1:45 PM - 3:15 PM
[O11-P04] Mobile sprites found in the central Sea of Japan
Keywords:sprite, column
§1. Motivation and purpose
Our school has been observing high-altitude luminescence phenomena since 2007.On July 12 and August 27,2023,many sprites were observed by a camera installed northeast of our school. Since observations of migratory sprites are extremely rare, we decided to
study the mode of occurrence of migratory sprites in relation to weather conditions.
§2.What are sprites?
Transient Luminous Events (TLES) is a general term for luminous phenomena that occur above thunderclouds and in the mesosphere and lower thermosphere due to cloud-to-ground discharge (CG), and are known as sprites, jets, elves, etc. Sprite shapes can be classified into
"column" (columnar) and "carrot" (with carrot-like parts) (Bor, 2013). Some sprite events occur in succession. Sprites that occur in one direction are called running sprites, and sprites that occur irregularly are called dancing sprites. In this study, running sprites and dancing sprites are collectively referred to as mobile sprites. In addition, this time we focused on mobile sprites that are composed of small columns densely packed together (hereafter referred to as column type).
§3.Research Method
Automatic observation is carried out by constantly monitoring the images taken by three highly sensitive CCD cameras using motion detection software. A PC automatically monitors the camera images and splices them. When a moving object such as a sprite is detected, the camera records video including three seconds before and after the object. The camera uses a GPS clock with an accuracy of 1/100 to determine the exact time when the sprite occurred. The camera also identifies the location where the sprite occurred based on the camera's field of view. The data obtained in this way is then analyzed in conjunction with weather data.
§4.Results and Consideration
4-1. Characteristics of Column-type sprites
A total of five Column-type sprites were observed in the northern part of the Noto Peninsula over two days, July 12 and August 27. They were running sprites that occurred continuously toward the west. When comparing the locations of Column-type sprites with the locations of lightning strikes at the same time, it was confirmed that the number of lightning strikes was smaller than the number of sprites that make up the moving sprites. Therefore, since the number of lightning strikes for Column-type sprites was less than the number of sprites included in the event, it is believed that multiple sprites were generated for one lightning strike.
4-2.Persentage of each sprite that makes up a moving sprite by shape
The shapes of the individual sprites that made up the migratory sprites that occurred over the two days were classified and the occurrence rate was calculated. Column had 56 cases, or 63.6%, and Carrot had 32 cases, or 36.3%.
4-3. Weather conditions when moving sprites occur
On July 12, 2023, the central part of the Sea of Japan where the migratory sprites occurred was covered by a low pressure system. A linear rain band was also formed in the northern part of the Noto Peninsula, and precipitation of 50mm/h to 80mm/h was confirmed.
On August 27, 2023, Japan was also covered by a low pressure system, and two typhoons were formed in the Pacific Ocean. Localized precipitation of 20mm/h to 50mm/h was confirmed in the northern part of the Noto Peninsula.
§5.Conclusion
- Column-type running sprites did not generate sprites in response to multiple lightning strikes with different time lags, but rather multiple sprites were generated for a single lightning strike.
- Low pressure and localized precipitation are necessary for the occurrence of migrating sprites.
§6.References
József Bór, 2013, Optically perceptible characteristics of sprites observed in Central Europe in 2007-2009
Utsunomiya, O., and T. Kamikawa, 2022, Relationship between winter sprite shape and meteorological conditions.
Blitzortung.org
§7. Acknowledgments
I would like to thank again Akira Aoshima, visiting researcher at the Fujinokuni Museum of Environmental History, Hiroyuki Kurematsu, advisor, Jin Kamogawa, professor in Shizuoka University, Tomoyuki Suzuki, visiting resarcher in Tokyo Gakugei University, and members of the Geoscience Department for their cooperation in my research.
Our school has been observing high-altitude luminescence phenomena since 2007.On July 12 and August 27,2023,many sprites were observed by a camera installed northeast of our school. Since observations of migratory sprites are extremely rare, we decided to
study the mode of occurrence of migratory sprites in relation to weather conditions.
§2.What are sprites?
Transient Luminous Events (TLES) is a general term for luminous phenomena that occur above thunderclouds and in the mesosphere and lower thermosphere due to cloud-to-ground discharge (CG), and are known as sprites, jets, elves, etc. Sprite shapes can be classified into
"column" (columnar) and "carrot" (with carrot-like parts) (Bor, 2013). Some sprite events occur in succession. Sprites that occur in one direction are called running sprites, and sprites that occur irregularly are called dancing sprites. In this study, running sprites and dancing sprites are collectively referred to as mobile sprites. In addition, this time we focused on mobile sprites that are composed of small columns densely packed together (hereafter referred to as column type).
§3.Research Method
Automatic observation is carried out by constantly monitoring the images taken by three highly sensitive CCD cameras using motion detection software. A PC automatically monitors the camera images and splices them. When a moving object such as a sprite is detected, the camera records video including three seconds before and after the object. The camera uses a GPS clock with an accuracy of 1/100 to determine the exact time when the sprite occurred. The camera also identifies the location where the sprite occurred based on the camera's field of view. The data obtained in this way is then analyzed in conjunction with weather data.
§4.Results and Consideration
4-1. Characteristics of Column-type sprites
A total of five Column-type sprites were observed in the northern part of the Noto Peninsula over two days, July 12 and August 27. They were running sprites that occurred continuously toward the west. When comparing the locations of Column-type sprites with the locations of lightning strikes at the same time, it was confirmed that the number of lightning strikes was smaller than the number of sprites that make up the moving sprites. Therefore, since the number of lightning strikes for Column-type sprites was less than the number of sprites included in the event, it is believed that multiple sprites were generated for one lightning strike.
4-2.Persentage of each sprite that makes up a moving sprite by shape
The shapes of the individual sprites that made up the migratory sprites that occurred over the two days were classified and the occurrence rate was calculated. Column had 56 cases, or 63.6%, and Carrot had 32 cases, or 36.3%.
4-3. Weather conditions when moving sprites occur
On July 12, 2023, the central part of the Sea of Japan where the migratory sprites occurred was covered by a low pressure system. A linear rain band was also formed in the northern part of the Noto Peninsula, and precipitation of 50mm/h to 80mm/h was confirmed.
On August 27, 2023, Japan was also covered by a low pressure system, and two typhoons were formed in the Pacific Ocean. Localized precipitation of 20mm/h to 50mm/h was confirmed in the northern part of the Noto Peninsula.
§5.Conclusion
- Column-type running sprites did not generate sprites in response to multiple lightning strikes with different time lags, but rather multiple sprites were generated for a single lightning strike.
- Low pressure and localized precipitation are necessary for the occurrence of migrating sprites.
§6.References
József Bór, 2013, Optically perceptible characteristics of sprites observed in Central Europe in 2007-2009
Utsunomiya, O., and T. Kamikawa, 2022, Relationship between winter sprite shape and meteorological conditions.
Blitzortung.org
§7. Acknowledgments
I would like to thank again Akira Aoshima, visiting researcher at the Fujinokuni Museum of Environmental History, Hiroyuki Kurematsu, advisor, Jin Kamogawa, professor in Shizuoka University, Tomoyuki Suzuki, visiting resarcher in Tokyo Gakugei University, and members of the Geoscience Department for their cooperation in my research.