Jets are observed in the low/hard state of a transient black hole binary (BHB). Jet production is proposed to be connected to the presence of a radiatively inefficient accretion flow (RIAF) and the large-scale magnetic fields close to the accreting black hole (BH). However, the source of the large-scale fields is not quite obvious. Two credible sources of the large-scale magnetic fields are: i) in-situ generation of the magnetic field by dynamo action and ii) advection of the large-scale field from an external source (e.g., the companion star in BHBs). In this talk, I will discuss the efficiency of both processes, which have been studied using state-of-the-art 3D global general relativistic magnetohydrodynamic (GRMHD) simulations. First, I will discuss large-scale magnetic field generation by a magneto rotational instability (MRI) driven dynamo and talk about its inefficiency in providing sufficient magnetic flux required to produce a strong jet in a geometrically thick RIAF. Next, I will discuss the other possibility, where the large-scale magnetic fields are advected inward from external sources (e.g. the companion star in X-ray binaries, magnetized ambient medium in AGNs). As a first study, we treat the external magnetic flux as closed field loops of different sizes, shapes and field strengths and study their transport. Then I will conclude the talk by drawing a connection between the magnetic flux transport efficiency and the possible formation of a magnetically dominated RIAF, potentially a magnetically-arrested disk close to the accretor.
I was awarded my PhD degree from the Indian Institute of Science, Bangalore, India, in 2019. Then I joined Tsinghua University as a postdoc with Xuening in September 2019 and was there till July 2021. Now, I am a postdoc at the Inter-University Centre for Astronomy and Astrophysics, Pune, India. Next, I am moving to JILA, UC Boulder, this semester.