Research Progress on Solar Small-Scale Dynamo
The small-scale solar dynamo theory, as the core mechanism explaining the origin of the persistent, disperse weak magnetic field in the quiet Sun regions, has made significant progress over the past three decades in the fields of observation, theory, and simulation. Breakthrough observations from high-resolution space-based and ground-based telescopes have revealed that the quiet Sun is ubiquitously populated by highly dynamic, mixed-polarity and possibly predominantly horizontal magnetic structures with complex topology. These observations confirm that their total magnetic flux is substantial, with a high and widely distributed magnetic flux emergence rate, strongly suggesting a local dynamo effect independent of the solar cycle and driven by intense turbulence and convection. Theoretical studies indicate that even in the challenging low magnetic Prandtl number ( Pm << 1) environment of the solar photosphere and convection zone, turbulent motions can self-excitedly convert kinetic energy into magnetic energy through the stretching, folding, and twisting of magnetic field lines. MHD simulations have successfully reproduced observed features, demonstrating that a pure small-scale dynamo can operate efficiently and sustain magnetic fields even in an open, stratified solar environment incorporating realistic physical processes. Current research strongly suggests that small-scale magnetic fields constitute the majority of the magnetic energy in the quiet Sun and also influence coronal heating, solar wind acceleration, and radiation distribution. This article conducts a literature review centered on observations, theoretical models, and numerical simulations of the small-scale dynamo, organizing and discussing the relevant research history and progress. Finally, it summarizes the content and provides an outlook on future research from multiple perspectives.