82 research outputs found
Ionization equilibrium and equation of state of hydrogen plasmas in strong magnetic fields
We study hydrogen plasmas at magnetic fields B ~ 10^{12}-10^{13} Gauss,
densities ~ 10^{-3}-10^3 g/cc and temperatures T ~ 10^{5.5}-10^{6.5} K, typical
of photospheres of middle-aged cooling neutron stars. We construct an
analytical free energy model of the partially ionized plasma, including into
consideration the decentred atomic states, which arise due to the thermal
motion across the strong field. We show that these states, neglected in
previous studies, may contribute appreciably into thermodynamics of the outer
atmospheric layers at density below 1 g/cc and typical B and T. We take into
account Coulomb non-ideality of the ionized component of the plasma affected by
intense magnetic field. Ionization degree, occupancies and equation of state
are calculated, and their dependences on the temperature, density and magnetic
field are studied.Comment: 4 pages, 1 figure, LaTeX using cpp.sty (included) and epsf.sty. Proc.
of the Workshop on Nonideal Plasmas PNP-9, Rostock, Germany, 7-11 Sept. 1998.
To be published in Contrib. Plasma Phy
Thomas-Fermi Calculations of Atoms and Matter in Magnetic Neutron Stars II: Finite Temperature Effects
We present numerical calculations of the equation of state for dense matter
in high magnetic fields, using a temperature dependent Thomas-Fermi theory with
a magnetic field that takes all Landau levels into account. Free energies for
atoms and matter are also calculated as well as profiles of the electron
density as a function of distance from the atomic nucleus for representative
values of the magnetic field strength, total matter density, and temperature.
The Landau shell structure, which is so prominent in cold dense matter in high
magnetic fields, is still clearly present at finite temperature as long as it
is less than approximately one tenth of the cyclotron energy. This structure is
reflected in an oscillatory behaviour of the equation of state and other
thermodynamic properties of dense matter and hence also in profiles of the
density and pressure as functions of depth in the surface layers of magnetic
neutron stars. These oscillations are completely smoothed out by thermal
effects at temperatures of the order of the cyclotron energy or higher.Comment: 37 pages, 17 figures included, submitted to Ap
Global MHD modeling of the impact of a solar wind pressure change
Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/95116/1/jgra16077.pd
Matter in Strong Magnetic Fields
The properties of matter are significantly modified by strong magnetic
fields, Gauss (), as are typically
found on the surfaces of neutron stars. In such strong magnetic fields, the
Coulomb force on an electron acts as a small perturbation compared to the
magnetic force. The strong field condition can also be mimicked in laboratory
semiconductors. Because of the strong magnetic confinement of electrons
perpendicular to the field, atoms attain a much greater binding energy compared
to the zero-field case, and various other bound states become possible,
including molecular chains and three-dimensional condensed matter. This article
reviews the electronic structure of atoms, molecules and bulk matter, as well
as the thermodynamic properties of dense plasma, in strong magnetic fields,
. The focus is on the basic physical pictures and
approximate scaling relations, although various theoretical approaches and
numerical results are also discussed. For the neutron star surface composed of
light elements such as hydrogen or helium, the outermost layer constitutes a
nondegenerate, partially ionized Coulomb plasma if , and may be in
the form of a condensed liquid if the magnetic field is stronger (and
temperature K). For the iron surface, the outermost layer of the
neutron star can be in a gaseous or a condensed phase depending on the cohesive
property of the iron condensate.Comment: 45 pages with 9 figures. Many small additions/changes. Accepted for
publication in Rev. Mod. Phy
Réponses transitoires de la convection ionosphérique dans le secteur jour aux stimuli du milieu interplanétaire
PARIS-BIUSJ-Thèses (751052125) / SudocCentre Technique Livre Ens. Sup. (774682301) / SudocPARIS-BIUSJ-Physique recherche (751052113) / SudocSudocFranceF
An evaluation of applying existing bioretention sizing methods to cold climates with snow storage conditions
Eight of the current sizing and design methods proposed for bioretention facilities were evaluated for rainfall runoff and snow storage volumes for a costal cold climate in Trondheim, Norway. The RECARGA bioretention infiltration model was used to compare the performance of the methods using 10 months of observed data from a pilot scale bioretention box. The surface areas, total ponding time, number and duration of overflow events, and snow storage volumes were compared. It was found that even in a costal cold climate with several intermittent melt cycles the snow storage requirements were an important design parameter, and if more than 25% of the total snow volume should stored this became the deciding design parameter.Godkänd; 2007; Bibliografisk uppgift: Evaluation de l'application des methodes existantes de dimensionnement de procédé de bioretention aux climates froids et en présence des neiges provenant de la chaussée; 20070926 (marvik)</p
Regional frequency analysis of extreme precipitation with consideration of uncertainties to update IDF curves for the city of Trondheim
Interior, atrium, detai
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Plasma structure within poleward-moving cusp-cleft auroral transients: EISCAT Svalbard radar observations and an explanation in terms of large local time extent of events
We report high-resolution observations of the southward-IMF cusp/cleft ionosphere made on December 16th 1998 by the EISCAT (European incoherent scatter) Svalbard radar (ESR), and compare them with observations of dayside auroral luminosity, as seen at a wavelength of 630 nm by a meridian scanning photometer at Ny Ålesund, and of plasma flows, as seen by the CUTLASS (co-operative UK twin location auroral sounding system) Finland HF radar. The optical data reveal a series of poleward-moving transient red-line (630 nm) enhancements, events that have been associated with bursts in the rate of magnetopause reconnection generating new open flux. The combined observations at this time have strong similarities to predictions of the effects of soft electron precipitation modulated by pulsed reconnection, as made by Davis and Lockwood (1996); however, the effects of rapid zonal flow in the ionosphere, caused by the magnetic curvature force on the newly opened field lines, are found to be a significant additional factor. In particular, it is shown how enhanced plasma loss rates induced by the rapid convection can explain two outstanding anomalies of the 630 nm transients, namely how minima in luminosity form between the poleward-moving events and how events can re-brighten as they move poleward. The observations show how cusp/cleft aurora and transient poleward-moving auroral forms appear in the ESR data and the conditions which cause enhanced 630 nm emission in the transients: they are an important first step in enabling the ESR to identify these features away from the winter solstice when supporting auroral observations are not available
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