Forecasting Nevada's economy

Nevada ; Forecasting

A vector autoregression model of the Nevada economy

Nevada ; Forecasting

An Archaeological Survey along Leon Creek from Bandera to Babcock Roads, San Antonio, Texas

An archaeological survey was conducted along Leon Creek from Bandera to Babcock roads from July 15 through July 24, and September 14 and 15, 1998, by the Center for Archaeological Research, University of Texas at San Antonio, for the San Antonio Parks and Recreation Department. Three newly identified prehistoric sites were documented within the project area. Sites 41BX1301 and 41BX1303 are not recommended as being eligible for State Archaeological Landmark status nor are they recommended as being eligible for inclusion in the National Register of Historic Places due to the paucity of materials present and to the secondary context in which they were found. The third site, 41BX1302 is located on a T1 terrace of Leon Creek and represents an intact deposit comprised of at least two components, an upper deposit and a buried component. Looting and erosion are disturbing this site and a course of action is strongly recommended to halt the destruction of 41BX1302. It is recommended that 41BX1302 has the potential for State Archaeological Landmark status and for listing in the National Register of Historic Places and that this site should be avoided during the construction of the Leon Creek Greenway. If complete avoidance of 41BX1302 is not possible, testing for site significance is recommended prior to ground-disturbing activities

Evidence of widespread hot plasma in a non-flaring coronal active region from Hinode/XRT

Nanoflares, short and intense heat pulses within spatially unresolved magnetic strands, are now considered a leading candidate to solve the coronal heating problem. However, the frequent occurrence of nanoflares requires that flare-hot plasma be present in the corona at all times. Its detection has proved elusive until now, in part because the intensities are predicted to be very faint. Here we report on the analysis of an active region observed with five filters by Hinode/XRT in November 2006. We have used the filter ratio method to derive maps of temperature and emission measure both in soft and hard ratios. These maps are approximate in that the plasma is assumed to be isothermal along each line-of-sight. Nonetheless, the hardest available ratio reveals the clear presence of plasma around 10 MK. To obtain more detailed information about the plasma properties, we have performed Monte Carlo simulations assuming a variety of non-isothermal emission measure distributions along the lines-of-sight. We find that the observed filter ratios imply bi-modal distributions consisting of a strong cool (log T ~ 6.3-6.5) component and a weaker (few percent) and hotter (6.6 < log T < 7.2) component. The data are consistent with bi-modal distributions along all lines of sight, i.e., throughout the active region. We also find that the isothermal temperature inferred from a filter ratio depends sensitively on the precise temperature of the cool component. A slight shift of this component can cause the hot component to be obscured in a hard ratio measurement. Consequently, temperature maps made in hard and soft ratios tend to be anti-correlated. We conclude that this observation supports the presence of widespread nanoflaring activity in the active region.Comment: 12 figures, accepted for publication on refereed journa

Enthalpy-based Thermal Evolution of Loops: II. Improvements to the Model

This paper develops the zero-dimensional (0D) hydrodynamic coronal loop model "Enthalpy-based Thermal Evolution of Loops" (EBTEL) proposed by Klimchuk et al (2008), which studies the plasma response to evolving coronal heating, especially impulsive heating events. The basis of EBTEL is the modelling of mass exchange between the corona and transition region and chromosphere in response to heating variations, with the key parameter being the ratio of transition region to coronal radiation. We develop new models for this parameter that now include gravitational stratification and a physically motivated approach to radiative cooling. A number of examples are presented, including nanoflares in short and long loops, and a small flare. The new features in EBTEL are important for accurate tracking of, in particular, the density. The 0D results are compared to a 1D hydro code (Hydrad) with generally good agreement. EBTEL is suitable for general use as a tool for (a) quick-look results of loop evolution in response to a given heating function, (b) extensive parameter surveys and (c) situations where the modelling of hundreds or thousands of elemental loops is needed. A single run takes a few seconds on a contemporary laptop

Highly Efficient Modeling of Dynamic Coronal Loops

Observational and theoretical evidence suggests that coronal heating is impulsive and occurs on very small cross-field spatial scales. A single coronal loop could contain a hundred or more individual strands that are heated quasi-independently by nanoflares. It is therefore an enormous undertaking to model an entire active region or the global corona. Three-dimensional MHD codes have inadequate spatial resolution, and 1D hydro codes are too slow to simulate the many thousands of elemental strands that must be treated in a reasonable representation. Fortunately, thermal conduction and flows tend to smooth out plasma gradients along the magnetic field, so "0D models" are an acceptable alternative. We have developed a highly efficient model called Enthalpy-Based Thermal Evolution of Loops (EBTEL) that accurately describes the evolution of the average temperature, pressure, and density along a coronal strand. It improves significantly upon earlier models of this type--in accuracy, flexibility, and capability. It treats both slowly varying and highly impulsive coronal heating; it provides the differential emission measure distribution, DEM(T), at the transition region footpoints; and there are options for heat flux saturation and nonthermal electron beam heating. EBTEL gives excellent agreement with far more sophisticated 1D hydro simulations despite using four orders of magnitude less computing time. It promises to be a powerful new tool for solar and stellar studies.Comment: 34 pages, 8 figures, accepted by Astrophysical Journal (minor revisions of original submitted version

Coronal heating in multiple magnetic threads

Context. Heating the solar corona to several million degrees requires the conversion of magnetic energy into thermal energy. In this paper, we investigate whether an unstable magnetic thread within a coronal loop can destabilise a neighbouring magnetic thread. Aims. By running a series of simulations, we aim to understand under what conditions the destabilisation of a single magnetic thread can also trigger a release of energy in a nearby thread. Methods. The 3D magnetohydrodynamics code, Lare3d, is used to simulate the temporal evolution of coronal magnetic fields during a kink instability and the subsequent relaxation process. We assume that a coronal magnetic loop consists of non-potential magnetic threads that are initially in an equilibrium state. Results. The non-linear kink instability in one magnetic thread forms a helical current sheet and initiates magnetic reconnection. The current sheet fragments, and magnetic energy is released throughout that thread. We find that, under certain conditions, this event can destabilise a nearby thread, which is a necessary requirement for starting an avalanche of energy release in magnetic threads. Conclusions. It is possible to initiate an energy release in a nearby, non-potential magnetic thread, because the energy released from one unstable magnetic thread can trigger energy release in nearby threads, provided that the nearby structures are close to marginal stability

Archaeological Testing at Crook\u27s Park in San Marcos, Hays County, Texas

Archaeological testing at site 41HY261 was conducted from March 26-31, 1997, by the Center for Archaeological Research (CAR) of The University of Texas at San Antonio, for the city of San Marcos Parks and Recreation Department. Testing demonstrates that 41HY261 contains deep, intact, stratified subsurface cultural deposits. Collectively, the artifacts recovered to date represent ca. 5,000 years of hunter-and-gatherer activity. Site 41HY261 has the potential to contribute significantly to the prehistory of the region, and is therefore recommended as eligible for nomination to the National Register of Historic Places

Archaeological Testing and Monitoring of a Service Drive at Mission San Juan Capistrano, San Antonio, Texas

Archaeological testing for the installation of a new service drive and monitoring the removal of the existing service drive at Mission San Juan Capistrano was conducted in November, 1997 and October, 1999 respectively, by the Center for Archaeological Research (CAR) at The University of Texas at San Antonio (UTSA) for the National Park Service (NPS). The results of the testing and monitoring indicated that no intact Colonial midden deposits were observed, and few Colonial artifacts were recovered within the proposed service drive right-ofway. Three post-Colonial trash deposits were documented within the project area; however, due to the disturbed nature of these deposits which contain stratigraphically mixed nineteenth and twentieth century materials the research potential of such deposits is considered minimal and it is recommended that no further archaeological investigations are required prior to the construction of the service drive. Also included as an Appendix to this report is a brief analysis of an isolated burial discovered during a monitoring project at Mission San Juan in 1999. These remains have since been reinterred by NPS