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We have performed a series of numerical experiments aimed at studying theactivation of Kerr black holes (BHs) by advection of small scale magneticfields. Such configurations may potentially give rise to the formation ofquasi-striped Blandford-Znajek jets. It can also lead to enhanced dissipationand generation of plasmoids in current sheets formed in the vicinity of the BHhorizon, which may constitute a mechanism to power the hard X-ray emission seenin many accreting BH systems (a la lamppost models). Our analysis suggests thatformation of quasi-striped jets with significant power may be possible providedloops with alternating polarity having sizes larger than $\sim 10 r_g$ or socan be maintained (either form sporadically or advected from outside) at aradius $\lesssim 10^2 r_g$. This conclusion is consistent with recent resultsof general relativistic force-free simulations. We also find that the accretiondynamics exhibits cyclic behaviour in MAD states, alternating between highaccretion phases and quenched accretion phases during which the magnetospherebecomes force-free out to radii $\gtrsim 10r_g$. We suggest that such abehaviour should lead to notable variations of the observed luminosity andimage of the inner disc (BH shadow image). Finally, we find that the transitionbetween accreted loops on the BH gives rise to the formation of current sheetsand energetic plasmoids on the jet boundary during intermittent periods whenthe jet becomes inactive, in addition to an equatorial current sheet that formsduring peaks in the jet activity.

GRMHD simulations of BH activation by small scale magnetic loops: Formation of striped jets and active coronae