Figures Captions
Figure 1. Interplanetary parameters during September 24, 2020.
IMF Bz and By (first panel), solar wind speed (second panel), solar wind
density (third panel) and interplanetary electric field (IEF) dawn-dusk
component (forth panel). The time interval for detailed analysis is
highlighted with cyan color from 05 to 06 UT, when the IMF Bz turned
northward and southward.
Figure 2. Same as Figure 1 but for September 26, 2920.
Figure 3. Interplanetary parameters from September 24, 05-06
2020. The 6 samples represent S-IMF to N-IMF cases. For the S-IMF cases,
the IEF dawn-dusk component is positive. During the N-IMF cases, the IEF
is mostly negative.
Figure 4a . High latitude potential map during the September 24,
05-06, 2020. The noon is on the top and midnight at bottom. The
equatorial boundary is at 40N. Dawn is on the right and dusk on the
left. During the S-IMF cases, the two-cell convection pattern dominates.
In case of N-IMF, the potential map shows multi-cell convection
patterns. The Cross Polar Cap Potential (CPCP) is estimated based on the
maximum and minimum values. The CPCP is much larger during the S-IMF
than in the N-IMF cases.
Figure 4b. Same as Figure 5a but extended to the equator. By
extending to the equator, the penetrating electric field effect to the
equatorial region can be seen. The yellow arrows indicate the direction
of the electric field during the S-IMF and N-IMF cases on the day and
nightside of the equatorial region.
Figure 5. IEF, CPCP, and equatorial potential drop (dawn/dusk
during S-IMF). Least squares fit for CPCP vs equatorial potential drop.
Figure 6a. Nightside vertical ion drift at the magnetic equator
(black arrows downward drift shown as pointing southward in the figure)
of September 24, 05-06 UT. Background is the nmf2 from the MAGE. Dusk is
on the left. EIAs are clearly seen on the duskside. PRE is present in
the first case. The vertical ion drift varies with IMF Bz component and
equatorial electric field. During S-IMF cases, the vertical ion drifts
are mostly downward. The scale vector is for 20 m/s.
Figure 6b. Same as Figure 6a but for dayside vertical ion
drift. In most cases, the vertical ion drifts are upward.
Figure 7. The equatorial thermospheric zonal wind during
September 24 05-06 UT at ~ 400 km. The eastward zonal
winds are positive shown as pointing northward with black vectors in the
figure. The scale vector is for 20 m/s.
Figure 8. Interplanetary parameters for September 26, 09-10 UT
in the same format as Figure 4.
Figure 9. Comparison of the ICON ExB meridional ion drift (cyan
and magenta vector lines from the ICON satellite track) with simulated
ExB meridional ion drift (black line above the ICON satellite track) for
September 26, 09-10 UT. The magenta vectors coincide with the time of
the MAGE simulation for that particular subplot. As the ICON satellite
cannot sample all spatial locations in the subplot simultaneously, the
satellite only measures a subsection for the section matching the time
of simulation. The background is the nmf2. The equatorial vertical ion
drift is shown as black vectors as in Figure 6b.
Figure 10. ICON IVM ExB meridional ion drift offset correction.
The uncorrected IVM ion drift from 9-10 UT on Sep 26, 2020 (green) and
daily magnetic local time hourly median values (orange). The 6-minute
MLT median values have an offset of 37 m/s at 18 MLT, when the value on
average should be zero. We use the 37 m/s offset corrected the IVM
meridional ion drift (blue). The IVM data have issue with low ion
density and photoelectron contamination before 12 MLT. Only the data
after 12 MLT are used to compare with the model simulation.
Figure 11. Same as Figure 9, but for the corrected ICON IVM ExB
meridional ion drift comparison with the model simulation.