  High temporal and high spatial resolution geoelectric field models of two
M\"ants\"al\"a, Finnish pipeline GIC intervals that occurred within the 7-8
September, 2017 geomagnetic storm have been made. The geomagnetic measurements
with 10 s sampling rate of 28 IMAGE ground magnetometers distributed over the
north Europe (from $52.07^\circ$ to $69.76^\circ$ latitude) are the bases for
the study. A GeoElectric Dynamic Mapping (GEDMap) code was developed for this
task. GEDMap considers 4 different methods of interpolation and allows a grid
of $0.05^\circ$ (lat.)$\times 0.2^\circ$ (lon.) spatial scale resolution. The
geoelectric field dynamic mapping output gives both spatial and temporal
variations of the magnitude and direction of fields. The GEDMap results show
very rapid and strong variability of geoelectric field and the extremely
localized peak enhancements. The magnitude of geoelectric fields over
M\"ants\"al\"a at the time of the two GIC peaks were 279.7 mV/km and 336.9
mV/km. The comparison of the GIC measurements in M\"ants\"al\"a and our
modeling results show very good agreement with a correlation coefficient higher
than 0.8. It is found that the auroral electrojet geoelectric field has very
rapid changes in both magnitude and orientation causing the GICs. It is also
shown that the electrojet is not simply oriented in the east-west direction. It
is possible that even higher time resolution base magnetometer data of 1 s will
yield even more structure, so this will be our next effort.
