Simulating the Solar Minimum Corona in UV and Visible/IR Wavelengths with Forward Modeling

The magnetic field in the corona is important for understanding solar activity, but is difficult to measure due to the tenuous plasma. Therefore many alternative methods have been adopted to get the 3D magnetic field in the corona, such as extrapolation methods relying on the photospheric magnetograms. Such extrapolations make problematic assumptions about the force-free nature of the photosphere, and are highly sensitive to uncertainties in the photosphere magnetic measurements. Measuring the coronal magnetic field directly is thus to be desired, and linear polarization measurements in the visible/IR are already obtained by the CoMP telescope providing information about coronal magnetic direction and topology. However other observations such as circular polarization in the visible/IR and UV unsaturated Hanle measurements are needed to better observe the 3D coronal field. Until such observations are available, we turn to the FORWARD model (Gibson et al. 2016) which simulates all of these polarization data. As a physical state to input into FORWARD, the analytic magnetic model in this work is adopted from Gibson et al.(1996), which gives a potential field with an exception at the boundary of the helmet streamer where current sheets are added between the open and closed fields. This analytic model has the benefit of matching white light and also photospheric magnetic flux observations at solar minimum. Given this model input of a 3D distribution of magnetic field and plasma, we obtain simulated polarization results in UV and visible/IR wavelengths under unsaturated and saturated Hanle effect regime, respectively. We compare the polarization signals under these two regimes, which will allow us to consider how such observations might be used together in future to diagnose the coronal magnetic field.