TY - JOUR
T1 - GRMHD simulations of BH activation by small scale magnetic loops
T2 - Formation of striped jets and active coronae
AU - Chashkina, Anna
AU - Bromberg, Omer
AU - Levinson, Amir
N1 - Publisher Copyright:
© 2021 The Author(s).
PY - 2021/11/1
Y1 - 2021/11/1
N2 - We have performed a series of numerical experiments aimed at studying the activation of Kerr black holes (BHs) by advection of small scale magnetic fields. Such configurations may potentially give rise to the formation of quasi-striped Blandford-Znajek jets. It can also lead to enhanced dissipation and generation of plasmoids in current sheets formed in the vicinity of the BH horizon, which may constitute a mechanism to power the hard X-ray emission seen in many accreting BH systems (a la lamppost models). Our analysis suggests that formation of quasi-striped jets with significant power may be possible provided loops with alternating polarity having sizes larger than ∼10rg or so can be maintained (either form sporadically or advected from outside) at a radius ≤ 102rg. This conclusion is consistent with recent results of general relativistic force-free simulations. We also find that the accretion dynamics exhibits cyclic behaviour in Magnetically Arrested Disc states, alternating between high accretion phases and quenched accretion phases during which the magnetosphere becomes force-free out to radii Z 10rg. We suggest that such a behaviour should lead to notable variations of the observed luminosity and image of the inner disc (BH shadow image). Finally, we find that the transition between accreted loops on the BH gives rise to the formation of current sheets and energetic plasmoids on the jet boundary during intermittent periods when the jet becomes inactive, in addition to an equatorial current sheet that forms during peaks in the jet activity.
AB - We have performed a series of numerical experiments aimed at studying the activation of Kerr black holes (BHs) by advection of small scale magnetic fields. Such configurations may potentially give rise to the formation of quasi-striped Blandford-Znajek jets. It can also lead to enhanced dissipation and generation of plasmoids in current sheets formed in the vicinity of the BH horizon, which may constitute a mechanism to power the hard X-ray emission seen in many accreting BH systems (a la lamppost models). Our analysis suggests that formation of quasi-striped jets with significant power may be possible provided loops with alternating polarity having sizes larger than ∼10rg or so can be maintained (either form sporadically or advected from outside) at a radius ≤ 102rg. This conclusion is consistent with recent results of general relativistic force-free simulations. We also find that the accretion dynamics exhibits cyclic behaviour in Magnetically Arrested Disc states, alternating between high accretion phases and quenched accretion phases during which the magnetosphere becomes force-free out to radii Z 10rg. We suggest that such a behaviour should lead to notable variations of the observed luminosity and image of the inner disc (BH shadow image). Finally, we find that the transition between accreted loops on the BH gives rise to the formation of current sheets and energetic plasmoids on the jet boundary during intermittent periods when the jet becomes inactive, in addition to an equatorial current sheet that forms during peaks in the jet activity.
KW - Accretion, accretion discs
KW - Galaxies: Jets
KW - MHD
KW - Magnetic fields
KW - Magnetic reconnection
KW - Methods: numerical
UR - http://www.scopus.com/inward/record.url?scp=85118125506&partnerID=8YFLogxK
U2 - 10.1093/mnras/stab2513
DO - 10.1093/mnras/stab2513
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AN - SCOPUS:85118125506
SN - 0035-8711
VL - 508
SP - 1241
EP - 1252
JO - Monthly Notices of the Royal Astronomical Society
JF - Monthly Notices of the Royal Astronomical Society
IS - 1
ER -