Soft X-ray Solar Activities Associated with Interplanetary Magnetic Flux Ropes

We studied the soft X-ray solar events that could be associated with the interplanetary magnetic flux ropes observed by the WIND satellite during 1995 through 1998. The timings of the launches of the magnetic flux ropes from the Sun were estimated using flux rope speeds derived by the fitting of a cylindrical model. In the reasonable time window, soft X-ray solar signatures were found in approximately 70% of the flux ropes. Parameters (e.g., axis direction, strength of magnetic field, radius, and helicity) of the magnetic flux ropes obtained by the model fitting were compared with the characteristics of the corresponding soft X-ray events observed by Yohkoh. According to the result of the comparison, the magnetic flux ropes with strong magnetic fields or high speeds were observed in association with higher soft X-ray solar activities.     

THE BASTILLE DAY (14 JULY 2000) EVENT IN HISTORICAL LARGE SUN–EARTH CONNECTION EVENTS

One of the large Sun–Earth connection events in solar cycle 23 occurred between 14 and 16 July 2000. Anomalies occurring on several satellites were reported in association with this event. Statistical study of extreme events is important not only for a view of space weather but for seeking ways to predict such kinds of large events. The Bastille Day event was characterized by a large flux (24 000 p.f.u. at its maximum) of solar energetic protons and a fast average transit speed of approximately 1500 km s⁻¹ of the interplanetary disturbance. A geomagnetic Kp index of more than 9 was observed after an interval of approximately eleven years since 1989. We found that return periods of extreme space weather (e.g., large flares, solar energetic proton events, and large geomagnetic storms) satisfied the Weibull distribution.     

Resonant behaviour of MHD waves on magnetic flux tubes

The resonances that appear in the linear compressible MHD formulation of waves are studied for equilibrium states with flow. The conservation laws and the jump conditions across the resonance point are determined for 1D cylindrical plasmas. For equilibrium states with straight magnetic field lines and flow along the field lines the conserved quantity is the Eulerian perturbation of total pressure. Curvature of the magnetic field lines and/or velocity field lines leads to more complicated conservation laws. Rewritten in terms of the displacement components in the magnetic surfaces parallel and perpendicular to the magnetic field lines, the conservation laws simply state that the waves are dominated by the parallel motions for the modified slow resonance and by the perpendicular motions for the modified Alfvén resonance.The conservation laws and the jump conditions are then used for studying surface waves in cylindrical plasmas. These waves are characterized by resonances and have complex eigenfrequencies when the classic true discontinuity is replaced by a nonuniform layer. A thin non-uniform layer is considered here in an attempt to obtain analytical results. An important result related to earlier work by Hollweg et al. (1990) for incompressible planar plasmas is found for equilibrium states with straight magnetic field lines and straight velocity field lines. For these equilibrium states the incompressible and compressible surface waves have the same frequencies at least in the long wavelength limit and there is an exact correspondence with the planar case. As a consequence, the conclusions formulated by Hollweg et al. still hold for the straight cylindrical case. The effects of curvature are subsequently considered.     

Stereoscopic determination of the three-dimensional geometry of coronal magnetic loops

The three-dimensional shape of coronal magnetic loops is restored from extreme ultraviolet (XUV) images of the Sun (Skylab mission 3, 1973) by using the perspective effect due to the solar rotation. An original method is developed which only depends on the assumption that the magnetic structures under consideration are (at least geometrically) stable within the time interval used for restoration. Large scale loops interconnecting different active regions are studied by applying this method. They are found to lie approximately in planes inclined from the local vertical. Generally these loops are asymmetric, i.e. their apices are shifted toward one of the footpoints. This tendency is also confirmed by the computation of coronal magnetic fields based on the photospheric magnetic data.On leave from Observatoire de Paris-Meudon, 91190 Meudon, France.     

Acute toxicity of temporally varying seawater CO2 conditions on juveniles of Japanese sillago (Sillago japonica)

CO(2) ocean storage by which liquefied CO(2) is injected into the deep-sea to mitigate the climate change would increase the CO(2) concentrations of the surrounding seawater. The biological impacts of such dynamic CO(2) environments are, however, unknown. We examined the acute toxicity of temporally changing seawater CO(2) concentrations on juveniles of Sillago japonica. Step-wise increases in ambient CO(2) to fCO(2) (fractional CO(2) concentration of the gas mixture bubbled into seawater) levels of 7% and 9% resulted in mortalities of 0.15 and 0.40-0.67 after 18 h, respectively. In contrast, one-step increases to these CO(2) levels killed all fish within 15 min. Further, a sudden drop of fCO(2) from 9-10% CO(2) to normocapnia (0.038%) killed all the surviving fish within a few minutes. These results demonstrate that impacts of ocean CO(2) storage need to be examined under conditions mimicking the dynamic changes in CO(2) levels expected to occur by the CO(2) injection procedure.     

Seasonal and annual change in community structure of meso-sized copepods in Tokyo Bay, Japan

Seasonal change in the meso-sized copepod community structure in the central part of Tokyo Bay was investigated from January 2006 to December 2008. Three seasonal community groups were detected, and seasonal shifts of these communities are explained by life history characteristics of indicator species and seasonal changes in the hydrographical environment. In the winter-spring community, Acartia omorii and Centropages abdominalis dominate because of high growth rates at low temperature. A shift to the early summer community is caused by a diapause of Ce. abdominalis as resting eggs and an increase in the growth and egg-production rate of Pseudodiaptomus marinus at high temperature. A shift to the summer-fall community is caused by a diapause of A. omorii at hypoxic and high temperature conditions and an increase of Temora turbinata, Paracalanus parvus and other oceanic species by an enhancement of the estuary circulation. Then, the community returns to a winter-spring one by the recovery of A. omorii and Ce. abdominalis with low temperatures and oxygenation of bottom water and by the disappearance of oceanic warm-water species at low temperature. Seasonal community shifts occurred almost regularly, but the shift from a winter-spring community to an early summer one occurred 1 month early in 2007 when the water temperature was warmer than in other years.     

The origin of fluoride-rich groundwater in Mizunami area, Japan — Mineralogy and geochemistry implications

The aim of this paper was to explore new factors that might be reasons for the occurrence of fluoride-rich groundwater in the area around a construction site. During the construction of two deep shafts of the Mizunami Underground Research Laboratory (MIU) in Mizunami city, central Japan, a large quantity of groundwater with high fluoride concentration was charged into the shafts. Chemical investigation carried out during the excavation revealed that fluoride concentrations in the area around the MIU site greatly exceeded those prescribed by Japanese standards. Therefore, the origin of fluoride ion was experimentally investigated. Samples were collected from the core of a deep borehole drilled in the study area. The weathering - and alteration levels of the collected granites varied greatly. Granitic powders were used to measure fluoride content in the granitic rock mass. The fluoride content ranged between 200 and 1300 mg/kg. The powders were reacted with purified water for 80 days. The results of water–rock interaction showed granitic rock to be one of the main sources of fluoride-rich groundwater in Mizunami area. Fluoride concentrations in these solutions that were shaken for 80 days varied between 2 and 7 mg/l. This change may have occurred as a result of the spatial distribution of fluoride ions in the granite mass as evidenced by mineralogical analysis of fluoride content in several specimens. X-ray powder diffraction analysis of the rock before- and after the water–rock interaction tests manifested that the presence of fluorite mineral was relatively small compared to other minerals. The degree of weathering and alteration might be an additional factor causing dissolution of fluoride-rich minerals. However, it was difficult to interpret the change in fluorite composition by X-ray diffraction analysis.     

Synplutonic mafic injections into crystallizing granite pluton from Gurgunta area,northern part of Eastern Dharwar Craton: Implications for magma chamber processes

In this paper we document widespread coeval felsic-mafic magma interaction and progressive hybridization near Gurgunta in the northern part of Eastern Dharwar Craton (EDC) where mafic magma pulses have injected into a 2.5 Ga granite pluton. The pluton contains voluminous pink porphyritic facies with minor equigranular grey facies. The mafic body shows compositional variation from diorite to meladiorite with hornblende as the chief mafic mineral with lesser clinopyroxene and biotite. The observed variation on binary diagrams suggests that granite was evolved by fractional crystallization. Chemical characteristics such as higher Al₂O₃ and moderate to high CaO, Mg#, Ni, Cr, Co and V are interpreted by slab-melting. Mafic bodies show lower SiO₂, Na₂O and K₂O; but higher CaO, Mg#, FeO, Cr, Ni and V; higher LREE with moderate to higher HREE which suggest their derivation from mantle. A major active shear zone has played an important role at the time of synplutonic mafic injection and hybridization process. Field evidences suggest that the synplutonic mafic body has injected into the crystallizing felsic magma chamber in successive stages. The first stage injection has resulted in extensive mixing and hybridization due to the liquidus state of resident felsic magma to which hot mafic magma was injected. However, progressive mixing produced heterogeneity as the xenocrysts started mechanically dispersed into hybrid magma. The second stage injection, after a time gap, encountered colder and viscous hybrid magma in the magma chamber, which inhibited free injection. As a consequence, the mafic magma spread into magma chamber as flows, producing massive mafic bodies. However, with the continued mafic pulses and the heat gradient, the viscosity contrasts of mafic magma and felsic magma were again lowered resulting in second stage mixing. This episode was followed by mingling when the granite was almost crystallized, but still viscous enough to accommodate lamellar and ribbon like mafic penetrations to produce mingling. The successive mixing and mingling processes account for the observed heterogeneity in the granite pluton.     

The Hinode X-Ray Telescope (XRT): Camera Design, Performance and Operations

The X-ray Telescope (XRT) aboard the Hinode satellite is a grazing incidence X-ray imager equipped with a 2048×2048 CCD. The XRT has 1 arcsec pixels with a wide field of view of 34×34 arcmin. It is sensitive to plasmas with a wide temperature range from < 1 to 30 MK, allowing us to obtain TRACE-like low-temperature images as well as Yohkoh/SXT-like high-temperature images. The spacecraft Mission Data Processor (MDP) controls the XRT through sequence tables with versatile autonomous functions such as exposure control, region-of-interest tracking, flare detection, and flare location identification. Data are compressed either with DPCM or JPEG, depending on the purpose. This results in higher cadence and/or wider field of view for a given telemetry bandwidth. With a focus adjust mechanism, a higher resolution of Gaussian focus may be available on-axis. This paper follows the first instrument paper for the XRT (Golub et al., Solar Phys. 243, 63, 2007) and discusses the design and measured performance of the X-ray CCD camera for the XRT and its control system with the MDP.