Transient luminous event coordinated observations using FORMOSAT-2 satellite and Taiwan sprites campaign

Abstract

The Imager of Sprites and Upper Atmospheric Lightning (ISUAL), on board the FORMOSAT-2 satellite launched in 2004, is the first instrument primarily dedicated to transient luminous event (TLE) surveys from space. The ISUAL TLE geolocation accuracy and detection efficiency are validated in this paper through two coordinated observation events using ISUAL and the Taiwan TLE ground campaign, the first coordinated space and ground observations. Due to the long distances between TLEs and the observation stations, triangulation required taking the Earth’s curvature into account using spherical trigonometry. After a series of systematic triangulation procedures, the results indicate that the coordinated ISUAL and ground station geolation accuracy is less than 7 km. Moreover, three columniform sprites were recorded at multiple sites during the ground campaign. The triangulation of individual elements shows that the map projection of columniform sprites is nearly circular, parallel and fan shaped. The aforementioned events demonstrate that the columniform sprite distribution patterns are diverse. The average base altitude of the columns is 72.4 ± 2.4 km, and the average terminal altitude is 82.3 ± 1.8 km. The sprite column width is estimated to be < 0.5 km.