The ability of the most recent version of PRISM (1.6b) to accurately specify real-time TEC values was validated against "ground truth" TEC data obtained by the Ocean TOPography EXperiment (TOPEX). PRISM "driver" data came from a variety of ground- and space-based sources, including the Digital Ionospheric Sounding System (DISS - critical frequencies and heights) and the International GPS Service for Geodynamics (IGS - TEC values). The TEC "ground truth" data were obtained by the NASA dual-frequency radar altimeter on-board the TOPEX satellite during 1995. TEC output from 720 runs of PRISM 1.6b was compared with corresponding values observed by the TOPEX satellite along multiple orbital tracks. Comparison points were chosen to be representative of different seasons (equinox, summer, and winter), local times (0000L, 0600L, 1200L, and 1800L), and latitudes (30\deg N and equatorial). The results of PRISM-TOPEX chi- square goodness-of-fit tests are presented to quantify the accuracy of PRISM across seasons, local times, latitudes, and varying subsets of input data.
[CA.02] Unfolding the high energy electron flux from CCRES fluxmeter measurements
B. D. McKellar, K. A. Mathews (Air Force Institute of Technology)
The Combined Release and Radiation Effects Satellite (CRRES) was launched on 25 July 1990 to collect measurements in the earth's radiation belts. One instrument, the High Energy Electron Fluxmeter (HEEF), measured the flux of electrons in 10 channels with energies between 1 MeV and 10 MeV. The channel sensitivities, R_i (E), have been calibrated and partially re- calibrated. We explore the errors introduced in unfolding the electron flux spectrum from the channel measurements and the propagation and growth of calibration and measurement errors. Using numerical experimentation, we fold the responses with known spectra to obtain simulated measurements, add random measurement and calibration errors, and unfold the spectra as 10-bin histograms which are compared with histograms of the original spectra. We observe that the shape (of the response functions) is the major factor in the growth of error in unfolding and in determining which type of error dominates the unfolding process. We conclude that successful unfolding of the electron flux is critically dependent upon the shape of the response functions. The re-calibration of the HEEF must be accurately completed if reliable unfolds of the high energy electron flux are to be obtained.
[CA.03] The Analytic Solution to Burgers Equation in 3-D Curvilinear Coordinates
Steven Nerney (Physics, Ohio University, Lancaster, OH 43130), Edward Schmahl (Astronomy Department, University of Maryland, College Park, MD 20742)
Burgers' equation is a well-known example of a non-linear partial differential equation whose solution can be constructed from a linear partial differential equation. It is, to the best of our knowledge, the only such example. Much of the interest in this equation arises because it is a very simple form of the Navier-Stokes equation in the one-dimensional, cartesian, time-dependent, compressible, viscous limit. It has been used in studying the decay of free turbulence. The importance of the equation is due to the non-linear advection term which allows the calculation of the modification of the velocity due to the exchange of momentum between a variety of different length scales. Burger's equation is the simplest type that shows the complicated interplay between the non-linear steepening and diffusion of a wave. In this study, we examine extensions of the basic class of solutions of the vector Burgers' equation to three dimensions and to arbitrary orthogonal curvilinear coordinate systems.
[CA.04] CO Photodissociation in Circumstellar Envelopes
Steven Doty (The Johns Hopkins University), Sandra Doty (GMI Engineering amp; Management Inst.)
The outflowing circumstellar envelopes (CSEs) of evolved stars are rich chemical environments, with over 40 different molecular species observed to date. Averaged over the galaxy, evolved stars return about one solar mass of reprocessed material to the interstellar medium per year, and thus account for a major source of elemental and chemical processing from one generation of stars to the next. Key to understanding this reprocessing is the photodissociation of one of the most abundant and easily observable molecular species -- carbon monoxide (CO). Due to its ubiquity in CSEs and its easy observability, CO has long been the molecule of choice for observations to better understand these sources.
We have self-consistently solved for the photodissociation of CO in CSEs, including for the first time the effects of scattering by small (a \sim 0.1\mum) dust grains. We find that these dust grains have a measurable effect on the dissociation of CO, and hence on our understanding of circumstellar envelopes.
In particular, the temperature structures, mass loss rates, and chemistry of these source are all tied to our understanding of the radial extent of CO in CSEs.
If time permits, we will present preliminary results on how we are using these new CO photodissociation results along with self-consistent chemical and radiative transfer models to re-analyze the mass loss rates for 50 evolved stars, with an eye toward better understanding the role of evolved stars in replenishing the interstellar medium.
[CA.05] Detailed Modeling of Dense Molecular Clouds
Steven Doty, David Neufeld (The Johns Hopkins University)
Observationally, dense molecular interstellar clouds have long been identified as the sites of star formation. However, modeling and understanding these regions is challenging. In particular, for such a cloud to collapse, it must cool and radiate away its gravitational potential energy. However, the ability to radiate depends upon the chemical composition, which (in turn) depends upon the thermal structure.
In order to better understand these dense molecular clouds, we have constructed a self-consistent detailed model for the thermal balance, chemistry, and radiative transfer in these sources. In this paper, we discuss our model, present general results from our work, and if time permits discuss our model in light of current and upcoming observations from the Infrared Space Observatory and the Submillimeter Wave Astronomy Satellite.
[CA.06] The Spectroscopy of Excited States of ^8He
T.N. Massey, S.M. Grimes (Ohio University, Athens, Ohio), T. Stolla, H.G. Bohlen, B. Gebauer, W. von Oertzen, A.N. Ostrowski, M. Wilpert, T. Wilpert (Hahn-Meitner-Institut, Glienicker Strasse 100, D-14109 Berlin,Germany), R. Kalpakchieva (Flerov Laboratory of Nuclear Reactions, Joint Institut for Nuclear Research, 141980 Dubna, Russia)
We have recently completed the study of ^8He by the binary reaction ^10Be(^12C,^14O)^8He. The previously known ground state and 3.6 Mev 2^+ excited state were observed. Three new excited states were observed at excitation energies of E_x = 4.54(25), 6.03(10) and 7.16 MeV. Their measured widths of the new excited states have been used to place limits on their possible spins and parities.
[CA.07] Meson Cloud Contribution to Nucleon Structure in Semi-Relativistic Constituent Quark Model
Joowon Cho, D. S. Onley (Ohio University)
The quark pair creation operator added to a convensional confined-quark Hamiltonian generates an extended Fock space wavefunction for a nucleon including meson cloud. In the harmonic oscillator basis, we consider the \frac12^+ baryons as mixed states of the three low lying SU multiplets truncated at the sd ( n=0,2 ) shell.
Including the effect of antisymmetrization, we study the meson cloud contribution to one-body and two-body observables calculated for the ground states of nucleons. The form factor and magnetic moment as well as charge, mass, and magnetic radii will be investigated as they should provide good size constraints.
[CA.08] Potential Scattering without Angular Momentum Decomposition^
J.H. Thomas, Ch. Elster (Ohio University)
The scattering of two bosonic nucleons is studied using the Malfliet-Tjon Potential. The Lippmann-Schwinger equation for the t-matrix in three dimensional space is solved directly without angular momentum decomposition. The energy dependence of the half-shell t-matrix is studied between 50 and 1000 MeV scattering energy and compared to results obtained from summing the partial wave solutions. Furthermore, differential cross sections for scattering of distinguishable as well as identical particles are calculated. The properties of these cross sections as function of the potential parameters as well as the scattering energy are investigated.
[2mm] ^ This work is supported in part by the U.S. Department of Energy under contract No. DE-FG02-93ER40756 and the Ohio Supercomputer Center.
[CA.09] Sensitivity of nucleon-nucleus scattering observables to the off-shell behavior of realistic NN potentials ^
S.P. Weppner, Ch. Elster (Ohio Univ.)
Advances in a consistent microscopic derivation of the first-order term within the spectator expansion of multiple scattering theory have allowed for a more detailed understanding of the important underlying physical degrees of freedom. A full-folding model has been developed which integrates a fully off-shell NN t-matrix with a fully off-shell realistic density matrix. The formal and computational set-up of this full-folding calculation allows one to explore the sensitivity of elastic nucleon-nucleus observables to the input quantities of the theory, here the NN interaction. At energies below pion-production threshold there exist several well based NN potentials (Nijmegen, Argonne V18, and charge dependent Bonn). They essentially have a \chi^2 \sim 1 with respect to the NN observables and thus can be considered as on-shell equivalent. We performed full-folding calculations for a variety of nuclei at energies between \sim100 and 300 MeV with those NN models in order to probe the sensitivity of nucleon-nucleus observables to the off-shell structure of the NN t-matrix. [2mm] ^ This work is supported in part by the U.S. Department of Energy under contract Nos. DE-FG02-93ER40756, the Ohio Supercomputer Center, and the Pittsburgh Supercomputer Center.
