16,687 research outputs found
Some aspects of metallic ion chemistry and dynamics in the mesosphere and thermosphere
The relationship between the formation of sporadic layers of metallic ion and the dumping of these ions into the upper mesosphere is discussed in terms of the tidal wind, classical (i.e., windshear) and other more complex, perhaps highly nonlinear layer formation mechanisms, and a possible circulation mechanism for these ions. Optical, incoherent scatter radar, rocket, and satellite derived evidence for various layer formation mechanisms and for the metallic ion circulation system is reviewed. The results of simple one dimensional numerical model calculations of sporadic E and intermediate layer formation are presented along with suggestions for more advanced models of intense or blanketing sporadic E. The flux of metallic ions dumped by the tidal wind system into the mesosphere is estimated and compared with estimates of total particle flux of meteoric origin. Possible effects of the metallic ion flux and of meteoric dust on D region ion chemistry are discussed
An Axisymmetric Object-Based Search for a Flat Compact Dimension
A method is presented to search for a hypertorus symmetry axis by the
alignment of distant objects. This offers greater sensitivity than previously
proposed object-based methods that rely on accurate true distances. When
applied to the catalog of objects with z > 1, we find no evidence for a compact
dimension. We deduce a lower limit to the compact dimension size D > 0.9 of the
distance to the cosmic horizon. This is consistent with independent constraints
from the recent analysis of the WMAP microwave background data.Comment: 12 pages, 10 figures, minor revision, accepted by JCA
Externalities revisited: the use of an environmental equity account
This exploratory paper attempts to restart a debate about the incorporation of environmental
externalities into the cost structure of the organisation. A number approaches are considered;
regulation together with all that would follow such as audit and policing; pollution permits, which
probably can only be used with a sinking lid application; and other charging mechanisms such as
making the private sector pay for public sector capital funding. The fourth alternative, the use of an
environmental equity account, has not been widely considered in the literature.
The paper proposes the use of an environmental equity account (after Boone and Rubenstein,
1997) with the express intent of generating a charge for environmental impact based on the cost of
control. That is, the cost of implementing state of the art technology compared to that currently in
use within the organisation, is used as a balance which may be either paid as a capital sum or
carried as a balance sheet entry upon which dividend payments would have to be made. It is
envisaged that both capital sums and dividend payments would go to an agency responsible for
environmental remediation activity
Nuclear Equation of State and Internal Structure of Magnetars
Recently, neutron stars with very strong surface magnetic fields have been
suggested as the site for the origin of observed soft gamma repeaters (SGRs).
We investigate the influence of a strong magnetic field on the properties and
internal structure of such strongly magnetized neutron stars (magnetars). The
presence of a sufficiently strong magnetic field changes the ratio of protons
to neutrons as well as the neutron appearance density. We also study the pion
production and pion condensation in a strong magnetic field. We discuss the
pion condensation in the interior of magnetars as a possible source of SGRs.Comment: 5 pages with 3 figures, To appear in the Proceedings of the 5th
Huntsville Gamma Ray Burst Symposium, Huntsville, Alabama, USA, Oct. 18-22,
199
X-ray Isophotes in a Rapidly Rotating Elliptical Galaxy: Evidence of Inflowing Gas
We describe two-dimensional gasdynamical computations of the X-ray emitting
gas in the rotating elliptical galaxy NGC 4649 that indicate an inflow of about
one solar mass per year at every radius. Such a large instantaneous inflow
cannot have persisted over a Hubble time. The central constant-entropy
temperature peak recently observed in the innermost 150 parsecs is explained by
compressive heating as gas flows toward the central massive black hole. Since
the cooling time of this gas is only a few million years, NGC 4649 provides the
most acutely concentrated known example of the cooling flow problem in which
the time-integrated apparent mass that has flowed into the galactic core
exceeds the total mass observed there. This paradox can be resolved by
intermittent outflows of energy or mass driven by accretion energy released
near the black hole. Inflowing gas is also required at intermediate kpc radii
to explain the ellipticity of X-ray isophotes due to spin-up by mass ejected by
stars that rotate with the galaxy and to explain local density and temperature
profiles. We provide evidence that many luminous elliptical galaxies undergo
similar inflow spin-up. A small turbulent viscosity is required in NGC 4649 to
avoid forming large X-ray luminous disks that are not observed, but the
turbulent pressure is small and does not interfere with mass determinations
that assume hydrostatic equilibrium.Comment: 21 pages, 9 figures, accepted for publication by Ap
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