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Field line distribution of mass density at geostationary orbit
Get PDFThe distribution of mass density along the field lines affects the ratios of toroidal (azimuthally oscillating) Alfven frequencies, and given the ratios of these frequencies, we can get information about that distribution. Here we assume the commonly used power law form for the field line distribution, m=m,eq(LRE∕R), where m,eq is the value of the mass density (m) at the magnetic equator, L is the L shell, R-E is the Earth's radius, R is the geocentric distance to a point on the field line, and is the power law coefficient. Positive values of indicate that (m) increases away from the magnetic equator, zero value indicates that (m) is constant along the magnetic field line, and negative indicates that there is a local peak in (m) at the magnetic equator. Using 12years of observations of toroidal Alfven frequencies by the Geostationary Operational Environmental Satellites, we study the typical dependence of inferred values of on the magnetic local time (MLT), the phase of the solar cycle as specified by the F-10.7 extreme ultraviolet solar flux, and geomagnetic activity as specified by the auroral electrojet (AE) index. Over the mostly dayside range of the observations, we find that decreases with respect to increasing MLT and F-10.7, but increases with respect to increasing AE. We develop a formula that depends on all three parameters, 3Dmodel=2.2+1.3.cos(MLT15 degrees)+0.0026AEcos(MLT-0.8)15 degrees)+2.110-5AEF10.7-0.010F10.7, that models the binned values of within a standard deviation of 0.3. While we do not yet have a complete theoretical understanding of why should depend on these parameters in such a way, we do make some observations and speculations about the causes. At least part of the dependence is related to that of (m,eq); higher , corresponding to steeper variation with respect to magnetic latitude, occurs when (m,eq) is lower.Publishe
Increased nitrogen export from eastern North America to the Atlantic Ocean due to climatic and anthropogenic changes during 1901-2008
Get PDFWe used a process-based land model, Dynamic Land Ecosystem Model 2.0, to examine how climatic and anthropogenic changes affected riverine fluxes of ammonium (NH4+), nitrate (NO3-), dissolved organic nitrogen (DON), and particulate organic nitrogen (PON) from eastern North America, especially the drainage areas of the Gulf of Maine (GOM), Mid-Atlantic Bight (MAB), and South Atlantic Bight (SAB) during 1901-2008. Model simulations indicated that annual fluxes of NH4+, NO3-, DON, and PON from the study area during 1980-2008 were 0.0190.003 (mean1 standard deviation) TgNyr(-1), 0.180.035TgNyr(-1), 0.100.016TgNyr(-1), and 0.043 +/- 0.008TgNyr(-1), respectively. NH4+, NO3-, and DON exports increased while PON export decreased from 1901 to 2008. Nitrogen export demonstrated substantial spatial variability across the study area. Increased NH4+ export mainly occurred around major cities in the MAB. NO3- export increased in most parts of the MAB but decreased in parts of the GOM. Enhanced DON export was mainly distributed in the GOM and the SAB. PON export increased in coastal areas of the SAB and northern parts of the GOM but decreased in the Piedmont areas and the eastern parts of the MAB. Climate was the primary reason for interannual variability in nitrogen export; fertilizer use and nitrogen deposition tended to enhance the export of all nitrogen species; livestock farming and sewage discharge were also responsible for the increases in NH4+ and NO3- fluxes; and land cover change (especially reforestation of former agricultural land) reduced the export of the four nitrogen species.PublishedYe
Electronic Theses and Dissertations: Differences in Behavior for Local and Non-Local Users
Get PDFThis study examines two research questions: (1) How do users in different locations find Auburn University Electronic Theses and Dissertations? (2) Do users in different locations interact differently with the collection and, if so, how? Google Analytics data for user visits, landing pages, and page views were separated into groups based on user location. Visits data were also correlated with source (referring Web site), and landing pages and page views were grouped by type. Most local users came to the repository via Auburn University Web pages. This group usually landed on the collection home page and used internal navigation pages to find what they needed. Submission page views showed that most ETD depositors were local. Most out-of-state users came to the repository via Web search engines. This group usually landed directly on bibliographic information pages for individual ETDs. They used internal navigation pages less frequently than local users. Users located within the state but outside of the local area interacted with the collection in a way that was intermediate between the two groups. Institutions interested in improving repository access for depositors will probably find it helpful to focus on in-state usage reports, while institutions seeking to improve access for end-users should exclude in-state users from their assessments. This is the first detailed examination of ETDs usage published since 2001 and shows that filtering tools available in Google Analytics allow comparisons of user behavior based on location and source (referring Web site).PublishedYe
TWINS stereoscopic imaging of multiple peaks in the ring current
Get PDFGlobal, ion equatorial flux distributions and energy spectra are presented from stereoscopic Two Wide-Angle Imaging Neutral-Atom Spectrometers (TWINS) 1 and TWINS 2 energetic neutral atom (ENA) images for two time periods, 29 May 2010, 1330-1430 UT and 26 May 2011, 1645-1715 UT. The first is just after the main phase of a weak (minimum SYM/H approximate to-70 to -80 nT) corotating interaction region-driven geomagnetic storm. The second is during a relatively quiet period. The global ion distributions show multiple spatial peaks that are coincident with peaks in the AE index. The energy spectra have a primary maximum in the 15-20keV range. Below the energy maximum, the flux is Maxwellian. Above the main maximum, the flux is either significantly below that of a Maxwellian or has a second component with a maximum in the 40-50keV range. For the 29 May 2010, 1330-1430 UT time period, the flux from the TWINS stereoscopic images is compared to the results from TWINS 1 and TWINS 2 alone illustrating the advantage of stereoscopic viewing. The flux deconvolved from the TWINS images also shows spatial and temporal correlations with Time History of Events and Macroscale Interactions during Substorms (THEMIS) in situ measurements. Magnetic field dipolarizations observed by GOES support the existence of a peak in the ion flux in the midnight/dawn sector. In summary, increased spatial resolution from TWINS stereoscopic ENA images is demonstrated. Multiple peaks in the ion flux of trapped particles in the ring current are observed. THEMIS electrostatic analyzer in situ ion flux measurements and GOES geosynchronous magnetic field measurements are consistent with the spatial and temporal structure obtained.PublishedYe
Building a Sustainable Life Science Information Literacy Program Using the Train-the-Trainer Model
Get PDFThe train-the-trainer model has great potential for expanding information literacy programs without placing undue burden on already overextended librarians; it is surprisingly underused in academic libraries. At the University of Kentucky, we employed this model to create a new information literacy program in an introductory biology lab. We trained biology teaching assistants (TAs), each of whom was responsible for teaching two lab sections, to teach scientific database searching and Endnote Online to undergraduates. Over the first two semesters, we taught or co-taught 78 sessions of BIO 155 (nearly 2,200 attendees), with the librarian only in attendance at TA training and a total of 14 class sessions. Here we describe the program from its inception in late 2012 through the present, covering such topics as course coordinator buy-in, class design, active learning exercises, and assessment. Of particular note is the progression of our training program, which evolved from a style encouraging imitation toward one inspiring TAs to personalize the subject matter. We believe this approach inspired TAs to reflect on the importance of information literacy in their own research and to emphasize its relevance to undergraduates.PublishedYe
EUV emissions from solar wind charge exchange in the Earth's magnetosheath: Three-dimensional global hybrid simulation
Get PDFIn this paper, a three-dimensional (3-D) global hybrid simulation code and a 3-D geocoronal hydrogen model are used to systematically study the extreme ultraviolet (EUV) emissions at 30.4nm produced by solar wind charge exchange (SWCX) in the Earth's magnetosheath, associated with different solar wind-interplanetary magnetic field (SW-IMF) conditions and different imaging perspectives. We have found that the EUV emission intensities in the magnetosheath are highly variable from several mR to similar to 1200 mR and increase with the flow speed, the density, the temperature, and the He2+/H+ density ratio of the solar wind; the northward IMF leads to a minimum emission in the magnetosheath, whereas the southward IMF generates a maximum emission; with the increase of the magnitude of IMF, the emission pattern in the nightside splits from single field-aligned shape into a butterfly shape around the magnetic equator; and the EUV emissions vary with the imaging positions, reflecting different latitudinal and longitudinal information of the magnetosheath. It is noted that the SWCX EUV emissions in the magnetosheath for highly disturbed solar wind conditions should be considered in processing the Moon-based plasmaspheric EUV images. We suggest that EUV imaging of the global magnetosheath requires an EUV imager with large field-of-view, high-sensitivity, large dynamic range, and low intrinsic dark count rate. This investigation could provide us with an overall understanding on SWCX EUV emissions in the magnetosheath which can potentially be used to image the global magnetosheath to study the solar wind-magnetosphere coupling in the future.Publishe
Anthropogenic and climatic influences on carbon fluxes from eastern North America to the Atlantic Ocean: A process-based modeling study
Get PDFThe magnitude, spatiotemporal patterns, and controls of carbon flux from land to the ocean remain uncertain. Here we applied a process-based land model with explicit representation of carbon processes in streams and rivers to examine how changes in climate, land conversion, management practices, atmospheric CO2, and nitrogen deposition affected carbon fluxes from eastern North America to the Atlantic Ocean, specifically the Gulf of Maine (GOM), Middle Atlantic Bight (MAB), and South Atlantic Bight (SAB). Our simulation results indicate that the mean annual fluxes (1 standard deviation) of dissolved organic carbon (DOC), particulate organic carbon (POC), and dissolved inorganic carbon (DIC) in the past three decades (1980-2008) were 2.370.60, 1.060.20, and 3.570.72TgCyr(-1), respectively. Carbon export demonstrated substantial spatial and temporal variability. For the region as a whole, the model simulates a significant decrease in riverine DIC fluxes from 1901 to 2008, whereas there were no significant trends in DOC or POC fluxes. In the SAB, however, there were significant declines in the fluxes of all three forms of carbon, and in the MAB subregion, DIC and POC fluxes declined significantly. The only significant trend in the GOM subregion was an increase in DIC flux. Climate variability was the primary cause of interannual variability in carbon export. Land conversion from cropland to forest was the primary factor contributing to decreases in all forms of C export, while nitrogen deposition and fertilizer use, as well as atmospheric CO2 increases, tended to increase DOC, POC, and DIC fluxes.PublishedYe
