Collaborator (Black Holes)
I am a professor at the Canadian Institute for Theoretical Astrophysics at the University of Toronto. My research focuses on the fundamental plasma physics of neutron star and black hole magnetospheres, jets, coronae and accretion disks to understand their high-energy emission. I am also a member of the Event Horizon Telescope where I focus mostly on understanding the multiwavelength emission from radio to gamma-rays coming from nearby the event horizon of Sgr A* and M87*.
I am fascinated by the most extreme regions in the universe, and these are exactly the places the SCEECS wants to tackle. I am a plasma physicist by nature, and I see the universe as our plasma physics laboratory.
I am currently most excited about the multimessenger and multiwavelength signals that we have observed from isolated and binary black holes and neutron stars. Modeling and understanding these signals require a combination of theoretical and numerical (general) relativistic kinetic and fluid methods to capture the large astrophysical scales and the microscopic particle scales where the emission is powered. The universe, and in particular the environment of neutron stars and black holes is a testbed for energy, mass, and length scales that are unreachable on Earth. This synergy and combination of different areas of physics (quantum electrodynamics, general relativity, plasma physics, particle physics) that is required to understand the regions of extreme gravity and energy is what drives my curiosity.
I have developed numerical methods that can capture dissipation and particle acceleration mechanisms like turbulence and magnetic reconnection in global magnetohydrodynamics simulations of accreting black holes. We have been able to simulate the formation of a reconnection layer nearby the event horizon of a supermassive black hole that can power high-energy flares through synchrotron and inverse Compton radiation. Recently I have been most interested on applying the methods I developed to multiwavelength emission (fast radio bursts, X-ray and gamma-ray flares) from magnetars and neutron star-black hole binaries. Our collaborators in the SCEECS are world-renowned experts in these topics so I am very excited to learn from them and work with them to solve these open questions in high-energy astrophysics.
Five recent relevant references
A. Galishnikova, A.A. Philippov, E. Quataert, F. Bacchini. K. Parfrey, B. Ripperda, Collisionless accretion onto black holes: dynamics and flares, PRL (2023), 130, 115201, DOI: https://doi.org/10.1103/PhysRevLett.130.115201
H. Hakobyan, B. Ripperda, A.A. Philippov, Radiative reconnection-powered TeV flares from the black hole magnetosphere in M87, ApJ Letters (2023), 943, L29, DOI: https://doi.org/10.3847/2041-8213/acb264
B. Ripperda, M. Liska, K. Chatterjee, G. Musoke, A.A. Philippov, A. Tchekhovskoy, Z. Younsi, S.B. Markoff, Black hole flares: ejection of accreted magnetic flux regulated by plasmoid-mediated reconnection, ApJ Letters (2022), 924, L32 DOI: https://doi.org/10.3847/2041-8213/ac46a1
A. Bransgrove, B. Ripperda, A.A. Philippov, Magnetic hair and reconnection in black hole magnetospheres, PRL (2021), 127, 055101, DOI: https://doi.org/10.1103/PhysRevLett.127.055101
B. Ripperda, F. Bacchini, A. Philippov, Magnetic reconnection and hot spot formation
in black hole accretion disks, ApJ (2020), 900, 2, DOI: https://doi.org/10.3847/1538-4357/ababab