic heating computations.