Frequency selective surfaces for radio astronomy

Frequency selective surfaces (FSSs) with the Jerusalem-cross array configuration have been developed for simultaneous observations of radio astronomical sources at the 40GHz and 80GHz bands. For supporting material, PET(polyethylene terephthalate: 200×220mm large, 12m thick, permittivity 3.0) was used, and copper was used for the conducting array. The measured characteristics were in good agreement with the calculated ones. The fabricated FSS has low insertion losses of less than 0.2dB and little distortion of polarization for each band. The characteristics of the developed FSS satisfy radio astronomical requirements.     

Ice cloud microphysics,radiative transfer and large-scale cloud processes

Summary Parameterization programs for cloud microphyscs and radiative transfer involving ice clouds have been developed in terms of the mean effective size and ice water path. The mean effective size appears to be adequate in representing the ice crystal size distribution for radiative parameterizations. For a given ice water path, smaller mean effective sizes reflect more solar radiation, emit more IR radiation and enhance net radiative heating/cooling at the cloud top and bottom than larger sizes. The presence of small ice crystals may generate steeper lapse rates in clouds. A 3-D global cloud model that prescribes the horizontal wind fields in a 24 hour period is used to investigate the sensitivity of the mean effective size of ice crystals on the simulation of radiative heating, temperature, cloud cover and ice water content. A variation in the mean effective size from 75 to 50 m in a 24 hour prediction on simulation generates more cooling above the high cloud top and a decrease of temperature. These results lead to an increase of high cloud cover in some latitudes by as much as 4% and, at the same time, a decrease of middle cloud cover by 3–4% in latitudes between 60°S and 60°N.With 7 Figures     

Finite difference analog of the Coriolis force in papers by Endoh

A wrong finite difference form is used for the rotation of the Coriolis force in the vorticity equation with bottom topography in a series of papers byEndoh.     

Sequence-stratigraphic signatures of hemipelagic siltstones in deep-water successions: the Lower Pleistocene Kiwada and Otadai Formations, Boso Peninsula, Japan

Sequence-stratigraphic signatures of hemipelagic siltstones were investigated using profiles of the magnetic susceptibility and selected chemical composition of the Early Pleistocene deep-water successions of the Kiwada and Otadai Formations on the Boso Peninsula, Japan. In the context of an independently developed sequence-stratigraphic framework for the submarine-fan deposits of the Otadai Formation, the magnetic susceptibility and chemical composition, such as the concentrations of TiO₂, MgO and Fe₂O₃, show that the lowstand systems tract deposits have higher values of these parameters than the transgressive and highstand systems tract deposits. In contrast, the CaO contents have inverse relationships with the magnetic susceptibility and are higher in the transgressive and highstand systems tract deposits. The positions of sequence boundaries largely coincide with the horizons from which the magnetic susceptibility and the contents of mafic component increase abruptly. The sequence-stratigraphic variations in the magnetic susceptibility and chemical composition of the submarine-fan hemipelagic siltstones are due to increases in the input of fine-grained, terrigenous clastic sediments from midwater flow suspension, in addition to the direct fluvial supply of relatively unmodified terrigenous clastic sediments during relative sea-level lowstands, although grain size of hemipelagic siltstones does not exhibit any distinct variation through depositional sequences. The Kiwada Formation is characterized by siltstone-dominated basin-plain deposits and its sequence-stratigraphic classification has been difficult when using just lithofacies features. Nevertheless, the profiles of the magnetic susceptibility and chemical composition of the basin-plain deposits are similar to those of the submarine-fan deposits with duration largely equivalent to the 41,000-years obliquity cycle of the Early Pleistocene oxygen isotope sea-level index. This finding indicates that the profiles of the magnetic susceptibility and chemical composition of hemipelagic siltstones reflect sequence-stratigraphic variation in the input of fine-grained terrigenous clastic sediments to the deep-water environments and are crucial for the recognition of cryptic sequence boundaries in hemipelagic successions.     

Three-dimensional finite strain analysis in the high-grade part of the Sanbagawa Belt using deformed meta-conglomerate

Abstract   Regional ductile deformation of the Sanbagawa belt is generally thought to be characterized by constrictional strain, based on strain analysis using deformed radiolarians in the low-grade regions. Similar strain analysis could not be carried out in the medium- to high-grade zones, because it is very difficult to identify individual radiolarians after strong recrystallization. However, discovery of the first known meta-conglomerate in the high-grade region of the Sanbagawa Belt allows quantitative 3-D strain to be estimated in this region. Using a development of the Rf-φ method, an evaluation of appropriate errors for this estimate can be determined. The principal strain ratios and estimated errors are X/Y = 5.4–6.6 and Y/Z = 3.8–3.9 implying deformation in the flattening field and refuting the idea of uniform constrictional strain. Semi-quantitative markers of the shape of the strain ellipse throughout the high-grade regions suggest that the deformation of the Sanbagawa Belt is dominantly in the flattening field. The difference with the earlier results may be due to late-stage overprinting by upright folding of the main ductile fabric in the low-grade region of western Shikoku.     

Laboratory Experiment of Plasma Flow Around Magnetic Sail

To propel a spacecraft in the direction leaving the Sun, a magnetic sail (MagSail) blocks the hypersonic solar wind plasma flow by an artificial magnetic field. In order to simulate the interaction between the solar wind and the artificially deployed magnetic field produced around a magnetic sail spacecraft, a laboratory simulator was designed and constructed inside a space chamber. As a solar wind simulator, a high-power magnetoplasmadynamic arcjet is operated in a quasisteady mode of 0.8 ms duration. It can generate a simulated solar wind that is a high-speed (above 20 km/s), high-density (10¹⁸ m⁻³) hydrogen plasma plume of ∼0.7 m in diameter. A small coil (2 cm in diameter), which is to simulate a magnetic sail spacecraft and can obtain 1.9-T magnetic field strength at its center, was immersed inside the simulated solar wind. Using these devices, the formation of a magnetic cavity (∼8 cm in radius) was observed around the coil, which indicates successful simulation of the plasma flow of a MagSail in the laboratory.     

Response of a summertime anticyclonic eddy to wind forcing in Funka Bay,Hokkaido, Japan

Flow fluctuations inside an anticyclonic eddy in summertime Funka Bay were examined using three moorings and hydrographic data. The flow pattern above a sharp pycnocline with a concave isopycnal structure during the mooring period was characterized by high mean kinetic energy and relatively low eddy kinetic energy. The ratios of eddy to mean kinetic energy were equal to or less than one, and the mean flow field and isopycnal structure indicated the existence of a stable anticyclonic eddy above the sharp pycnocline under approximate geostrophic balance. Larger flow fluctuations with periods longer than 7 days were dominant inside the eddy. The low-frequency flow fluctuations are accompanied by north to northeastward movement of the eddy with deepening of the pycnocline and spin-up of the anticyclonic circulation. The wind field over Funka Bay is characterized by bay-scale wind fluctuations. The bay-scale winds are greatly influenced by the land topography around Funka Bay, resulting in non-uniform structure with significant wind stress curl. The bay-scale wind fluctuations are termed “locally modified wind” in the present study. The locally modified wind has a negative (positive) wind stress curl in the central–northeastern (southwestern) region of Funka Bay. The north to northeastward movement of the eddy is caused by horizontal non-uniform supply of vorticity from the locally modified wind forcing by the Ekman pumping process. Through this process, the anticyclonic circulation is enhanced (weakened) in the central–northeastern (southwestern) part of the eddy, resulting in the eddy moving north to northeastward with the pycnocline deepening and spin-up of the anticyclonic circulation. The locally modified wind forcing induces low-frequency flow fluctuations through the movement of the eddy in summertime Funka Bay.