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    Exploration of mesospheric metal layers from Chatanika, Alaska

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    Author
    Martus, Cameron M.
    Chair
    Collins, Richard L.
    Committee
    Mölders, Nicole
    Sassen, Kenneth
    Metadata
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    URI
    http://hdl.handle.net/11122/4597
    Abstract
    Layers of free metal atoms exist in the mesopause region of the atmosphere, generally between 80 and 100 km altitude. Resonance fluorescence lidar provides the best way to measure the structure and dynamics of these metal layers. Resonance lidar observations using tunable dye lasers are conducted at the Lidar Research Laboratory (LRL) of Poker Flat Research Range (PFRR), Chatanika, Alaska (65°N, 147°W). In this thesis, we present three fundamental aspects of mesospheric resonance lidar studies: lidar system commissioning and operation, analysis of temporal variations in the metal layers based on observations, and observations of the nickel layer. An excimer-pumped dye laser system has been used in the past for observations at LRL-PFRR, and we report on the alignment and testing of this system as well as the deployment of a new Nd:YAG-pumped dye laser system. Both of these systems are tested with observations of the sodium layer at 589 nm. Through an analysis of simultaneous observations of the sodium and iron layers taken in the past at LRL-PFRR, we study the common motion of the two layers and suggest an external forcing mechanism for the motions. We find that the motion of the layers is, in most of the observations, consistent with downward propagating gravity waves. Based on elemental abundances in meteors, the most likely source of mesospheric metal layers, we expect to find a nickel layer, yet such a layer has not been reported. We attempt to detect the layer using resonance lidar at the 337 nm nickel absorption line. We make several likely detections of the layer and present an initial estimate of the nickel profile. Signals received in the nickel measurements are as expected from a simulation based on signals received in past observations of sodium and iron.
    Table of Contents
    1. Introduction -- 1.1. Structure of the atmosphere -- 1.2. Mesopheric metal layers -- 1.3. Resonance lidar -- 1.4. Lidar observations at Poker Flat Research Range -- 1.5. Scope of this study -- 2. Resonance lidar principles and performance -- 2.1. Lidar equation -- 2.2. Scattering cross-sections -- 2.2.1. Sodium (Na) -- 2.2.2. Iron (Fe) -- 2.3. Lasers for resonance lidar -- 2.4. Excimer-pumped dye laser system -- 2.5. Nd:YAG-pumped dye laser system -- 2.6. Lidar operations -- 2.7. Wavelength alignment -- 2.8. Na observations -- 2.8.1. 23-24 October 2012 -- 2.8.2. Alignment after first observations -- 2.8.3. 1-2 November 2012 -- 2.8.4. 19 February 2013 -- 2.8.5. 12-13 March 2013 -- 2.8.6. 16 March 2013 -- 2.9. Analysis of lidar system performance -- 3. Waves in mesospheric metal layers -- 3.1. Wave motions in the mesosphere -- 3.2. Seasonal characteristics of the Na and Fe layers -- 3.3. Concurrent Na and Fe observations at LRL-PFRR -- 3.4. Contour fits to wave motions -- 3.5. Conclusions -- 4. Nickel observations -- 4.1. Spectroscopy of Ni -- 4.2. Choosing the laser dye and receiver filter -- 4.3. Simulation of Ni lidar observations -- 4.3.1. Estimation of Ni signal -- 4.3.2. Resonance layer simulation program -- 4.3.3. First-order Fe-based Ni simulation -- 4.3.4. Layer signal significance technique -- 4.4. Search for Ni -- 4.4.1. 7-8 November 2012 -- 4.4.2. 27-28 November 2012 -- 4.4.3. 20-21 December 2012 -- 4.4.4. 18-19 January 2012 -- 4.4.5. 25-26 January 2012 -- 4.5. Ni layer characteristics -- 4.5.1. Evaluation of Ni observations -- 4.5.2. Ni density estimate -- 4.5.3. Specific Na-based Ni simulation -- 4.6. Detection threshold simulation -- 4.6.1. Background scaling -- 4.6.2. Laser power scaling -- 4.6.3. Ni abundance scaling -- 5. Summary and conclusions -- References -- Appendix: Na and Fe density plots.
    Date
    2013-08
    Type
    Thesis
    Collections
    Atmospheric Sciences

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