Identification of sprites in JEM-GLIMS nadir observations and their spatial distributions

The Global Lightning and Sprite Measurements on Japanese Experiment Module (JEM-GLIMS) started the continuous nadir observations of lightning and transient luminous events (TLEs) at the International Space Station (ISS) since November 2012 and finished the observations on August 2015. As JEM-GLIMS uses the nadir observation technique, the JEM-GLIMS optical instruments have to simultaneously measure both incomparably intense lightning emissions and weak sprite emissions. To distinguish them, we adopted combined data analytical methods: (1) a subtraction of the wideband LSI-1 image from the narrowband LSI-2 image, (2) a calculation of the intensity ratio between different photometer channels, and (3) an estimation of the charge moment change (CMC) of the suspected sprite-producing CG discharge. In this report, one sprite event detected at 19:50:40.30580 UT on September 28, 2013 and identified by above analytical methods is presented as a case study. From the results derived from detailed data analyses, we judged that the optical emission measured by LSI-2 is the sprite emission. We have carried out the geometry conversion toward the LSI-1 and subtracted images and found that the location of the sprite emission is shifter by 3.5 km from the location of the peak lightning emission, which well agree with the previous repots. Thus, the detailed horizontal distributions of sprites and the relation between the sprite location and the parent lightning location are quantitatively revealed for the first time.