|
|
Nishitani, N.; Ogawa, T.; Sato, N.; Yamagishi, H.; Pinnock, M.; Villain, J.-P.; Sofko, G.; Troshichev, O. (2002). A study of the dusk convection cell's response to an IMF southward turning. J. Geophys. Res., 107.
Keywords: 2463 Ionosphere: Plasma convection; 2431 Ionosphere: Ionosphere/magnetosphere interactions; 2437 Ionosphere: Ionospheric dynamics; 2784 Magnetospheric Physics: Solar wind/magnetosphere interactions
Programme: 312;911
|
|
|
|
Bhattacharya, S.K.; Chakraborty, S.; Savarino, J.; Thiemens, M.H. (2002). Low-pressure dependency of the isotopic enrichment in ozone: Stratospheric implications. J. Geophys. Res., 107.
Abstract: Stratospheric ozone is enriched in the heavy isotopes (17O and 18O) relative to the ambient oxygen from which it is formed. This enrichment varies with altitude, attaining very high values between 30 and 40 km. A recent theory of Y. Q. Gao and R. A. Marcus explores the reasons for isotopic enrichment in the process of ozone formation and is particularly useful to understand the laboratory results. The stratospheric variations are sought to be explained in terms of temperature dependence of isotopic enrichment, but the magnitude of variation does not match with predictions accurately. We demonstrate here that isotopic enrichment in ozone generated by oxygen photolysis depends on the pressure of the oxygen reservoir and can have very high values (at about 15 torr), comparable to the highest observed stratospheric values. Analysis of the data shows that secondary enrichment through ozone dissociation can add to the primary enrichment associated with ozone formation. The effect of dissociation is found to be more pronounced in the pressure range of 15 to 50 torr, resulting in high enrichment. It is shown that the relative kinetics, pressure and temperature conditions of ozone formation and dissociation play an important role in determining the ultimate value of the enrichment. The results are particularly useful to understand the stratospheric data and resolve the observed discrepancy.
Keywords: 1040 Geochemistry: Isotopic composition/chemistry; 4852 Oceanography: Biological and Chemical: Photochemistry
Programme: 399
|
|
|
|
. (2002). Effect of density on electrical conductivity of chemically laden polar ice. J. Geophys. Res., 107.
Abstract: Electrical conductivity measurements made using the dielectric profiling technique (DEP) are compared to chemical data from the top 350 m of the Dome C ice core in Antarctica. The chemical data are used to calculate the concentration of the major acidic impurities in the core: sulphuric acid and hydrochloric acid. The conductivity coefficients in solid ice for sulphuric acid (?H2SO4) and hydrochloric acid (?HCl) are found to be 4.9 and 4.5 S m?1M?1. These are consistent with previously found values for the acid conductivity coefficient at different sites and suggest that the same conductivity mechanisms are important in all polar ice. A method of rolling regression analysis is used to find the variation of the pure ice conductivity (?? pure) and the conductivity coefficient of sulphuric acid, ?H2SO4, with depth. Then ?? pure and ?H2SO4are assessed against changes in core density and hence volume fraction of ice, v, due to the inclusion of air bubbles in the firn. Looyenga's model for dielectric mixtures applied to conduction in firn broadly predicts the variation observed in ?? purebut does not fit well for ice above 110 m. A previous application of the theory of percolation in random lattices is used to model the conductivity coefficient in firn. The coefficient ?H2SO4 is linked to vby the power law: ?H2SO4(v) ? ?H2SO4(1) (v ? vc)t; where vc is a threshold volume fraction below which no conduction can take place and is related to the geometry of the conducting lattice being modeled. The value of the exponent tis also dependent on the structure of the lattice and is here found to be t = 2.5, which is slightly lower than the previously obtained value of t = 2.7 for a structure where each grain has between 14 and 16 nearest neighbors. This model is consistent with the concept of conduction, via liquid H2SO4, taking place at two grain boundaries for firn. The model does not, however, preclude conduction taking place via acid situated at three grain boundaries or in an interconnected vein network at densities above 640 kg m?3.
Keywords: 0634 Electromagnetics: Measurement and standards; 1863 Hydrology: Snow and ice; 1894 Hydrology: Instruments and techniques; 9310 Information Related to Geographic Region: Antarctica
Programme: 960
|
|
|
|
Thorolfsson A. & Cerisier J.C. (2001). Flow transients in teh postnoon ionosphere: the role of solar wind dynamic pressure. J. Geophys. Res., 106(a2), 1887–1901.
|
|
|
|
Jourdain B. & Legrand M. (2001). Seasonal variations of atmospheric dimethylsulfide, dimethylsulfoxide, sulfur dioxide, methanesulfonate, and non-sea-salt sulfate aerosols at Dumont d'Urville (coastal Antartica) (December 1998 to July 1999). J. Geophys. Res., 106(d1), 14391–14408.
|
|
|
|
Huang C.S., Sofko G.J., Koustov A.V., Mcdougall J.W., Greenwald R.A., Ruohoniemi J.M., Villain J.P., Lester M., . & a.l. (2001). Long-period magnetospheric-ionospheric perturbations during northward interplanetary magnetic field. J. Geophys. Res., 106(a7), 13091–13103.
|
|
|
|
Lagabrielle Y., Garel E., Dauteuil O. & Cormier M.H. (2001). Extensional faulting and caldera collapse in the axial region of fast spreading ridges: Analog modeling. J. Geophys. Res., 106(b2), 2005–2015.
|
|
|
|
Dubouloz N., Bouhram M., Senior C., Delcourt D. & Malingre M. (2001). Spatial structure of the cusp/cleft ion fountain: a case study using a magnetic conjugacy between Interball AP and a pair of SuperDARN radars. J. Geophys. Res., 106(a1), 261–274.
|
|
|
|
Camps P., Henry B., Prevot M. & Faynot L. (2001). Geomagnetic paleosecular variation recorded in Plio-Pleistocene volcanic rocks from Possession Island (Crozet Archipelago, southern Indian ocean). J. Geophys. Res., 106(b1), 1961–1971.
|
|
|
|
Ritz C., Rommelaere V. & Dumas C. (2001). Modeling the evolution of Antarctic ice sheet over the last 420000 years: implications for altitude changes in the Vostok region. J. Geophys. Res., 106(d23), 31943–31964.
|
|
