Observational Evidence of Dissipative Small Scale Processes: Geotail Spacecraft Observation and Simulation of Electrostatic Solitary Waves

In recent spacecraft observations, coherent microscale structures such as electrostatic solitary waves are observed in various regions of the magnetosphere. The Geotail spacecraft observation has shown that these solitary waves are associated with high energy non-thermal electrons flowing along the magnetic field. The solitary structures are generated as a result of a long time evolution of coherent nonlinear trapping of electrons as found in bump-on-tail, bi-stream and Buneman instabilities. It is noted that these solitary waves can be generated at distant regions far away from the spacecraft locations, because these trapped electrons, or electron holes, are drifting much faster than the local thermal plasmas. Some of the solitary waves are accompanied by perpendicular electric fields indicating that two-or three-dimensional potential structures are passing by the spacecraft. Depending on the local plasma parameters, these multi-dimensional solitary structures couple with perpendicular modes such as electrostatic whistler modes and lower-hybrid modes. In a long time evolution, these perpendicular modes are dissipated via self-organization of small solitary potentials, leading to formation of one-dimensional potential troughs as observed in the deep magnetotail. The above dissipative small-scale processes are reproduced in particle simulations, and they can be used for diagnostics of electron dynamics from spacecraft observation of multi-dimensional solitary waves in various regions of the magnetosphere. This revised version was published online in July 2006 with corrections to the Cover Date.     

Petrological and Geochemical Characteristics of the Cerro Colorado Plutonic Complex in the Precordillera of Northern Chile

Abstract. The Cerro Colorado intrusive stock in the northeastern Chilean Precordillera is a plutonic complex formed during Late Cretaceous (64–72 Ma), and consists predominantly of pyroxene-bearing biotite monzogabbro (Colorado Unit), with lesser amounts of pyroxene-bearing hornblende biotite diorite (Pucaquisca Unit) and biotite hornblende monzonite (Pabellón Unit). Compositional variations of major and trace elements suggest that the Cerro Colorado complex is composed of shoshonitic alkali granitoids generated at the active continental margin. The basic to intermediate rocks of the Colorado Unit are characterized by high contents of A1₂O₃ (>20 wt%), CaO and LIL elements (K, Sr, Ba), high Fe/Mg ratio and fairly low contents of Cr, Ni and Y. These characteristics suggest that the Colorado Unit was formed by plagioclase-free source magma originated from asthenospheric mantle or mafic lower crust. All the Cerro Colorado rocks generally display linear compositional trends, and the latest Pabellón Unit rocks are richer in SiO₂ than the Colorado Unit and Pucaquisca Unit rocks. These indicate that the Pabellón Unit rocks were produced by assimilation-fractional crystallization process of the basic to intermediate magma genetically related to the voluminous Colorado Unit.     

Continuing observation of disturbed reproductive cycle and ovarian spermatogenesis in the giant abalone, Haliotis madaka from an organotin-contaminated site of Japan

Histological examination of gonads as well as chemical analysis of organotin compounds in tissues of the giant abalone, Haliotis madaka, was conducted to evaluate continuing endocrine disruption in abalone populations in Japan. Abalone specimens were collected from two different areas, Tsushima as a reference site and Jogashima as a site representative of declining abalone populations where serious organotin contamination had been observed, each month from January 1998 to March 1999. Scores were given to the development stages of reproductive cells in the ovary and testis. The degree of sexual maturation was evaluated by calculating the mean value of a histogram of these scores for the reproductive cells of each abalone. The temporal variations in degree of sexual maturation showed that female and male abalone from Tsushima matured synchronously, while those from Jogashima did not, which were similar to results of the previous study during September 1995–November 1996. Approximately 19% of the female abalone from Jogashima were masculinized with an ovo-testis, which was also similar to the result of the previous study. The masculinization of female abalone is reported to be induced by tributyltin (TBT) and triphenyltin (TPhT) from antifouling paints. Concentrations of the sum of butyltins (TBT, dibutyltin (DBT) and monobutyltin (MBT): ΣBTs) and the sum of phenyltins (TPhT, diphenyltin (DPhT) and monophenyltin (MPhT): ΣPhTs) in the muscle of abalone from Jogashima (n = 73) of 7.8 ± 9.0 ng/g wet wt. and 4.5 ± 6.8 ng/g wet wt., respectively, were significantly higher than those from Tsushima (n = 87) of 4.7 ± 4.9 ng/g wet wt. and 0.8 ± 1.7 ng/g wet wt., respectively (p < 0.05 for ΣBTs; p < 0.001 for ΣPhTs), although concentrations of TBT and TPhT in the muscle of abalone from Jogashima (n = 73) of 2.2 ± 2.5 ng/g wet wt. and 5.8 ± 5.1 ng/g wet wt., respectively, were insignificantly and significantly higher than those from Tsushima (n = 87) of 0.4 ± 0.6 ng/g wet wt. and 0.5 ± 0.9 ng/g wet wt., respectively, (p > 0.05 for TBT; p < 0.001 for TPhT). Thus, endocrine disruption as well as contamination by organotins in the giant abalone from Jogashima is still persisting.