电离层O<sup>+</sup>83.4 nm日辉辐射传输特性研究

doi:10.3964/j.issn.1000-0593(2020)05-1334-06

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Abstract Extreme Ultraviolet (10～100 nm) dayglow emission is produced primarily by photoionization excitation and photoelectron impact ionization. Observing extreme ultraviolet dayglow by using space-based remote sensing, we can obtain the information of electron density, ion density and spatial distribution of ionospheric F layer in the daytime. The EUV dayglow remote sensing technology started earlier in foreign countries, especially in Europe, America, Japan and other countries, and have come to maturity now. However, there are very few studies on EUV dayglow remote sensing in China, and the detection of ionosphere is mainly at night. For example, the ionospheric photometer loaded on the D-Star of the FengYun-3 meteorological satellite launched by China in 2017 can obtain the nighttime ionospheric peak electron density. Remote sensing in extreme ultraviolet (EUV) emission, especially the detection of the radiation characteristics of O⁺ ion 83.4 nm in the ionosphere, is an important means to obtain daytime ionospheric radiation characteristics, and is also the research hotspot of ionospheric optical remote sensing in the world. Firstly, we have studied the main radiative transfer theory of EUV dayglow in this paper, and introduces the excitation process, impact ionization process and multiple resonant scattering process. On this basis, we focus on the generation mechanism and radiation transmission characteristics of 83.4 nm dayglow. O⁺ 83.4 nm dayglow is generated by photoionization of the O atoms in the low thermosphere by solar EUV and is the brightest emission in EUV. The altitude distribution of the 83.4 nm dayglow can provide some information about the density profile of the O⁺ ions, and by charge neutrality, the electron density, which provide an effective method for ionospheric detection in the daytime. Secondly, we have analyzed the band characteristics of 83.4 nm dayglow. Based on the Mass Spectrometer Incoherent Scatter (MSIS-00) model, we calculate the initial volume emission rates, the volume emission rates under resonant scattering and limb column emission intensity of 83.4 nm dayglow emission by using the AURIC v1.2 model, and then we analyze the correlation with altitude, latitude, solar activity index, geomagnetic activity index and so on. Based on the extreme ultraviolet radiation algorithm, and the particularity of the radiation transmission at O⁺ ion 83.4 nm, considering the multiple scattering effects of the radiation, the radiation calculation method of oxygen ion 83.4 nm dayglow is proposed. Assuming that the ionosphere is electrical neutrality, the O⁺ density of the ionosphere in the daytime can be inverted by obtaining the EUV dayglow intensity of oxygen ion 83.4 nm, and then we can obtain the electron density distribution of the ionosphere F layer in the daytime, providing an important basis for studying the radiation transmission characteristics of the daytime ionosphere.

Key words：O⁺ 83.4 nm; Dayglow; Radiative transfer; Ionosphere

Received: 2019-04-15 Accepted: 2019-08-22

ZTFLH:

P352

Corresponding Authors: FU Li-ping E-mail: fuliping@nssc.ac.cn

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https://www.gpxygpfx.com/EN/10.3964/j.issn.1000-0593(2020)05-1334-06 OR https://www.gpxygpfx.com/EN/Y2020/V40/I05/1334