Active Region Photospheric Magnetic Properties Derived from Line-of-sight and Radial Fields

The effect of using two representations of the normal-to-surface magnetic field to calculate photospheric measures that are related to active region (AR) potential for flaring is presented. Several AR properties were computed using line-of-sight ($B_{\rm los}$) and spherical-radial ($B_{r}$) magnetograms from the Space-weather HMI Active Region Patch (SHARP) products of the \emph{Solar Dynamics Observatory}, characterizing the presence and features of magnetic polarity inversion lines, fractality, and magnetic connectivity of the AR photospheric field. The data analyzed corresponds to $\approx$ 4,000 AR observations, achieved by randomly selecting 25 % of days between September 2012 and May 2016 for analysis at 6-hr cadence. Results from this statistical study include: i) the $B_{r}$ component results in a slight upwards shift of property values in a manner consistent with a field-strength underestimation by the $B_{\rm los}$ component; ii) using the $B_{r}$ component results in significantly lower inter-property correlation in one-third of the cases, implying more independent information about the state of the AR photospheric magnetic field; iii) flaring rates for each property vary between the field components in a manner consistent with the differences in property-value ranges resulting from the components; iv) flaring rates generally increase for higher values of properties, except Fourier spectral power index that has flare rates peaking around a value of $5/3$. These findings indicate that there may be advantages in using $B_{r}$ rather than $B_{\rm los}$ in calculating flare-related AR magnetic properties, especially for regions located far from central meridian.