Temporal 1/fα Fluctuations from Fractal Magnetic Fields in Black-Hole Accretion Flow

Rapid fluctuation with a frequency dependence of 1/fα (with α ≃ 1–2) is characteristic of radiation from black-hole objects. Its origin remains poorly understood. We examined three-dimensional magnetohydrodynamical simulation data, finding that a magnetized accretion disk exhibits both 1/fα fluctuation (with α ≃ 2) and a fractal magnetic structure (with the fractal dimension of D ∼ 1.9). The fractal field configuration leads to reconnection events with a variety of released energy and duration, thereby producing 1/fα fluctuations.