scholarly journals The Radio Luminosity of Pulsars and the Distribution of Interstellar Electron Density

2001 ◽  
Vol 182 ◽  
pp. 175-179
Author(s):  
R.R. Andreasyan ◽  
T.G. Arshakian
Keyword(s):  
Density Distribution ◽  
Electron Density ◽  
Time Variation ◽  
Electron Density Distribution ◽  
Large Scale ◽  
Radio Luminosity ◽  
The Galaxy ◽  
Dispersion Measures ◽  
Average Electron ◽  
Spiral Arm

AbstractThe radio luminosities of pulsars are given as functions of their period and the time variation of the period. The parameters of that dependence are calculated and independent distances are determined for pulsars. The average electron densities toward the pulsars are determined from the known dispersion measures. The results obtained are used to study the large-scale electron density distribution in the Galaxy. The distribution maximum lies in the vicinity of the Sagittarius spiral arm. The electron density falls off exponentially in the regions between spiral arms.

scholarly journals Is there a Depolarization Horizon?

2018 ◽  
Author(s):  
A. S. Hill
Keyword(s):  
Interstellar Medium ◽  
Density Distribution ◽  
Electron Density ◽  
High Frequency ◽  
Electron Density Distribution ◽  
Low Frequency ◽  
Line Of Sight ◽  
Low Frequencies ◽  
Ionic Medium ◽  
Spiral Arm

Modern radio spectrometers make measurement of polarized intensity as a function of Faraday depth possible. I investigate the effect of depolarization along a model line of sight. I model sightlines with two components informed by observations: a diffuse interstellar medium with a lognormal electron density distribution and a narrow, denser component simulating a spiral arm or H~{\sc ii} region, all with synchrotron-emitting gas mixed in. I then calculate the polarized intensity from 300-1800 MHz and calculate the resulting Faraday depth spectrum. The idealized synthetic observations show far more Faraday complexity than is observed in Global Magneto-Ionic Medium Survey observations. In a model with a very nearby H~{\sc ii} region observed at low frequencies, most of the effects of a ``depolarization wall'' are evident: the H~{\sc ii} region depolarizes background emission and less (but not zero) information from beyond the H~{\sc ii} region reaches the observer. In other cases, the effects are not so clear, as significant amounts of information reach the observer even through significant depolarization, and it is not clear that low-frequency observations sample largely different volumes of the interstellar medium than high-frequency observations. The observed Faraday depth can be randomized such that it does not always have any correlation with the true Faraday depth.

Modelling the Electron Density Distribution in the July 1991 Solar Corona

1994 ◽  
Vol 144 ◽  
pp. 535-539 ◽  
Author(s):  
F. Clette ◽  
P. Cugnon ◽  
J.-R. Gabryl
Keyword(s):  
Magnetic Field ◽  
Density Distribution ◽  
Electron Density ◽  
Legendre Polynomials ◽  
Electron Density Distribution ◽  
Large Scale ◽  
Symmetry Axis ◽  
Rotation Axis ◽  
Magnetic Field Axis ◽  
The Mean

AbstractUsing intensity and polarization maps computed from white-light observations of the July 11, 1991 solar eclipse, we present axisymmetrical models of the large-scale electron density distribution in the corona. These models are based on an expansion in Legendre polynomials, and are flexible enough to fit individual features, like streamers and holes. Furthermore, as the symmetry axis of our models can take any orientation, we consider two plausible configurations, aligned on the rotation axis or the mean bipolar magnetic field axis. Their respective abilities to reproduce a strongly non-spherical global magnetic structure are then compared.

scholarly journals Hectometer and Kilometer Solar Observations

1980 ◽  
Vol 86 ◽  
pp. 405-413
Author(s):  
R. G. Stone
Keyword(s):  
Density Distribution ◽  
Radio Source ◽  
Electron Density ◽  
Electron Density Distribution ◽  
Large Scale ◽  
Three Dimensional ◽  
Dipole Antennas ◽  
Magnetic Field Topology ◽  
Solar Observations ◽  
Field Geometry

Three dimensional “snapshots” of the large scale solar magnetic field topology as well as the solar wind electron density distribution from about 0.1 to 1 AU are obtained by tracking traveling solar radio bursts at hectometer and kilometer wavelengths with instruments aborad the ISEE-3 satellite and the HELIOS-2 solar probe. Both instruments observe in the frequency range from 30 kHz to 1 MHz and both are equipped with dipole antennas located in the vehicle spin plane. ISEE-3 also has a dipole along the spin axis and the signals from the two ISEE-3 antennas are combined to give the azimuth and elevation angles of the radio source. Triangulation between HELIOS-2 and ISEE-3 provides the additional observation necessary to uniquely determine the position of the radio source in space at each observing frequency. The techniques will be outlined, and illustrated by an example of the three dimensional field geometry and electron density distribution determined by the observations.

scholarly journals Model modulation to add smaller scale structures to large scale electron density models

2005 ◽  
Vol 3 ◽  
pp. 441-447
Author(s):  
R. Leitinger ◽  
E. Feichter ◽  
M. Rieger
Keyword(s):  
Density Distribution ◽  
Electron Density ◽  
Electron Density Distribution ◽  
Large Scale ◽  
Scale Model ◽  
Spatial Structures ◽  
Large Scale Model ◽  
Modulation Model ◽  
Anchor Points ◽  
Scale Structures

Abstract. Usually regional and global electron density models provide large scale spatial structures only and smooth out the smaller scale features of the electron density distribution. We present a method to modulate existing electron density models by multiplication: M(h, φ, λ, t) = L(h, φ, λ, t) × S1(h, φ, λ, t) × S2(h, φ, λ, t) × ... Sn(h, φ, λ, t) M: resulting electron density distribution, L: large scale model, S1...Sn: modulating models for n the smaller scale structures; h: height; φ, λ: geographic coordinates, t: Universal Time. There are no restrictions to the nature of the large scale model provided it takes height and horizontal coordinates as input. Examples are models of the "profiler" type which use large scale "maps" for profile anchor points (e.g., E, F1, F2 peak properties) like the International Reference Ionosphere (IRI). Typical examples for smaller scale structures are ridges, troughs and wavelike disturbances. The advantage of modulation by multiplication is that there is no danger to get zero or negative values of electron density as long as the background and modulations are >0 everywhere. For each modulation model, unity means "undisturbed".

A study on α-RuCl3 crystal structure by scanning tunneling microscopy

1989 ◽  
Vol 47 ◽  
pp. 30-31
Author(s):  
H.-J. Cantow ◽  
H. Hillebrecht ◽  
S. Magonov ◽  
H. W. Rotter ◽  
G. Thiele
Keyword(s):  
Crystal Structure ◽  
Density Distribution ◽  
Scanning Tunneling Microscopy ◽  
Electron Density ◽  
Structure Determination ◽  
Electron Density Distribution ◽  
Scanning Tunneling ◽  
Monoclinic Space Group ◽  
Tunneling Microscopy ◽  
X Ray

From X-ray analysis, the conclusions are drawn from averaged molecular informations. Thus, limitations are caused when analyzing systems whose symmetry is reduced due to interatomic interactions. In contrast, scanning tunneling microscopy (STM) directly images atomic scale surface electron density distribution, with a resolution up to fractions of Angstrom units. The crucial point is the correlation between the electron density distribution and the localization of individual atoms, which is reasonable in many cases. Thus, the use of STM images for crystal structure determination may be permitted. We tried to apply RuCl3 - a layered material with semiconductive properties - for such STM studies. From the X-ray analysis it has been assumed that α-form of this compound crystallizes in the monoclinic space group C2/m (AICI3 type). The chlorine atoms form an almost undistorted cubic closed package while Ru occupies 2/3 of the octahedral holes in every second layer building up a plane hexagon net (graphite net). Idealizing the arrangement of the chlorines a hexagonal symmetry would be expected. X-ray structure determination of isotypic compounds e.g. IrBr3 leads only to averaged positions of the metal atoms as there exist extended stacking faults of the metal layers.

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