Poster Presentation
Production of intense episodic Alfvén pulses: GRMHD simulation of black hole accretion discs
Presenter: Akira Mizuta (RIKEN)
We have performed three dimensional general relativistic magnetohydrodynamic simulations of accretion flows onto spinning supermassive black holes to see the magnetic field activities in the accretion disk. Magnetic fields are amplified by growth of magnetorotational instability (MRI) and then dissipate due to magnetic reconnection. Soon magnetic field is amplified again. These cycle episodically occurs, generating timevariavlities in the system. Such disc activities cause short-time variabilities in mass accretion rate at the event horizon. We also find that the eruption events produce intensive Alfvén pulses from the accretion disk to outside the accretion disk, when magnetic fields in the accretion disk dissipates. Some of vertically emitted Alfvén pulses propagate through the jets. Since such Alfvén pulses is ultrarelativistic waves, charged particles such as protons and electrons in the jet are accelerated via ponderomotive force, manifesting as ultra-high-energy cosmic rays and electrons, which finally emit gamma-rays.
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