Long-term comparison of the ionospheric F2 layer electron density peak derived from ionosonde data and Formosat-3/COSMIC occultations

Abstract

Electron density profiles (EDPs) derived from GNSS radio occultation (RO) measurements provide valuable information on the vertical electron density structure of the ionosphere and, among others, allow the extraction of key parameters such as the maximum electron density NmF2 and the corresponding peak height hmF2 of the F2 layer. An efficient electron density retrieval method, developed at the UPC (Barcelona, Spain), has been applied in this work to assess the accuracy of NmF2and hmF2 as determined from Formosat-3/COSMIC (F-3/C) radio occultation measurements for a period of more than half a solar cycle be- ) and local times (LT) accounting for different ionospheric conditions at night (02:00 LT ± 2 h), dawn (08:00 LT ± 2 h), and day (14:00 LT ± 2 h). The mean differences of F2 layer electron density peaks observed by F-3/C and ionosondes are found to be insignificant. Relative variations of the peak differences are determined in the range of 22%-30% for NmF2 and 10%-15% for hmF2. The consistency of observations is generally high for the equatorial and mid-latitude sectors at daytime and dawn whereas degradations have been detected in the polar regions and during night. It is shown, that the global averages of NmF2 and hmF2 derived from F-3/C occultations appear as excellent indicators for the solar activity.

An investigation of the ionospheric F region near the EIA crest in India using OI 777.4 and 630.0 nm nightglow observations

“…Moreover, these observations of the EIA crests are in the winter months of October-December; the transequatorial neutral winds blowing across the summer-winter hemisphere might have possibly pushed the EIA to latitudes as high as Allahabad (Luan et al, 2015). Our results on the observations of EIA are in reasonable agreement with some of the earlier reports (Rao and Malhotra, 1964;Rama Rao et al, 1977;Lin et al, 2007;Chakraborty and Hajra, 2009;Zhao et al, 2009). Studies by Rao and Malhotra (1964) on the latitudinal variation of foF2 in the Asian sector suggest that the EIA can persist at least until 02:00 LT at ∼ 30 • dip latitude.…”

“…Because of this [O 2 ] association, the intensity of OI 630.0 nm (I 6300 ) depends upon the height of the F layer apart from the electron density. Link and Cogger (1988) found that the intensity of this emission depends on [N 2 ] and [O 2 ] of the neutral atmosphere. As the density of the neutral atmosphere decreases exponentially with height around the OI 630.0 nm emission altitude, such dependency is also likely to exist between its intensity and the height of the F layer.…”

“…Next, the determination of hmF2 is based on the chemistry of OI 630.0 nm emission. During night-time, this emission feature is primarily due to the following dissociative recombination reaction involving an O + 2 ion and an electron (Link and Cogger, 1988):…”

“…As the density of the neutral atmosphere decreases exponentially with height around the OI 630.0 nm emission altitude, such dependency is also likely to exist between its intensity and the height of the F layer. Using the emission rate of OI 630.0 nm nightglow given by Link and Cogger (1988), and adopting the approach of Tinsley and Bittencourt (1975) and Sahai et al (1981), Makela et al (2001) arrived at the following expression relating the √ I 7774 /I 6300 ratio with the height of the F layer (in km):…”

Testing and validating IRI-2016 model over Ethiopian ionosphere

“…As the ionizing radiation from the sun penetrates deeper and deeper into the Earth's atmosphere, it encounters a larger and larger density of gas particles, producing more and more electrons per unit volume (Bittencourt 2004). The recombination of free electrons with positive ions is a reversion of the photoionization and the recombination process is the main driver to produce neutral atoms (Limberger et al 2015).…”