A photometric perturbation of the counterglow

A weakening of the radiance of the counterglow in the anti-solar direction relative to the regions 5°–15° away is interpreted as evidence for a cloud of scattering material in the general region of the Earth-Moon system. Further evidence is indicated, by the relative brightening at ?180° in the vicinity of the L4 libration point, that the cloud is significantly denser there than in adjacent locations.     

Coronal holes

Coronal holes are extensive regions of extremely low density in the solar corona within 60° of latitude from the equator. (They are not to be confused with the well-known coronal cavities which surround quiescent prominences beneath helmet streamers.) We have superposed maps of the calculated current-free (potential) coronal magnetic field with maps of the coronal electron density for the period of November 1966, and find that coronal holes are generally characterized by weak and diverging magnetic field lines. The chromosphere underlying the holes is extremely quiet, being free of weak plages and filaments. The existence of coronal holes clearly has important implications for the energy balance in the transition region and the solar wind.The National Center for Atmospheric Research is sponsored by the National Science Foundation.     

Permeability of Wellbore-Cement Fractures Following Degradation by Carbonated Brine

Fractures in wellbore cement and along wellbore-cement/host-rock interfaces have been identified as potential leakage pathways from long-term carbon sequestration sites. When exposed to carbon-dioxide-rich brines, the alkaline cement undergoes a series of reactions that form distinctive fronts adjacent to the cement surface. However, quantifying the effect of these reactions on fracture permeability is not solely a question of geochemistry, as the reaction zones also change the cement’s mechanical properties, modifying the fracture geometry as a result.This paper describes how these geochemical and geomechanical processes affect fracture permeability in wellbore cement. These competing influences are discussed in light of data from a core-flood experiment conducted under carbon sequestration conditions: reaction chemistry, fracture permeability evolution over time, and comparative analysis of X-ray tomography of unreacted and reacted cement samples. These results are also compared to predictions by a complementary numerical study that couples geochemical, geomechanical and hydrodynamic simulations to model the formation of reaction fronts within the cement and their effect on fracture permeability.     

The anticipated role of the large format camera in future earth observation strategies

The development of the National Aeronautics and Space Administration's Large Format Camera has added a new dimension to remote sensing. Offering inexpensive large area coverage imagery with excellent geometric fidelity, the LFC was successfully flown in late 1984 aboard the Space Shuttle. The success of this initial flight has encouraged scientists to propose that the LFC be included as part of the earth observation sensor bed on the planned space station.

The relatively low costs associated with LFC photography provide an opportunity for developing countries to learn more about the capabilities and advantages of exploiting remotely sensed imagery. In particular, by using LFC imagery to study an array of local and global phenomena, these developing countries can quickly increase their knowledge of earth observation techniques and join the “community”; of nations currently active in remote sensing efforts.     

The Colorado East River Community Observatory Data Collection

The U.S. Department of Energy's (DOE) Colorado East River Community Observatory (ER) in the Upper Colorado River Basin was established in 2015 as a representative mountainous, snow-dominated watershed to study hydrobiogeochemical responses to hydrological perturbations in headwater systems. The ER is characterized by steep elevation, geologic, hydrologic and vegetation gradients along floodplain, montane, subalpine, and alpine life zones, which makes it an ideal location for researchers to understand how different mountain subsystems contribute to overall watershed behaviour. The ER has both long-term and spatially-extensive observations and experimental campaigns carried out by the Watershed Function Scientific Focus Area (SFA), led by Lawrence Berkeley National Laboratory, and researchers from over 30 organizations who conduct cross-disciplinary process-based investigations and modelling of watershed behaviour. The heterogeneous data generated at the ER include hydrological, genomic, biogeochemical, climate, vegetation, geological, and remote sensing data, which combined with model inputs and outputs comprise a collection of datasets and value-added products within a mountainous watershed that span multiple spatiotemporal scales, compartments, and life zones. Within 5 years of collection, these datasets have revealed insights into numerous aspects of watershed function such as factors influencing snow accumulation and melt timing, water balance partitioning, and impacts of floodplain biogeochemistry and hillslope ecohydrology on riverine geochemical exports. Data generated by the SFA are managed and curated through its Data Management Framework. The SFA has an open data policy, and over 70 ER datasets are publicly available through relevant data repositories. A public interactive map of data collection sites run by the SFA is available to inform the broader community about SFA field activities. Here, we describe the ER and the SFA measurement network, present the public data collection generated by the SFA and partner institutions, and highlight the value of collecting multidisciplinary multiscale measurements in representative catchment observatories.     

The large-scale solar magnetic field

The large-scale photospheric magnetic field, measured by the Mt. Wilson magnetograph, has been analyzed in terms of surface harmonics (P _n ^m )()cosm and P _n ^m ()sinm) for the years 1959 through 1972. Our results are as follows. The single harmonic which most often characterized the general solar magnetic field throughout the period of observation corresponds to a dipole lying in the plane of the equator (2 sectors, n = m = 1). This 2-sector harmonic was particularly dominant during the active years of solar cycles 19 and 20. The north-south dipole harmonic (n = 1, m = 0) was prominent only during quiet years and was relatively insignificant during the active years. (The derived north-south dipole includes magnetic fields from the entire solar surface and does not necessarily correlate with either the dipole-like appearance of the polar regions of the Sun or with the weak polar magnetic fields.) The 4-sector structure (n = m = 2) was prominent, and often dominant, at various times throughout the cycle. A 6-sector structure (n = m = 3) occasionally became dominant for very brief periods during the active years. Contributions to the general solar magnetic field from harmonics of principal index 4 n 9 were generally relatively small throughout this entire solar cycle with one outstanding exception. For a period of several months prior to the large August 1972 flares, the global photospheric field was dominated by an n = 5 harmonic; this harmonic returned to a low value shortly after the August 1972 flare events. Rapid changes in the global harmonics, in particular, relative and absolute changes in the contributions of harmonics of different principal index n to the global field, imply that the global solar field is not very deep or that very strong fluid flows connect the photosphere with deeper layers.The National Center for Atmospheric Research is sponsored by the National Science Foundation.     

Tabulation of the harmonic coefficients of the solar magnetic fields

Tables of spherical harmonic coefficients for the global photospheric magnetic field between 1959 and 1974 are now available on microfilm. (These are the same coefficients which were used to construct the maps of the coronal magnetic atlas.)The National Center for Atmospheric Research is sponsored by the National Science Foundation.