1:45 PM - 3:15 PM
[O11-P103] Statistical analysis of transient luminous event sprites
Keywords:Sprites, transient luminous event, statistical analysis
1 Purpose of the Study
We conducted this study to statistically analyze the simultaneous observation events that have been accumulated up to now, and to verify the correlation between the location and altitude (top and bottom) of the occurrence of sprites in the vicinity of the Sea of Japan, mainly in the Wakasa Bay area, and geographical conditions.
2. Methods
2-1 Filming Method
A CCD camera Watec WAT-100N (ultra-sensitive monochrome camera) was used for the observation, and videos before and after the emission were automatically recorded on a PC by UFO Capture HD2 (motion detection software).
The analysis software, UFO Analyzer V2, analyzes the sprite's position from one observation point, and here the sprite's altitude is estimated. Sprite Analyze analyzes the position of a sprite from two or more observation points. It is possible to identify the location of the sprites based on the relative positions of the sprites and the stars reflected in the observed images.
2-2Analysis Method
First, we extracted the data that were successfully observed simultaneously with the co-observation school. 500 simultaneous observations of two or more points were made. The data used in this study (Figure 1) consisted of 73 events (162 image data) that met the following conditions: the data for analysis was available, and the top and bottom edges of the sprites could be recognized. Next, the coordinates of each sprite were obtained using UFO Analyzer V2. Assuming that the top and bottom edges of the sprites were 80 km and 70 km, respectively, the azimuth and elevation angles were estimated. This analysis data was then run through the Sprite Analyzer to calculate the location and altitude of the sprites without estimating the altitude at which they were generated. In this way, the point of origin and the upper and lower edges of the sprites were investigated.
3 Results
3-1 Observations at each school
The total number of observations was 6,616, and by year, the largest number was 391 in 2019 among the most recent five years, followed by a decrease. By high school, Kagawa Prefectural Sanbonmatsu High School had the largest number of observations (2,237), accounting for 31% of the total, followed by Shizuoka Prefectural Iwata Minami High School (1,885), accounting for 28% of the total. Kochi Ozu High School (Kochi Prefectural Kochi Ozu High School) had the fourth highest number of observations (412), accounting for 6% of the total, following Kobe High School (Hyogo Prefectural Kobe High School). (Figure 2)
3-22 Comparison of accuracy between point-to-point and 3-point observations
Comparing the analysis results between 2-point and 3-point observations, the difference in latitude and longitude were both about 0.15 degrees, the difference in upper end was about 6 km, and the difference in lower end was about 4.5 km.
3-3 Results of Data Analysis
The results of plotting the locations of sprites on a map are shown in Figure 3. The locations of occurrence are concentrated near the coastal areas. The average altitude of the sprites is about 80 km at the upper end and about 70 km at the lower end (Figure 4). The correlation coefficient between the top and bottom altitudes was 0.193, showing no correlation (Figure 5). The upper end tended to be higher at higher latitudes (Figure 6), while no such trend was observed at the lower end (Figure 7).
4 Considerations and Future Issues
The fact that the sprites were concentrated in coastal areas indicates that cold winter winds blowing from the continent hit the mountains along the Japan Sea coast, causing the formation of large thunderclouds that can easily generate sprites and cause positive polarity lightning strikes.The upper end tended to have a higher altitude at higher latitudes, the cause of which will be discussed further in the future.The difference between the top and bottom of the sprite was found to have no correlation, but since we have not considered factors such as the type and location of the sprite, there is nothing we can say at this time.Since this analysis has not progressed to the analysis of the relationship between the altitude of the sprite, the point of lightning strike, and the point of maximum luminescence, we would like to further the analysis.
We conducted this study to statistically analyze the simultaneous observation events that have been accumulated up to now, and to verify the correlation between the location and altitude (top and bottom) of the occurrence of sprites in the vicinity of the Sea of Japan, mainly in the Wakasa Bay area, and geographical conditions.
2. Methods
2-1 Filming Method
A CCD camera Watec WAT-100N (ultra-sensitive monochrome camera) was used for the observation, and videos before and after the emission were automatically recorded on a PC by UFO Capture HD2 (motion detection software).
The analysis software, UFO Analyzer V2, analyzes the sprite's position from one observation point, and here the sprite's altitude is estimated. Sprite Analyze analyzes the position of a sprite from two or more observation points. It is possible to identify the location of the sprites based on the relative positions of the sprites and the stars reflected in the observed images.
2-2Analysis Method
First, we extracted the data that were successfully observed simultaneously with the co-observation school. 500 simultaneous observations of two or more points were made. The data used in this study (Figure 1) consisted of 73 events (162 image data) that met the following conditions: the data for analysis was available, and the top and bottom edges of the sprites could be recognized. Next, the coordinates of each sprite were obtained using UFO Analyzer V2. Assuming that the top and bottom edges of the sprites were 80 km and 70 km, respectively, the azimuth and elevation angles were estimated. This analysis data was then run through the Sprite Analyzer to calculate the location and altitude of the sprites without estimating the altitude at which they were generated. In this way, the point of origin and the upper and lower edges of the sprites were investigated.
3 Results
3-1 Observations at each school
The total number of observations was 6,616, and by year, the largest number was 391 in 2019 among the most recent five years, followed by a decrease. By high school, Kagawa Prefectural Sanbonmatsu High School had the largest number of observations (2,237), accounting for 31% of the total, followed by Shizuoka Prefectural Iwata Minami High School (1,885), accounting for 28% of the total. Kochi Ozu High School (Kochi Prefectural Kochi Ozu High School) had the fourth highest number of observations (412), accounting for 6% of the total, following Kobe High School (Hyogo Prefectural Kobe High School). (Figure 2)
3-22 Comparison of accuracy between point-to-point and 3-point observations
Comparing the analysis results between 2-point and 3-point observations, the difference in latitude and longitude were both about 0.15 degrees, the difference in upper end was about 6 km, and the difference in lower end was about 4.5 km.
3-3 Results of Data Analysis
The results of plotting the locations of sprites on a map are shown in Figure 3. The locations of occurrence are concentrated near the coastal areas. The average altitude of the sprites is about 80 km at the upper end and about 70 km at the lower end (Figure 4). The correlation coefficient between the top and bottom altitudes was 0.193, showing no correlation (Figure 5). The upper end tended to be higher at higher latitudes (Figure 6), while no such trend was observed at the lower end (Figure 7).
4 Considerations and Future Issues
The fact that the sprites were concentrated in coastal areas indicates that cold winter winds blowing from the continent hit the mountains along the Japan Sea coast, causing the formation of large thunderclouds that can easily generate sprites and cause positive polarity lightning strikes.The upper end tended to have a higher altitude at higher latitudes, the cause of which will be discussed further in the future.The difference between the top and bottom of the sprite was found to have no correlation, but since we have not considered factors such as the type and location of the sprite, there is nothing we can say at this time.Since this analysis has not progressed to the analysis of the relationship between the altitude of the sprite, the point of lightning strike, and the point of maximum luminescence, we would like to further the analysis.