David Elmore

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Cosmogenic 10 Be exposure ages from moraines in the Wallowa Mountains, Oregon, identify two maximal late Pleistocene glaciations at 21.1 ؎ 0.4 ka and 17.0 ؎ 0.3 ka and a minor glacial event at 10.2 ؎ 0.6 ka. Our new high-resolution chronology, integrated with other well-dated glacial records from the western United States, demonstrates substantial(More)
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Deposits from mountain glaciers provide an important record of Quaternary climatic fluctuations but have proved difficult to date directly. A chronology has been obtained for glacial deposits at Bloody Canyon, California, by measurement ofthe accumulation of chlorine-36 produced by cosmic rays in boulders exposed on moraine crests. The accumulation(More)
The effect of a background signal on the signal-to-noise ratio is discussed, with particular application to ground-based observations of emission lines in the solar corona with the proposed Advanced Technology Solar Telescope. The concepts of effective coronal aperture and effective coronal integration time are introduced. Specific expressions are developed(More)
Because of the reaction of cosmic rays with elements in minerals, chlorine-36 accumulates in rocks exposed at the earth's surface. This suggests that the ratio of chlorine-36 to stable chloride can be used as a geochronometer. Reasonable agreement has been obtained between measurements of chlorine-36 in volcanic rocks of known age and calculations of(More)
Measurements have been made of the ratios of chlorine-36 to chlorine in five halite samples from Searles Lake sediments, previously dated by carbon-14, thorium-230, and magnetostratigraphic techniques. The ages calculated from the chlorine ratios are generally concordant with those from the other methods, implying the constancy of the chlorine input ratio(More)
Polarization in the telescope can limit high accuracy polarization measurements by introducing cross talk among the input solar Stokes parameters. The larger the degree of telescope polarization the more difficult it is to remove through calibration. This calibration itself is often difficult as it is not practical to routinely place calibration optics over(More)
Mk4 calibrated intensity data from 2004 through early 2006 have been analyzed in an effort to understand instrumental and sky brightness values and variations. Data are calibrated using an opal glass attenuator. Its transmission value has an uncertainty of 30%. Wavelength is set by the quantum efficiency of the line array detector, RG695 cut on filter, and(More)
This trade study presents a summary of several COSMO Technical Notes in an effort to evaluate the relative performance of reflecting vs refracting coronagraphs. Both large aperture and very low instrumental scattered light are required to measure Gauss-level line-of-sight integrated magnetic fields with scientifically interesting spatial and temporal(More)
Cosmogenic 3 He and 10 Be ages measured on surface boulders from the moraine sequence deposited by the northern outlet glacier of the Yellowstone ice cap indicate that the outlet glacier reached its terminal position at 16.5 ؎ 0.4 3 He ka and 16.2 ؎ 0.3 10 Be ka, respectively. Concordance of these ages supports the scaled production rates used for 3 He(More)