George B. Field

Bio: George B. Field is an academic researcher from Smithsonian Astrophysical Observatory. The author has contributed to research in topics: Shock waves in astrophysics & Galactic plane. The author has an hindex of 3, co-authored 10 publications receiving 33 citations.

Hot H_{2} and Interstellar Shocks

Abstract: The rotational excitation of H2 molecules by interstellar shock waves is calculated. Level populations integrated through a shock in a cloud with a density of 10 per cu cm have nearly exponential distributions, with effective rotational temperatures T sub r = 15 V to the 1.5 power K, where V is the shock velocity in km/sec. Ortho-para conversion is effective for high shock velocities, but not for low ones, so that the degree of alternation of intensities of rotational lines in the Lyman absorption band should be correlated with V, and therefore with T sub 2. The results are compared with observations of H2 rotational levels made by the Copernicus satellite.

Hot gas in and between galaxies

Abstract: The fate of interstellar gas heated by energetic radiation and far from the galactic plane is considered. It is shown that for plausible heating rates a very hot corona forms, separated from the cooler gas in the disk by a conductive boundary layer. For heating rates exceeding a critical value a galactic wind is set up, as first shown by Mathews and Baker for elliptical galaxies. Such winds may fill the intracluster space in clusters of galaxies; further heating may drive a cluster wind, as shown by Yahil and Ostriker. It is believed that the flow problem of intracluster gas in the presence of intercluster gas is not yet adequately solved. A variety of observations at X-ray and ultraviolet wavelengths are needed to resolve these questions.

Astrophysical Magnetic Fields and Topics in Galaxy Formation

Abstract: The grant was used to support theoretical research on a variety of astro-physical topics falling broadly into those described by the proposal: galaxy formation, astrophysical magnetic fields, magnetized accretion disks in AGN, new physics, and other astrophysical problems. Work accomplished; references are to work authored by project personel.

Sonne und Fixsterne

Abstract: ... Sonnenflecken entstehen und vergehen uber mehr oder weniger lange Zeitraume; einige verkleinern sich, andere dehnen sich von einem Tag zum anderen aus; sie verandern ihre Gestalt, und einige von ihnen sind sehr unregelmasig geformt; an einigen Stellen sind sie sehr dunkel, an anderen weniger. Ihre Masse mus auf jeden Fall gewaltig sein, da sie sich ja entweder auf der Sonne befinden oder doch sehr nahe von ihr. Wegen ihrer ungleichmasigen Durchsichtigkeit halten sie das Sonnenlicht in verschiedenem Mase zuruck. Manchmal treten viele Sonnenflecken auf, manchmal wenige und gelegentlich uberhaupt keine.

The dynamical state of the interstellar gas and fields. VII.

Abstract: Attractive and disruptive forces in conversion of interstellar gas into stars, discussing self gravitation, galactic magnetic field and cosmic ray pressure

Molecular Hydrogen Optical Depth Templates for FUSE Data Analysis

Abstract: The calculation and use of molecular hydrogen optical depth templates to quickly identify and model molecular hydrogen absorption features longward of the Lyman edge at 912 Angstroms are described. Such features are commonly encountered in spectra obtained by the Far Ultraviolet Spectroscopic Explorer and also in spectra obtained by the Space Telescope Imaging Spectrograph, albeit less commonly. Individual templates are calculated containing all the Lyman and Werner transitions originating from a single rotational state (J'') of the 0th vibrational level (v'') of the ground electronic state. Templates are provided with 0.01 Angstrom sampling for doppler parameters ranging from 2 <= b <= 20 km s^-1 and rotational states 0 <= J'' <= 15. Optical depth templates for excited vibrational states are also available for select doppler parameters. Each template is calculated for a fiducial column density of log[N(cm^-2)] = 21 and may be scaled to any column less than this value without loss of accuracy. These templates will facilitate the determination of the distribution of molecular hydrogen column density as a function of rotational level. The use of these templates will free the user from the computationally intensive task of calculating profiles for a large number of lines and allow concentration on line profile or curve-of-growth fitting to determine column densities and doppler parameters. The templates may be downloaded freely from http://www.pha.jhu.edu/~stephan/h2ools2.html

Toward a 0 th Law of Thermodynamics: Order-Creation Complexity Dynamics from Physics and Biology to Bioeconomics

Abstract: The evolutionary economics part of bioeconomics has its origins in attempts to justify why only rational firms survive, or to introduce dynamics into economic orthodoxy. To the extent that these views persist, this aspect of bioeconomics appears outdated. A more recent view is that the most significant dynamics in bio- and econospheres are not variances around equilibria. Instead order is now seen to be due to the interactions of autonomous, heterogeneous agents energized by contextually imposed tensions induced by energy differentials. While Darwinian selection is still an important process at the tail end of the order-creation process, other natural forces surrounding the biosphere are seen as causing the more significant changes in biological entities over the millennia. This view is set forth within the framework of thermodynamics. It also calls for a change away from the definition of science rooted in the equilibrium mathematics of Newton's orbital mechanics. This new message from natural science is about rapid-fire dynamics calling for a fast-motion science of order-creation before the equilibria of the 1st Law of Thermodynamics take hold. The 2nd Law of Thermodynamics is seen to dominate the 1st Law as the root cause of change. The possibility of a 0th law – of agents' self-organization toward order creation – is considered. Key works by Prigogine, Ashby, Lorenz, Haken, Kelso et al., Salthe, Gell-Mann, Mainzer, Omnes, and Kauffman are reviewed. Nine premises – tracing the path toward an emerging 0th law – are discussed, with some variance also evident. The view of Kelso et al. most easily leads to a one-sentence statement of a possible 0th law of order creation that could offer something of value to bioeconomists.

Molecular Hydrogen in the Direction of ζ Orionis A

Abstract: A spectrum of ζ Ori A over the wavelength interval 950-1150 A recorded by the Interstellar Medium Absorption Profile Spectrograph (IMAPS) on the ORFEUS-SPAS I mission shows Lyman and Werner band absorption features from molecular hydrogen in rotational levels J = 0, 1, 2, 3, and 5. Most of the molecules are found in two distinct velocity components. One is at a heliocentric radial velocity of about -1 km s-1 with log N(H2) = 14.5 and a rotational temperature Trot = 950 K, while the other is at +25 km s-1 with log N(H2) = 15.9 and Trot = 320 K. Some extra H2 exists in a much weaker component [log N(H2) = 14.0] between the two main peaks. The H2 component at -1 km s-1 exhibits profile shapes that become broader and show small displacements toward more negative velocities as J increases. These changes are inconsistent with a simple interpretation that UV optical pumping in an optically thin, uniform medium creates the H2 in excited rotational levels. Differential shielding of the UV radiation at certain velocities does not appear to be a satisfactory explanation for the effect. Evidence from atomic features at other velocities may offer some insight into the origin of this unusual behavior exhibited by the H2 profiles. Absorption features from moderately ionized atoms at -94 km s-1 and more highly ionized species at about -36 km s-1 suggest that along the line of sight to ζ Ori A, there may be a standing bow shock with an initial compression ratio of 2.6. This shock is probably created when a negative-velocity gas flow collides with an obstruction, in this case a neutral cloud at 0 km s-1. If this interpretation is correct, the H2 with the changing profiles may represent molecules forming in the postshock gas that is undergoing further compression as it recombines and cools. We suggest that molecules can form initially by associative detachment of H- in a moving, warm, partly ionized medium behind the front. The H2 in this area is most conspicuous in the higher J levels. Later, when the gas becomes very cool, neutral, and more compressed as it comes nearly to a halt, it is more easily seen in the lowest J levels. In this part of the medium, the principal way of producing H2 should be from reactions on the surfaces of dust grains, as one expects for quiescent interstellar clouds.