Description
The magnetic field in the solar corona plays a dominant role in determining the dynamics of the high temperature, low density coronal plasma. Despite the importance of the coronal magnetic field, there is a distinct lack of analytical models based on empirical data. How fast the magnetic field expands with height is known as the expansion factor and this is intrinsically related to the acceleration of the solar wind. The magnetic decay index is dependent upon the characteristic scale of the coronal magnetic field and determines the onset of the torus instability which can drive coronal mass ejections (CMEs). We aim to quantify the variation of magnetic field strength with altitude, B(h), in the solar corona to better understand the expansion factor and the decay index. B(h) differs across the Sun, in part depending on the magnetic field strength and distribution in the photosphere. We fit the B(h) profiles from >24,000 magnetic field extrapolations from >4,000 unique active region patches. We report on the B(h) profiles we find, including the typical best fit parameters and how they relate to the photospheric magnetic field distribution. In doing so, we will give insight into the expansion factor and the decay index, and therefore the driving of the solar wind and CMEs.
