The Origin and Structure of the Magnetic Fields and Currents of AGN Jets
This paper reviews observational evidence obtained to date about the overall structure of the magnetic fields in the jets of Active Galactic Nuclei (AGN). Because they are sensitive to the line-of-sight magnetic-field component, Faraday rotation observations of AGN jets provide an effective tool for s...
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| Format: | Article |
| Language: | English |
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MDPI AG
2017-02-01
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| Series: | Galaxies |
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| Online Access: | http://www.mdpi.com/2075-4434/5/1/11 |
| _version_ | 1818042343331201024 |
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| author | Denise Gabuzda |
| author_facet | Denise Gabuzda |
| author_sort | Denise Gabuzda |
| collection | DOAJ |
| description | This paper reviews observational evidence obtained to date about the overall structure of the magnetic fields in the jets of Active Galactic Nuclei (AGN). Because they are sensitive to the line-of-sight magnetic-field component, Faraday rotation observations of AGN jets provide an effective tool for searching for toroidal jet magnetic fields, whose line-of-sight component changes systematically across the jet. Transverse Faraday rotation measure (RM) gradients providing direct evidence for helical/toroidal magnetic fields have been reliably detected in nearly 40 AGN on parsec scales. Helical magnetic fields are believed to form due to the combined action of the rotation of the central black hole and accretion disk, and these observations demonstrate that at least some of this helical field survives to distances well beyond the Very Long Baseline Interferometry (VLBI) core. Observations of reversals in the direction of the transverse RM gradients in a number of AGN provide evidence for a“return”magnetic field forming a nested helical-field structure with oppositely directed azimuthal components in the inner and outer regions of the helical magnetic field. The collected data now provide firm evidence for a predominance of inward jet currents on parsec scales and outward currents on scales greater than a few tens of parsecs. This suggests a global pattern of magnetic fields and currents with an inward current near the jet axis and an outward current farther from the jet axis, with these currents closing in the accretion disk and far out in the radio lobes, forming a self-consistent set of fields and currents together with the implied nested helical-field structure. |
| first_indexed | 2024-12-10T08:44:48Z |
| format | Article |
| id | doaj.art-287ba06af35f443e8673538842fc740d |
| institution | Directory Open Access Journal |
| issn | 2075-4434 |
| language | English |
| last_indexed | 2024-12-10T08:44:48Z |
| publishDate | 2017-02-01 |
| publisher | MDPI AG |
| record_format | Article |
| series | Galaxies |
| spelling | doaj.art-287ba06af35f443e8673538842fc740d2022-12-22T01:55:46ZengMDPI AGGalaxies2075-44342017-02-01511110.3390/galaxies5010011galaxies5010011The Origin and Structure of the Magnetic Fields and Currents of AGN JetsDenise Gabuzda0Physics Department, University College Cork, Cork, IrelandThis paper reviews observational evidence obtained to date about the overall structure of the magnetic fields in the jets of Active Galactic Nuclei (AGN). Because they are sensitive to the line-of-sight magnetic-field component, Faraday rotation observations of AGN jets provide an effective tool for searching for toroidal jet magnetic fields, whose line-of-sight component changes systematically across the jet. Transverse Faraday rotation measure (RM) gradients providing direct evidence for helical/toroidal magnetic fields have been reliably detected in nearly 40 AGN on parsec scales. Helical magnetic fields are believed to form due to the combined action of the rotation of the central black hole and accretion disk, and these observations demonstrate that at least some of this helical field survives to distances well beyond the Very Long Baseline Interferometry (VLBI) core. Observations of reversals in the direction of the transverse RM gradients in a number of AGN provide evidence for a“return”magnetic field forming a nested helical-field structure with oppositely directed azimuthal components in the inner and outer regions of the helical magnetic field. The collected data now provide firm evidence for a predominance of inward jet currents on parsec scales and outward currents on scales greater than a few tens of parsecs. This suggests a global pattern of magnetic fields and currents with an inward current near the jet axis and an outward current farther from the jet axis, with these currents closing in the accretion disk and far out in the radio lobes, forming a self-consistent set of fields and currents together with the implied nested helical-field structure.http://www.mdpi.com/2075-4434/5/1/11active galactic nucleirelativistic jetsmagnetic fieldsradio interferometry |
| spellingShingle | Denise Gabuzda The Origin and Structure of the Magnetic Fields and Currents of AGN Jets Galaxies active galactic nuclei relativistic jets magnetic fields radio interferometry |
| title | The Origin and Structure of the Magnetic Fields and Currents of AGN Jets |
| title_full | The Origin and Structure of the Magnetic Fields and Currents of AGN Jets |
| title_fullStr | The Origin and Structure of the Magnetic Fields and Currents of AGN Jets |
| title_full_unstemmed | The Origin and Structure of the Magnetic Fields and Currents of AGN Jets |
| title_short | The Origin and Structure of the Magnetic Fields and Currents of AGN Jets |
| title_sort | origin and structure of the magnetic fields and currents of agn jets |
| topic | active galactic nuclei relativistic jets magnetic fields radio interferometry |
| url | http://www.mdpi.com/2075-4434/5/1/11 |
| work_keys_str_mv | AT denisegabuzda theoriginandstructureofthemagneticfieldsandcurrentsofagnjets AT denisegabuzda originandstructureofthemagneticfieldsandcurrentsofagnjets |