Rocket observation of conjugate photoelectrons in the predawn ionosphere

Photoelectron flux in the energy range 6–70 eV coming from the sunlight conjugate ionosphere has been measured directly by the rocket borne low energy electron spectrometer in the altitude region of 210–350 km. Pitch angle distribution of the measured flux is nearly isotropic, the flux decreasing slightly with pitch angle. The photoelectron fluxes measured at 350 km at the energies of 15 and 30 eV are 3 × 10⁶ and 1 × 10⁶ (cm² s str eV)^?1 respectively which decrease to 1 × 10⁶ and 1 × 10⁵ at 250 km at the same energies. These values are consistent with the vertical profile of the 630 nm airglow intensity measured simultaneously. The fluxes obtained near apogee show peaks in the range 20–30 eV which also appear in the daytime photoelectron flux, indicating reduced loss of electrons during the passage from the conjugate ionosphere through the plasmasphere at the low geomagnetic latitude where observation was made. Photoelectron fluxes observed below the apogee height are compared to the calculated fluxes to investigate the interaction of electrons with the atmospheric species during the passage in the ionosphere. Calculated fluxes obtained by using continuous slowing-down approximation and neglecting pitch angle scattering are in good agreement with the observations although there still remain disagreements in detailed comparison which may be ascribed to the assumptions inherent in the calculation and/or to the uncertainties of the input data for the calculation.     

Locations of Jovian decametric radiation sources

The location of the Jovian decametric radiation main source is determined to be the south magnetic pole while the location of the early source is found to be near the north magnetic pole, with an equal contribution from a region near the south magnetic pole. The results are based on calculations of the region observable from the Earth (ROE) for Jovian decametric radio waves that are emitted in the direction ± 10° centered on the direction perpendicular to the Jovian magnetic field and based on a Pioneer 11 model of the field at the level of the topside region of the Jovian ionosphere. Ground-based observations of the occurrence frequency of the decametric radiation as a function of Jovian longitude, which indicate a remarkable asymmetry between the early and main sources, agree with the calculated ROE area that varies as a function of CML observed from the Earth. The observations support a recent theory for the origin of the decametric radiation which is based on a wave-mode conversion from plasma waves into electromagnetic waves.     

Use of sorbents for oil spills

It is generally acknowledged that removing spilled oil from the sea is preferable to dispersing it, but there have been severe problems in devising methods of collecting oil from thin slicks. In this article the merits of various methods of absorbing spilled oil are reviewed.     

Characteristic heat transfer coefficients near the ground at night during strong winds

Based on theoretical radiative cooling values and observed temperature changes with time near the surface during the night, the bulk heat transfer coefficient C _H is estimated from standard meteorological observations obtained from stations representative of open rural, small town and large urban areas, for nights with clear skies and relatively strong winds. It is shown that C _H is smaller than the drag coefficient C _M, and that C _H/C _M over urban areas is smaller than that over open countryside.     

A simple model of drainage flow on a slope

The concept of a cold air ‘Parcel’ is introduced for describing the bulk properties of drainage flow. By means of a model based on the momentum and sensible heat transports under calm conditions, the thickness h and velocity u of the Parcel are derived in simple forms. It is shown that h and u correspond to the inversion height and maximum velocity of actual drainage flow. The governing parameters for h and u are the length and vertical drop of the slope, potential temperature difference between the ambient atmosphere and the Parcel, aerodynamic condition of the slope surface expressed by the mean bulk coefficients, and ambient stability. The mean bulk coefficients depend on the roughness lengths for the velocity and potential temperature profiles and are decreasing functions of the slope length. The Parcel Model agrees qualitatively with Manins and Sawford's (1979) model under neutral ambient stratification. But agreement is not so good under stable conditions. The thickness and velocity of drainage flow predicted by the Parcel Model agree with observations on slopes several tens of meters to several hundred kilometers long.     

Long-term changes in distribution and chemistry of middle Miocene to Quaternary volcanism in the Chokai-Kurikoma area across the Northeast Japan Arc

Abstract To understand the characteristics of long‐term spatial and temporal variation in volcanism within a volcanic arc undergoing constant subduction since the cessation of back‐arc opening, a detailed investigation of middle Miocene to Quaternary volcanism was carried out within the Chokai‐Kurikoma area of the Northeast Japan Arc. This study involved a survey of available literature, with new K–Ar and fission track dating, and chemical analyses. Since 14 Ma, volcanism has occurred within the Chokai‐Kurikoma area in specific areas with a ‘branch‐like’ pattern, showing an east–west trend. This is in marked contrast to the widespread distribution of volcanism with a north–south trend in the 20–14 Ma period. The east–west‐ trending ‘branches’ are characterized by regular intervals (50–100 km) of magmatism along the arc. These branches since 14 Ma are remarkably discrepant to the general northwest–southeast or north‐northeast–south‐southwest direction of the crustal structures that have controlled Neogene to Quaternary tectonic movements in northeast Japan. In addition, evidence indicating clustering and focusing of volcanism into smaller regions since 14 Ma was verified. Comparison of the distribution and chemistry of volcanic rocks for three principal volcanic stages (11–8, 6–3 and 2–0 Ma) revealed that widely but sparsely distributed volcanic rocks had almost the same level of alkali and incompatible element concentrations throughout the area (with the exception of Zr) in the 11–8 Ma stage. However, through the 6–3 Ma stage to the 2–0 Ma stage, the concentration level in the back‐arc cluster increased, while that in the volcanic front cluster remained almost constant. Therefore, the degree of partial melting has decreased, most likely with a simultaneous increase in the depth of magma segregation within the back‐arc zone, whereas within the volcanic front zone, the conditions of magma generation have changed little over the three stages. In conclusion, the evolution of the thermal structure within the mantle wedge across the arc since 14 Ma has reduced the extent of ascending mantle diapirs into smaller fields. This has resulted in the tendency for the distribution of volcanism to become localized and concentrated into more specific areas in the form of clusters from the late Miocene to Quaternary.     

Balloon-Borne Optical Counter for in Situ Aerosol Measurements

A new balloon-borne optical particle counter has been developed to make in situ measurements of stratospheric aerosols. The intensity of light scattered at 60° from the forward direction by individual particles is measured. Aerosol number concentrations in seven size channels can be inferred. The counter has been calibrated using polystyrene and polyvinyl toluene latex spheres. There is good agreement between measured and calculated individual pulse intensities for aerosol with radii from 0.16 to 2.6 µm. The size resolution is limited by broadening of the pulse count/pulse height spectrum, arising mainly from the photoelectron statistics of photomultipliers. Stratospheric aerosol measurements have been made using this instrument at Kiruna (68°N, 21°E), Sweden, in February 1995, and at Aire sur l'Adour (44°N, 0°W), France, in 1992, 1993, and 1994. The uncertainties in the measurements are discussed. The retrieved aerosol concentrations and size distributions are presented, and shown to be broadly consistent with measurements made by the University of Wyoming optical particle counter.     

A fault scarp in an urban area identified by LiDAR survey: A Case study on the Itoigawa–Shizuoka Tectonic Line, central Japan

A light detection and ranging (LiDAR) survey was conducted in a densely built-up area to generate a high-resolution digital elevation model (DEM) to look for active faults. The urban district of Matsumoto City in central Japan is located in a 3-km² basin along the Itoigawa–Shizuoka Tectonic Line active fault system, one of Japanese onshore fault systems with the highest earthquake probability. A high-resolution DEM at a 0.5-m-grid interval was obtained after removing the effects of laser returns from buildings, clouds and vegetation. It revealed a continuous scarp, up to ~ 2 m in height. Borehole data and archaeological studies indicate the scarp was formed during the most recent faulting event associated with historical earthquakes. In addition, the fault scarp strongly supports that the urban district is in a pull-apart basin related to a fault step-over between two left-lateral strike-slip faults. Consequently, accurate interpretation of fault geometry is crucial to provide estimates of future surface deformation and to allow modeling of basin structure and strong ground motion. Thus, the LiDAR mapping survey in urban districts is effective for detailed active fault mapping in order to constrain basin structure and to forecast the exact location of surface rupturing associated with large earthquakes.     

Composition and pressure dependence of lattice thermal conductivity of (Mg,Fe)O solid solutions

We measured the lattice thermal conductivities of Fe_0.98O wüstite and iron-rich (Mg,Fe)O magnesiowüstite using the pulsed light heating thermoreflectance technique with a diamond anvil cell up to 61 GPa at 300 K. We found that the thermal conductivity of wüstite does not show a monotonic increase as a function of pressure, contrary to that of MgO periclase. Rocksalt (B1) to rhombohedral B1 transition is likely to induce an abnormal pressure response in the conductivity of wüstite. Our results also show that magnesiowüstite has a lower conductivity than that of MgO and FeO endmembers due to a strong iron impurity effect, which is well reproduced by a model considering phonon-impurity scattering in a binary solid solution.     

A GPU based real-time GPS software receiver

Off-the-shelf graphics processing units provide low-cost massive parallel computing performance, which can be utilized for the implementation of a GPS software receiver. In order to realize a real-time capable system the crucial stages of the receiver should be optimized to suit the requirements of a parallel processor. Moreover, the receiver should be capable to provide wider correlation functions and provide easy access to the spectral domain of the signals. Thus, the most suitable correlation algorithm, which forms the core part of each receivers should be chosen and implemented on the graphics processor. Since the sampling rate of the received signal limits the real-time capabilities of the software radio it is necessary to determine an optimum value, considering that the precision of the observable varies with sampling bandwidth. We are going to discuss details and present our single frequency multi-channel implementation, which is capable of operating in real-time mode. Our implementation differs from other solutions by the wideness of the correlation function and allows simple handling of data in the spectral domain. Comparison with output from a commercial hardware receiver, which shares the antenna with the software radio, confirms the consistency and accuracy of our development.