## 4 Discussion on the Corresponding Processes in Ionosphere  
### The Comparison of Plasma Parameters at Different Altitudes  
Among the three satellites of Swarm, Ne, and Te from satellite A and B, different altitudes were collected and plotted in Figure 6. For Swarm-A, the local daytime was mainly between 13:00-15:00 at low and middle latitudes from 24-29 August, being close to the local time of CSES at 14:00. However, the altitude of Swarm-A was 435-455 km, about 60 km lower than CSES. As shown in Figure 6, the similar evolutional features were detected from Swarm-A as those on CSES, with significant increases in Ne in the equatorial area following the last few hours on 25 August to the first few hours on 26 August and the enhanced equatorial Te valley at the same time. From 27-29 August, the peak equatorial Ne was still enhanced, and the double peaks were illustrated clearly at the altitude of Swarm-A. In the meantime, the strong valley in Te continued with an obvious extension to the southern side. For Swarm-B, its altitude was close to CSES, but its local daytime from 24-29 August was mainly in the morning from about 08:00-11:00. In Figure 7 Ne from Swarm-B was relatively smaller than that on Swarm-A, due to its higher altitude and the early local time. Around this magnetic storm, the obvious increase in equatorial Ne can be found in the last few hours on 25 August. However, on 26 August, there was no distinct enhancement most of the time throughout the whole day. Since 27 August, the typical equatorial peak of Ne recovered again. From the temporal distribution of Te in Figure 7, its minimum values at the equatorial area occurred on 27 and 28 August, during the recovery phase, not in the main phase. These phenomena demonstrate that the difference in local time, as Swarm-B will severely influence the distribution features of Ne and Te during the magnetic storm. \begin{table}
\begin{tabular}{l c c c c c c c c} \hline \hline
**Latitudes** & **45–60° S** & **30–45° S** & **15–30° S** & **0–15° S** & **0–15° S** & **15–30° N** & **30–45° N** & **45–60° N** \\ \hline
1125 Hz & \(-\)0.51 & **0.68** & 0.085 & 0.37 & 0.076 & \(-\)0.096 & \(-\)0.091 & \(-\)**0.76** \\ \hline \hline \end{tabular}
\end{table} 
Table 2: _Cont._  
Figure 6: The electron density (**a**) and electron temperature (**b**) from Swarm-A in local daytime during 24 to 29 August in 2018. In ionospheric research, scientists use the GNSS signals to obtain the total electron content (TEC) for monitoring the ionospheric environment. Here we collected the global TEC mapping data published by CODE [44] and transferred the universal time to local time to compare with the observations of CSES and Swarm. Figure 8 showed the global TEC at local time of 09, 11, 13, and 15 for each day from 25 to 28 August. By the panels at LT09:00 in four days, the increase in TEC was not so clear at the main phase on 26 August, which was consistent with that on Swarm-B. At LT 13-15, the double peaks at the equatorial area were enhanced on 26 August (Figure 9b), especially in the eastern hemisphere. Until 28 August (Figure 9d), the double peaks occurred almost globally, which verified the observations of Ne from Swarm-A at lower altitudes. At the altitude 507 km of CSES, the double peak effect was only distinct on 26 August at the main phase of the storm, but during 27-29 it was widely flat without double peaks. Compared with the observations of foF2 and TEC in South American sector [21], TEC from CODE exhibited little increase at LT09 on 26 August relative to that on 25 August, and an obvious increase at LT 11-15 from 26-28 August, even with double peaks occurring at low latitudes of this region at LT 13-15 on 28 August during the slow recovery phase, while the small decrease in foF2 at the equator and low latitude at the initial stage of the main phase was not revealed in our results.