The comparison shows that the SAMI3 model more accurately reproduces the MIDAS GPS TEC data when using the AMPERE-derived potential. The location and extent of the tongue of ionization is more accurately modeled by SAMI3/AMPERE than by SAMI3/Weimer. Some common biases are present in both model runs, especially at lower latitudes (45 – 60° N). TEC is overestimated in the evening sector (0-90° W) and underestimated in the morning sector (150° E – 90° W). Although these biases are unrelated to the high-latitude potential, they play a role in skewing the formation of the tongue of ionization towards the evening sector in both model runs.
For most of this event, the Weimer potential is much larger than the AMPERE-derived potential. On average, the Weimer cross-cap potential is 77 kV whereas the AMPERE-derived potential is only 60 kV. This large potential causes an over-extension of the tongue of ionization in SAMI3/Weimer as compared to the GPS-derived TEC data. Figure 7 shows the extent of the two cross-cap potential options over the 23 May 2014 case (the plot shows the maximum and minimum values of the polar cap potential estimated by each technique).