Study of low frequency hydromagnetic waves using ATS-1 data

The low-frequency oscillations observed at ATS-1 are the result of an attempt by the magnetospheric plasma to conserve its angular momentum as it convects through the magnetosphere

Uncovering Multiple Populations with Washington Photometry: I. The Globular Cluster NGC 1851

The analysis of multiple populations (MPs) in globular clusters (GCs) has become a forefront area of research in astronomy. Multiple red giant branches (RGBs), subgiant branches (SGBs), and even main sequences (MSs) have now been observed photometrically in many GCs. UV photometry has been crucial in discovering and analyzing these MPs, but the Johnson U and the Stromgren and Sloan u filters that have generally been used are relatively inefficient and very sensitive to reddening and atmospheric extinction. In contrast, the Washington C filter is much broader and redder than these competing UV filters. Here we investigate the use of the Washington system to uncover MPs using only a 1-meter telescope. Our analysis of the well-studied GC NGC 1851 finds that the C filter is both very efficient and effective at detecting its previously discovered MPs in the RGB and SGB. Remarkably, we have also detected an intrinsically broad MS best characterized by two distinct but heavily overlapping populations that cannot be explained by binaries, field stars, or photometric errors. The MS distribution is in very good agreement with that seen on the RGB, with ~30% of the stars belonging to the second population. There is also evidence for two sequences in the red horizontal branch, but this appears to be unrelated to the MPs in this cluster. Neither of these latter phenomena have been observed previously in this cluster. The redder MS stars are also more centrally concentrated than the blue MS. This is the first time MPs in a MS have been discovered from the ground, and using only a 1-meter telescope. The Washington system thus proves to be a very powerful tool for investigating MPs, and holds particular promise for extragalactic objects where photons are limited.Comment: 25 pages, 10 figure

Study of low frequency hydromagnetic waves using ATS-1 data

Summaries are presented on the use of ATS-1 data to analyze low frequency oscillations of the earth's magnetic field and hydromagnetic wave polarization

The dominant mode of standing Alfven waves at synchronous orbit

Low-frequency oscillations of the earth's magnetic field recorded by the UCLA magnetometer on board ATS-1, have been examined for the six-month interval, January-June, 1968. The initial interpretation, that these oscillations represent the second harmonic of a standing Alfven wave, has been re-examined, and it is concluded that this hypothesis must be withdrawn. Using evidence from OGO-5 and ATS-5, as well as the data from ATS-1, it is argued that the dominant mode at the synchronous orbit must be the fundamental rather than the second harmonic. From 14 instances when the oscillations of distinctly different periods occurred during the same time interval at ATS-1 it is concluded that higher harmonics can exist. The period ratio in 7 of the 14 cases corresponds to the simultaneous occurrence of the second harmonic with the fundamental, and 4 other cases could be identified as the simultaneous occurrence of the fourth harmonic with the fundamental

Ultracold neutral plasma expansion in two dimensions

We extend an isothermal thermal model of ultracold neutral plasma expansion to systems without spherical symmetry, and use this model to interpret new fluorescence measurements on these plasmas. By assuming a self-similar expansion, it is possible to solve the fluid equations analytically and to include velocity effects to predict the fluorescence signals. In spite of the simplicity of this approach, the model reproduces the major features of the experimental data

Geosciences for Elementary Educators: A Course Assessment

Geosciences for Elementary Educators engages future elementary teachers in a hands-on investigation of topics aligned with the third and fifth grade Earth/Space Science and Scientific Inquiry benchmarks of the Oregon Content Standards. The course was designed to develop the content background of elementary teachers within the framework of the science described in the content standards, to provide an opportunity for future teachers to explore the content area in relation to what takes place in the classrooms of elementary schools, and to initiate a community of learners focused on teaching science to elementary students. The course focused on four themes: the classroom teacher as an activity and curriculum developer using diverse resources to keep the content current and alive; the classroom teacher as educator dealing with the diverse backgrounds of students in a developmentally appropriate manner; the classroom teacher as reflective practitioner exploring the links among pedagogy, content, and student learning; and, the classroom teacher as citizen staying current with emerging policy issues and debates that impact education. In a course where process is extremely important, participants are assessed on what they can do with content and process knowledge through preparing lesson plans, presenting lessons in a simulated classroom environment, and developing a portfolio and journal. Lesson plans demonstrate participant understanding of inquiry, using models, deductive and inductive approaches, links between communication skills and content knowledge, and effective use of technology, including the Internet. For each topic, the mixture of demonstration, experimentation, inquiry, and lecture models are explored through investigation, discovery, and analysis

Study of low frequency hydromagnetic waves using ATS-1 data

Low frequency oscillations of the magnetic field at ATS-1 were analyzed for the 25 month data interval, Dec., 1966 through 1968. Irregular oscillations and those associated with magnetic storms were excluded from the analysis. Of the 222 events identified, 170 were found to be oscillating predominantly transverse to the background magnetic field. The oscillations were observed to occur most frequently in the early afternoon hours. They also seemed to occur more frequently during Dec., Jan., and Feb. than at any other time of the year. During a given event, the frequency was fairly constant. The event duration varied between a minimum of 10 min. and a maximum of 14 hrs and 26 min. During a given event the amplitude varied

Modelling Air Bubble Entrainment by Plunging Breakers

The aeration characteristics of plunging breakers in the deep sea are described using a similarity with plunging jets. A large two-dimensional jet facility provides new experimental data on the number and sizes of the entrained bubbles and the resulting air-water interface area. The results enable new calculations of the air-water gas transfer contribution of the plunging breakers. The results are consistent with experimental field observations and emphasise the role of plunging breakers in the aeration process of the oceans