Striped Blandford/Znajek jets from advection of small-scale magnetic field
ABSTRACT Black hole – accretion disc systems are the central engines of relativistic jets from stellar to galactic scales. We numerically quantify the unsteady outgoing Poynting flux through the horizon of a rapidly spinning black hole endowed with a rotating accretion disc. The disc supports small-...
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Veröffentlicht in: | Monthly notices of the Royal Astronomical Society 2020-05, Vol.494 (3), p.4203-4225 |
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Black hole – accretion disc systems are the central engines of relativistic jets from stellar to galactic scales. We numerically quantify the unsteady outgoing Poynting flux through the horizon of a rapidly spinning black hole endowed with a rotating accretion disc. The disc supports small-scale, concentric, flux tubes with zero net magnetic flux. Our general relativistic force-free electrodynamics simulations follow the accretion on to the black hole over several hundred dynamical time-scales in 3D. For the case of counter-rotating accretion discs, the average process efficiency reaches up to 〈ϵ〉 ≈ 0.43, compared to a stationary energy extraction by the Blandford/Znajek process. The process efficiency depends on the cross-sectional area of the loops, i.e. on the product l × h, where l is the radial loop thickness and h its vertical scale height. We identify a strong correlation between efficient electromagnetic energy extraction and the quasi-stationary setting of ideal conditions for the operation of the Blandford/Znajek process (e.g. optimal field line angular velocity and fulfillment of the so-called Znajek condition). Remarkably, the energy extraction operates intermittently (alternating episodes of high and low efficiency) without imposing any large-scale magnetic field embedding the central object. Scaling our results to supermassive black holes, we estimate that the typical variability time-scale of the system is of the order of days to months. Such time-scales may account for the longest variability scales of TeV emission observed, e.g. in M87. |
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Black hole – accretion disc systems are the central engines of relativistic jets from stellar to galactic scales. We numerically quantify the unsteady outgoing Poynting flux through the horizon of a rapidly spinning black hole endowed with a rotating accretion disc. The disc supports small-scale, concentric, flux tubes with zero net magnetic flux. Our general relativistic force-free electrodynamics simulations follow the accretion on to the black hole over several hundred dynamical time-scales in 3D. For the case of counter-rotating accretion discs, the average process efficiency reaches up to 〈ϵ〉 ≈ 0.43, compared to a stationary energy extraction by the Blandford/Znajek process. The process efficiency depends on the cross-sectional area of the loops, i.e. on the product l × h, where l is the radial loop thickness and h its vertical scale height. We identify a strong correlation between efficient electromagnetic energy extraction and the quasi-stationary setting of ideal conditions for the operation of the Blandford/Znajek process (e.g. optimal field line angular velocity and fulfillment of the so-called Znajek condition). Remarkably, the energy extraction operates intermittently (alternating episodes of high and low efficiency) without imposing any large-scale magnetic field embedding the central object. Scaling our results to supermassive black holes, we estimate that the typical variability time-scale of the system is of the order of days to months. Such time-scales may account for the longest variability scales of TeV emission observed, e.g. in M87.</description><identifier>ISSN: 0035-8711</identifier><identifier>EISSN: 1365-2966</identifier><identifier>DOI: 10.1093/mnras/staa943</identifier><language>eng</language><publisher>Oxford University Press</publisher><ispartof>Monthly notices of the Royal Astronomical Society, 2020-05, Vol.494 (3), p.4203-4225</ispartof><rights>2020 The Author(s) Published by Oxford University Press on behalf of the Royal Astronomical Society 2020</rights><lds50>peer_reviewed</lds50><woscitedreferencessubscribed>false</woscitedreferencessubscribed><citedby>FETCH-LOGICAL-c336t-4c43367e601291a5e0ee6bfdbc97e6abc43cd3c17680d4e3b6a410b5440a0b653</citedby><cites>FETCH-LOGICAL-c336t-4c43367e601291a5e0ee6bfdbc97e6abc43cd3c17680d4e3b6a410b5440a0b653</cites><orcidid>0000-0002-5552-7681 ; 0000-0002-5349-7116</orcidid></display><links><openurl>$$Topenurl_article</openurl><openurlfulltext>$$Topenurlfull_article</openurlfulltext><thumbnail>$$Tsyndetics_thumb_exl</thumbnail><link.rule.ids>314,778,782,1601,27911,27912</link.rule.ids><linktorsrc>$$Uhttps://dx.doi.org/10.1093/mnras/staa943$$EView_record_in_Oxford_University_Press$$FView_record_in_$$GOxford_University_Press</linktorsrc></links><search><creatorcontrib>Mahlmann, J F</creatorcontrib><creatorcontrib>Levinson, A</creatorcontrib><creatorcontrib>Aloy, M A</creatorcontrib><title>Striped Blandford/Znajek jets from advection of small-scale magnetic field</title><title>Monthly notices of the Royal Astronomical Society</title><description>ABSTRACT
Black hole – accretion disc systems are the central engines of relativistic jets from stellar to galactic scales. We numerically quantify the unsteady outgoing Poynting flux through the horizon of a rapidly spinning black hole endowed with a rotating accretion disc. The disc supports small-scale, concentric, flux tubes with zero net magnetic flux. Our general relativistic force-free electrodynamics simulations follow the accretion on to the black hole over several hundred dynamical time-scales in 3D. For the case of counter-rotating accretion discs, the average process efficiency reaches up to 〈ϵ〉 ≈ 0.43, compared to a stationary energy extraction by the Blandford/Znajek process. The process efficiency depends on the cross-sectional area of the loops, i.e. on the product l × h, where l is the radial loop thickness and h its vertical scale height. We identify a strong correlation between efficient electromagnetic energy extraction and the quasi-stationary setting of ideal conditions for the operation of the Blandford/Znajek process (e.g. optimal field line angular velocity and fulfillment of the so-called Znajek condition). Remarkably, the energy extraction operates intermittently (alternating episodes of high and low efficiency) without imposing any large-scale magnetic field embedding the central object. Scaling our results to supermassive black holes, we estimate that the typical variability time-scale of the system is of the order of days to months. Such time-scales may account for the longest variability scales of TeV emission observed, e.g. in M87.</description><issn>0035-8711</issn><issn>1365-2966</issn><fulltext>true</fulltext><rsrctype>article</rsrctype><creationdate>2020</creationdate><recordtype>article</recordtype><recordid>eNqFkLtOxDAURC0EEmGhpHdJY3IdO86mhBVPrUQBNDTRjX2NEvKSHZD4ewK7PdVIM0dTHMbOJVxKKFXaDwFjGmfEUqsDlkhlcpGVxhyyBEDlYl1IecxOYmwBQKvMJOzxeQ7NRI5fdzg4PwaXvg3Y0gdvaY7ch7Hn6L7Izs048NHz2GPXiWixI97j-0BzY7lvqHOn7MhjF-lsnyv2envzsrkX26e7h83VVlilzCy01UsWZEBmpcScgMjU3tW2XEqsl9k6ZWVh1uA0qdqgllDnWgNCbXK1YmL3a8MYYyBfTaHpMXxXEqpfEdWfiGovYuEvdvz4Of2D_gAoy2H5</recordid><startdate>20200521</startdate><enddate>20200521</enddate><creator>Mahlmann, J F</creator><creator>Levinson, A</creator><creator>Aloy, M A</creator><general>Oxford University Press</general><scope>AAYXX</scope><scope>CITATION</scope><orcidid>https://orcid.org/0000-0002-5552-7681</orcidid><orcidid>https://orcid.org/0000-0002-5349-7116</orcidid></search><sort><creationdate>20200521</creationdate><title>Striped Blandford/Znajek jets from advection of small-scale magnetic field</title><author>Mahlmann, J F ; Levinson, A ; Aloy, M A</author></sort><facets><frbrtype>5</frbrtype><frbrgroupid>cdi_FETCH-LOGICAL-c336t-4c43367e601291a5e0ee6bfdbc97e6abc43cd3c17680d4e3b6a410b5440a0b653</frbrgroupid><rsrctype>articles</rsrctype><prefilter>articles</prefilter><language>eng</language><creationdate>2020</creationdate><toplevel>peer_reviewed</toplevel><toplevel>online_resources</toplevel><creatorcontrib>Mahlmann, J F</creatorcontrib><creatorcontrib>Levinson, A</creatorcontrib><creatorcontrib>Aloy, M A</creatorcontrib><collection>CrossRef</collection><jtitle>Monthly notices of the Royal Astronomical Society</jtitle></facets><delivery><delcategory>Remote Search Resource</delcategory><fulltext>fulltext_linktorsrc</fulltext></delivery><addata><au>Mahlmann, J F</au><au>Levinson, A</au><au>Aloy, M A</au><format>journal</format><genre>article</genre><ristype>JOUR</ristype><atitle>Striped Blandford/Znajek jets from advection of small-scale magnetic field</atitle><jtitle>Monthly notices of the Royal Astronomical Society</jtitle><date>2020-05-21</date><risdate>2020</risdate><volume>494</volume><issue>3</issue><spage>4203</spage><epage>4225</epage><pages>4203-4225</pages><issn>0035-8711</issn><eissn>1365-2966</eissn><abstract>ABSTRACT
Black hole – accretion disc systems are the central engines of relativistic jets from stellar to galactic scales. We numerically quantify the unsteady outgoing Poynting flux through the horizon of a rapidly spinning black hole endowed with a rotating accretion disc. The disc supports small-scale, concentric, flux tubes with zero net magnetic flux. Our general relativistic force-free electrodynamics simulations follow the accretion on to the black hole over several hundred dynamical time-scales in 3D. For the case of counter-rotating accretion discs, the average process efficiency reaches up to 〈ϵ〉 ≈ 0.43, compared to a stationary energy extraction by the Blandford/Znajek process. The process efficiency depends on the cross-sectional area of the loops, i.e. on the product l × h, where l is the radial loop thickness and h its vertical scale height. We identify a strong correlation between efficient electromagnetic energy extraction and the quasi-stationary setting of ideal conditions for the operation of the Blandford/Znajek process (e.g. optimal field line angular velocity and fulfillment of the so-called Znajek condition). Remarkably, the energy extraction operates intermittently (alternating episodes of high and low efficiency) without imposing any large-scale magnetic field embedding the central object. Scaling our results to supermassive black holes, we estimate that the typical variability time-scale of the system is of the order of days to months. Such time-scales may account for the longest variability scales of TeV emission observed, e.g. in M87.</abstract><pub>Oxford University Press</pub><doi>10.1093/mnras/staa943</doi><tpages>23</tpages><orcidid>https://orcid.org/0000-0002-5552-7681</orcidid><orcidid>https://orcid.org/0000-0002-5349-7116</orcidid></addata></record> |
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title | Striped Blandford/Znajek jets from advection of small-scale magnetic field |
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