Long-term evolution of the aerosol debris cloud produced by the 2009 impact on Jupiter

We present a study of the long-term evolution of the cloud of aerosols produced in the atmosphere of Jupiter by the impact of an object on 19 July 2009 (Sánchez-Lavega, A. et al. [2010]. Astrophys. J. 715, L155-L159). The work is based on images obtained during 5 months from the impact to 31 December 2009 taken in visible continuum wavelengths and from 20 July 2009 to 28 May 2010 taken in near-infrared deep hydrogen-methane absorption bands at 2.1-2.3 μm. The impact cloud expanded zonally from ∼5000 km (July 19) to 225,000 km (29 October, about 180° in longitude), remaining meridionally localized within a latitude band from 53.5°S to 61.5°S planetographic latitude. During the first two months after its formation the site showed heterogeneous structure with 500-1000 km sized embedded spots. Later the reflectivity of the debris field became more homogeneous due to clump mergers. The cloud was mainly dispersed in longitude by the dominant zonal winds and their meridional shear, during the initial stages, localized motions may have been induced by thermal perturbation caused by the impact’s energy deposition. The tracking of individual spots within the impact cloud shows that the westward jet at 56.5°S latitude increases its eastward velocity with altitude above the tropopause by 5-10 m s⁻¹. The corresponding vertical wind shear is low, about 1 m s⁻¹ per scale height in agreement with previous thermal wind estimations. We found evidence for discrete localized meridional motions with speeds of 1-2 m s⁻¹. Two numerical models are used to simulate the observed cloud dispersion. One is a pure advection of the aerosols by the winds and their shears. The other uses the EPIC code, a nonlinear calculation of the evolution of the potential vorticity field generated by a heat pulse that simulates the impact. Both models reproduce the observed global structure of the cloud and the dominant zonal dispersion of the aerosols, but not the details of the cloud morphology. The reflectivity of the impact cloud decreased exponentially with a characteristic timescale of 15 days; we can explain this behavior with a radiative transfer model of the cloud optical depth coupled to an advection model of the cloud dispersion by the wind shears. The expected sedimentation time in the stratosphere (altitude levels 5-100 mbar) for the small aerosol particles forming the cloud is 45-200 days, thus aerosols were removed vertically over the long term following their zonal dispersion. No evidence of the cloud was detected 10 months after the impact.     

Metal flux as an alternative parameter in evaluating the resource potential for co-rich ferromanganese crusts

We propose a geochemical parameter, “metal flux” in evaluating hydrogenetic Co-rich ferromanganese crust deposits in the Pacific seamount area, that is based on physical, chemical, and geological characterization of the integrated growth piles of crusts. We calculated the metal flux for fifteen sites from different depths ranging between 900-6000m from different seamounts. The secular and areal variations of metal flux indicate a strong geological controls, and also can be a reliable tool for estimating an economic potential of the crusts. The Co flux decreases with increasing water depth, followed by almost constant flux of Ni and Mn. The Al and Fe fluxes vary with regions, indicating higher values in the western regions near the island arc probably related to a supply from the Asian continents. The results imply that Co, a redox sensitive metal element, is controlled by redox conditions of seawater, while Fe and Al are by terrigenous input. The metal flux reflects global and regional conditions and controls the compositional diversity of metals, thus consequently, the parameter can be a reliable powerful tool to estimate or single out more potential areas.     

红外相机CASCAM光学设计

介绍紫金山天文台研制的光学-近红外相机CASCAM（Chinese Academy of Science，CAMera)的光学系统设计．CASCAM相机以红外列阵HAWAII-1和光学CCD为探测器，配备国家天文台兴隆观测站2．16米和1．26米望远镜进行0．4—2．5μm波长范围的成像和偏振成像观测．相机的光学系统由F／9→F／6缩焦系统和Offner反射成像系统构成．优化设计结果表明，光学设计方案已满足天文观测的要求．CASCAM相机在设计上实现了光学-近红外很宽波段的消色差变焦，并在楔形分柬片、常温滤光片轮和折射式焦面摆动技术等方面进行了新的尝试．     

Exponential instability of collision orbit in the anisotropic Kepler problem

The straight-line collision solution in the anisotropic Kepler problem is extended to a periodic solution by means of Sundman's analytic continuation. It is shown that this collision periodic solution is always exponentially unstable.     

A note on Kowalevski exponents and the non-existence of an additional analytic integral

In Hamiltonian systems with a homogeneous rational potential and two degrees of freedom, the presence of imaginary Kowalevski exponents implies the non-existence of an additional analytic integral, i.e., non-integrability of the system.     

Is the periodicity in the distribution of quasar redshifts evidence for the universe being multiply-connected ?

If the cosmological space is a topolegically compactified manifold, e.g. a three-dimensional torus, then the periodicity in the distribution of quasar redshifts can be explained. The present scale of such a compactified space is estimated to be on the order of 600 Mpc.     

Responses of the polar ionosphere to the Bastille Day solar event

Simultaneous observations at Zhongshan Station, Antarctica, are presented for the interval of 13–17 July 2000 to show responses of the polar ionosphere to the Bastille Day (14 July 2000) solar event. The polar ionosphere was highly disturbed, as shown by frequently large deviations of the geomagnetic H-component, large riometer absorption events and strong ULF waves. Associated with the huge solar proton event produced by the X5/3B flare, a polar cap absorption (PCA) was observed. It began at ∼ 10:40 UT on 14 July and ended at ∼ 19:40 UT on 17 July. Superposed on it, there was a large absorption event with a peak of 26 dB, starting at ∼ 03:00 UT and ending at ∼ 11:10 UT on 15 July. This kind of absorption was probably produced by an intense `cloud of energetic electrons' during an auroral substorm. The ULF waves were very intense during the main phase and the recovery phase of the severe magnetic storm on 15 and 16 July. The ionospheric absorption was so strong that the digisonde signal was blacked out most of the time. The ionosphere returned to normal in the afternoon on 17 July.