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).