Analysis of UVSP Dopplergrams and magnetograms and their calibration using the orbital velocity of the SMM spacecraft

To infer velocities and longitudinal magnetic fields from Dopplergram and magnetogram signals obtained by the Ultraviolet Spectrometer and Polarimeter on the Solar Maximum Mission, one must know the width of the observed emission line. Although the instrument control system provided for a line-width calibration feature which utilized periodically commanded shifts of the line, it was not always used. However, it is possible to use the time-varying line-of-sight component of the orbital velocity of the spacecraft as a means of calibrating the line width for each pixel in a raster. Such a method based on a least-squares fit of the observed Doppler signal to the line-of-sight component of the spacecraft velocity is described here; it then applied to magnetogram observations. As background, the theoretical expressions for the interpretation of the observed Dopplergram and magnetogram signals for both wide and narrow exit slits are also summarized.     

On the physics of a long decay X-ray event

A long decay X-ray event (LDE) which appeared as an expanding loop system on the solar limb on 13–14 August 1973 was well observed temporally (with Skylab ATM S056 and S054 X-ray telescopes) and spectrally (with S082A XUV spectroheliograph). We summarize and supplement the extensive discussion in the literature. In addition, a one-dimensional hydrodynamic study is undertaken to investigate both increasing and decreasing phases of the event. Results indicate that the inferred temperature gradients along the loops during the heating phase are consistent with unrestricted dynamic and conductive flows along magnetic field lines. Furthermore, we conclude that it cannot be unequivocally stated that enhanced emission at the tops of loops is due to pressure gradients along the field lines. Finally, the large emission measure variations in the 10⁵–10⁶ K plasma during the event's decline may be due simply to the temperature dependence of radiative decay within a multi-loop configuration.Presently a NRC Associate at NASA/MSFC, Space Sciences Laboratory, MSFC, Ala. 35812, U.S.A.Presently at NASA/MSFC, Space Sciences Laboratory, MSFC, Ala. 35812, U.S.A.     

Computer model of wind, waves, and longshore currents during a coastal storm

A mathematical model has been developed to forecast or hindcast wind, waves, and longshore currents during the passage of a coastal storm. Storm intensity is a function of the barometric pressure gradient which is modeled by rotating an inverted normal curve around the center of an ellipse. The length and orientation of the major and minor axes of the ellipse control the size and shape of the storm. The path of the storm is determined by a sequence of storm positions for the hindcast mode, and by interpolated positions assuming constant speed and direction for the forecast mode. The site location, shoreline orientation, and nearshore bottom slope provide input data for the shore position. The geostrophic wind speed and direction at the shore site are computed from the latitude and barometric pressure gradient. The geostrophic wind is converted into surface wind speed and direction by applying corrections for frictional effects over land and sea. The surface wind speed and direction, effective fetch, and wind duration are used to compute wave period, breaker height, and breaker angle at the shore site. The longshore current velocity is computed as a function of wave period, breaker height and angle, and nearshore slope. The model was tested by comparing observed data for several coastal locations with predicted values for wind speed, wave period and height, and longshore current velocity. Forecasts were made for actual storms and for hypothetical circular and elliptical storms.     

Starspot modelling of the RS CVn binary HK lacertae

Investigating more than 270 nightly mean magnitudes of the long-period RS CVn binary HK Lac, we can draw some conclusions about the nature of its complicated light variations. The mean brightness, the apparent photometric period, and the shape of the light curve all show strong variations. Analysis with a starspot model, assuming two large spots and a general uniform spottedness, indicates two comparably large spots which appear to have maintained their separate identities for the last 15 yr and drifted in longitude separation from each other smoothly by only about 45°. The phase of the two spots indicates both are rotating very nearly synchronously with the orbital motion, one slightly (0.025%) faster and the other slightly (0.080%) slower. the latitudes of the two spots, one farther above the equator and one closer to the equator, are consistent with solar-type differential rotation and yield an estimate of 25±12° for the co-rotating latitude. A correlation between mean spot latitude and instantaneous photometric period yields another estimate of 31±2°, in agreement with the first.     

The Application of Conditional Beta Density Functions to Model Time- Delay Measurement Errors

A conditional beta probability density function is employed to model time-delay measurement errors associated with sensors used in triangulation ranging applications. This type of density function is less restrictive than the beta density used in previous analyses in that end points can be extended out beyond the imposed range constraints and data editing is allowed before range calculations. The resulting conditional range density function is computed along with the mean and variance. Comparisons are made of the pertinent range statistics associated with the beta and conditional beta density functions. Finally, the conditional beta density function range statistics are compared with those obtained from a gated Gaussian density function for equivalent values of time-delay measurement error standard deviation. The Gaussian statistics are determined via Monte-Carlo simulation.     

Lunar cartography with the Apollo 17 Alse radar imagery

Lunar position differences between thirteen lunar craters in Mare Serenitatis were computed from VHF radar-imagery obtained by the Lunar Sounder instrument flown on the Apollo 17 Command Module. The radar-derived position differences agree with those obtained by conventional photogrammetric reductions of Apollo metric photography. This demonstrates the feasibility of using the Apollo Lunar Sounder data to determine the positions of lunar features along the Apollo 17 orbital tracks. This will be particularly useful for western limb and farside areas, where no Apollo metric camera pictures are available.This paper presents the results of one phase of research carried out at the Jet Propulsion Laboratory, California Institute of Technology, under Contract No. NAS 7-100, sponsored by the National Aeronautics and Space Administration.     

Geochemical response of acid groundwater to neutralization by alkaline recharge

Solute transport and chemical neutralization (pH 3 to 7) within a shallow heterogeneous aquifer producing acid mine drainage (AMD) are examined at an abandoned surface coal mine in West Virginia. The aquifer is undergoing partial neutralization by mixing with alkalinity from a leaking sludge disposal pond, extending in preferential zones controlled by aquifer heterogeneity. Hydraulic heads interpolated from wells indicate leakage from a central alkaline (pH 7.1, 0.72 meq/L alkalinity) sludge pond is a principal source of recharge. Chemically-conservative sodium, added to AMD during treatment and leaked into the aquifer with the sludge, develops a dispersion plume over a restricted portion of the aquifer that correlates with pH, hydraulic head, and dissolved metals distributions. Concentrations of aluminum, iron, sulfate and acidity display higher concentrations downgradient from the pond as sludge alkalinity is consumed along flow paths. Before reaching springs, most dissolved iron is oxidized and hydrolyzed, likely precipitating in the aquifer as a ferric hydroxide or hydroxysulfate phase. The spatial pattern of iron and aluminum concentrations suggests accelerated oxidation caused by gas transport along the outer slopes of the spoil. Dissolved aluminum concentrations increase with total acidity, suggesting that dissolution of silicate minerals results from acidity released by iron hydrolysis. Neutralization reactions and higher pH are favored in more highly permeable portions of the spoil, where ferrihydrite and aluminum hydroxysulfate minerals (such as basaluminite) are supersaturated. In acid-producing zones at pH < 4.5, jurbanite is near equilibrium and an aluminum-sulfate phase with similar properties may limit aluminum concentrations, but become undersaturated in zones of advancing neutralization. At this particular site, ferrous iron produced by pyrite oxidation is almost completely oxidized over short transport distances, allowing hydrolysis of iron and aluminum should sufficient alkalinity be added to these acid waters.     

The Acoje Block Platiniferous Dunite Horizon, Zambales Ophiolite Complex, Philippines: Melt Type and Associated Geochemical Controls

Abstract: The Zambales Ophiolite Complex, a supra-subduction zone ophiolite, is made up of the mid-ocean ridge-related Coto block and the island arc-related Acoje block. This crust-mantle sequence hosts platinum-group elements (PGE) in the Acoje block. The melts responsible for the PGE-bearing nickel sulfide and chromitite deposits are of magmatic origin characterized by high-MgO basalt to boninitic composition which, being second or third-stage melts, carry higher PGE budgets. Metal ratio diagrams, utilizing base and precious metals, reveal that the distribution and deposition of the PGE in the Acoje block are affected by olivine, chromite and sulfide crystallization. The generation, accumulation and segregation of the PGE, oxide and sulfide minerals from the melts are governed by the combined factors of high degrees of partial melting, multiple melt replenishment with concomitant magma mixing and fractional crystallization. Although previous sulfide segregation events could have occurred below the PGE-bearing nickel sulfide horizon as shown by the Ni/Cu (>1), the Cu/Pd and Ni/Pd strongly suggest that the main platiniferous zone is confined within the Acoje block transition zone dunite.     

Healthier Geographies: Mediating the Gaps between the Needs of People Living with HIV and AIDS and Health Care in Chiang Mai,Thailand

In this article, I contribute to our understanding of the plurality of approaches that construct the geographies of health care through an examination of the distribution of health care services for people living with HIV/AIDS (PLWHA) in Chiang Mai Province, Thailand. In particular, I focus on the development of a network of support groups for PLWHA in order to examine the differences in the sociospatial organization of these groups, the practices of social actors participating in the groups' activities, and how these activities are mediated through place‐based social relations. The first section of the article analyzes the spatial distribution of PLWHA support groups in relation to the distribution of AIDS cases over two time periods, 1994 and 1997. The second section goes below the surface of the spatial distribution, examining similarities and differences in PLWHA support groups through an analysis of survey data collected on thirty‐five groups in 1997. The final section deepens this examination through an analysis of ethnographic data collected on the outreach efforts of one nongovernmental organization (NGO) and one PLWHA support group with which it worked. Each section offers opportunities for the extension of our understanding of the development of PLWHA support groups, their distribution in relation to the spread of AIDS cases, and their place‐based meanings.