Now showing items 1-20 of 12647

    • Radiowave absorption coefficients based on Sen-Wyller magneto-ionic formula

      Chorbajian, Jean; Sugiura, Masahisa; Parthasarathy, R. (Geophysical Institute at the University of Alaska Fairbanks, 1962-11)
    • Alaska Homicide Arrest Rates, by Place: 1985-2022

      Sampson, Rus'sel (Alaska Justice Information Center, 2024-10-04)
      This fact sheet presents Alaska homicide arrests rates per 1,000 population in Anchorage and 1,000 population outside of Anchorage from 1985-2022.
    • Homicides Reported to Police in Alaska, by Place: 1985-2022

      Sampson, Rus'sel (Alaska Justice Information Center, 2024-10-04)
      This fact sheet presents data on homicides reported to police in Alaska per 1,000 population in Anchorage and 1,000 population outside of Anchorage from 1985-2022.
    • Latitudinal and seasonal variations in the night airglow

      Davis, T. Neil; Smith, L. L. (Geophysical Institute at the University of Alaska Fairbanks, 1964-08)
      A four-color turret photometer has been used for shipboard observations of the night airglow and the aurora. Zenith observations have been obtained during 1962 close to the 70° W meridian from the northern auroral zone to the Antarctic pack ice. Most of the observations were taken during the Southern Hemisphere Winter. Maximums in the [0I] 5577 Å intensity were found near 30-40° N and 40° S, with the Southern Hemisphere level being generally lower than that in the Northern Hemisphere. The [0I] 6300Å latitudinal variation was similar to that of 0Iλ 5577Å except that maximums in the latitudinal distribution were found near 15° geomagnetic north and south latitudes. In contrast with the [0I] emissions, the sodium group (NaD doublet and OH bands near 5893Å) generally increased to the south with maximums near 20-30° N and 40-50° S geographic latitude. The total 5340Å background increased from north to south. When the integrated starlight and zodiacal light components were subtracted from the total background, the resultant terrestrial component showed a pronounced minimum at low latitudes and apparent symmetry about the geomagnetic equator.
    • Comments on wave forms in noctilucent clouds

      Haurwitz, Bernhard (Geophysical Institute at the University of Alaska Fairbanks, 1964-12)
    • An interpretation of the auroral breakup

      Swift, Daniel W. (Geophysical Institute at the University of Alaska Fairbanks, 1965-07)
      A dynamical model of the magnetosphere is presented to account for the main morphological features of the aurora, and the auroral breakup in particular. The aurora is the result of an internal process in the magnetosphere. It is suggested that a fluting instability on the outer boundary of the ring current belt is responsible for auroral breakup. This instability leads to a rapid flow of the ring current plasma into the tail of the magnetosphere. Particular attention is focused on the mechanisms for energizing electrons, the dynamics of the fluting instability in the magnetosphere including the dissipative effects of the ionosphere, and the structure of the ring current belt. It is stressed that the aurora gets its energy from the DR (ring current) belt. It is shown that the asymmetry of the DR belt and the observed asymmetry of the radiation belts can be accounted for by the asymmetric injection of charged particles on the day side of the geomagnetic field.
    • The auroral display of February 13-14, 1958

      Davis, T. Neil; Kimball, D. S. (Geophysical Institute at the University of Alaska Fairbanks, 1962-01)
      Detailed synoptic maps of the auroral display of February 13-14, 1958 are presented. These maps depict both the auroral configurations and the magnitude and direction of magnetic disturbance at intervals of five minutes as determined from several observing stations in Alaska. The maps demonstrate pronounced but imperfect relationships of the position, magnitude, and orientation of magnetic disturbance with the position, intensity, and configuration of auroral forms.
    • Types Pc 1-2 and IPDP micropulsations at the auroral zone

      Heacock, Richard R. (Geophysical Institute at the University of Alaska Fairbanks, 1971-01)
      A micropulsation recording program was carried out at College and Anchorage, Alaska and at Bar I, Canada, with induction magnetometers. The analysis program centered mainly on synoptic and polarization characteristic for types Pc 1-2, IPDP, and Pi burst micropulsation events. Summaries of the known morphological features for structured Pc 1 and unstructured Pc 1-2 micropulsations are given. The synoptic studies disclosed latitude relationships between unstructured Pc 1-2, IPDP, and Pi burst events. At the onset of a polar substorm, Pi bursts occur near midnight at 65°-70° geomagnetic latitudes. IPDP events follow the Pi burst and are seen in evening hours at 60°-65° latitudes. IPDP events seen in afternoon hours are often preceded by unstructured Pc 1-2 activity which maximizes a few degrees polewards of the IPDP. The IPDP events are seen in the evening “bulge” region of the plasmasphere. The proton plasma requirement for IPDP wave generation suggests that protons which are injected near midnight in the Pi burst event drift westwards into the bulge and generate unstructured Pc 1-2 and IPDPs there. The polarization characteristics of Pc 1 activity indicate that simple structured Pc 1 events originate on a stable tube of force. Unstructured Pc 1 events and events which are superpositions of several events usually display pronounced time-variability in the polarization characteristics.
    • Computed HF auroral backscatter traces for various distances

      Bates, Howard F. (Howard Francis) (Geophysical Institute at the University of Alaska Fairbanks, 1966-02)
      Computed ionospheric backscatter traces in the HF portion of the radio spectrum are illustrated for a number of distances between the auroral belt and the observing radar. The type, frequency range, and observed scattering height of HF auroral backscatter traces are strongly dependent upon the ionospheric propagation conditions existing between the auroral belt and the observer. Backscatter echoes produced in a given region of space by a single backscattering mechanism can have completely different range versus frequency characteristics when observed at sites located at different distances from the scattering region. Even though a given bank of auroral-belt irregularities extends through both the E and F regions, it is possible that only E-scatter is detected at one distance, and F-scatter at another. Trace type, scattering height, and frequency range of the observed backscatter echoes are strongly dependent upon the distance between the auroral belt and the observer.
    • Noctilucent clouds : a survey with special reference to recent observations

      Fogle, Benson; Chapman, Sydney; Echols, Carol (Geophysical Institute at the University of Alaska Fairbanks, 1965-03)
    • The relationship between submarine melt and subglacial discharge from observations at a tidewater glacier

      Jackson, Rebecca H.; Motyka, Roman J.; Amundson, Jason M.; Abib, Nicole; Sutherland, David A.; Nash, Jonathan D.; Kienholz, Christian (John Wiley & Sons, Inc., 2022-10)
      At tidewater glacier termini, ocean-glacier interactions hinge on two sources of freshwater—submarine melt and subglacial discharge—yet these freshwater fluxes are often unconstrained in their magnitude, seasonality, and relationship. With measurements of ocean velocity, temperature and salinity, fjord budgets can be evaluated to partition the freshwater flux into submarine melt and subglacial discharge. We apply these methods to calculate the freshwater fluxes at LeConte Glacier, Alaska, across a wide range of oceanic and atmospheric conditions during six surveys in 2016–2018. We compare these ocean-derived fluxes with an estimate of subglacial discharge from a surface mass balance model and with estimates of submarine melt from multibeam sonar and autonomous kayaks, finding relatively good agreement between these independent estimates. Across spring, summer, and fall, the relationship between subglacial discharge and submarine melt follows a scaling law predicted by standard theory (melt ∼ discharge1/3), although the total magnitude of melt is an order of magnitude larger than theoretical estimates. Subglacial discharge is the dominant driver of variability in melt, while the dependence of melt on fjord properties is not discernible. A comparison of oceanic budgets with glacier records indicates that submarine melt removes 33%–49% of the ice flux into the terminus across spring, summer, and fall periods. Thus, melt is a significant component of the glacier's mass balance, and we find that melt correlates with seasonal retreat; however, melt does not appear to directly amplify calving.
    • The preliminary analysis of IGY magnetic results from Alaskan observatories

      Cain, Joseph C. (Geophysical Institute at the University of Alaska Fairbanks, 1960-08)
      A preliminary analysis has been made of the magnetic data from the IGY network stations in Alaska. A few examples of magnetic bays were selected, and the distribution of electric current responsible for them was studied with a simple model for the current system, namely, line, or sheet, currents. The records obtained by the differential magnetometer were analyzed and compared with the gradient of the magnetic elements computed from the regular magnetograms taken at neighboring stations. The differential records were found not in agreement with the latter computed values. The discrepancy is probably due to local electric currents induced in the ground. A suggestion is made for future work on the auroral electrojets.
    • Whalesong 2006-03-02 (v.26 no.9)

      Galeana, Sandra K.; Coleman, Jess; Crondahl, Shana; Marvel, Alex; Moniak, Rich; Ricci, Stefan; Sonin, John S.; KRT; Lagundino, Flordelino; Squires, Marsha; et al. (University of Alaska Southeast, 2006-03-02)
    • Clustering for the neophyte: An R Shiny app for self-organizing maps

      Akman, Olcay; Betzab-Marroquin, Zury; Hay-Jahans, Christopher; Wlash, Joshua; Wesley, Trenton (Intercollegiate Biomathematics Alliance, 2022)
      This article provides an outline of clustering, key stages in creating self-organizing maps for purposes of clustering, instructions on how to use a free online R Shiny app that constructs self-organizing maps for data provided by users, and interpretations of the graphics produced.
    • Agent-based modeling for the neophyte: An application of NetLogo

      Akman, Olcay; Bhumpelli, Siddharth; Hay-Jahans, Christopher (Intercollegiate Biomathematics Alliance, 2024)
      Agent-based modeling has found applications in a wide range of fields including economics, sociology, ecology, epidemiology, transportation planning, and more. Its versatility allows researchers to investigate various “what-if” scenarios, test the effects of different policies or interventions, and gain insights into the underlying mechanisms driving complex systems. This article is intended for the curious student or researcher who is unfamiliar with agentbased modeling and is looking for a quick but reasonably informative exposure to the field.
    • Linking dissolved organic matter composition to landscape properties in wetlands across the United States of America

      Kurek, Martin R.; Wickland, Kimberly P.; Nichols, Natalie A.; McKenna, Amy M.; Anderson, Steven M.; Dornblaser, Mark M.; Koupaei-Abyazani, Nikaan; Poulin, Brett A.; Bansal, Sheel; Fellman, Jason; et al. (American Geophysical Union, 2024-05-03)
      Wetlands are integral to the global carbon cycle, serving as both a source and a sink for organic carbon. Their potential for carbon storage will likely change in the coming decades in response to higher temperatures and variable precipitation patterns. We characterized the dissolved organic carbon (DOC) and dissolved organic matter (DOM) composition from 12 different wetland sites across the USA spanning gradients in climate, landcover, sampling depth, and hydroperiod for comparison to DOM in other inland waters. Using absorption spectroscopy, parallel factor analysis modeling, and ultra-high resolution mass spectroscopy, we identified differences in DOM sourcing and processing by geographic site. Wetland DOM composition was driven primarily by differences in landcover where forested sites contained greater aromatic and oxygenated DOM content compared to grassland/herbaceous sites which were more aliphatic and enriched in N and S molecular formulae. Furthermore, surface and porewater DOM was also influenced by properties such as soil type, organic matter content, and precipitation. Surface water DOM was relatively enriched in oxygenated higher molecular weight formulae representing HUPHigh O/C compounds than porewaters, whose DOM composition suggests abiotic sulfurization from dissolved inorganic sulfide. Finally, we identified a group of persistent molecular formulae (3,489) present across all sites and sampling depths (i.e., the signature of wetland DOM) that are likely important for riverine-to-coastal DOM transport. As anthropogenic disturbances continue to impact temperate wetlands, this study highlights drivers of DOM composition fundamental for understanding how wetland organic carbon will change, and thus its role in biogeochemical cycling.
    • A note on the DS variation of geomagnetic storms : a critical examination of method of analysis.

      Sugiura, Masahisa (1961-09)
      The determination of DS variation of magnetic storms as a function of storm time is critically examined. The regular changes in the phase angles of harmonics for DS, found by Yokouchi (1958), are attributed to irregular features that are not adequately averaged out. This apparently paradoxical circumstance is explained with an illustrative example.
    • Summary of noctilucent cloud reports from 1885-1964

      Fogle, Benson; Echols, Carol (Geophysical Institute at the University of Alaska Fairbanks, 1965-06)
    • IQSY ascaplots from 20 U.S. all-sky camera stations

      Young, M. J. (Geophysical Institute at the University of Alaska Fairbanks, 1967)
    • Outline geology of the Aleutian Islands with paleomagnetic data from Shemya and Adak Islands

      Cameron, Christopher P.; Stone, David B. (Geophysical Institute at the University of Alaska Fairbanks, 1970-07)
      A brief review of the general geology and tectonic setting of the Aleutian Island Arc is presented, followed by an account of the paleo-magnetism of selected areas. Paleomagnetic results are presented for Tertiary and Quaternary volcanic rocks from Shemya and Adak Islands. The specimens were collected and measured using standard paleomagnetic methods. Alternating field demagnetization techniques were applied to test the stability of the remanence and to remove unwanted secondary components of magnetization. The variation of the intensity of the NRM with the bulk susceptibility is discussed from the standpoint of the magnetic stability of the rocks. Mid-Late Tertiary and Quaternary specimens satisfy several criteria of magnetic stability in igneous rocks, and derived pole positions are thought to reflect the ambient geomagnetic field at the time of the origin of the rocks. By comparison, the remanent magnetization of Early Tertiary rocks investigated is less stable and yields uncertain results in terms of pole positions. The paleomagnetic results from the various sites are discussed with respect to the background geology of each island. Paleomagnetic pole positions derived from the results are compared with pole positions from other Tertiary and Quaternary sites in North Pacific tectonic belts.