Observational Study on Connection between Sprites and TGFs with GRT-WF

Although it is known that terrestrial gamma-ray flashes (TGFs) can be caused by the electron-cosmic ray Bremsstrahlung in the presence of the Earth magnetic field, the acceleration process of electrons in the Earth atmosphere is not clearly understood. On the other hand, electrons inside thunderclouds produce lightnings (under the clouds) as well as sprites (above the clouds). We study the connection between sprites and TGFs since both of them require free atmospheric electrons. We constructed Goddard Robotic Telescope - Wide Field (GRT-WF) in June 2011, which is composed of seven wide field optical camera located at Florida Gulf Coast University (FGCU), to observe sprites in all the sky. We have recorded about 600 sprites so far, and studied possible associations with TGFs detected by NASA’s Fermi/GBM and RHESSI. The location of GRT-WF has been chosen because the area is one of the highest TGF detection regions by Fermi/GBM (others are Africa and South-East Asia).