## 4 Result and Discussion
### Comparison and Results  
The ratio \(\delta\) calculated using Equation (4), the AD and RMSE of the initial electron density, MART0, and MART1 at 00:00, 06:00, and 12:00 are listed in Table 1.  
It can be inferred from Table 1 that the process of MART iterations optimizes the initial values toward the background true electron density values, and the AD and RMSE values of the reconstructed electron densities for both MART0 and MART1 are smaller than the initial values. At 00:00, \(|\delta-1|=0.1222\); the AD of the initial electron density is 2.1 times the AD of MART0 and 2.5 times the AD of MART1; and the RMSE of the initial electron density \begin{table}
\begin{tabular}{c c c c c c} \hline \hline  & \multicolumn{2}{c}{**00:00**} & \multicolumn{2}{c}{**06:00**} & \multicolumn{2}{c}{**12:00**} \\  & \(\delta\) = **0.8778** & \(\delta\) = **1.4368** & \(\delta\) = **1.0092** \\  & **AD** & **RMSE** & **AD** & **RMSE** & **AD** & **RMSE** \\ \hline Initial & 2.33 \(\times\) 10\({}^{10}\) & 3.64 \(\times\) 10\({}^{10}\) & 4.82 \(\times\) 10\({}^{10}\) & 7.42 \(\times\) 10\({}^{10}\) & 3.95 \(\times\) 10\({}^{10}\) & 7.25 \(\times\) 10\({}^{10}\) \\ MART0 & 1.10 \(\times\) 10\({}^{10}\) & 1.96 \(\times\) 10\({}^{10}\) & 1.61 \(\times\) 10\({}^{10}\) & 2.74 \(\times\) 10\({}^{10}\) & 1.36 \(\times\) 10\({}^{10}\) & 3.02 \(\times\) 10\({}^{10}\) \\ MART1 & 9.15 \(\times\) 10\({}^{9}\) & 1.67 \(\times\) 10\({}^{10}\) & 9.34 \(\times\) 10\({}^{9}\) & 1.53 \(\times\) 10\({}^{10}\) & 1.36 \(\times\) 10\({}^{10}\) & 2.99 \(\times\) 10\({}^{10}\) \\ \hline \hline \end{tabular}
\end{table} 
Table 1: Electron density comparison at 00:00, 06:00 and 12:00.  
is 1.86 times the RMSE of MART0 and 2.18 times the RMSE of MART1. The AD and the RMSE is improved by 16.8% and 14.8% by MART1 and MART0, respectively. At 06:00, \(|\delta-1|=0.4368\); the AD of the initial value is 3 times the AD of MART0 and 5.16 times the RMSE of MART1; and the RMSE is 2.7 times the RMSE of MART0 and 4.85 times that of MART1. The improvements in the 3D electron density reconstruction at 00:00 and at 06:00 are evident. The AD and the RMSE are improved by 42% and 44.2% by MART1 and MART0, respectively. Thus, our new method effectively improves the quality of the 3D electron density reconstruction at 00:00 and at 06:00, in the condition that the adjustment factor \(\delta\) deviates from 1. At 12:00, \(|\delta-1|=0.0092\); the AD and RMSE values for MART0 and MART1 are similar, with the initial values of AD being 2.9 times that of MART0 and MART1; and the RMSE is 2.4 times that of MART0 and MART1. Therefore, the adjustment factor \(\delta\), which is the ratio between the simulated STEC and the STEC calculated using the initial value and parameter matrix, is an important parameter affecting the iteration accuracy of the MART1 method. In the CIT process, we can evaluate the chosen initial electron density by examining the relation between \(\delta\) and 1. If the discrepancy between \(\delta\) and 1, which can be written as \(|\delta-1|\), is smaller and closer to 0, as is the case at 12:00, it means that the initial electron density is well selected, so the initial value of the MART1 iteration is not much different from that of MART0 iteration and its AD and RMSE are also similar. In this case, a closer match between the initial value and the background true electron density also provides better iterative results, and there is no need to use \(\delta\) to optimize the initial electron density before the MART process. In cases where \(|\delta-1|\) is larger than 0.1 at 00:00 and 06:00, MART1 performs better than MART0 because the discrepancy between the simulated STEC and true STEC is larger, and the adjustment factor \(\delta\) is optimized the initial electron density as a whole, especially at the altitudes of maximum electron density, which is the most important part of the ionosphere.