Spatiotemporal Characteristics of Sprites and Sprite-related VHF Signals Measured by JEM-GLIMS

Wednesday, 17 December 2014
Mitsuteru Sato1, Toru Adachi2, Masahiro Mihara1, Tomoo Ushio3, Takeshi Morimoto4, Hiroshi Kikuchi3, Makoto Suzuki5, Atsushi Yamazaki6 and Yukihiro Takahashi1, (1)Hokkaido University, Sapporo, Japan, (2)Meteorological Research Institute, Ibaraki, Japan, (3)Osaka University, Osaka, Japan, (4)Kinki University, Osaka, Japan, (5)JAXA Japan Aerospace Exploration Agency, Sagamihara, Japan, (6)ISAS/JAXA, Sagamihara, Kanagawa, Japan
JEM-GLIMS conducts the first comprehensive nadir observations of lightning and TLEs using optical instruments and electromagnetic wave receivers. JEM-GLIMS started continuous orbital observations from November 2012 and has succeeded in detecting thousands of lightning events including TLEs. The global distribution of the detected lightning events clearly shows that most of the events were detected over continental regions. In addition, the global distributions of these lightning events show clear seasonal variations and were centered in the local summer hemisphere. To identify the sprite occurrences, it is necessary to perform the following data analysis: (1) a subtraction of the appropriately scaled wideband camera (LSI-1) image from the narrowband camera (LSI-2) image; (2) a calculation of intensity ratio between different spectrophotometer channels; and (3) an estimation of the polarization and charge moment changes for the parent CG discharges of the event using ground-based ELF measurement data. From a synthetic comparison of these results, we confirmed that JEM-GLISM succeeded in detecting sprite events. The VHF receiver onboard JEM-GLIMS uses two patch-type antennas separated by a 1.6-m interval and can detect VHF pulses emitted by lightning discharges in the 70-100 MHz frequency range. Using an interferometric technique, we successfully identified the source locations of VHF pulses excited by lightning discharges. At the presentation, we will show detailed spatiotemporal characteristics of sprite events detected by JEM-GLIMS optical instruments and the relation between the spatial distribution of sprites and source locations of VHF pulses excited by the parent lightning discharges of sprites.