scholarly journals Pulsars as Probes of the Galactic Magnetic Field

1990 ◽  
Vol 140 ◽  
pp. 41-43
Author(s):  
A. G. Lyne
Keyword(s):  
Magnetic Field ◽  
Faraday Rotation ◽  
Linear Polarization ◽  
Dispersion Measure ◽  
Radio Sources ◽  
Galactic Magnetic Field ◽  
Pulsar Emission ◽  
Pulsar Radiation ◽  
Rotation Measure

The high linear polarization of pulsar radiation allows a reasonably easy determination of the Faraday rotation measure. Unlike other radio sources, the impulsive nature of pulsar emission also permits a determination of the number of electrons responsible for the rotation, through the dispersion measure, DM.

scholarly journals A new look at the galactic magnetic field

1979 ◽  
Vol 84 ◽  
pp. 317-319
Author(s):  
P. P. Kronberg ◽  
M. Simard-Normandin
Keyword(s):  
Magnetic Field ◽  
Faraday Rotation ◽  
Linear Polarization ◽  
Radio Sources ◽  
Galactic Magnetic Field ◽  
Equal Area ◽  
Large Sample ◽  
Extragalactic Radio Sources ◽  
First Order ◽  
New Look

We have measured the linear polarization of a new large sample of extragalactic radio sources, and by combining these with polarization values already in the literature, we have been able to compute a large number of rotation measures, with improved quality. We have also investigated the depolarization properties of these sources and as a result have been able to identify most sources with a large internally generated Faraday rotation. Figure 1 shows the rotation measures of 475 extragalactic radio sources on an equal-area projection, after “cleaning out” the extragalactic effects to first order.

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 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.

scholarly journals F. Magnetic Fields, Pulsars, X-Ray And Gamma-Ray Emission

1985 ◽  
Vol 19 (1) ◽  
pp. 431-435
Keyword(s):  
Magnetic Field ◽  
Large Scale ◽  
Gamma Ray ◽  
Logarithmic Spiral ◽  
Radio Sources ◽  
Galactic Magnetic Field ◽  
Rotation Measure ◽  
The Galaxy ◽  
Magnetic Field Model ◽  
Characteristic Features

During the triennium under review many papers reported on studies of the structure of the galactic magnetic field. Andreasyan used rotation measures (RM) of large samples of extra-galactic radio sources and pulsars (29.156.001) or radio sources (32.156.002), and Inoue and Tabara (31.156.011) used in addition optical polarization of stars to investigate the direction of the large-scale regular magnetic field. Thomson and Nelson analyse the RMs of 459 extragalactic sources (32. 161.001) to determine the best fit parameters for a galactic magnetic-field model, and find agreement with their earlier work using pulsars (27.156.009). Similarly, Sofue and Fujimoto (33.155.011) show that the characteristic features of the RM distribution on the sky are well reproduced by a model in which the magnetic field is in a bisymmetric, two-armed logarithmic spiral configuration. Finally, Welter, Perry and Kronberg (37.159.096) present a statistical analysis of the (Galaxy-corrected) residual rotation measure (RRM) of 116 QSOs.

scholarly journals Broadband radio spectro-polarimetric observations of high-Faraday-rotation-measure AGN

2018 ◽  
Vol 613 ◽  
pp. A74 ◽  
Author(s):  
Alice Pasetto ◽  
Carlos Carrasco-González ◽  
Shane O’Sullivan ◽  
Aritra Basu ◽  
Gabriele Bruni ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Faraday Rotation ◽  
Complex Structure ◽  
High Sensitivity ◽  
Radio Spectrum ◽  
Radio Sources ◽  
Very Large Array ◽  
Rotation Measure ◽  
Field Geometry ◽  
Sensitivity Data

We present broadband polarimetric observations of a sample of high-Faraday-rotation-measure (high-RM) active galactic nuclei (AGN) using the Karl. G. Jansky Very Large Array (JVLA) telescope from 1 to 2 GHz, and 4 to 12 GHz. The sample (14 sources) consists of very compact sources (linear resolution smaller than ≈5 kpc) that are unpolarized at 1.4 GHz in the NRAO VLA Sky Survey (NVSS). Total intensity data have been modeled using a combination of synchrotron components, revealing complex structure in their radio spectra. Depolarization modeling, through the so-called qu-fitting (the modeling of the fractional quantities of the Stokes Q and U parameters), has been performed on the polarized data using an equation that attempts to simplify the process of fitting many different depolarization models. These models can be divided into two major categories: external depolarization (ED) and internal depolarization (ID) models. Understanding which of the two mechanisms is the most representative would help the qualitative understanding of the AGN jet environment and whether it is embedded in a dense external magneto-ionic medium or if it is the jet-wind that causes the high RM and strong depolarization. This could help to probe the jet magnetic field geometry (e.g., helical or otherwise). This new high-sensitivity data shows a complicated behavior in the total intensity and polarization radio spectrum of individual sources. We observed the presence of several synchrotron components and Faraday components in their total intensity and polarized spectra. For the majority of our targets (12 sources), the depolarization seems to be caused by a turbulent magnetic field. Thus, our main selection criteria (lack of polarization at 1.4 GHz in the NVSS) result in a sample of sources with very large RMs and depolarization due to turbulent magnetic fields local to the source. These broadband JVLA data reveal the complexity of the polarization properties of this class of radio sources. We show how the new qu-fitting technique can be used to probe the magnetized radio source environment and to spectrally resolve the polarized components of unresolved radio sources.

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 DETERMINATION OF THE ROTATION MEASURE VALUE SIGN WHEN RECEIVING A SINGLE LINEAR POLARIZATION OF THE PULSAR RADIO EMISSION

2020 ◽  
Vol 25 (4) ◽  
pp. 253-267
Author(s):  
O. M. Ulyanov ◽  
◽  
A. I. Shevtsova ◽  
S. M. Yerin ◽  
◽  
...  
Keyword(s):  
Magnetic Field ◽  
Radio Emission ◽  
Linear Polarization ◽  
Pulsar Radio ◽  
Absolute Value ◽  
The Earth ◽  
Rotation Measure ◽  
The Absolute ◽  
Pulsar Radio Emission

Purpose: The studies of pulsars allow enriching our knowledge in determination of parameters of both the exotic electron-positron plasma in the pulsar magnetosphere with strong magnetic field and the ordinary ion-electron plasma of the interstellar medium, which exists in a weak magnetic field. To determine the parameters of the both plasma types it is reasonable to use polarization characteristics of a pulsed radio emission of pulsars. An accurate determination of these characteristics is quite a complex problem. For its solving, primarily we have to determine two parameters of the propagation medium – its dispersion and rotation measures. Their absolute values can be determined with the relative precision of 10-4, but the problem of rotation measure value sign determination arises. This sign depends on the interstellar magnetic field direction along the line of sight. Hear, a new method of rotation measure value sign determination is proposed. Design/methodology/approach: Muller polarization matrices are usually used for determination of such a propagation parameter as the rotation measure absolute value. When only one linear polarization is received, using of these matrices allows quite accurate determining the absolute value of the rotation measure, but not the sign of this parameter due to a certain symmetry of these matrices with respect to the direction of the linear polarization rotation plane. If we complement the system of equations, which determines the rotation measure value, with some new additional components, which take into account the contributions of the Earth ionosphere and magnetosphere to the rotation measure value, one can notice that this contribution is always positive in the Southern magnetic hemisphere (the majority of the Northern geographical hemisphere) and is always negative in the Northern magnetic hemisphere (the majority of the Southern geographical hemisphere). Moreover, the absolute value of this contribution is maximal at noon and minimal at midnight, when the concentration of ions in the Earth ionosphere is maximal and minimal, respectively. Accounting for these regularities allows to determine not only the absolute value of the rotation measure, but also its sign by means of two independent time-shifted estimations of the observed absolute value of this parameter for various ionization degrees of the Earth ionosphere. Findings: We show that using of additional equations, which take into account the contribution of the Earth ionosphere and magnetosphere to the value of the rotation measure parameter, allows full determination of this parameter accounting for the sign of this value even for the antennas, which can record a single linear polarization only. This approach allows to determine all polarization parameters of the pulsar radio emission as well as of the pulsed or continuum polarized radio emission of other cosmic sources. Conclusions: The paper presents the results of measurement of the rotation measure for the two closest to the Earth pulsars, namely J0814+7429 (B0809+74), J0953+0755 (B0950+08), and the comparison of the proposed technique for this parameter determination with other existing techniques. Key words: pulse, dispersion measure, rotation measure, plasma, polarization, pulsar, radio telescope

STATIONARY SHEATH OF FARADAY ROTATION IN THE JET OF 3C 120

2010 ◽  
Vol 19 (06) ◽  
pp. 917-922
Author(s):  
JOSÉ L. GÓMEZ ◽  
MAR ROCA-SOGORB ◽  
IVÁN AGUDO ◽  
ALAN P. MARSCHER ◽  
SVETLANA G. JORSTAD
Keyword(s):  
Magnetic Field ◽  
Faraday Rotation ◽  
Radio Galaxy ◽  
External Medium ◽  
Degree Of Polarization ◽  
Polarization Structure ◽  
Rotation Measure ◽  
Helical Magnetic Field ◽  
3C 120 ◽  
Two Fluid

We present a sequence of 12 monthly polarimetric multi-frequency VLBA observations of the radio galaxy 3C 120. The motion of multiple superluminal components allows the mapping of the polarization structure along most of the jet and across its width, revealing a coherent in time Faraday screen and RM-corrected polarization angles. Gradients in Faraday rotation and degree of polarization across the jet are observed, together with a localized region of high rotation measure superposed on this structure. This is explained as produced by the presence of a helical magnetic field in a two-fluid jet model, consisting of an inner emitting jet and a sheath containing nonrelativistic electrons. Interaction of the jet with the external medium would explain the confined region of enhanced Faraday rotation.

scholarly journals On the magnetoionic environments of fast radio bursts

2020 ◽  
Vol 499 (1) ◽  
pp. 355-361 ◽  
Author(s):  
Wei-Yang Wang ◽  
Bing Zhang ◽  
Xuelei Chen ◽  
Renxin Xu
Keyword(s):  
Magnetic Field ◽  
Mean Value ◽  
Line Of Sight ◽  
Galactic Centre ◽  
Dispersion Measure ◽  
Radio Bursts ◽  
Host Galaxies ◽  
Surface Magnetic Field ◽  
Rotation Measure ◽  
The Mean

ABSTRACT Observations of the Faraday rotation measure, combined with the dispersion measure, can be used to infer the magnetoionic environment of a radio source. We investigate the magnetoionic environments of fast radio bursts (FRBs) by deriving their estimated average magnetic field strengths along the line of sight 〈B∥〉 in their host galaxies and comparing them with those of Galactic pulsars and magnetars. We find that for those FRBs with RM measurements, the mean 〈B∥〉 are $1.77^{+9.01}_{-1.48}\, \rm \mu G$ and $1.74^{+14.82}_{-1.55}\, \rm \mu G$ using two different methods, which is slightly larger but not inconsistent with the distribution of Galactic pulsars, $1.00^{+1.51}_{-0.60}\, \rm \mu G$. Only six Galactic magnetars have estimated 〈B∥〉. Excluding PSR J1745–2900 that has an anomalously high value due to its proximity with the Galactic Centre, the other five sources have a mean value of $1.70\, \rm \mu G$, which is statistically consistent with the 〈B∥〉 distributions of both Galactic pulsars and FRBs. There is no apparent trend of evolution of magnetar 〈B∥〉 as a function of age or surface magnetic field strength. Galactic pulsars and magnetars close to the Galactic Centre have relatively larger 〈B∥〉 values than other pulsars/magnetars. We discuss the implications of these results for the magnetoionic environments of FRB 121102 within the context of magnetar model and the model invoking a supermassive black hole, and for the origin of FRBs in general.

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