Isual Publications 2014

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200112 11 S. B. Mende, L.C. Lee, J. L. Chern, R. R. Hsu, H. T. Su, H. Fukunishi, and Y. Takahashi( 200112 ).Satellite Observations of Upper Atmospheric Discharges With the ISUAL Instrument on the ROCSAT-2 Satellite, American Geophysical Union, Fall Meeting 2001, San Francisco, USA. (invited) The Imager of Sprites and Upper Atmospheric Lightning (ISUAL) experiment on ROCSAT 2 satellite will make the first synoptic spacecraft based measurements of lightning induced luminous phenomena. Science objectives of the ISUAL instrument are the determination of the spatial, temporal and spectral properties of lightning induced upper atmospheric optical flash transients (sprites, elves, blue jets etc.) and the global (geographic/seasonal) distribution of upper atmospheric optical flash transients. The ISUAL instruments consist of a limb viewing low light level imager with a set of bore sighted photometers and a dual channel high time resolution array photometer. The ISUAL imager spectrophotometer and array photometer will measure the spectral content, the spatial and temporal intensity distribution of the optical flashes uninhibited by the effects of lower atmospheric absorption. Intensity ratios of the various emissions will be used to determine the energetics of the excitation processes. The investigation will take advantage of coordinated observations with ground based simultaneous measurements of electric fields and VLF waves and optical imaging and photometry. The ISUAL payload flying at 891 km altitude in a 1000-2200 local time near sun-synchronous near polar orbit will be able to provide the first unbiased survey of lightning induced optical flashes over the entire globe in the midnight sector. From such a survey we will be able to determine whether the occurrence frequency of sprites depend on factors other than the magnitude of the storms such as the prevailing tropospheric or mesospheric conditions.
200112 12 R. R. Hsu, H. T. Su, A. B. Chen, M. H. Chang, and L.C. Lee ( 200112 ).Ground Observation of Sprites in Taiwan, American Geophysical Union, Fall Meeting 2001, San Francisco, USA. During the Sprites¡œ01 campaign, sprites were observed over thunderstorm systems in the southeast region of China and in the oceans around Taiwan. The observation location was on the Ali Mountain of Taiwan¡œs Central Ridge area with an altitude of 2413m and on the campus of National Cheng Kung University with an altitude of 50m. For the land sprites, 90% of them are either carrot or columniform sprites and 70% of the sprites occurring in groups. Their forms and occurrence frequency are very similar to those observed over the North American continent. For the oceanic sprites, carrot sprites account for 89% of the observed events, and 83% of the sprites occurring in singles. If one defines the thunderstorm, which continuously produces at least a sprite in 10 minutes interval to be a sprite active system. The active sprites generating periods for the observed thunderstorms are typically very short with an average time span around 30 minutes. The sprite production intensities for these Asian thunderstorms are estimated to be between I = 5.0 x10-4 sprites/km^2/hr to I = 1.2 x 10-3 sprites/km2/hr.
200208 13 H. T. Su, J. L. Chern, H. Fukunishi, R. R. Hsu, L.C. Lee, S. B. Mende, and Y. Takahashi( 200208 ).Global survey of lightning-induced transient luminous events on the rocsat-2 satellite, URSI-GA, Maastricht, Nederland. E4.O.4
200208 14 Y. Takahashi, T. Adachi, J. L. Chern, H. Fukunishi, R. R. Hsu, L.C. Lee, S. B. Mende, and H. T. Su( 200208 ).Observation of transient optical emissions in the middle and upper atmosphereusing array photometer, URSI-GA, Maastricht, Nederland. E4.P.4
200208 15 J.L. Chern, R.R. Hsu, H. T. Su, S.B. Mende, H. Fukunishi, Y. Takahashi, and L.C. Lee( 200208 ).Sprites observation on the ROCSAT-2 satellite, URSI-GA, Maastricht, Nederland. (invited)
200212 16 H. T. Su, R. R. Hsu, A. B. Chen, W. S. Hsiao, W. C. Lai, Y. C. Wang, and L.C. Lee ( 200212 ).Gigantic transient luminous events with long duration*, American Geophysical Union, Fall Meeting 2002, San Francisco, USA. A62D-03 During the Sprites 2002 campaign in Taiwan, five gigantic transient luminous events (TLEs) were observed to occur over an oceanic thunderstorm. The morphology of these transient luminous events appears to be a hybrid of blue jet and sprite. The upper part resembles a sprite while the lower half is jet-like. These events visually span from the lower atmosphere to the E-layer ionosphere at 100 km. The luminous duration of these events ranges between 200ms to 400ms, which is much longer than that of typical sprites. In this paper, the morphology, temporal evolution, and possible generating mechanism of these gigantic TLE events will be presented. * This work was supported in parts by research grants NSC91-NSPO(B)-ISUAL-FA09-01 and NSC91-2111-M006-002.
200312 17 H. T. Su, R. R. Hsu, A. B. Chen, Y. C. Wang, M. Sato, H. Fukunishi, and L.C. Lee( 200312 ).Fine structures, velocity and the ELF signature of gigantic jets*, American Geophysical Union, Fall Meeting 2003, San Francisco, USA. AE41B-04(invited) Gigantic jet is a type of transient luminous events that optically connect thundercloud-top and the ionosphere [Su et al., Nature 423, p974-976, 2003]. The dynamical evolution of gigantic jets can be divided into three stages: the leading jet, the fully developed stage, and the trailing jet. At the fully developed stage, the upper portion of the gigantic jets is very similar to classical sprites, and the lower portion remembers blue jets. In this talk, a few interesting properties and the spatial-temporal evolution of the fine structures of gigantic jets will be discussed. The ELF and the lightning signatures of the gigantic will also be compared, and a possible generating mechanism will be presented. * This work was partially supported by 92-NSPO(B)-ISUAL-FA09-01 and NSC 92-2111-M-006-002
200312 18 A. B. Chen, T. T. Wang, T. H. Huang, C. L. Kuo, R. R. Hsu, H. T. Su, J. L. Chern, S. B. Mende, Y. Takahashi, H. Fukunishi, and L.C. Lee( 200312 ).Observations of transient luminous events on the ROCSAT-2 satellite using ISUAL instruments*, American Geophysical Union, Fall Meeting 2003, San Francisco, USA. AE42A-0792 ISUAL is a scientific payload of ROCSAT2 satellite, which is to be launched in November of 2003. The ISUAL instrument consists of a high-speed CCD imager, a six-channel spectrophotometer, and a red/blue band array photometer. Operating from a low-earth orbit, the instruments will facilitate long term, global survey of transient luminous events (TLES), and measure the spatial-temporal evolution of these upper atmospheric luminous phenomena. Through the ISUAL payload, we hope to learn the global distribution of TLES and to explore the possible unknown properties of TLEs from space. In this presentation, the salient characteristics of the ISUAL instruments will be introduced, as well as the observation strategy and the operation scenario. Besides devoting the majority of time towards observing TLEs, the project also will allocate a portion of time to other worthy scientific causes. International collaborations and observation proposals using ISUAL instruments are welcomed.
200312 19 C. L. Kuo, R. R. Hsu, A. B. Chen, H. T. Su, Y. C. Wang, C. K. Chang, Y. J. Lee, H. C. Wang, W. Y. Wang, and L.C. Lee( 200312 ).ICCD imagery of oceanic sprites*, American Geophysical Union, Fall Meeting 2003, San Francisco, USA. AE42A-0793 As reported in Su et al [GRL vol. 29(4), doi 10.1029/2001GL013737, 2002] and Hsu et al [JASTP vol. 65, p561-566, 2003], the oceanic sprites tend to appear in single column, which is in sharp contrast with the clustering land sprites. In the 2003 Taiwan Sprites campaign, one of the scientific goals is to study the oceanic sprites in detail. The recorded images confirm the oceanic/land morphology disparity as reported before. Three of the ICCD cameras deployed in this campaign were equipped with R, G, B filters to obtain high spatial resolution and tri-color optical images. From the red and blue bands images, the spatial distribution and the energy of oceanic sprites could be evaluated. We will also compare the energy distribution of various types of oceanic sprites. Using stars in the star field as standard luminous gauges, the optical brightness of the oceanic sprites was estimated to exceed 5 MR. Using ICCD cameras set to different gain levels; the spatial brightness distribution of the oceanic sprites was also explored. * This work is supported in part by 92-NSPO(B)-ISUAL-FA09-01 and NSC 92-2111-M-006-002.
200312 20 Y. C. Wang, C. L. Kuo, A. B. Chen, R. R. Hsu, H. T. Su, and L.C. Lee( 200312 ).ELF/VLF monitoring of lightning activity in Taiwan*, American Geophysical Union, Fall Meeting 2003, San Francisco, USA. AE42A-0799 Currently, there are two long-range lightning monitoring systems operating in Taiwan; one is a VLF/ELF electric field detection system and the other one is an ELF (SR) magnetic field system. The electric field system detect the electric sferics emitted by lightning in the 1 Hz to 22 kHz range. The magnetic system operates in the frequency range of 1 Hz to 100 Hz. In the 2003 Taiwan Sprites campaign, these two systems worked in parallel with a set of ICCD cameras to study oceanic sprites occurring in the South China Sea. From the ELF and optical data, the correlation between optical luminosity of sprites and amplitudes of their associate ELF emission was found. We will also discuss the possible correlation between the morphology of sprites and the waveform of their associate ELF signals. * This work was partially supported by 92-NSPO(B)-ISUAL-FA09-01 and NSC 92-2111-M-006-002
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