The Effects of Including Farside Observations on In Situ Predictions of Heliospheric Models

Abstract

A significant challenge facing heliospheric models is the lack of full Sun observational coverage. The lack of information about the farside photospheric magnetic field necessitates the use of various techniques to approximate the structure and appearance of this field. However, a recently developed technique that uses He ii 304 Å emission observed by the Solar Terrestrial Relations Observatory (STEREO) enables developing a magnetic flux proxy by imaging of active regions on the far side of the Sun. Incorporating information about these active regions on the far side of the Sun may have the potential to drastically improve heliospheric models. In this work, we run multiple heliospheric models with and without farside information obtained from STEREO observations of He ii 304 Å emission and compare the predicted in situ measurements from the models with real in situ data from STEREO and Earth. We find that although there are noticeable quantitative differences between the in situ predictions from the two models, they are dwarfed by the overall disagreement between the heliospheric model and the actual in situ data. Nevertheless, our results indicate that active regions that significantly change the ratio of open-to-closed and open-to-total flux create the biggest change in the predicted in situ measurements.