[P-PS05] Recent advances in the science of Venus

[PPS05-P06] A Novel Technique for Handling Plasma Asymmetry in Radio Occultation Experiments

*Keshav R Tripathi¹、Takeshi Imamura² (1.JSPS International Research Fellow, The University of Tokyo, Japan 、2.The University of Tokyo, Japan )

キーワード：Radio Occultation , Planetary Ionosphere, Venusian Ionosphere , Akatsuki radio Science

The Radio Occultation (RO) experiment often employs the geometrical optics (GO) approximation and Abel transformation, assuming spherical symmetry of the planetary atmosphere or ionosphere, to retrieve electron density profiles of the ionosphere. This assumption is extended to derive temperature, pressure, and neutral density profiles of the lower atmosphere as well [1]. However, the spherical symmetry approximation may not always be valid, potentially introducing significant uncertainties in the retrieved electron density profiles. This study proposes and demonstrates a simple yet novel approach to address these uncertainties by accounting for deviations from spherical symmetry in the ionospheric medium. It sans the use of Abel transformation apart from doing away with the limitation of spherical symmetry and hence can be used under different geophysical conditions. The method has been applied to RO observations conducted around Venus by the Akatsuki and Venus Express (VEX) radio science experiments. Results indicate that the electron density profiles derived using the spherical symmetry assumption overestimate the main peak electron density by 2–5% and the electron density at lower altitudes by 400–800%. This new method offers a more accurate framework for retrieving electron density profiles, particularly in regions where spherical symmetry is a poor approximation.



References:

[1] Fjeldbo, G., Kliore, A.J. and Eshleman, V.R., 1971. The neutral atmosphere of Venus as studied with the Mariner V radio occultation experiments. Astronomical Journal, Vol. 76, p. 123 (1971), 76, p.123.