The effects on the ionosphere of inertia in the high latitude neutral thermosphere

High-latitude ionospheric currents, plasma temperatures, densities, and composition are all affected by the time-dependent response of the neutral thermosphere to ion drag and Joule heating through a variety of complex feedback processes. These processes can best be studied numerically using the appropriate nonlinear numerical modeling techniques in conjunction with experimental case studies. In particular, the basic physics of these processes can be understood using a model, and these concepts can then be applied to more complex realistic situations by developing the appropriate simulations of real events. Finally, these model results can be compared with satellite-derived data from the thermosphere. We used numerical simulations from the National Center of Atmospheric Research Thermosphere/Ionosphere General Circulation Model (NCAR TIGCM) and data from the Dynamic Explorer 2 (DE 2) satellite to study the time-dependent effects of the inertia of the neutral thermosphere on ionospheric currents, plasma temperatures, densities, and composition. One particular case of these inertial effects is the so-called 'fly-wheel effect'. This effect occurs when the neutral gas, that has been spun-up by the large ionospheric winds associated with a geomagnetic storm, moves faster than the ions in the period after the end of the main phase of the storm. In these circumstances, the neutral gas can drag the ions along with them. It is this last effect, which is described in the next section, that we have studied under this grant

SLIDES: Ground-Water Resources in the Western United States: Status and Trends

Presenter: Alan Burns, U.S. Geological Survey. 68 slides

SLIDES: Ground-Water Resources in the Western United States: Status and Trends

Presenter: Alan Burns, U.S. Geological Survey. 68 slides

The Deadline Floor Protocol and Ada

At the 2013 IRTAW Workshop it was accepted that the Deadline Floor Protocol (DFP) has many advantaged over the Stack Resource Protocol (SRP), and that it should be incorporated into a future version of the language, and that ideally the support for SRP should be deprecated. This short position paper summarises the current status of proposed language changes that would be needed to make this happen. The context is single processor systems

An optimal fixed-priority assignment algorithm for supporting fault-tolerant hard real-time systems

The main contribution of this paper is twofold. First, we present an appropriate schedulability analysis, based on response time analysis, for supporting fault-tolerant hard real-time systems. We consider systems that make use of error-recovery techniques to carry out fault tolerance. Second, we propose a new priority assignment algorithm which can be used, together with the schedulability analysis, to improve system fault resilience. These achievements come from the observation that traditional priority assignment policies may no longer be appropriate when faults are being considered. The proposed schedulability analysis takes into account the fact that the recoveries of tasks may be executed at higher priority levels. This characteristic is very important since, after an error, a task certainly has a shorter period of time to meet its deadline. The proposed priority assignment algorithm, which uses some properties of the analysis, is very efficient. We show that the method used to find out an appropriate priority assignment reduces the search space from O(n!) to O(n/sup 2/), where n is the number of task recovery procedures. Also, we show that the priority assignment algorithm is optimal in the sense that the fault resilience of task sets is maximized as for the proposed analysis. The effectiveness of the proposed approach is evaluated by simulation

Self-dual vortices in nonabelian gauge theories

Using the Atiyah-Ward construction, we examine the solutions of the self-dual Yang-Mills equations for an SU (2) gauge theory, dimensionally reduced from | R(^4) to R(^2). There are two main reasons for doing this: (i) To provide a large class of relatively simple examples which elucidate how non-singularity and physical field configurations are related to the parameterization of the Atiyah-Ward construction. (ii) To construct analogues, for pure non-abelian gauge theories, of the superconducting vortex solutions of the abelian Higgs model, in the hope that these will provide the dominant field configurations describing the QCD vacuum. First, Băcklund transformations are used to construct axially symmetric solutions, and the analogues of the ’t Hooft instantons. These results are then generalised, within the twister theoretic framework of the Atiyah-Ward construction, to produce an infinite dimensional parameter space of complex non-singular solutions in each of the Atiyah-Ward ansătze. The field configurations are expressible as unitary group integrals occurring in lattice gauge theories - this leads to a simple proof of non-singularity, and a convenient means of calculating properties of the field configurations using strong and weak coupling expansions. The structure of the field configurations is further elucidated using symmetry arguments and numerical computations. Finally, suggestions are made as to how these solutions may play a role in the QCD confinement mechanism