The solar occultation for ice experiment

The Solar Occultation For Ice Experiment (SOFIE) was launched onboard the Aeronomy of Ice in the Mesosphere (AIM) satellite on 25 April 2007, and began science observations on 14 May 2007. SOFIE conducts solar occultation measurements in 16 spectral bands that are used to retrieve vertical profiles of temperature, O₃, H₂O, CO₂, CH₄, NO, and polar mesospheric cloud (PMC) extinction at wavelengths from 0.330 to 5.006 μm. SOFIE performs 15 sunset measurements at latitudes from 65° to 85°S and 15 sunrise measurements from 65° to 85°N each day. This work describes the SOFIE instrument, measurement approach, and retrieval results for the northern summer of 2007.     

An early-time infrared and optical study of the Type Ia Supernova 1998bu in M96

We present first-season infrared (IR) and optical photometry and spectroscopy of the Type Ia Supernova 1998bu in M96. We also report optical polarimetry of this event. SN 1998bu is one of the closest type Ia supernovae of modern times, and the distance of its host galaxy is well determined. We find that SN 1998bu is both photometrically and spectroscopically normal. However, the extinction to this event is unusually high, with     We find that SN 1998bu peaked at an intrinsic     Adopting a distance modulus of 30.25 (Tanvir et al.) and using Phillips et al.'s relations for the Hubble constant, we obtain     Combination of our IR photometry with those of Jha et al. provides one of the most complete early-phase IR light curves for a SN Ia published so far. In particular, SN 1998bu is the first normal SN Ia for which good pre- t _{B max} IR coverage has been obtained. It reveals that the J , H and K light curves peak about 5 days earlier than the flux in the B -band curve.     

Comparison of proxy records of Late Pleistocene climate change from a high‐resolution loess–palaeosol sequence in north‐central China

A micromorphologically based pedosedimentary reconstruction of a 40‐m loess–palaeosol sequence from the western part of the Chinese Loess Plateau provides a sensitive proxy record of changing processes and associated environmental conditions in this region between ca. 150 000 and 10 000 yr BP. Depth functions of more traditional climate proxies, such as magnetic susceptibility, calcium carbonate content and median grain size, support the broad pattern of environmental changes inferred from the micromorphology, although the bulk properties sometimes lag behind or are out of phase with each other and do not match all the fluctuations in the micromorphological record. The reasons for the disparities are probably complex, although they partly reflect differences in response rates and sensitivities of proxies to different climate parameters, as well as genuine out‐of‐phase changes in strength of monsoonal climate controls. This work illustrates the sensitivity of micromorphology in detecting past environmental changes within rapidly aggrading landscapes, and emphasises the need to understand more fully the local and regional significance of bulk proxies currently used in global correlations with marine‐ and ice‐core records. Copyright © 1999 John Wiley & Sons, Ltd.     

Short-range variations in the micromorphology of a palaeosol from Wivenhoe in southeast England

The pedogenic histories of four adjacent profiles of a polygenetic palaeosol developed on a Middle Pleistocene terrace of the proto-Thames from Wivenhoe in southeast England are reconstructed on the basis of superposition of key micromorphological features. Despite a considerable variation in macromorphology, partly resulting from large-scale periglacial features, three of the profiles have similar micromorphological records in that they retain evidence for two phases of clay illuviation separated by a period of periglacial disruption. This reconstruction, however, seems to be incomplete because the fourth profile contains micromorphological evidence for a further illuviation–disruption cycle. The extent of this variation suggests that soil micromorphology should be used only with care to reconstruct pedogenic or pedosedimentary histories of complex polygenetic palaeosols, or to compare such palaeosols on different surfaces of chronosequences spanning periods of major climatic change. The variable and possibly limited resolution of micromorphology, together with the current uncertainty over the exact environmental signifiance of illuvial clay features, means that inferred pedogenic phases should be correlated with specific climatic stages only with considerable caution. © 1998 John Wiley & Sons, Ltd.     

Cyber Literacy for GIScience: Toward Formalizing Geospatial Computing Education

The unprecedented availability of geospatial data and technologies is driving innovation and discovery but not without the risk of losing focus on the geographic foundations of space and place in this vast “cyber sea” of data and technology. There is a pressing need to educate a new generation of scientists and citizens who understand how space and place matter in the real world and who understand and can keep pace with technological advancements in the computational world. We define cyberliteracy for GIScience (cyberGIScience literacy) and outline eight core areas that serve as a framework for establishing the essential abilities and foundational knowledge necessary to navigate and thrive in this new technologically rich world. The core areas are arranged to provide multiple dimensions of learning ranging from a technological focus to a problem solving focus or a focus on GIScience or computational science. We establish a competency matrix as a means of assessing and evaluating levels of cyberGIScience literacy across the eight core areas. We outline plans to catalyze the collaborative development and sharing of instructional materials to embed cyberGIScience literacy in the classroom and begin to realize a cyberliterate citizenry and academe. Key Words: big data, computational thinking, geographic education, GIS, spatial thinking.     

An integrated zircon geochronological and geochemical investigation into the Miocene plutonic evolution of the Cyclades, Aegean Sea, Greece: part 2—geochemistry

Zircons from 14 compositionally variable granitic rocks were examined in detail using CL image-guided micro-analysis to unravel the complex magmatic history above the southward retreating Hellenic subduction zone system in the Aegean Sea. Previously published U–Pb ages document an episodic crystallisation history from 17 to 11?Ma, with peraluminous (S-type) granitic rocks systematically older than closely associated metaluminous (I-type) granitic rocks. Zircon O- and Hf isotopic data, combined with trace element compositions, are highly variable within and between individual samples, indicative of open-system behaviour involving mantle-derived melts and evolved supracrustal sources. Pronounced compositional and thermal fluctuations highlight the role of magma mixing and mingling, in accord with field observations, and incremental emplacement of distinct melt batches coupled with variable degrees of crustal assimilation. In the course of partial fusion, more fertile supracrustal sources dominated in the earlier stages of Aegean Miocene magmatism, consistent with systematically older crystallisation ages of peraluminous granitic rocks. Differences between zircon saturation and crystallisation temperatures (deduced from zircon Ti concentrations), along with multimodal crystallisation age spectra for individual plutons, highlight the complex and highly variable physico-compositional and thermal evolution of silicic magma systems. The transfer of heat and juvenile melts from the mantle varied probably in response to episodic rollback of the subducting lithospheric slab, as suggested by punctuated crystallisation age spectra within and among individual granitic plutons.     

Holocene lake salinity changes in the Wimmera,southeastern Australia,provide evidence for millennial-scale climate variability

Palaeosalinity records for groundwater-influenced lakes in the southwest Murray Basin were constructed from an ostracod-based, weighted-averaging transfer function, supplemented with evidence from Campylodiscus clypeus (diatom), charophyte oogonia, Coxiella striata (gastropod), Elphidium sp. (foraminifera), Daphniopsis sp. ephippia (Cladocera), and brine shrimp (Parartemia zietziana) faecal pellets, the δ¹⁸O of ostracods, and > 130 μm quartz sand counts. The chronology is based on optically stimulated luminescence and calibrated radiocarbon ages. Relatively wet conditions are marked by lower salinities between 9600 yr and 5700 yr ago, but mutually exclusive high- and low-salinity ostracod communities suggest substantial variability in effective precipitation in the early Holocene. A drier climate was firmly in place by 4500 yr and is marked at the groundwater-dominated NW Jacka Lake by an increase in aeolian quartz and, at Jacka Lake, by a switch from surface-water to groundwater dominance. Short-lived, low-salinity events at 8800, 7200, 5900, 4800, 2400, 1300 and 400 yr are similar in timing and number to those recorded on Australia's southern continental shelf, and globally, and provide evidence for the existence of the ~ 1500-yr cycle in mainland southern Australia. We surmise that these are cool events associated with periodic equatorward shifts in the westerly wind circulation.     

The distribution and utility of sea‐level indicators in Eurasian sub‐Arctic salt marshes (White Sea,Russia)

In support of efforts to reconstruct relative sea level (RSL), we investigated the utility of foraminifera, diatoms and bulk‐sediment geochemistry (δ¹³C, C:N and parameters measured by Rock‐Eval pyrolysis) as sea‐level indicators in Eurasian sub‐Arctic salt marshes. At three salt marshes (<15 km apart) in Dvina Bay (White Sea, Russia), we collected surface sediment samples along transects from subtidal to Taiga forest environments. Foraminifera at all sites formed bipartite assemblages, where elevations below mean high higher water (MHHW) were dominated by Miliammina spp. and elevations between MHHW and the highest occurrence of foraminifera were dominated by Jadammina macrescens and Balticammina pseudomacrescens. Five high‐diversity groups of diatoms were identified and they displayed pronounced variability amongst the study sites. Bulk‐sediment geochemistry recognized two groups (clastic‐dominated environments below MHHW and organic‐rich environments above MHHW). As one group included subtidal elevations and the other included supratidal elevations, we conclude that the measured geochemical parameters are not stand‐alone sea‐level indicators. Core JT2012 captured a regressive sediment succession of clastic, tidal‐flat sediment overlain by salt‐marsh organic silt and freshwater peat. The salt‐marsh sediment accumulated at 2804±52 years before present and preserved foraminifera (Jadammina macrescens and Balticammina pseudomacrescens) with good analogy to modern assemblages indicating that RSL was +2.60±0.47 m at this time. Diatoms confirm that marine influence decreased through time, but the lack of analogy between modern and core assemblages limited their utility as sea‐level indicators. Geochemical parameters also indicate a reduction in marine influence through time. We conclude that RSL reconstructions derived from salt‐marsh sediment preserved beneath Eurasian sub‐Arctic peatlands can provide valuable insight into the spatio‐temporal evolution of the Fennoscandian and Eurasian ice sheets.     

Laboratory Simulation of Magnetospheric Plasma Shocks

An experimental simulation of planetary magnetospheres is being developed to investigate the formation of collisionless shocks and their effects. Two experimental situations are considered. In both, the solar wind is simulated by laser ablation plasmas. In one case, the “solar wind” flows across the magnetic field of a high-current discharge. In the other, a transverse magnetic field is embedded in the plasma flow, which interacts with a conductive obstacle. The ablation plasma is created using the “Tomcat” laser, currently emitting 5 J in a 6 ns pulse at 1 μm wavelength and irradiance above 10¹³ W/cm². The “Zebra” z-pinch generator, with load current up to 1 MA and voltage up to 3.5 MV produces the magnetic fields. Hydrodynamic modeling is used to estimate the plasma parameters achievable at the front of the plasma flow and to optimize the experiment design. Particle-in-cell simulations reveal details of the interaction of the “solar wind” with an external magnetic field, including flow collimation and heating effects at the stopping point. Hybrid simulations show the formation of a bow shock at the interaction of a magnetized plasma flow with a conductor. The plasma density and the embedded field have characteristic spatial modulations in the shock region, with abrupt jumps and fine structure on the skin depth scale.