资源环境科技发展态势分析平台

The primary power gap of chorus waves is statistically investigated using 7-year waveform data from THEMIS probes for the first time. Overall, similar to 2/3 of chorus events have a power gap between the lower and upper bands. Both the gap frequency and the frequency bandwidth of the gap have a broad distribution, which peaks at frequencies of similar to 0.49f(ce) and similar to 0.07f(ce) respectively. The gap frequency tends to increase with increasing IMLATI (magnetic latitude), while the frequency width gradually increases with L-shell. In most of banded events, the peak frequency of upper band is roughly twice that of lower band. Two types of events are studied. For Type I events, one population is located around P-up/P-low = 10(-1), and the other is around P-up/P-low = 10(-3). However, Type II events are roughly concentrated around P-up/P-low = 10(-3). The gap frequency positively correlates with the frequency of upper band. Our study provides detailed observational constraints on potential mechanisms of the power gap formation.