ED43A-0260 1340h
The Earth's Bow Shock: The Outermost Terrestrial Boundary
The solar wind is a continuous stream of charged particles originating from the Sun, and approaches the Earth with a speed of 300 - 800 km/s. This stream also carries the magnetic field of solar origin known as the interplanetary magnetic field. The first sign of an interaction of the solar wind with the Earth's magnetic field is a standing shock wave in space on the Sun-facing side. This shock wave is like the sonic shock wave caused by an aircraft flying with supersonic speed. This bow shock slows down the solar wind, deflects particles around the Earth's magnetosphere, which acts as a gigantic shield against cosmic particles. In this project we have analyze data from the CLUSTER spacecraft crossing the Earth's bow shock on their orbit around the Earth. Investigating numerous bow shock crossings we have surveyed of plasma properties upstream and downstream and related these parameters to conservation laws. The survey also covers the distinct regions: the perpendicular and the parallel site of the Earth's bow shock where we investigated the differences in topology and the reflection properties of this collisionless shock. This work represents the efforts of two high school students who participated in the UNH program Project SMART during the summer of 2004.
ED43A-0261 1340h
Response of the Terrestrial Magnetosphere to an Interplanetary Shock
We use global magnetohydrodynamic (MHD) simulations to analyze the response of the terrestrial magnetosphere to an interplanetary pressure discontinuity. We perform time-of-flight analyses on the discontinuity as it propagates through the magnetosphere. We find that as the disturbance interacts with the bow shock, new disturbances (a fast mode wave and another contact discontinuity) are launched in the magnetosheath. These new waves are further reflected/transmitted when they make contact with the magnetopause. Eventually, the magnetosphere reaches a new steady state configuration, with the bow shock and magnetopause at new locations (slightly Earthward) which are consistent with the new solar wind pressure.
ED43A-0262 1340h
Hydraulic Characteristics of the San Gregorio Creek Drainage Basin, California: a Preliminary Study.
Population pressures within the greater San Francisco Bay Area are forcing development into nearby rural communities, and are impacting local environments. This study of the San Gregorio Creek Watershed is designed as a baseline for evaluating the effect increasing development within the drainage basin has on its river system. We hope to provide evidence for that impact through laboratory and field studies that provide a snap-shot of this drainage basin's current characteristics. The San Gregorio Creek watershed, in the Coast Ranges, is located in the southwestern portion of San Mateo County, California. It drains the western slopes of the Santa Cruz Mountains, in the Coast Ranges into the Pacific Ocean at the town of San Gregorio. Most of its fingertip tributaries flow into the trunk from the north and west, with elevations as high as 2050 feet. The watershed includes an area of approximately 51.6 square miles and San Gregorio Creek, the trunk stream, is roughly 12 miles long. San Gregorio Creek is a fourth order perennial stream. It is fed by a number of major tributaries, the largest of which are Alpine, Mindego, and La Honda creeks. The U.S. Geological Survey maintains a stream gauging station for San Gregorio Creek at the town of San Gregorio, where it has been monitoring stream flows for more than 30 years through its Water Resources Department. The resulting data indicate a mean discharge of 36.4 cfs. Map studies of hydraulic geometry for the drainage basin reveal geometric characteristics for San Gregorio Creek that coincide with similar streams in comparable climatic and environmental settings. Stream table studies are used to further investigate fundamental stream processes. Field studies at selected reaches throughout the drainage basin will document hydraulic characteristics. The results of this study will contribute to more comprehensive studies demonstrateing channel response to changing environmental conditions.
ED43A-0263 1340h
Soil-gas Radon Emanation in Active Hydrothermal Areas at Lassen Volcanic Center, Northern California
Located along the Southern Cascade Range in Northern California, the Lassen Volcanic Center is one of the youngest major Cascade volcanoes. Aside from Mount Saint Helens, Lassen is the only Cascade volcano to erupt in the 20th century. In an effort to assess outgassing in and around Lassen, and to provide information that will contribute to a better understanding of its hydrothermal system, we have conducted detailed soil-gas radon emanation surveys in several active hydrothermal areas, which possess bubbling mud pots, steaming fumaroles, and boiling hot springs. Dozens of measurements have been made in each of these areas, which are then used to create maps that indicate areas of high outgassing. These maps are then employed to assess the degree to which volcanic and other gases are currently being emitted at Lassen, as well as to investigate patterns associated with these emissions. The mean of measurements made in a specific survey area is considered to represent the average radon flux in that area. Individual values exceeding the mean plus one standard deviation are considered to represent anomalously high emanation, while values less than the mean minus one standard deviation represent anomalously low emanation. Based on preliminary analysis of data collected so far, significant outgassing occurs along well-defined, northwest-southeast trending elongate zones in several areas. Values obtained in these zones are as much as three times background radon flux. These zones are believed to contain fractures that act as pathways for migrating gases. The results of studies conducted thus far indicate that further emanation surveys will generate very useful information.
ED43A-0264 1340h
The Different Faces of San Francisco's Ocean Beach: Analyzing Sand Size and Beach Shape
Ocean Beach is located along the western edge of San Francisco adjacent to the Pacific Ocean. Erosion along the southern part of the beach is threatening a nearby highway and water treatment plant. To better understand this beach and the processes that form it, our SF-ROCKS research group collected data from seven locations along its length. We used an auto-level surveying instrument to measure beach profiles and we collected sand samples that were measured using sieves and a sieve shaker. We plotted profiles and grain-size data using Excel and Surfer software. The sediment is mostly fine sand, and the means of all samples range between 0.19-0.26 mm. There may be little variation along the beach because only small sand grains have survived the long journey from their Sierra Nevada source. Profile shape does vary along the beach. The profile at the northern end is about three times wider than the profile at the southern end. The northern profile is flatter overall, but all profiles had a steep beach face in August, when the data were collected. The differences in beach profiles may be related to position relative to the offshore bar, which appears to provide sand to the northern part of the beach. Our group will collect more data in November to see what changes have occurred after the large-wave season has begun. We will use Surfer software to compare summer and fall profiles, to see where sediment has been added and where sediment has been removed. We will also compare our results to the data collected by Dr. Patrick Barnard and his research group at the U.S. Geological Survey, who are using an All-Terrain Vehicle to measure beach profiles and a camera to measure sediment size. We will use our analysis of beach variations to make recommendations for reducing beach erosion.
http://sf-rocks.sfsu.edu/
ED43A-0265 1340h
Abundance, Health and Status of Sand Crabs at Ocean Beach, San Francisco: Comparisons From two Summers, 2003 and 2004
Interns from the California Academy of Sciences in San Francisco monitored Pacific mole crabs, Emerita analoga, commonly known as sand crabs, at Ocean Beach, San Francisco for the second consecutive summer. Comparisons from two data sets revealed trends in crab abundance, size and location. Changes in abundance and location may have been related to water temperature and predation. Dissections of random crabs from all gender classes allowed inspection of parasitism on the crabs. The dissections revealed increased numbers of parasites in larger crabs (especially females with eggs) and in crabs collected later in the summer season. Crab parasitism may be connected to population changes of species predating the sand crabs.
ED43A-0266 1340h
Drinking Water Contamination Due To Lead-based Solder
The presence of lead in drinking water creates many health hazards. Exposure to lead-contaminated water can affect the brain, the central nervous system, blood cells, and kidneys, causing such problems as mental retardation, kidney disease, heart disease, stroke, and death. One way in which lead can contaminate our water supply is through the use of lead solder to join pipes. Lead solder was widely used in the past because of its ease of application as well as its low cost. Lead contamination in residential areas has previously been found to be a particularly serious problem in first-draw samples, of water that has sat stagnant in pipes overnight. To investigate the time-dependence of drinking water lead contamination, we analyzed samples taken hourly of water exposed to lead solder. While our preliminary data was insufficient to show more than a rough correlation between time of exposure and lead concentration over short periods (1-3 hours), we were able to confirm that overnight exposure of water to lead-based solder results in the presence high levels of lead. We also investigated other, external factors that previous research has indicated contribute to increased concentrations of lead. Our analysis of samples of lead-exposed water at various pH and temperatures suggests that these factors can be equally significant in terms of their contribution to elevated lead concentration levels. In particular, water that is slightly corrosive appears to severely impact the solubility of lead. As this type of water is common in much of the Northeast United States, the presence of lead-based solder in residential areas there is especially problematic. Although lead-based solder has been banned since the 1980s, it remains a serious concern, and a practical solution still requires further research.
ED43A-0267 1340h
Sustainable Seas Student Intertidal Monitoring Project at Duxbury Reef in Bolinas, CA
The Sustainable Seas Student Monitoring Project at the Branson School in Ross, CA has monitored Duxbury Reef in Bolinas, CA since 1999, in cooperation with the Farallones Marine Sanctuary Association. Goals of the project include: 1) To monitor the rocky intertidal habitat and develop a baseline database of invertebrates and algal density and abundance; 2) To contribute to the conservation of the rocky intertidal habitat through education of students and visitors about intertidal species and requirements for maintaining a healthy, diverse intertidal ecosystem; and 3) To increase stewardship in the Gulf of the Farallones National Marine Sanctuary. Student volunteers complete an intensive training course on the natural history of intertidal invertebrates and algae, identification of key species, rocky intertidal ecology, interpretation and monitoring techniques, and history of the sanctuary. Students conduct two baseline monitoring surveys three times per year (fall, winter, and late spring) to identify and count key invertebrate and algae species. During four seasons of monitoring (2000-2004), the density of black turban snails, Tegula funebralis, showed very low density in the high intertidal zone the winter of 2000-2001 with very little seasonal variability in the remainder of its range and throughout the period monitored. Most algae species had consistently higher densities in the northern (A) transects than the more accessible southern (B) transects. To test the reliability of the student counts, replicate counts of all species were performed. Replicate counts for invertebrate species within the same quadrat along the permanent transects revealed a very small amount of variability, giving us confidence that our monitoring program can provide reliable data. Student volunteers helped to design and install a rocky intertidal information kiosk to greet visitors at the entrance of Duxbury Reef. The kiosk includes pictures and natural history information on key intertidal species as well as tidepooling etiquette and continues to serve as a focal point of education and interest for visitors to Agate Beach. Students have led annual intertidal walks for the public at Duxbury Reef since 2001.
ED43A-0268 1340h
Studies of Contrasting Summer Weather Patterns in Northern California
The weather of San Francisco and the California coast during the summer tends to be cool and cloudy for most of the day. The summer winds come mostly from the ocean and can be very strong during the afternoon. By September, the weather occasionally turns warmer, with mostly clear skies and low humidity. During the warm periods, the winds tend to blow offshore, from the land toward the ocean. In this project, we monitor the weather conditions in northern California from August to October 2004 to better understand how and why the weather in San Francisco changes from cloudy and cool to clear and warm and back again. We analyze the regional patterns of atmospheric pressure and cloud cover using weather data and satellite pictures available at the Weather Graphics and Simulation Laboratory at San Francisco State University and other data sources available over the Internet. Special case studies of particularly warm/clear and cool/cloud events will be discussed.
ED43A-0269 1340h
Correlation Between Surface Area and Dissolving Properties of Lead - A Step in the Investigation of Higher than Standard Lead Concentration in Drinking Water in Washington, D.C.
Several recently published articles by the Washington Post exposing the alarming concentration of lead in drinking water from schools and homes in the Washington D.C. area sparked our interest in the correlation between lead-containing materials used in plumbing and rate of lead solubility. Elementary children who attend schools in various regions of the District were contacted by San Francisco Bay Area- based high school students who are participants in the NSF-sponsored Environmental Science Information Technology Activities (ESITA) project. After receiving a thorough explanation of required sampling procedures, the elementary school children sent 500 ml water samples from their homes and schools to Berkeley along with information on the locations from which the water samples were collected. These water samples were analyzed for lead content at the Environmental Science Research Program laboratory at Lawrence Hall of Science. The majority of the samples contained more than 15 ppb of lead, which is the EPA action level. We hypothesize that there are three possible sources of lead in the drinking water: 1) lead pipes in the water main; 2) lead pipes in the service main; and 3) lead soldering that was often previously used to connect piping. We chose to investigate the effect of lead-based solder on the overall lead concentration in water. Using a soldering iron, we melted lead solder to create discs ranging from one to five centimeter diameter and one to thirty-six grams of mass. These discs were then placed into a beaker with 500 ml of 7.1pH distilled water and allowed to stand for 48 hours. At the end of 48 hours, the water samples were prepared for analysis using the EPA approved lead-dithizone procedure. Results showed an exponential relationship between disc surface area and the concentration of dissolved lead measured in the sample. Therefore, lead-based solder can represent a possible major source of lead contamination.
ED43A-0270 1340h
Analysis of Serpentine Soils in the Presidio of San Francisco, CA
Serpentine soils and their associated serpentine prairie habitats are extremely rare. Within California, serpentine-derived soil comprises only 2,860 km2 of the State and represents less than 1% of the total land surface. The Presidio, a National Park located in San Francisco, CA, hosts several patches of serpentine habitat, which are currently being encroached by non-native plant species. The serpentine soils support threatened and endangered plant species, and are defined by the geochemical properties inherent to the soils. We analyzed the physical and geochemical properties of soils within the West Grassland area of the Presidio to characterize the distribution of serpentine soils across the study site. Our goal is to further understand sub-surface conditions, including depth to bedrock and changes in lithology with depth. Nine locations throughout the West Grassland portion of the Park were randomly selected and hand augured to a depth of 3-5 feet, and soil samples were obtained at 1-foot intervals. Physical properties including color and texture were obtained in the field. Soils overlying serpentine bedrock were found to have a clayey-loam texture. Depth to bedrock was shallow in hilly areas underlain by resistant, hill-forming serpentine bedrock. Auguring further revealed that topographic lows correlated to changes in lithology from soils that were serpentine-derived to sandy loams consistent with sand dune deposits found elsewhere in the vicinity. The geochemistry of selected samples is being analyzed for namely pH, nitrogen, calcium, and magnesium concentrations. Geochemical data will be compared to an existing database and a statistical analysis of the geochemical data will be used to correlate physical and textural data.
ED43A-0271 1340h
Probing the Dayside Magnetosphere: Measurements by ACE Soon After Launch, August 25, 1997
Spacecraft ACE was launched on Aug. 25, 1997. In this poster we shall examine magnetic field data obtained by this spacecraft as it crossed through the dayside magnetosphere, entered a region around the magnetosphere called the magnetosheath (twice), and eventually crossed a weak bow shock. Then it entered the interplanetary medium characterized by a slow solar wind and a lower-than-usual magnetic field. Another craft called WIND was making measurements inside the solar wind. In this presentation we shall investigate the various regions of the Earth's dayside magnetosphere and magnetosheath encountered by ACE, highlighting their different magnetic properties. Finally we make comparisons between ACE magnetic field data and WIND solar wind data. The work represents the efforts of two New Hampshire high school students who participated in the UNH program Project SMART during the summer of 2004. Project SMART is an E/PO effort run by UNH to bring gifted high school students into the research environment and to motivate them to pursue a scientific career.
ED43A-0272 1340h
Wave and Plasma Simulations
Rapidly moving streams of plasma emanate from the Sun and team with long magnetized waves which are called Alfven waves. The waves have sharp edges showing evidence of nonlinear wave steepening. They are also arc-polarized wherein the total magnetic intensity is a constant but the magnetic field direction sweeps back and forth along a circular arc like a wiper-blade. The solar-wind plasma is nearly collisionless and shows evidence of preferred ion heating. There are also distinct beams of various atoms which stream relative to the main component of solar-wind protons. The detailed individual motions of the ions are important to follow in order to understand the behavior of the plasma and waves. We employ hybrid numerical simulations using particle ions and fluid electrons. We present results from 3 simulation projects which will demonstrate how small but resonant forces can cumulatively lead to large changes: (1) Small amplitude and linearly polarized Alfven waves propagating parallel to the background magnetic field nonlinearly steepen. We have measured the time of steepening as a function of the ratio of plasma to magnetic pressure, especially for ratios of order unity where analytical calculations cannot determine the steepening time. (2) Arc-polarized Alfven waves can propagate without changing form, but we show that small disturbances can lead to their decay into new waves. (3) Beams of ions streaming relative to one another can drive up waves from the smallest starting disturbances. We show that this slows the relative streaming speed below a threshold where the speed becomes steady. This work was completed at the University of New Hampshire through the Science and Mathematics Achievement through Research Training (SMART) program.