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Magnetic dynamos refer to the transfer of kinetic energy to magnetic energy in plasmas. A non-zero average of kinetic helicity greatly helps the magnetic field amplification at scales larger than the turbulence scale--the so-called alpha effect. However, numerical simulations have revealed that with the help of a background shear flow (e.g., differential rotation), a non-helical turbulence can also produce a large-scale dynamo. Such dynamos may operate in stellar radiative zones, accretion disks, or binary neutron star mergers. A clear understanding of the mechanism of shear dynamos is still lacking. In this talk, I will first introduce astrophysical dynamos, followed by a brief history of the shear dynamo problem. I will then explain the two plausible shear dynamo drivers, the shear-current effect and the incoherent alpha effect, and numerical evidence supportive or against each of them. Some concluding remarks will be made regarding the connection to accretion systems.
Hongzhe Zhou obtained his PhD degree at University of Rochester in 2020. He was then a Postdoc Fellow at Nordita in Stockholm for two years. He is now a Postdoc Fellow at TDLI.