摘要： We report the blue luminous events observed by the Imager of Sprite/Upper Atmospheric Lightning (ISUAL) payload on board the FORMOSAT‐2 satellite. The ISUAL 427.8 nm filtered Imager campaign was conducted near Australia in the summer of the Southern Hemisphere during February–March 2008. On 18 February 2008, the 427.8 nm filtered Imager recorded a series of blue luminous events. One blue starter and nine smaller blue starters were recorded in 2 min and 34 s in a localized region with the radius < 4 km over the cloud top. The average time interval between subsequent blue luminous events was ~ 17 s. The occurrence rate of blue luminous events was 3.5 events per minute, slightly lower than the occurrence rate of pixies (4.2 events per minute) but higher than the occurrence rate of gnomes and blue jets in the previous observations. The recorded first blue starter lasted up to 2–3 frame times (60–90 ms) and extended its altitude about 8 ± 0.3 km with a width of ~2–4 km over the cloud top. After the first blue starter, subsequent nine smaller blue starters had the decreased heights of ~2–4 km, and their optical duration was shorter and is down to 1 ms. But their major emissions were 2PN2 and 1NN2+, without lightning OI 777.4 nm emission. The ISUAL recorded blue smaller starters had the spatial average brightness of 130 kR for the 427.8 nm filtered Imager with exposure time (29 ms) and 1.2 MR for the spectrophotometer (337 nm). Using the spectrophotometer, the emission time of blue starters was 1 ms. It is estimated that the 1NN2+ emission was ~ 22 MR and the 2PN2 emission was ~ 132 MR. We can estimate the degree of ionization was 10−11–10−12 in these blue luminous events using the 427.8 nm filtered Imager measured 1NN2+ (0,1) emission. Key Points ISUAL observed one blue starter and nine subsequent smaller blue starters after the lightning The integrated brightness over 29 ms is 130 kR (1NN2+) and 1.2 MR (2PN2) The degree of ionization is estimated as 10−11–10−12 in ISUAL observed blue starters 其他題名： J. Geophys. Res. Space Physics 出版者： Washington: Blackwell Publishing Ltd 出版日期： 2015-11 出處： Journal of geophysical research : Space physics (2013 - Present), 2015-11, Vol.120 (11), p.9795-9804 資源來源： Wiley Online Library All Journals 版權： 2015. American Geophysical Union. All Rights Reserved. 版權： Copyright Blackwell Publishing Ltd. Nov 2015 識別號： ISSN: 2169-9380 識別號： ISSN: 2169-9402 識別號： EISSN: 2169-9402 識別號： DOI: 10.1002/2015JA021386
