# Automatic Detection of Whistler Waves in the Top-Side Ionosphere: The WhISPER Technique
## 3 Results  
Although the generation and propagation mechanisms of whistlers are relatively well understood, the location and extent of lightning source region for the observed whistlers remain uncertain [48]. Moreover, the geophysical conditions governing whistler occurrence are poorly understood [49; 50]. These uncertainties make whistler events difficult to predict, hindering a quantitative understanding of their propagation and ionospheric impact. Addressing these limitations requires a comprehensive statistical analysis of an extensive event dataset. Here, we present the results of a statistical investigation of whistler wave occurrence, derived from CSES-01 observations between 1 January 2019 and 31 December 2022. This study concentrates on whistler occurrence rates, with a detailed analysis of \begin{table}
\begin{tabular}{c c c c} \hline \hline
**Metrics** & **Set 1** & **Set 2** & **Set 3** \\ \hline \begin{tabular}{c} **Accuracy** \\ \(\text{ACC}=\frac{\text{TP}_{\text{k}}+\text{TN}}{\text{P}_{\text{k}}+\text{N} }\) \\ \end{tabular} & 0.96 & 0.42 & 0.92 \\ \hline \begin{tabular}{c} **True Positive Rate** \\ \(\text{TPR}=\frac{\text{TP}}{\text{P}}\) \\ \end{tabular} & 0.96 & 0.37 & 1 \\ \hline \begin{tabular}{c} **False Negative Rate** \\ \(\text{FNR}=\frac{\text{FN}}{\text{P}}\) \\ \end{tabular} & 0.04 & 0.63 & 0 \\ \hline \begin{tabular}{c} **False Positive Rate** \\ \(\text{FPR}=\frac{\text{FP}}{\text{N}}\) \\ \end{tabular} & 0.06 & 0.04 & 0.99 \\ \hline \begin{tabular}{c} **True Negative Rate** \\ \(\text{TNR}=\frac{\text{TN}}{\text{N}}\) \\ \end{tabular} & 0.94 & 0.96 & 0.01 \\ \hline \begin{tabular}{c} **Positive Predictive Value** \\ \(\text{PPV}=\frac{\text{TP}}{\text{TP}+\text{FP}}\) \\ \end{tabular} & 0.99 & 0.99 & 0.92 \\ \hline \begin{tabular}{c} **False Omission Rate** \\ \(\text{FOR}=\frac{\text{FN}}{\text{TN}+\text{FN}}\) \\ \end{tabular} & 0.33 & 0.88 & 0 \\ \hline \begin{tabular}{c} **False Discovery Rate** \\ \(\text{FDR}=\frac{\text{FP}}{\text{TP}+\text{FP}}\) \\ \end{tabular} & 0.01 & 0.01 & 0.08 \\ \hline \
\begin{tabular}{c} **Negative Predicted Value** \\ \(\text{NPV}=\frac{\text{TN}}{\text{TN}+\text{FN}}\) \\ \end{tabular} & 0.67 & 0.12 & 1 \\ \hline
\begin{tabular}{c} **F1 score** \\ \(\text{F}_{1}=\frac{2\text{TP}}{2\text{TP}+\text{FP}+\text{FN}}\) \\ \end{tabular} & 0.98 & 0.54 & 0.96 \\ \hline \hline \end{tabular}
\end{table} 
Table 5: Metrics used for the evaluation of the three parameter sets. whistler wave characteristics, including duration, dispersion parameter, polarization, and propagation direction, to be presented in Part 2. In light of the findings presented in the previous sections, WhISPER was applied to SCM-ELF data using Parameter Set 1 to maximize accuracy. Restricting the whistler search to a latitudinal range of \(-40^{\circ}\) to \(40^{\circ}\) and considering a total of 1290 days of CSES-01 data (due to some missing data in the database, last access: 3 September 2024), corresponding to 35,964 semiorbits, WhISPER identified 860,623 whistler events. Figure 8 presents the geographical distribution of detected whistlers with color scale indicating the number of whistlers per m\({}^{2}\). Although whistlers are observed globally, higher densities are concentrated in central America, western central Africa, and parts of southeast Asia. To investigate potential seasonal variations in the geographical distribution of whistlers, we decomposed the whistler dataset obtained with WhISPER into four seasonal periods: (a) from March to May; (b) from June to August; (c) from September to November; and (d) from December to February. Figure 9 illustrates the geographical distribution of whistlers across each seasonal period. Observational evidence in Figure 9 shows a clear seasonal modulation of whistler density, characterized by increased densities during local summer. This is manifested as higher densities from June to August in the Northern Hemisphere (panel b) and from December to February in the Southern Hemisphere (panel d).