Jovian magnetosphere-ionosphere current system characterized by diurnal variation of ionospheric conductance

We developed a new numerical model of the Jovian magnetosphere-ionosphere coupling current system in order to investigate the effects of diurnal variation of ionospheric conductance. The conductance is determined by ion chemical processes that include the generation of hydrogen and hydrocarbon ions by solar EUV radiation and auroral electrons precipitation. The model solves the torque equations for magnetospheric plasma accelerated by the radial currents flowing along the magnetospheric equator. The conductance and magnetospheric plasma then change the field-aligned currents (FACs) and the intensity of the electric field projected onto the ionosphere. Because of the positive feedback of the ionospheric conductance on the FAC, the FAC is the maximum on the dayside and minimum just before sunrise. The power transferred from the planetary rotation is mainly consumed in the upper atmosphere on the dayside, while it is used for magnetospheric plasma acceleration in other local time (LT) sectors. Further, our simulations show that the magnetospheric plasma density and mass flux affect the temporal variation in the peak FAC density. The enhancement of the solar EUV flux by a factor of 2.4 increases the FAC density by 30%. The maximum density of the FAC is determined not only by the relationship between the precipitating electron flux and ionospheric conductance, but also by the system inertia, i.e., the inertia of the magnetospheric plasma. A theoretical analysis and numerical simulations reveal that the FAC density is in proportion to the planetary angular velocity on the dayside and to the square of the planetary angular velocity on the nightside. When the radial current at the outer boundary is fixed at values above 30 MA, as assumed in previous model studies, the peak FAC density determined at latitude 73°-74° is larger than the diurnal variable component. This result suggests large effects of this assumed radial current at the outer boundary on the system.     

Observation of wave transformation on a sloping type B shore platform under wind-wave and swell conditions

An instrumented field study of the across-shore evolution of wave characteristics was conducted under wind-wave and swell-wave conditions on a sloping type B shore platform along the mesotidal, fetch-limited coast of Auckland, New Zealand, based on spectral analysis of hydrodynamic data recorded in pressure-sensor time series during a 24-h deployment on 24–25 November 2008. The results highlight the ability of the shore platform in dissipating wave energy reaching the cliff toe under wind-wave and swell-wave conditions, and the spectral redistribution of wave energy. As waves propagated onto the platform surface and towards the cliff toe, infragravity-wave energy became progressively more dominant, while gravity waves were dissipated. Wave height and period in the central sector of the platform and at the cliff toe were not markedly affected by differences in incident-wave conditions observed during the survey. The findings confirm the importance of platform morphology in modulating wave-energy delivery to the cliff toe. In contrast to previous studies, infragravity-wave height at the cliff toe did not appear to be correlated to incident-wave conditions.     

Structural characteristics and tectonisms around the microcontinent in the outer margin of the Paleozoic-Mesozoic geosyncline of Japan

Consideration of the paleogeography and large and small structures in the outer part (the Sakawa Fold Belt) of the Paleozoic—Mesozoic geosyncline of Japan suggests that the main part of the Japanese Islands has grown up not from an arc—trench system but from a marginal sea basin—microcontinent system: the Chichibu Geosyncline and the Kurosegawa — Ofunato Island Arc, Minor structures are superposed in a complicated way and they are analyzed in terms of the concepts of tectonic level and multiple deformation.Stratigraphic evidence shows that an early deformation was pre-middle Triassic in the Chichibu Terrain but northwards in the Sambagawa terrain it may have continued until early Cretaceous in relation to minor scale subduction within the marginal basin. A late Cretaceous phase of deformation produced the greatest crustal shortening in the microcontinent area of the Kurosegawa Tectonic Zone and was nearly contemporaneous with the intrusion of granitic rocks in the Ryoke Zone Younger secondary eugeosynclines were developed by progressive encroachment on the arc—trench gap south of the Kurosegawa zone from late Permian times onwards.     

The turbulent structure of the internal boundary layer near the shore

A field experiment to measure the turbulent structure of the internal boundary layer near the shore was conducted using three instrumented meteorological poles, a kytoon, and a crane-mounted ultrasonic anemometer-thermometer, as well as three reference ultrasonic anemometer-thermometers positioned near the poles. Part 1 of this study gives the explicit details and general characteristics for one run of the experiment. Part 2 (Ohara and Ogawa, 1984) will present a similarity and energy budget analysis. The mean velocity profiles showed that there was wind speed acceleration due to the sea-land temperature difference. In addition, the velocity profiles consisted of three distinct regions; the region near the ground had the largest gradient followed by a transition zone which had a small velocity gradient, while above, the profile resembled the oncoming sea breeze. In general, the turbulence was greatest near the shore, gradually decreasing inland. The lowest region had large turbulence intensities and the transition region had some intermittent turbulence characteristics between the lower strong unstable layer and the relatively turbulent-free region above.Deceased March 1984.Present address: The Institute of Behavioral Sciences, Yoyagi, Tokyo 151, Japan.     

Excitation processes of infrared atmospheric emissions

Excitation rates of the infrared emissions which are likely to occur in the mesosphere and thermosphere are quantitatively evaluated. They include the 9.6 μm band of O₃, the 15 and 4.3 μm bands of CO₂ and the 5.3 and 2.8 μm bands of NO. These emissions may be excited through nonthermal processes such as chemiluminescent reactions and resonant fluorescence in the thermosphere, whereas they are of thermal origin in the stratosphere and mesosphere. Increase of the non-thermal excitation rate caused by precipitating electrons could be responsible for the enhancement of the 4.3 μm band of CO₂, and the 5.3 and 2.8 μm bands of NO observed in the auroral thermosphere.     

Frequency dependent power fluctuations: a feature of the ESR system or physical?

The k-dependence of the Reviced power in high signal-to-noise ratio (SNR) conditions, occurring for naturally enhanced ion-acoustic lines (NEIALs) and for real satellites, is investigated by using the EISCAT Svalbard Radar (ESR), where the data are recorded in eight separate channels using different frequencies. For the real satellites we find large variations of the relative powers from event to event, which is probably due to a different number of pulses catching the satellite over the integration period. However, the large power difference remains unexpected in one case. Over short time scale (10 s) the relative power difference seems to be highly stable. For most NEIAL events the differences between channels are within noise level. In a few cases variations of the relative power well above both the estimated and expected 1-sigma level occur over a signal preintegrated profile. We thus suggest that the frequency dependence of the power in NEIAL events has its origin in the scattering medium itself as the most plausible explanation.     

Factors Controlling the Fractionation and Seasonal Mobility Variations of Ga and In in Systems Impacted by Acidic Thermal Waters: Effects of Thermodynamics and Bacterial Activity

This work assessed both the fractionation and the seasonal mobility variations of Ga and In in systems impacted by acidic thermal waters. This was accomplished by performing thermodynamic calculations using the PHREEQC algorithm and by assessing the activity of acidophilic iron-oxidizing bacteria. The pH of the Kusatsu thermal waters in Gunma Prefecture, central Japan, is rapidly increased following the addition of a lime suspension. After an abrupt pH increase, under which conditions free ions of Ga and In and their complexes with Cl^? and SO₄^2? exist only in negligible quantities, the majority of dissolved Ga and In is removed by sorption onto suspended hydrous ferric oxides (HFOs). These HFOs are then transported to an artificial lake without significant sedimentation along the river. Subsequently, the suspended HFOs settle out and are added to sediments without significant fractionation between Ga and In. The Tamagawa thermal waters in Akita Prefecture, northeast Japan, are also treated with lime. However, complete neutralization requires mixing with some tributary streams, leading to a gradual downstream increase in pH. Dissolved Ga is, in general, sorbed by HFOs in upstream areas, leading to wide dispersal of Ga across the entire watershed. In comparison, In is transported to the lake inlet predominantly as a Cl^? complex species without significant removal along the river, with the majority being precipitated in an artificial lake, where Cl^? concentrations are too low to form stable complex species with In, and thus, dissolved In is sorbed by HFOs. As a result, In is effectively concentrated within downstream lakebed sediments, whereas Ga is dispersed along the river. Seasonal variations in Ga mobility within the Tamagawa field between snowmelt and low-flow seasons are primarily controlled by pH, because hydrolysis reactions of these metals, which are related to sorption reactions, tend to occur in the upstream regions in the snowmelt season. However, under warmer conditions, HFO formation preferably occurs due to the activity of acidophilic iron-oxidizing bacteria. Thus, under similar pH variations, dissolved Ga is more effectively removed by HFOs during warmer seasons. On the contrary, because HFOs are abundantly formed in low-flow season, even under colder conditions, before In hydrolysis reaction starts to occur, In mobility is less affected by water temperature and then bacterial activity.