scholarly journals The Production of Rotation Measure Gradients in the Lobes of Extragalactic Radio Sources

1990 ◽  
Vol 140 ◽  
pp. 477-481
Author(s):  
G.V. Bicknell ◽  
R.A. Cameron ◽  
R.A. Gingold
Keyword(s):  
Magnetic Field ◽  
Surrounding Medium ◽  
Small Scale ◽  
Radio Sources ◽  
Large Rotation ◽  
Extragalactic Radio Sources ◽  
Cygnus A ◽  
Rotation Measure ◽  
Order Of Magnitude ◽  
Scale Turbulence

It is proposed that the large rotation measure gradients observed in the lobes of some extragalactic radio sources are produced by non–linear Kelvin–Helmholtz surface waves. Related small scale turbulence is responsible for a “diffuse spray” of relativistic plasma and magnetic field into the surrounding medium. The mixture of magnetic field and thermal plasma causes large rotation measure variations on the scale of the Kelvin–Helmholtz waves. An order of magnitude prediction of the effect is in good agreement with the observations of Cygnus A and PKS 2104–25 N.

scholarly journals Search for Extragalactic Radio Sources with Large Rotation Measure

1990 ◽  
Vol 140 ◽  
pp. 472-472
Author(s):  
Ko Aizu ◽  
Makoto Inoue ◽  
Hiroto Tabara ◽  
Tatsnji Kato
Keyword(s):  
Radio Sources ◽  
Polarization Data ◽  
Large Rotation ◽  
Extragalactic Radio Sources ◽  
Rotation Measure

Intrinsic large rotation measures (RM) were searched for 128 extragalactic sources based on polarization data obtained at the NRO 45–m telescope. The number of sources with RM > 500 rad m−2 is only seven.

scholarly journals A bisymmetric spiral magnetic field in the Milky Way

1985 ◽  
Vol 106 ◽  
pp. 251-252
Author(s):  
Y. Sofue ◽  
M. Fujimoto
Keyword(s):  
Magnetic Field ◽  
Faraday Rotation ◽  
Large Scale ◽  
Milky Way ◽  
Radio Sources ◽  
Extragalactic Radio Sources ◽  
Large Scale Magnetic Field ◽  
Rotation Measure ◽  
The Galaxy ◽  
Field Lines

The distribution of Faraday rotation measure (RM) of extragalactic radio sources shows that a large-scale magnetic field in the Galaxy is oriented along the spiral arms. The field lines change direction from one arm to the next in the inter-arm region.

Fluctuations in the Galactic Magnetic Field

1990 ◽  
Vol 140 ◽  
pp. 55-58
Author(s):  
James M. Cordes ◽  
Andrew Clegg ◽  
John Simonetti
Keyword(s):  
Magnetic Field ◽  
Large Scale ◽  
Measure Data ◽  
Small Scale ◽  
Radio Sources ◽  
Galactic Magnetic Field ◽  
Rotation Measure ◽  
Scale Field ◽  
Large Scale Field ◽  
The Magnetic Field

We discuss small scale structure in the Galactic magnetic field as inferred from Faraday rotation measurements of extragalactic radio sources. The rotation measure data suggest a continuum of length scales extending from parsec scales down to at least 0.01 pc and perhaps to as small as 109 cm. Such turbulence in the magnetic field comprises a reservoir of energy that is comparable to the energy in the large scale field.

scholarly journals The Rotation Measure of Background Radio Sources Seen Through the Supernova Remnant OA184 (G166.2+2.5)

1988 ◽  
Vol 101 ◽  
pp. 355-358
Author(s):  
K.-T. Kim ◽  
P.P. Kronberg ◽  
T.L. Landecker
Keyword(s):  
Magnetic Field ◽  
Supernova Remnant ◽  
Active Plasma ◽  
Radio Sources ◽  
Galactic Magnetic Field ◽  
Rotation Measure ◽  
Polarity Change ◽  
Larger Sample

AbstractRadio sources in the field of the extended SNR OA184 (G166.2+2.5) have been studied to determine the excess rotation measure (RM) arising from the SNR. Of a total of 32 radio sources observed with the VLA in the C configuration, eight are found to be polarized above 7σ The sources seen through the SNR show significantly high RM in comparison to background sources. The excess RM due to the Faraday active plasma in the SNR is estimated to be 150±20 rad m−2, which corresponds to . The sign of RMs of the sources within an area of about 2°×2° centred on the SNR shows a systematic longitudinal polarity change on either side of l ≈ 166°.2. Although a larger sample is needed to justify this, we tentatively interpret this “flip” as due to the reversal of an irregular component of the galactic magnetic field on a scale of order 100 pc.

scholarly journals Interstellar Scintillation of Radio Sources as a Probe for Investigations of the Local Interstellar Medium

1997 ◽  
Vol 166 ◽  
pp. 215-218
Author(s):  
N. Bochkarev ◽  
M. Ryabov
Keyword(s):  
Interstellar Medium ◽  
Small Scale ◽  
Radio Sources ◽  
Local Interstellar Medium ◽  
Star Formation Region ◽  
X Ray ◽  
Extragalactic Radio Sources ◽  
Hot Gas ◽  
The North ◽  
Scintillation Indices

AbstractA possibility of obtaining information on small scale inhomogeneities of the electron component of the local interstellar medium (LISM) is investigated using interstellar scintillations of extragalactic radio sources. We analyse Culgoora array observational data on variability of 190 extragalactic radio sources, covering most of the sky, at 80 and 160 MHz. The variability at time scales from 1 month to 15 years is interpreted as refractive interstellar scintillations in fast-moving nearby (less than 150 pc) hot gas near shock waves in the LISM. All-sky map of scintillation indices m averaged over 3–5 sources closest to one another shows several m maxima. Two of the 3 most pronounced maxima are probably connected with Loop I; the third one coincides with the soft X-ray (0.1–0.3 keV) background maximum near the South Galactic Pole. Other, less certain, m maxima probably correspond to the Orion star-formation region and to a soft X-ray maximum near the North Galactic Pole. The ”free-of-gas” tunnel in the direction l = 240° corresponds to low values of m. The estimated time scale of interstellar scintillations on the above-mentioned LISM structures is in agreement with that of the observed radio-source variations.

Turbulent relaxation of a confined magnetofluid to a force-free state

1987 ◽  
Vol 37 (2) ◽  
pp. 299-321 ◽  
Author(s):  
Jill P. Dahlburg ◽  
David Montgomery ◽  
Gary D. Doolen ◽  
Leaf Turner
Keyword(s):  
Magnetic Field ◽  
Energy State ◽  
Minimum Energy ◽  
Three Dimensional ◽  
Small Scale ◽  
Current Profile ◽  
Transit Times ◽  
Uniform Current ◽  
Scale Turbulence ◽  
Pseudo Spectral

Three-dimensional, pseudo-spectral computation is used to follow the evolution of a resistive, incompressible magnetofluid. The magnetofluid is confined by rigid, free-slip, perfectly-conducting square boundaries in the x, y directions (‘poloidal’ boundaries), and periodic boundary conditions are assumed in the z direction (‘toroidal’ direction). A constant, uniform d.c. magnetic field B0 is assumed in the z direction and a non-uniform current density j flows along it initially. Starting from a non-equilibrium hollow current profile, the evolution is followed for several tens of Alfvén transit times. Considerable small-scale turbulence develops, which causes energy to decay more rapidly than magnetic helicity. The average toroidal magnetic field at the (x, y) boundary reverses sign spontaneously. The near spatial constancy of the ratio jB/(jB) ≡ cos θ, in the relaxed state at late times, suggests that the state is nearly force-free. However, the ratio j. B/B2 ≡ α is considerably less uniform than is cos θ suggesting more residual disorder than a pure minimum-energy state would display.

scholarly journals On the Magnetic Fields of Galaxies

2021 ◽  
pp. 470-477
Author(s):  
R. R. Andreasyan
Keyword(s):  
Magnetic Field ◽  
Magnetic Fields ◽  
Faraday Rotation ◽  
Radio Galaxies ◽  
Morphological Properties ◽  
Radio Sources ◽  
Extragalactic Radio Sources

We bring results of some our investigations of magnetic field of our Galaxy and extragalactic radio sources. For the study were used data of Faraday rotation of pulsars and extragalactic radio sources as well as data of physical and morphological properties of more than 500 radio galaxies of different morphological classes.

scholarly journals Dynamics of turbulence under the effect of stratification and internal waves

2015 ◽  
Vol 2 (1) ◽  
pp. 329-359
Author(s):  
O. A. Druzhinin ◽  
L. A. Ostrovsky
Keyword(s):  
Turbulent Mixing ◽  
Vertical Direction ◽  
Internal Gravity Wave ◽  
Turbulent Energy ◽  
Horizontal Layer ◽  
Small Scale ◽  
Turbulent Eddies ◽  
Order Of Magnitude ◽  
Scale Turbulence ◽  
Initial Turbulence

Abstract. The objective of this paper is to study the dynamics of small-scale turbulence near a pycnocline, both in the free regime and under the action of an internal gravity wave (IW) propagating along a pycnocline, using direct numerical simulation (DNS). Turbulence is initially induced in a horizontal layer at some distance above the pycnocline. The velocity and density fields of IW propagating in the pycnocline are also prescribed as initial condition. The IW wavelength is considered to be by the order of magnitude larger as compared to the initial turbulence integral length scale. Stratification in the pycnocline is considered to be sufficiently strong so that the effects of turbulent mixing remain negligible. The dynamics of turbulence is studied both with and without initially induced internal wave. The DNS results show that in the absence of IW turbulence decays, but its decay rate is reduced in the vicinity of the pycnocline where stratification effects are significant. In this case, at sufficiently late times most of turbulent energy is located in a layer close to the pycnocline center. Here turbulent eddies are collapsed in the vertical direction and acquire the "pancake" shape. IW modifies turbulence dynamics, in that the turbulence kinetic energy (TKE) is significantly enhanced as compared to the TKE in the absence of IW. As in the case without IW, most of turbulent energy is localized in the vicinity of the pycnocline center. Here the TKE spectrum is considerably enhanced in the entire wavenumber range as compared to the TKE spectrum in the absence of IW.

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