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.