[P-EM12] Coupling Processes in the Atmosphere-Ionosphere System

[PEM12-P35] Reconstruction of ionospheric oxygen ion density distribution from ISS-IMAP/EUVI data

*Shin ya Nakano^1,2,3, Yuta Hozumi^4,5, Akinori Saito⁶, Ichiro Yoshikawa⁷, Atsushi Yamazaki⁸, Kazuo Yoshioka⁷, Go Murakami⁸ (1.The Institute of Statistical Mathematics, 2.Joint Support Center for Data Science Research, 3.Graduate Institute for Advanced Studies, SOKENDAI, 4.Catholic University of America, 5.NASA Goddard Space Flight Center, 6.Graduate School of Science, Kyoto University, 7.Graduate School of Frontier Sciences, University of Tokyo, 8.Institute of Space and Astronautical Science, Japan Aerospace Exploration Agency)

Keywords:Extreme ultraviolet tomography, oxygen ions, Poisson noise, F-region

We have developed a method for reconstructing the oxygen ion density distribution in the nightside ionosphere from EUV images taken by the EUVI-B imager of ISS-IMAP. The EUVI-B imager mainly observed the 91.1 nm emission from the recombination of O+ ions and electrons. Assuming that the electron density is equal to the O+ density in the F-region where the imager observes, the EUV intensity observed by EUVI-B is approximately proportional to the line-of-sight integral of the square of the O+ density. This enables us to estimate the O+ density distribution in the F-region from a sequence of EUVI-B data in each International Space Station (ISS) orbit. We represent the square of the O+ density with 2nd-order B-spline functions. The weights of the basis functions are then estimated to reconstruct the density distribution. To guarantee that the estimated density is non-negative, we convert each weight into a logarithm and the optimal value of the logarithm is obtained with a Bayesian approach. An estimate of the O+ distribution was obtained each orbital period of ISS, approximately every 90 minutes. It is demonstrated that the proposed method successfully reconstruct the O+ density distribution in the ionosphere.