The sun's magnetic field during the past two minima

The past three years have been characterized by very weak sunspot and CME activity making this a long and deep solar minimum. In spite of the lack of magnetic activity at the Sun, white light and EUV images have shown that a relatively complex corona with multiple streamers and low latitude coronal holes persisted during most of this extended minimum. At the same time, solar wind observations indicated that the heliospheric current sheet was more warped during the declining and minimum phase of this cycle. This morphology of the corona and heliosphere differs from the one observed during the previous solar minimum when coronal streamers were confined to low heliolatitudes and the heliospheric current sheet was nearly flat. Interestingly, the polar magnetic fields observed at the solar photosphere during the present minimum are about 40% weaker than during the previous minimum. We use a potential field model to test if the weaker polar fields (and associated weaker dipole moment) can explain the differences observed in the corona and heliosphere during the past two minima.