Presentation Information
[O12-P51]Characteristics of the gigantic jet jets that occurred off the coast of the Boso Peninsula on June 26, 2025, as determined by image analysis
*eito suzuki1, *souta takagi1 (1. Shizuoka Prefectural Iwata Minami High School)
Keywords:
gigantic jet,Transient Luminous Event
Since 2007, Iwata Minami High School has been conducting observations of high-altitude luminous phenomena from its campus in Iwata City, Shizuoka Prefecture. High-altitude luminous phenomena is a general term for luminous phenomena that occur in the mesosphere and lower thermosphere as a result of ground-to-cloud discharges from thunderclouds. A giant jet (hereinafter referred to as a “jet”) is an inverted cone-shaped luminous phenomenon with a lower boundary at an altitude of approximately 20 km and an upper boundary between 70 km and 90 km.June 26, 2025, approximately 30 jets clustered off the coast of the Boso Peninsula, and we successfully observed them. We therefore compared the luminous characteristics of the clustered jets based on a series of photographs and the observation times. We also focused on the distribution of lightning strikes at the same time and examined the spatial relationship between the jets and the lightning.
Our institute conducts continuous observations using a high-sensitivity CCD camera operating at 60 fps.
2-1 Investigation via Image Analysis
We analyzed the footage of the jets frame by frame to investigate their occurrence times and developmental stages. We divided the jets into the following four sections:
① The strongly luminous lower section, ② the strongly luminous section at the structural center, ③ the narrow luminous section connecting these two locations, and ④ the section extending upward above them.
Based on this, we decided to compare the luminous characteristics of the jets from the following perspectives:
The size at the peak, how section ① fades, whether section ③ is consolidated into a single entity, whether section ④ remains after the peak, and whether a secondary jet exists.
“peak” is defined as the time when the jet first developed to its maximum size. “secondary jet” is defined as a jet that grew larger again after the peak.
Furthermore, we examined the time from the start of the glow to the peak, and from the peak to the end of the glow, to investigate the development and decay times of the jets.
2-2 Investigation of the Relationship with Lightning Phenomena
Using lightning strike data from Blitzortong.org, we examined the spatial distribution of jets based on their occurrence locations and the latitude and longitude of lightning strikes to investigate any correlation. We also compared lightning strikes occurring during jet events with those occurring at other times, breaking down the data into one-second intervals.
Previous research concluded that the number of lightning strikes decreased before and after a single jet event that occurred off the coast of Ibaraki Prefecture in 2017, suggesting that the accumulated energy was dissipated upward as a jet.
4-1 Investigation via Image Analysis
The size at its peak was approximately 67 km; since typical sizes range from about 60 km to 80 km, it was determined to be of a typical size. Regarding the dissipation pattern in ①, approximately 50% of the jets showed no significant changes, with the light gradually fading; approximately 25% flickered as they disappeared; and the remaining approximately 25% emitted a strong burst of light just before disappearing. Regarding ③, approximately 70% of the jets appeared as a single, rod-shaped structure. However, the remaining 30% were not rod-shaped but branched. Regarding ④, approximately 60% had disappeared in the frame immediately following the peak. Furthermore, a secondary jet was clearly observed in only one instance.
Additionally, when data were divided into pre- and post-peak periods, the average duration of emission before the peak was 4 frames, while the average duration after the peak was 13.8 frames. Since the typical duration of a jet is 300 ms to 500 ms, the average duration of 290 ms for the jets observed in this study is considered slightly shorter.
3-2 Relationship with Lightning Phenomena
A comparison of the distribution of lightning strikes and the distribution of jets revealed that the jets occurred in a manner that seemed to surround the distribution of lightning strikes. Furthermore, according to data from Blitzortong.org, it became clear that lightning strikes occurred in clusters within a single second. Furthermore, the jets appeared to occur in sync with these clusters, with lightning occurring in clusters at the same time the jets were generated. Therefore, we grouped the total number of lightning clusters and the number of lightning clusters occurring during jet generation into one-second intervals and performed a t-test to compare them. The results showed no significant difference in the number of lightning occurrences between times when jets were generated and times when they were not.
Our institute conducts continuous observations using a high-sensitivity CCD camera operating at 60 fps.
2-1 Investigation via Image Analysis
We analyzed the footage of the jets frame by frame to investigate their occurrence times and developmental stages. We divided the jets into the following four sections:
① The strongly luminous lower section, ② the strongly luminous section at the structural center, ③ the narrow luminous section connecting these two locations, and ④ the section extending upward above them.
Based on this, we decided to compare the luminous characteristics of the jets from the following perspectives:
The size at the peak, how section ① fades, whether section ③ is consolidated into a single entity, whether section ④ remains after the peak, and whether a secondary jet exists.
“peak” is defined as the time when the jet first developed to its maximum size. “secondary jet” is defined as a jet that grew larger again after the peak.
Furthermore, we examined the time from the start of the glow to the peak, and from the peak to the end of the glow, to investigate the development and decay times of the jets.
2-2 Investigation of the Relationship with Lightning Phenomena
Using lightning strike data from Blitzortong.org, we examined the spatial distribution of jets based on their occurrence locations and the latitude and longitude of lightning strikes to investigate any correlation. We also compared lightning strikes occurring during jet events with those occurring at other times, breaking down the data into one-second intervals.
Previous research concluded that the number of lightning strikes decreased before and after a single jet event that occurred off the coast of Ibaraki Prefecture in 2017, suggesting that the accumulated energy was dissipated upward as a jet.
4-1 Investigation via Image Analysis
The size at its peak was approximately 67 km; since typical sizes range from about 60 km to 80 km, it was determined to be of a typical size. Regarding the dissipation pattern in ①, approximately 50% of the jets showed no significant changes, with the light gradually fading; approximately 25% flickered as they disappeared; and the remaining approximately 25% emitted a strong burst of light just before disappearing. Regarding ③, approximately 70% of the jets appeared as a single, rod-shaped structure. However, the remaining 30% were not rod-shaped but branched. Regarding ④, approximately 60% had disappeared in the frame immediately following the peak. Furthermore, a secondary jet was clearly observed in only one instance.
Additionally, when data were divided into pre- and post-peak periods, the average duration of emission before the peak was 4 frames, while the average duration after the peak was 13.8 frames. Since the typical duration of a jet is 300 ms to 500 ms, the average duration of 290 ms for the jets observed in this study is considered slightly shorter.
3-2 Relationship with Lightning Phenomena
A comparison of the distribution of lightning strikes and the distribution of jets revealed that the jets occurred in a manner that seemed to surround the distribution of lightning strikes. Furthermore, according to data from Blitzortong.org, it became clear that lightning strikes occurred in clusters within a single second. Furthermore, the jets appeared to occur in sync with these clusters, with lightning occurring in clusters at the same time the jets were generated. Therefore, we grouped the total number of lightning clusters and the number of lightning clusters occurring during jet generation into one-second intervals and performed a t-test to compare them. The results showed no significant difference in the number of lightning occurrences between times when jets were generated and times when they were not.