ISUAL multi-band recorded images for transient luminous events in limb view observation from space
Abstract
The ISUAL (Imager of Sprites and Upper Atmospheric Lightning) is a satellite project for the global survey of transient luminous events (TLEs) as one of the mission objectives. The ISUAL payload contains three sensor packages: a filter-wheel equipped intensifier CCD Imager, a six-channel spectrophotometer (SP) and a dual-band array photometer (AP) [Hsu et al., 2017]. The ISUAL Imager have six filter wheel with bandpass: N2 1P filter (623 - 750 nm), 762 nm filter (758 - 769 nm), 630 nm filter (626 - 633 nm), 427.8 nm filter (425 - 432 nm), 557.7 nm filter (555 - 563 nm) and open filter. Here we summarized the observed TLEs with N2 1P-, 762 nm-, 630 nm- and 427.8 nm-filtered Imager. For sprites, we compared sprites with N2 1P-filtered, 762 nm-filtered, 630 nm-filtered and 427.8 nm-filtered recorded images of sprites. The 557.7 nm sprite emission associated with O2 first negative band is too weak and is lower than detection threshold. To date, our ISUAL campaign have no significant brightness in our past 557.7 nm campaign. For elves, the typical N2 1P brightness is 170±80 kR while the spatially averaged brightness for 762 nm, 630, 557.7 and 427.8 nm emissions for individually recorded elves are 20±5 kR, 4±2.5 kR, 2±1 kR and 13±10 kR. Their corresponding maximum brightness are 60±15 kR, 10±2.5 kR, 4±1 kR and 25±10 kR. From 427.8nm emission analyses for blue luminous events, the occurrence rate of ISUAL recorded blue starters is 3.5 events per minute, slightly lower to the occurrence rate of blue starters (4.5 min-1 [Wescott et al., 1996]) but higher than the occurrence rate of gnomes (0.9 min-1 [Lyons et al., 2003]) and blue jets (2.5 min-1 [Wescott et al., 1996; Wescott et al., 2001a] and 0.9 [Suzuki et al., 2012]). The ISUAL recorded smaller blue starters have the spatial average brightness of 130 kR for the 427.8 nm-filtered Imager and 1.2 MR for SP2 (337 nm) time-integrated over the exposure time (29 ms). The degree of ionization is 10-11 - 10-12 in our recorded blue luminous events [Kuo et al., 2015]. In comparison with N2 1P-filtered and 427.8 nm-filtered images for recorded gigantic jets, two distinct characteristics are shown: (1) very strong 427.8 nm emission in the main trunk of gigantic jet, and (2) spark like 427.8 nm emission at tips of branches. That may reflect the strong ionization region in gigantic jets.
- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2018
- Bibcode:
- 2018AGUFMAE21B3124K
- Keywords:
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- 3304 Atmospheric electricity;
- ATMOSPHERIC PROCESSESDE: 3324 Lightning;
- ATMOSPHERIC PROCESSESDE: 3394 Instruments and techniques;
- ATMOSPHERIC PROCESSES