Analysis software for upper atmospheric data developed by the IUGONET project and its application to polar science

To comprehensively understand the Arctic and Antarctic upper atmosphere, it is often crucial to analyze various data that are obtained from many regions. Infrastructure that promotes such interdisciplinary studies on the upper atmosphere has been developed by a Japanese inter-university project called the Inter-university Upper atmosphere Global Observation Network （1UGONET）. The objective of this paper is to describe the infrastructure and tools developed by IUGONET. We focus on the data analysis software. It is written in Interactive Data Language （IDL） and is a plug-in for the THEMIS Data Analysis Software suite （TDAS）, which is a set of IDL libraries used to visualize and analyze satellite- and ground-based data. We present plots of upper atmospheric data provided by IUGONET as examples of applications, and verify the usefulness of the software in the study of polar science. We discuss IUGONET＇s new and unique developments, i.e., an executable file of TDAS that can run on the IDL Virtual Machine, IDL routines to retrieve metadata from the IUGONET database, and an archive of 3-D simulation data that uses the Common Data Format so that it can easily be used with TDAS.     

Distribution of Changjiang Diluted Water detected by satellite chlorophyll-a and its interannual variation during 1998–2007

Sea-viewing Wide Field-of-view Sensor (SeaWiFS) chlorophyll-a distribution in summer in the East China Sea during 1998–2007 was analyzed. Statistical analysis with K-means clustering technique allowed us to define the proper satellite chlorophyll-a concentration indicating the Changjiang Diluted Water (CDW). The spatial distributions of the higher satellite chlorophyll-a concentrations (>0.48 mg m⁻³) corresponded well with the distributions of lower salinity CDW (<30–32) every year. Interannual variation of the CDW area, indicated by the high satellite chlorophyll-a, correlated with the interannual variation of the Changjiang summer freshwater discharge. The correlation analysis indicated that the CDW spread eastward in the East China Sea with a time lag of 1 to 2 months after the discharge.     

Morphological classification of nearby galaxies based on asymmetry and luminosity concentration

We investigate the behaviour of the asymmetry parameter A as a morphological parameter using a 'volume-limited' sample of 349 galaxies  (distance ≤25 Mpc,  M_V ≤−18.5 mag)  and a larger magnitude-limited sample of 707 nearby galaxies. We confirm the correlation of A with morphological type. The late-type galaxies (Sdm, Sm and Im) have larger A than early-type galaxies, and they tend to have larger A than spiral galaxies. We investigate the usefulness of the A versus concentration index C _in diagram as a tool for the regular–irregular and early–late classification. The diagram is not very useful to the regular versus late-type irregular classification, as inferred previously, but it is found to be useful to the early–late classification.     

Mechanical response of the south flank of kilauea volcano, hawaii, to intrusive events along the rift systems

Increased earthquake activity and compression of the south flank of Kilauea volcano, Hawaii, have been recognized by previous investigators to accompany rift intrusions. We further detail the temporal and spatial changes in earthquake rates and ground strain along the south flank induced by six major rift intrusions which occurred between December 1971 and January 1981. The seismic response of the south flank to individual rift intrusions is immediate; the increased rate of earthquake activity lasts from 1 to 4 weeks. Horizontal strain measurements indicate that compression of the south flank usually accompanies rift intrusions and eruptions. Emplacement of an intrusion at a depth greater than about 4 km, such as the June 1982 southwest rift intrusion, however, results in a slight extension of the subaerial portion of the south flank.Horizontal strain measurements along the south flank are used to locate the January 1983 east-rift intrusion, which resulted in eruptive activity. The intrusion is modeled as a vertical rectangular sheet with constant displacement perpendicular to the plane of the sheet. This model suggests that the intrusive body that compressed the south flank in January 1983 extended from the surface to about 2.4 km depth, and was aligned along a strike of N66°E. The intrusion is approximately 11 km in length, extended beyond the January 1983 eruptive fissures, which are 8 km in length and is contained within the 14-km-long region of shallow rift earthquakes.     

The absence of apparent correlations between iras and optical spectral features of late-type stars

The spectral signatures of circumstellar dust shells (CS) of late-type stars cannot be tied in a simple manner to their optical spectral features. The spectral indices of featureless low-resolution spectrometer (LRS) spectra of K and early-M (M0-M5) stars are consistent with that of the Rayleigh-Jeans law and those of late-M (M6 and later) stars tend to have lower values showing CS radiation. There is no correlation observed between the optical sub-type and the 10 m emission strength for M stars. The absence of a simple relationship is also evident for C stars where the temperature and abundance indices show no correlation with the 11 m emission strength. The sample is confined to the IRC stars identified with accurate spectra observed by the LRS of IRAS. The IRC stars are the whole sky survey done with the 2 m band, where late-type stars are bright and interstellar extinction is one-tenth of the visual colour band.     

Fault-related folds and an imbricate thrust system on the northwestern margin of the northern Fossa Magna region, central Japan

Abstract   The Nishikubiki Mountains, which are located on the northwestern margin of the northern Fossa Magna region, central Japan, and the area offshore to the north of the mountains are underlain by folded and faulted Neogene and Quaternary sequences. The folds are composed of open, symmetric anticlines or tight, asymmetric anticlines trending north 20–70° east. On the basis of the geometry of the anticlines and growth strata, the symmetric and asymmetric anticlines are interpreted as fault-bend folds and fault-propagation folds, respectively. The formation of the anticlines is attributed to the growth of an imbricate thrust system composed of three thrust sheets that developed, from southeast to northwest, mainly in the late Pliocene, early Pleistocene, and middle Pleistocene–Holocene. The horizontal component of the northwestern-most sheet was estimated to be approximately 1.2 km on the basis of the width of the growth triangle, and the thickness of the sheet at its southeast margin was estimated to be 8.5 km on the basis of area balancing along one of the seismic profiles. The thrust is inferred to extend to a depth of more than 10 km toward the southwest. The three thrust sheets are probably connected by a detachment zone along the boundary between the upper and lower crusts. The anticlines are bounded by the Itoigawa–Shizuoka Tectonic Line (ISTL) to the west and by lateral ramps or tip lines to the northeast. The ISTL possibly continues northward offshore into the Toyama Trough. The structural model proposed in this paper suggests that similar thrust systems are wide spread in the northern Fossa Magna region and that active deformation zones have migrated and switched during the past 2–3 million years along the fold belt.     

The crystal structure of CaFe3+SiAlO6 and the crystal chemistry of Fe3+—Al3+ substitution in calcium Tschermak's pyroxene

The crystal structure of a synthetic CaFe³⁺Al-SiO₆ pyroxene (20 kb, 1,375° C) with unit cell dimensions a=9.7797(16), b=8.7819(14), c=5.3685(5) Å, =105.78(1), space group C2/c has been refined by the method of least squares to an R-factor of 0.025 based on 812 reflections measured on an automatic single crystal diffractometer. The octahedral M1 site is occupied by 0.82 Fe³⁺ and 0.18 Al³⁺. Within the tetrahedral T site, Si⁴⁺ (0.50), Al³⁺ (0.41) and Fe³⁺ (0.09) ions are completely disordered, although submicroscopic domains with short-range order are very likely. The octahedral site preference energy of the Fe³⁺ ions with respect to Al³⁺ ions in CaFe³⁺AlSiO₆ is about 10 kcal/mole, which is much higher than that found in Y₃Al _x Fe_5–2O₁₂ garnets. Topologically the structure of CaFe³⁺AlSiO₆ is intermediate between that of diopside and calcium Tschermak's pyroxene, CaAlAlSiO₆. For CaM³⁺ AlSiO₆ clinopyroxenes an increase in the size of the M1 octahedron is accompanied by an increase in the average M2-0, bridging T-0 and 03-03 distances and kinking of the tetrahedral chain.     

Active tectonics around the junction of Southwest Japan and Ryukyu arcs: Control by subducting plate geometry and pre‐Quaternary geologic structure

The origin of active faults in the Inner zone of the western part of Southwest Japan was explained by a decrease of the minimum principal stress and reactivation of ancient geologic structures. Although the E–W maximum principal stress in Southwest Japan due to the collision of the Southwest and Northeast Japan arcs along the Itoigawa–Shizuoka Tectonic Line is assumed to decrease westward, the density of active strike‐slip faults increases in the western margin of the Southwest Japan Arc (western Chugoku and northern Kyushu) where the subducting Philippine Sea Plate dips steeply. The E–W maximum compressional stress is predominant throughout Southwest Japan, while the N–S minimum principal stress that is presumably caused by coupling between Southwest Japan arc and Philippine Sea Plate decreases due to the weak plate coupling as the plate inclination increases under the western margin of Southwest Japan. The increase of the fault density in the western margin of the arc is attributed to a decrease of the minimum principal stress and consequent increase of shear stress. Low slip rates of the active faults in this region support the view that the westward increase of fault density is not a response to increasing maximum stress. These faults of onshore and offshore lie in three distinct domains defined on the basis of fault strike. They are defined domains I, II, and III which are composed of active faults striking ENE–WSW, NW–SE, and NE–SW, respectively. Faulting in domains I, II, and III is related to Miocene rift basins, Eocene normal faults, and Mesozoic strike‐slip faults, respectively. Although these active faults are strike‐slip faults due to E–W maximum stress, it is unclear whether their fault planes are the same as those of pre‐Quaternary dip‐slip faults.     

Observation of Tidal Tilt On Kilauea Volcano, Hawaii

Summary. We have analysed the east-west tilt components, O₁, K₁, N₂, M₂ and S₂ from a continuously recording tiltmeter located in Uwekahuna Vault on Kilauea Volcano, Hawaii, for the period 1971—79. Detailed analysis of the M₂ component gives values of 30.9 ± 2.0 (95 per cent) nrad and 116.0 ± 2.0° for the amplitude and phase, respectively, compared to values of 48.5 nrad and 139.4° for the equilibrium tide. the total theoretical tide, found by summing the equilibrium and load tides, amounts to 37.2 nrad at a phase of 121.7°. the 20 per cent discrepancy with that observed may be due to an inaccurate cotical chart, cavity effects in the vault, strain—tilt coupling or an inappropriate solid earth model. In the vicinity of Hawaii (≤ 3°) two independent cotidal charts give almost identical results for the near field ocean load. At greater distances, we use the Schwiderski (1978) cotidal chart. We estimate that local cavity and strain—tilt coupling effects are less than 12 per cent owing to the agreement between geodetically determined and instrumental tilt but we can not rule out regional effects. Assuming these are small and the cotical charts correct, we find that the M₂ results are brought into satisfactory agreement if, instead of using an average oceanic earth model in the (< 75 km) vicinity of Hawaii, we use an earth model with nearly one-half the oceanic rigidity. Such a low upper mantle and crustal rigidity is consistent with Kilauea's position above the thermal upwelling associated with the Hawaiian hotspot.     

Prospects for Strongly Lensed Supernovae Behind Hubble Frontier Fields Galaxy Clusters with the James Webb Space Telescope

Measuring time delays from strongly lensed supernovae (SNe) is emerging as a novel and independent tool for estimating the Hubble constant (H₀). This is very important given the recent discord in the value of H₀) from two methods that probe different distance ranges. The success of this technique will rely of our ability to discover strongly lensed SNe with measurable time delays. Here, we present the magnifications and the time delays for the multiply-imaged galaxies behind the Hubble Frontier Fields (HFF) galaxy clusters, by using recently published lensing models. Continuing on our previous work done for Abell 1689 (A1689) and Abell 370, we also show the prospects of observing strongly lensed SNe behind the HFF clusters with the upcoming James Webb Space Telescope (JWST). With four 1-hour visits in one year, the summed expectations of all six HFF clusters are ~0.5 core-collapse (CC) SNe and 0.06 Type Ia SNe (SNe Ia) in F115W band, while with F150W the expectations are higher, ~0.9 CC SNe and ~0.06 SNe Ia. These estimates match those expected by only surveying A1689, proving that the performance of A1689 as gravitational telescope is superior. In the five HFF clusters presented here, we find that F150W will be able to detect SNe Ia (SNe IIP) exploding in 93 (80) pairsmultiply-imaged galaxies with time delays of less than 5 years.