A Possible Mechanism for the Origin of Emerging Flux in the Sunspot Moat

Mass and energy flow near sunspots are associated with the emergence of magnetic flux, which then moves outward in the sunspot moat. We present results of analytical and numerical studies of the interaction of horizontal magnetic flux and plasma flows in three-dimensional geometry. We show that nonlinear coupling of flux and plasma flows in the presence of a gravitational field lead to nonlinear dissipative instabilities that result in the formation of a solitary kink along the magnetic flux. The stability of a kink and its further evolution depend on the physical parameters of magnetic flux and the surrounding medium. We discuss two major cases—magnetic soliton-like and shocklike propagation along the magnetic flux—and specify the appropriate physical conditions for their realization. In photospheric conditions, the proposed mechanism may be a good candidate for understanding of the dynamics of small-scale magnetic flux in the enhanced network at the solar surface. We apply our results to the observed properties of emerging flux in the sunspot region associated with moving magnetic features and find reasonable qualitative and quantitative agreement.