Accounting for O2 absorption in ionospheric UV volume emission rate tomography
Current problems in remote sensing of the Earth from space
This paper presents the modelling results on peculiarities and importance of including thermospheric extinction within the UV ionospheric tomography problem. O 2 absorption and its influence on tomographic reconstructions of OI 135.6 nm volume emission rate in nighttime ionosphere are considered based on NRLMSIS-00 and NeQuick2 models. Iterative solvers of ART family with constraints are used for tomographic reconstructions. It is shown that when scanning directions whose perigee is less than
... igee is less than 200 km are included in the tomographic problem, neglecting of O 2 Schumann-Runge absorption leads to the destruction of the solution with pronounced periodic latitudinal artifacts. Excluding those rays in turn leads to narrowing of possible height region as well as to decreasing of horizontal resolution of reconstructions. At the same time, it is shown that using even significantly altered model for O 2 absorption (for example for solar maximum instead of solar minimum) does not seriously influence results of tomographic reconstructions while still causes latitudinal artifacts. It is caused by negligible absorption of UV nightglow at heights greater than 200 km where significant variations of O 2 concentrations with solar and geomagnetic activity are observed.