• A simulation study of three-dimensional magnetic reconnection

      Ma, Zhi-Wei; Lee, L. C.; Kan, J. R.; Shaw, G. E.; Smith, R. W.; Hawkins, J. G. (1994)
      The magnetic reconnection process plays an important role in the interaction between the solar wind and the magnetosphere. It leads to the transfer of energy from the solar wind into the magnetosphere. In this thesis, we study three-dimensional (3D) aspects of magnetic reconnection based on magnetohydrodynamic (MHD) simulations. First, we examine the magnetic field topology of magnetic flux ropes formed in multiple X line reconnection (MXR). It is found that the magnetic field topology depends on the relative extent and location of the two neighboring X lines. Magnetic flux ropes with either smooth or frayed ends are obtained in our simulations. For magnetic flux ropes with smooth ends, a major amount of magnetic flux is connected at each end to only one side of magnetopause. Second, the evolution of the core magnetic field in the magnetic flux tube is studied for various magnetic reconnection processes. We find that the 3D cases always lead to a larger enhancement of core field than the corresponding 2D cases since plasma can be squeezed out of the flux tube in the third direction. The MXR process gives rise to a larger increase of the core field than the single X line reconnection process. The core magnetic field can be enhanced to three times the ambient magnetic field strength in the 3D MXR process. Finally, we examine the generation and propagation of Alfven waves and field-aligned currents in the 3D reconnection process. For cases with a zero guide field, it is found that a large portion of the field-aligned currents ($\sim$40%) is located in the closed field line region. Both the pressure gradient term and inertia term contribute to the generation of field-aligned currents. For cases with nonzero guide field, one sense of field-aligned currents is dominant due to the presence of the initial field-aligned current. In these cases, the inertia term makes a major contribution to the redistribution of field-aligned currents. The influence of the initial guide field on the longitudinal shift of the current reversal site is found to be consistent with observations.
    • A Sounding Rocket Attitude Determination Algorithm Suitable For Implementation Using Low Cost Sensors

      Charlton, Mark Christopher; Hawkins, Joseph G. (2003)
      The development of low-cost sensors has generated a corresponding movement to integrate them into many different applications. One such application is determining the rotational attitude of an object. Since many of these low-cost sensors are less accurate than their more expensive counterparts, their noisy measurements must be filtered to obtain optimum results. This work describes the development, testing, and evaluation of four filtering algorithms for the nonlinear sounding rocket attitude determination problem. Sun sensor, magnetometer, and rate sensor measurements are simulated. A quatenion formulation is used to avoid singularity problems associated with Euler angles and other three-parameter approaches. Prior to filtering, Gauss-Newton error minimization is used to reduce the six reference vector components to four quaternion components that minimize a quadratic error function. Two of the algorithms are based on the traditional extended Kalman filter (EKF) and two are based on the recently developed unscented Kalman filter (UKF). One of each incorporates rate measurements, while the others rely on differencing quaternions. All incorporate a simplified process model for state propagation allowing the algorithms to be applied to rockets with different physical characteristics, or even to other platforms. Simulated data are used to develop and test the algorithms, and each successfully estimates the attitude motion of the rocket, to varying degrees of accuracy. The UKF-based filter that incorporates rate sensor measurements demonstrates a clear performance advantage over both EKFs and the UKF without rate measurements. This is due to its superior mean and covariance propagation characteristics and the fact that differencing generates noisier rates than measuring. For one sample case, the "pointing accuracy" of the rocket spin axis is improved by approximately 39 percent over the EKF that uses rate measurements and by 40 percent over the UKF without rates. The performance of this UKF-based algorithm is evaluated under other-than-nominal conditions and proves robust with respect to data dropouts, motion other than predicted and over a wide range of sensor accuracies. This UKF-based algorithm provides a viable low cost alternative to the expensive attitude determination systems currently employed on sounding rockets.
    • A statewide training model for supported employment using master trainers

      Wilcox, David Allen; Mohatt, Gerald; Risley, Todd R.; Dinges, Norman; Dowrick, Peter W.; Kleinke, Chris; Owens, Jesse; Ryan-Vincek, Susan; Ward, Karen M. (1996)
      Alaska's vast land mass and diversified urban, rural, and remote communities require innovative training curricula to meet training needs in supported employment. A competency-based training program using an independent learning format and master trainers was developed to meet these extreme needs. These training methods were evaluated with survey instruments at the time of training and at 3 months, 6 months, and 1 year follow up. The data demonstrate that the training materials as well as the independent study format and master trainer model were effective training methods. We conclude that the training methods developed are effective in meeting the diverse training needs of urban, rural, and remote sites.
    • A study of one-dimensional nonlinear hydromagnetic waves and collisionless shocks

      Lyu, Ling-Hsiao; Kan, J. R.; Akasofu, S.-I.; Biswas, N. N.; Olson, J. V.; Swift, D. W. (1991)
      A variety of nonlinear hydromagnetic waves have been observed in the collisionless solar wind plasma. A comprehensive theoretical study of nonlinear hydromagnetic waves, including rotational discontinuities and collisionless shocks, is carried out in this thesis by means of both analytical solutions and numerical simulations. Nonlinear hydromagnetic waves are governed by the interplay of the dispersion process, the collisionless dissipation process and the nonlinear steepening process. The purpose of this thesis is to understand the nonlinear behavior of hydromagnetic waves in terms of these fundamental processes. It is shown that the rotational discontinuity structures observed in the solar wind and at the magnetopause are nonlinear Alfven wave solutions of the collisionless two-fluid plasma equations. In these nonlinear wave solutions, nonlinear steepening is self-consistently balanced by dispersion. Collisionless viscous dissipation is the dominant dissipation in high Mach number shocks, which converts the flow energy into thermal energy. Hybrid simulations show that the collisionless viscous dissipation can result from the reflection and pitch-angle scattering of incoming ions flowing through the magnetic structures in the shock transition region. Collisionless dissipations in hydromagnetic shocks is governed by the magnetic structures in the shock transition region. The dissipation in turn can modify the wave structures and balance the nonlinear steepening. However, such delicate balance of the dispersion, dissipation, and nonlinear steepening has been observed to break down momentarily in high Mach number quasi-parallel shocks. This leads to the so-called cyclic shock front reformation seen in the hybrid simulations. The shock front reformation can be explained in terms of momentary off-balance between the dispersion-dissipation on the one hand and the nonlinear steepening on the other hand. The off-balance occurs after a significant fraction of incoming ions are reflected. Each off-balance lasts a few ion gyro periods, which governs the shock front reformation time scale.
    • A study of the link between cloud microphysics and climate change

      Hu, Yong-Xiang; Stamnes, Knut; Musgrave, David; Rees, Manfred; Shaw, Glenn E.; Tsay, Shee-Chee; Watkins, Brenton (1994)
      The climate related cloud radiative properties (fluxes and heating rates) are found to be determined by the second and the third moments of the cloud droplet size distribution. The detailed distribution of the cloud droplet size is unnecessary to obtain for climate purposes. An accurate parameterization of cloud optical properties suitable for climate models is developed. A new radiative-convective model has been developed and used for studying cloud-climate interactions. The energy balance at the Earth-atmosphere interface is treated in a self-consistent manner which avoids artificial tuning. The cloud radiative properties are accurately incorporated and are suitable for sensitivity studies of cloud-radiation-climate interactions. A sensitivity study of role of the cloud microphysical properties in the climate system is performed by studying the impact of cloud radiative forcing on the equilibrium state temperature. The cloud equivalent radius is found to be a very important variable in the climate system. A climate sensitivity study is performed to highlight the important role of the cloud absorption. An adjoint radiative transfer method is developed for use in the cloudy and aerosol-loaded atmospheres. The physical meaning of the adjoint radiative properties are discussed. The method is expected to be useful in climate modeling and remote sensing studies. A preliminary study of the atmospheric irreversibility is performed to elucidate the connection between cloud microphysical properties and the macrophysical direction of global climate. A variational principle which describes the macrophysical character of the climate system is established.
    • A study of the magnetosphere-ionosphere coupling processes

      Zhu, Lie; Kan, J. R. (1990)
      Magnetosphere-ionosphere (M-I) coupling processes are studied by using numerical modeling. An M-I coupling model of substorms on the ionospheric recombination time scale (tens of seconds) is developed. The model is two-dimensional (2-D) and time-dependent from which several signatures of substorms can be obtained and understood. The model is then extended to northward interplanetary magnetic field (IMF) conditions to study the effects of the M-I coupling on the high-latitude convection. Based on the model results, a mechanism for the origin of distorted two-cell ionospheric convection is proposed. The ionospheric and ground signatures of multiple field-aligned current sheets originating from dayside flux transfer events have been modeled. The interaction between Alfven waves and field aligned potential drops is studied by using a local model.
    • A study on the interaction of Alzheimer's disease beta amyloid protein with cultured mouse neuroblastoma cell line NB41A3

      Zhao, Xiaohong (1994)
      The $\beta$ amyloid protein is the primary constituent of amyloid plaques in the brains of Alzheimer's disease patients. The generation of $\beta$ amyloid protein from $\beta$ amyloid precursor protein and its interaction with neuronal cells were studied in the mouse neuroblastoma cell line NB41A3. Immunoreactivity to the carboxyl terminal of the precursor protein was detected among the membrane proteins of these cells, indicating that $\beta$ amyloid precursor protein is produced by NB41A3 cells. Also amyloid precursor protein carboxyl terminal immunoreactivity was observed in the conditioned medium of the cells, demonstrating various cytosolic peptide fragments are secreted during the cellular processing of the $\beta$ amyloid precursor protein. Synthetic $\beta$ amyloid peptide was shown to negatively affect NB41A3 neuroblastoma cells as judged by decreasing cell numbers, decreasing amount of cell protein, and release of the cytosolic enzyme, lactic dehydrogenase, into the medium. At the ultrastructural level, internal damage to the nucleus could be observed. Synthetic $\beta$ peptide showed specific binding with neuroblastoma cells. The internalization of the $\beta$ peptide into the cells suggest a direct mechanism for $\beta$ amyloid protein toxicity in vivo. This research contributes to the knowledge of the processing of Alzheimer's disease $\beta$ amyloid precursor protein in NB41A3 cells and demonstrates that NB41A3 cell provides a practical in vitro model for studying the mechanism of Alzheimer's disease and amyloid toxicity.
    • A Synoptic Climatology Of Alaska: Winter 700Mb Height Anomaly Patterns And Surface Climate Variability, 1956-1986

      Milkovich, Mary F.; Weller, Gunter; Fathauer, T. E.; Royer, T. C.; Shaw, G. E.; Tanaka, H. L.; Weadler, G. (1989)
      An objective, descriptive study of Alaska's winter season synoptic climatology is compiled to identify regional monthly 700mb anomaly height patterns and to investigate monthly-mean surface temperature and precipitation variability during the thirty-year period from 1956/57 to 1985/86. A total of 78% of the period's monthly 700mb anomaly height maps are classified into ten Basic Anomaly Pattern categories by a Kirchhofer/Lund-based pattern classification scheme. Patterns are described in terms of frequency of occurrence, climate associations, and specific climate events (case study format). Examination of the winter monthly-mean temperature and precipitation records for the nine NOAA-designated Alaska climate divisions, and the Gulf of Alaska indicates a cool, dry period in the January record from 1964-1977. The winters following 1977 are the most variable of the thirty-year record. Seasonal-scale linear trends indicate a warmer, drier shift in the interior divisions and a warmer, wetter shift in the southern coastal divisions. <p>
    • A temperature only formulation for ice sheets

      Gillispie, Lyman; Bueler, Edward; Allman, Elizabeth; Maxwell, David (2014-05)
      Temperature plays an important role in the dynamics of large flowing ice masses like glaciers and ice sheets. Because of this role many models for ice sheets model temperature in some form. One type of model for polythermal glaciers (glaciers which contain both ice below, and at the pressure-melting temperature) explicitly separates the ice into distinct cold and temperate regimes, and tracks the interface between them as a surface. Other models track the enthalpy (internal energy) across both domains, with temperature being a function of enthalpy. We present an alternative mathematical formulation for polythermal glaciers and ice-sheets, in the form of a variational inequality for the temperature field only. Using the calculus of variations, we establish some sufficient conditions under which our formulation is well-posed. We then present some numerical approximations of solutions obtained via the Finite Element Method.
    • A theoretical study of magnetosphere-ionosphere coupling processes

      Cao, Fei; Kan, J. R.; Akasofu, S-I.; Biswas, N.; Shaw, G.; Swift, D. (1991)
      Magnetosphere and ionosphere are coupled electrodynamically by waves, field-aligned currents and parallel electric fields. Several fundamental coupling processes are addressed in my thesis. It is shown that the Alfven wave is the dominant mode in transmitting field-aligned currents. Therefore, dynamic M-I coupling can be modeled by the Alfven wave bouncing between the ionosphere and the magnetospheric boundaries. The open magnetopause, separating the solar wind and the magnetosphere, behaves like a near perfect reflector to the Alfven wave because of the large solar wind inertia. At the plasma sheet, however, the reflection coefficient may extend over a wide range, depending on the location in the plasma sheet. As the Alfven wave propagates back and forth between the magnetosphere and ionosphere, the field-aligned current density increases dramatically at certain locations, especially near the head of the westward traveling surge, causing potential drops to develop along magnetic field lines. It is found that the existence of parallel potential drops can distort the global convection pattern and limit the upward field-aligned current. The magnetic reconnection at the dayside magnetopause is responsible for enhancing the convection in the magnetosphere, which subsequently propagates toward the ionosphere by the Alfven wave. The patchy and intermittent reconnection at the dayside magnetopause can be initiated by the 3-D tearing instability, leading to the isolated magnetic islands and X-line segments. The nonlinear evolution of tearing in terms of the magnetic island coalescence is also studied.
    • A theory of field-aligned current generation from the plasma sheet and the poleward expansion of aurora substorms

      Yamauchi, Masatoshi; Akasofu, Syun-Ichi (1990)
      This dissertation reports a study of the generation of field-aligned currents in the plasma sheet in terms of magnetosphere-ionosphere coupling. For the study, the plasma sheet and the ionosphere are treated as two-dimensional layers by height integration. In the magnetosphere between them, the Alfven wave transition time through this region is assumed to be zero. The ionospheric momentum is allowed to be transferred to the plasma sheet. Both linear analyses and numerical simulation are performed to study the field-aligned current generation. In the linear analysis, evolution from initial perturbations is studied. Zero order configurations are steady state without field-aligned currents. The field-aligned currents are treated as a perturbed quantity and linearly related with the other perturbed quantities. One result for the linear waves is that the magnetohydrodynamics (MHD) fast mode and Alfven mode are coupled through the ionospheric Hall current. The Hall current causes the dawn-dusk asymmetry: a westward-travelling wave is amplified on the region 1 current system, while an eastward-travelling wave is amplified elsewhere. The expansion phase of the magnetospheric substorm after the onset is numerically simulated on the near-earth plasma sheet. The inner edge of the plasma sheet is taken as the outflow boundary. As the initial condition, an enhanced earthward magnetospheric convection is assumed to cause a finite pressure increase at the inner edge of the plasma sheet. The numerical results are as follows. An MHD fast-mode wave is generated. It propagates tailward accompanied by the field-aligned currents. The wave propagation and the field-aligned currents account for the poleward expansion of the aurora and the region 1 field-aligned current during the expansion phase of the substorm. The region 1 field-aligned currents are linked with the dusk to dawn current on this wave, which is driven by the dynamo mechanism of the wave. The ionospheric Hall current causes asymmetry of the wave, and hence, of the field-aligned current distribution. This asymmetry accounts for the stronger field-aligned current in the premidnight sector.
    • A Walleye Pollock (Theragra Chalcogramma) Depletion Estimator For The Eastern Bering Sea

      Battaile, Brian Charles; Terrance J. Quinn, II; Kelly, Brendan; Sigler, Mike; Adkison, Milo (2005)
      The decline of the Steller Sea lion in the eastern Bering Sea over the last 25 years has resulted in increased management of the pollock fishery due to requirements of the Endangered Species Act, as food competition was hypothesized to contribute to the decline. Our research focused on determining if the pollock fishery was causing significant depletion in the eastern Bering Sea, particularly in Steller sea lion critical habitat. DeLury depletion models were fitted to catch and effort data from 1995 to 1999, from the observer program, which required considerable processing to obtain a database at a temporal and spatial scale that is much finer than that used for stock assessment in the eastern Bering Sea. The catch per unit effort (CPUE) data were standardized in a unique way in that the data were stratified in space and time and standardized using separate general linear models for each stratum. A significant amount of depletion was detected in the pollock fishery from 1995--1999. Depletion estimates of fishery mortality tended to be an order of magnitude smaller than those found in traditional stock assessments. Post hoc analyses indicated that depletion is detected more easily in areas of low abundance due to the hyperstable relationship between CPUE and biomass, possibly exacerbated by a lack of search time in the model. Evidence further suggested that dispersing exploitation pressure decreases local depletion, and pollock may repopulate a depleted area within weeks. Finally, a hierarchical spatial Bayesian analysis with a conditional autoregressive model was constructed to unify the analysis. Because the data were relatively clean of outliers and not over dispersed, significant changes in the results between the frequentist and Bayesian based analyses were not found as was little evidence of spatial autocorrelation in the estimates of catchability.
    • A World Of Difference: Emma Wolf, A Jewish-American Writer On The American Frontier

      Mandel, Dena Toni Cooper; Schuldiner, Michael (2008)
      "A World of Difference: Emma Wolf, A Jewish-American Writer on the American Frontier" is the first dissertation to undertake a scholarly inquiry of Wolf's Jewish novels, Other Things Being Equal and Heirs of Yesterday. Emma Wolf (1865--1932) was a Jewish-American literary pioneer who interrogated prevailing models of late nineteenth-century femininity, Judaism, and bifurcated, Jewish-American identity. This study retrieves the fiction of this native Californian from the margins of both Jewish and American literature. At the close of the nineteenth century, nearly all interest in American-Jewish life focused on the Eastern European Jewish immigrants on the Lower East Side of New York City. Emma Wolf's fiction imparts a singular glimpse of a Western American enclave of Jewish life. Remarkably, Wolf's Jewish novels resist the prevailing patterns of assimilation espoused by most Jewish writers at the end of the century. Instead of abandoning culture, faith, and family, Wolf embraces Jewish particularity. The preservation of Jewish identity in Wolf's fiction is a consequence of her American birth, her California origins, and her conviction that Jewish difference is as important as American conformity. Other Things Being Equal (1892) scrutinizes the struggle of a young Jewish woman who wants to marry a Christian. In sanctioning intermarriage, the novel abrogates religious precepts and contravenes the customary marital patterns of Jewish women. The implications of intermarriage afford Wolf the opportunity to expand on issues of Jewish affirmation and Jewish difference. In Heirs of Yesterday (1900) Wolf examines divergent responses of Jewish-Americans to anti-Semitism. In order to protect himself from discrimination, Dr. Philip May hides his Jewish birth. Wolf suggests that Jews who are forgetful of their ethnic identity are as misguided as the segment of American society that discriminates against them. This study of Emma Wolf's Jewish novels concludes that we must take a new literary census, one that embraces minority writers, like Emma Wolf, in order to appreciate the pluralism of the American literary canon and the full panoply of the nation's cultural productivity.
    • About time: chronological variation as seen in the burial features at Ipiutak, Point Hope

      Newton, Jennifer I. M. (2002-05)
      The burials at Ipiutak, Point Hope, Alaska, are best known for their spectacular grave goods and burial practices, considered by the excavators to be suggestive of a 'ghost cult', and more recently to be evidence of social complexity. Collections from the National Museum of Denmark, the American Museum of Natural History, and the University of Alaska Museum are studied and re-inventoried, and burial features on the Ipiutak peninsula are re-mapped. Examination of burial practices reveals four burial types, defined in terms of the structure and organization of associated wood. Differences between burial types and variation in artifact inventories are ascribed to taphonomic processes, and to variation in mortuary behavior over time. Accelerator Mass Spectronomy dates support the view that the cemetery was formed over at least 500 years, and reflects long term site use rather than differences in gender and social status.
    • Absolute measurement of excitation cross sections for the 2P-states of atomic hydrogen in charge exchange collisions of protons in argon and nitrogen

      Suchannek, Rudolf G. (1974-08)
      Cross sections for the excitation of the 2P-states of atomic hydrogen in charge exchange collisions of protons in argon and nitrogen were measured by observing the Lyman-α radiation emitted in transitions from this state. For the measurement of the target gas pressure, a modified ionization gauge was developed, which eliminated distortions of pressure measurements due to charging effects on the glass envelope. Because of the lack of light standards in the vacuum untraviolet region of the spectrum, the major problem of the measurements was the absolute calibration of the Lα-photometer. This calibration was obtained from coincidence measurements of Hα- and Lα-photons in the presence of an electric field. The measurements were corrected for the effect of Doppler shift on photometer sensitivity. For the evaluation of the coincidence measurements, the branching ratio of Hα-transitions to the 2S-state and the polarization of Lyman-α radiation, emitted in cascade processes, were needed. These quantities were obtained from quantum mechanical calculations of a hydrogen atom in a weak electric field. Cross sections for the 2P-states were obtained in the energy range from 0.5 to 30 keV. The 2P-cross sections in argon had maxima of 2.23x10-17 and 2.68x10-17 cm2 at 3.35 and 11.86 keV, respectively, and in N2 maxima of 2.17x10-17 and 2.10x10-17 cm2 were observed at 3.39 and 11.3 keV, respectively. The energy dependence of the measured cross sections is in agreement with that of published measurements. Differences in the absolute values are discussed.