A New Technique for Mapping Open Magnetic Flux from the Solar Surface into the Heliosphere

Abstract

The solar wind carries magnetic flux from the photosphere into the heliosphere, making it topologically open in the corona. Open magnetic flux is unevenly distributed at the solar surface, but at some distance in the outer corona it becomes uniformly distributed and approximately radial. Standard potential field models do not provide such uniform distribution of open flux in the heliosphere. A new technique for mapping open magnetic flux is presented here that addresses this deficiency and provides a simple tool to map any initial configuration of photospheric footpoints into the heliosphere. This technique is designed to result in a uniform open flux distribution in the heliosphere and is especially useful for models that include open flux emerging from topologically closed regions. We compare with observations of proton speed to quantify the amount of open flux emerging from these regions. We find that if the slow solar wind originates from topologically closed regions, then the open flux coming from these areas must form a significant component of the heliosphere. We explain this new methodology and discuss its application throughout the solar cycle.