The 4D‐var Estimation of North Korean Rocket Exhaust Emissions Into the Ionosphere

Abstract

AbstractWe have developed a four‐dimensional variation data assimilation technique (4D‐var) and utilized it to reconstruct three‐dimensional images of the ionospheric hole created during Kwangmyongsong‐4 rocket launch. Kwangmyongsong‐4 was launched southward from North Korea Sohae space center (124.7°E, 39.6°N) at 00:30 UT on 7 February 2016. The data assimilated were Global Positioning System total electron content from the South Korean Global Positioning System‐receiver network. Due to lack of publicized information about Kwangmyongsong‐4, the rocket was assumed to inherit its technology from previous launches (Taepodong‐2). The created ionospheric hole was assumed to be made by neutral molecules, water (H2O) and hydrogen (H2), deposited in exhaust plumes. The dispersion model was developed based on advection and diffusion equation, and a simple asymmetric diffusion model assumed. From the analysis, using the adjoint technique, we estimated an ionospheric hole with the largest depletion existing around 6–7 min after launch and gradually recovering within ~30 min. These results are in agreement with temporal total electron content analyses of the same event from previous studies. Furthermore, Kwangmyongsong‐4 second stage exhaust emissions were estimated as 1.9 × 1026 s−1 of which 40% was H2 and the rest H2O.