Emergence of solar magnetic flux from the convection zone into the photosphere and chromosphere

Abstract

A two-dimensional MHD code is used to study the nonlinear dynamics of solar magnetic flux emerging from the convection zone into the photosphere and chromosphere. An isolated horizontal magnetic flux with beta of about 4 is initially located in a convectively unstable layer (solar convection zone) beneath a two-temperature layered atmosphere (solar corona-chromosphere/photosphere). The combined effects of convection and magnetic buoyancy carry the magnetic flux from the convection zone into the photosphere, where it then expands through the photosphere and chromosphere. Gas slides down the expanding loop, resulting in its evacuation and subsequent rise due to enhanced magnetic buoyancy. Initially, weak convection zone magnetic flux (B of about 600 G) is amplified up to 1000 G or more after emerging into the photosphere. The resulting velocity fields are similar to those observed in arch filament systems. 19 refs.