Development and validation of solution-adaptive, parallel schemes for compressible plasmas

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/76300/1/AIAA-2001-2525-679.pd

Optimal interactions of light with magnetic and electric resonant particles

This work studies the limits of far and near-field electromagnetic response of sub-wavelength scatterers, like the unitary limit and of lossless scatterers, and the ideal absorption limit of lossy particles. These limit behaviors are described in terms of analytic formulas that approximate finite size effects while rigorously including radiative corrections. This analysis predicts the electric and/or magnetic limit responses of both metallic and dielectric nanoparticles while quantitatively describing near-field enhancements.Comment: 9 pages, 8 figures, 2 table

A parallel solution-adaptive scheme for ideal magnetohydrodynamics

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/77232/1/AIAA-1999-3273-200.pd

The Control, Development and Utilization of the Missouri River and its Tributaries

The speakers at this conference were Professors Condra, Caldwell, Stout, Phillips, Bengtson, and Gov. George L. Sheldon, with Dean Charles E. Bessey presiding. The principal object of the meeting was to make known reliable information in regard to the Missouri river, concerning which there is widespread interest and in some instances a tendency to magnify the future possibilities of the river. This paper is an account of the conference. It gives some of the thoughts that were emphasized at the symposium, reciting the facts as they were given by those who have investigated the respective phases of the theme. GEOGRAPHIC CONDITIONS IN THE MISSOURI RIVER BASIN. BY G. E. CONDRA EARLY NAVIGATION ON THE MISSOURI RIVER. BY H. W. CALDWELL THE RELATIONS OF POWER AND IRRIGATION AT THE HEADWATERS OF THE MISSOURI TO FLOODS IN THE LOWER COURSES OF THE RIVER BY O. V. P. STOUT THE RELATIONS OF FORES\u27fS TO RUN-OFF WATER. BY F. J. PHILLIPS MEANDERS OF THE MISSOURI RIVER AND THEIR EFFECTS. BY. N. A. BENGTSON WAYS AND MEANS. GOV. GEO. L, SHELDON

Accretion-Induced Lithium Line Enhancements in Classical T Tauri Stars: RW Aur

It is widely accepted that much of the stochastic variability of T Tauri stars is due to accretion by a circumstellar disk. The emission line spectrum as well as the excess continuum emission are common probes of this process. In this communication, we present additional probes of the circumstellar environment in the form of resonance lines of low ionization potential elements. Using a set of 14 high resolution echelle observations of the classical T Tauri star (CTTS), RW Aur, taken between 1986 and 1996, we carefully measure the continuum veiling at each epoch by comparing more than 500 absorption lines with those of an appropriate template. This allows us to accurately subtract out the continuum emission and to recover the underlying photospheric spectrum. In doing so, we find that selected photospheric lines are enhanced by the accretion process, namely the resonance lines of LiI and KI. A resonance line of TiI and a low excitation potential line of CaI also show weak enhancements. Simple slab models and computed line bisectors lead us to propose that these line enhancements are markers of cool gas at the beginning of the accretion flow which provides an additional source of line opacity. These results suggest that published values of surface lithium abundances of classical T Tauri stars are likely to be overestimated. This would account for the various reports of surface lithium abundances in excess of meteoritic values among the extreme CTTS. Computing LTE lithium abundances of RW Aur in a low and then high accretion state yields abundances which vary by one order of magnitude. The low accretion state lithium abundance is consistent with theoretical predictions for a star of this age and mass while the high accretion state spectrum yields a super-meteoritic lithium abundance.Comment: 28 pages, 8 figures, accepted by Ap

Parallel, Adaptive‐Mesh‐Refinement MHD for Global Space‐Weather Simulations

The first part of this paper reviews some issues representing major computational challenges for global MHD models of the space environment. These issues include mathematical formulation and discretization of the governing equations that ensure the proper jump conditions and propagation speeds, regions of relativistic Alfvén speed, and controlling the divergence of the magnetic field. The second part of the paper concentrates on modern solution methods that have been developed by the aerodynamics, applied mathematics and DoE communities. Such methods have recently begun to be implemented in space‐physics codes, which solve the governing equations for a compressible magnetized plasma. These techniques include high‐resolution upwind schemes, block‐based solution‐adaptive grids and domain decomposition for parallelization. We describe the space physics MHD code developed at the University of Michigan, based on the developments listed above. © 2003 American Institute of PhysicsPeer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/87656/2/807_1.pd