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Rotation measures in the fourth Galactic quadrant (Nota+, 2010)

June 2011

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We have re-examined the published rotation measures (RMs) of extragalactic point sources and pulsars with |b|

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Article

Small-scale variations in the Galactic Faraday rotation

April 1987 · Monthly Notices of the Royal Astronomical Society

J. P. Leahy

The variations of rotation measure across individual extragalactic 3C radio sources are analysed for two samples, selected at high and low Galactic latitudes, in order to investigate the RM contributions due to the Galactic foreground on angular scales 5–200 arcsec. These correspond to linear scales in the interstellar medium (ISM) of 0.05–2 pc, and RM variations due to the ISM are found on ... [Show full abstract] scales at least as small as 0.2 pc, with an amplitude requiring orders-of-magnitude enhancement of the typical magnetic field and/or thermal electron density in some regions. These variations may be due to small, faint H II regions along the line-of-sight. No plausible model of the local Faraday medium can account for the rotation measure structures in sources at high Galactic latitude without predicting even more Faraday rotation at low latitudes than is actually observed.

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The scale and strength of the galactic magnetic field according to the pulsar data

December 1977 · Astrophysics and Space Science

In accordance with the data on the Faraday rotation, angular coordinates, and dispersion measurements and distances of 38 pulsars, the strengthB=2.11.1 G and directionl=9924,b0 of the large-scale galactic magnetic field and the mean electron density in the galactic discN e=0.030.01 cm–3 are determined. A comparison with the results of a study of the measures of rotation of extragalactic radio ... [Show full abstract] sources enabled us to estimate the characteristic half-width of the distribution of the electron density on the Z-coordinate (h400 ps). The characteristic size of galactic magnetic field flucturations is shown to be =100–150 ps.

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MHD Simulations of Non-rotating Stellar Core Collapse with Neutrinos

July 2012

Using a new code for the solution of the coupled equations of magnetohydrodynamics (MHD) and neutrino transport, we simulate the collapse and post-bounce evolution of the core of a non-rotating massive star endowed with a poloidal magnetic field. Our code solves the hyperbolic system of the two-moment equations for the transport of electron neutrinos and antineutrinos and the MHD equations in ... [Show full abstract] a finite-volume discretisation using high-resolution shock capturing methods. The coupling between the neutrinos and the gas is accounted for by the most important weak interactions. Although the absence of rotation restricts the possible mechanisms for the amplification of the magnetic field, we find a strong growth of the initial field by flux-freezing compression during collapse and by hydrodynamic instabilities afterwards. From an initial field comparable to the results of current stellar-evolution calculations, the core reaches a field strength in the range observed typically at the surface of pulsars, while a much stronger initial field gives rise to magnetar-like final fields.

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Magneto-ionic content of compact extragalactic radio sources

August 1985 · Astronomy and Astrophysics

J. C. Carvalho

The author has analysed the data of Faraday rotation measurements of compact extragalactic radio sources and calculated their thermal electron density and magnetic field. A detailed discussion is made about the contribution of the intergalactic medium to the source rotation measure. The galactic contribution is subtracted by the use of an appropriate procedure. The thermal electron density of the ... [Show full abstract] radio emission zones is found to vary from 1 to 10-5cm-3 for sources whose size is in the range 1 - 103pc. This is several orders of magnitude smaller than the density of optical emission line regions. Also, the ratio between the density of relativistic and thermal electrons is calculated and is ≤108 for very compact sources.

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Effect of electron vortical motion on the ion dynamics in Hall plasmas

March 1996 · Plasma Physics Reports

A. V. Gordeev

The dynamics of a Hall plasma is considered under the conditions when the equalization of the Lagrange invariant I = Ω/n (where Ω is the vorticity due to the magnetic field B, which is transverse to the direction of the plasma motion; and n is the plasma density) over the plasma is caused by rapid oscillations. An equation for the ion motion with allowance for the electron rotational motion is ... [Show full abstract] obtained. The discontinuous solutions are studied for the scales equal to the collisionless skin depth c/ωpe.

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January 1985 · Proceedings of the International Astronomical Union

B. J. Brett

Faraday rotation occurs in the Galaxy according to the formula:

RM = k\int\limits_L {{n_e}{H_P}d\ell }

where: RM is the rotation measure ne density of electrons H| | component of the magnetic field parallel to line of sight L distance travelled through interstellar medium k constant depending on units.

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January 2002 · Physica E Low-dimensional Systems and Nanostructures

The dynamics of inhomogeneous current flow in a Corbino sample geometry under a perpendicular magnetic field has been studied using a nonlinear generation–recombination model of conducting electrons. A spontaneous symmetry-breaking development of high electron density streamers rotating in a Hall field has been found, preceding the formation of experimentally observable current filaments.

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PLASMA CONFINEMENT USING ROTATING MAGNETIC FIELDS

January 1970

An investigation was made of the current distribution set up by a ; magnetic field rotating about the axis of a cylindrical plasma. If the plasma ; resistivity was sufficiently small electrons rotated with the magnetic field ; producing a steady azimuthal current. In conjunction with an externally applied ; axial magnetic field such a system can be used to confine plasma away from the ; walls of ... [Show full abstract] a discharge tube. Experiments are described in which the radial density ; distribution was measured and compared with that calculated from theory. (auth);

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January 2008 · Geophysical Research Letters

Simultaneous observations obtained by the Solwind coronagraph and Faraday rotation of the Helios radio frequency carrier signal in 1979 showed that CMEs produce characteristic `W' or sigmoid transients in Faraday rotation observations similar to those observed by Pioneer 6 and 9 in 1968 and 1970. We demonstrate that a relaxed flux-rope model is capable of reproducing these observations. Through ... [Show full abstract] fitting the model to the observations, we can obtain information on the flux rope orientation, position, size, velocity, rate of change of rope radius and pitch angle. With electron density measurements, we can also obtain a measure of the magnetic field strength. These fits demonstrate that Faraday rotation observations can provide information on the magnetic field of a CME shortly after it erupts.

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Coherent Curvature Emission in Pulsar Magnetospheres - Non-Dipolar Geometric Effects

January 1993

Qinghuan Luo

The effects of the specific geometry of the magnetic field (such as field lines with torsion) on curvature emission and absorption in pulsar magnetospheres are discussed. Curvature maser emission can arise from two effects: the curvature drift, as has already been discussed in the literature, and field line torsion as discussed here in detail for the first time. Maser emission due to field line ... [Show full abstract] torsion can operate only when the Lorentz factor is larger than a certain value. However, when the Lorentz factor of electrons or positrons is sufficiently high, curvature masering is due to both curvature drift and magnetic field line torsion. The optical depth in the case of field line torsion is estimated. It is shown that if torsion is due to rotation, the resultant luminosity should be dependent on the rotation period in such a way that shorter periods correspond to larger luminosities.

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Magnetic field excess observed in a cluster of galaxies

January 1987

The first measurement of the magnetic field intensity in a cluster of galaxies is reported here. It has been obtained by combining the recent observations of cluster rotation measures (a product of thermal electron density with magnetic field and with path length), along with the earlier observations of cluster X-ray emission (a product of thermal electron density squared with path length and ... [Show full abstract] with other determined parameters). The magnetic field excess, obtained by integrating along the line-of-sight through a small number of randomly-oriented cells in the cluster core, amounts to about 0.2 microgauss. However the cell magnetic field itself is inferred to be around 2 microgauss, on a cell scale of about 20 kpc, in the cluster of galaxies Abell 2319.

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A Magnetic Field Model of the Milky Way Galaxy

January 2000

In the past, the galactic magnetic field was modeled from either the rotation measures of pulsars or the synchrotron radiation of high energy cosmic ray electrons. In this work, we have modeled the galactic magnetic field using both rotation measures and the synchrotron radiation for line of sight component and the perpendicular component. We have then used our model to obtain the brightness ... [Show full abstract] temperature at 408 MHz to compare with that of Haslam et al.(1982). It is shown that our model gives some significant results.

Rotation measures in the fourth Galactic quadrant (Nota+, 2010)

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