A long-term study on the deletion criterion of questionable electron density profiles caused by ionospheric irregularities - COSMIC radio occultation technique

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题名:	A long-term study on the deletion criterion of questionable electron density profiles caused by ionospheric irregularities - COSMIC radio occultation technique
作者:	朱延祥;Uma, G.;Brahmanandam, P.S.;Chu, Y.H.
贡献者:	太空科學與科技研究中心
关键词:	Atmospherics;Density;Density gradients;Electron density profiles;Fluctuation;Ionosphere;Irregularities;Mathematical models;Radio occultation technique;Spherical symmetry;Statistics;Topside ionosphere fluctuations
日期:	2016-06-15
上传时间:	2026-04-23 11:03:13 (UTC+8)
出版者:	Elsevier Ltd.;Elsevier Ltd
摘要:	摘要： •A reliable deletion criterion of questionable density profiles retrieved using the COSMIC RO technique is discussed.•Statistics of seven continuous years are presented.•Computed gradient and the slope of density profiles have shown solar activity dependency. The crucial assumption made in the retrieval of radio-occultated atmospheric parameters is the spherical symmetry of the atmospheric refractive index, which implies that no horizontal gradient of the refractive index exists along the spherical shell. Nevertheless, the presence of density irregularities will lead to scintillation and multipath effects that often create highly fluctuating and random electron density profiles. In this study, it is proposed a reliable data quality control (QC) approach to remove questionable electron density profiles (due to the presence of ionospheric irregularities) retrieved using the COSMIC radio occultation (RO) technique based on two parameters, namely, the gradient and fluctuation of the topside density profile. Statistics of seven years density profiles (July 2006–May 2013) are presented by determining the aforementioned parameters for every density profile. The main advantage of this data QC is that it uses COSMIC RO electron density profiles retrieved from the slant total electron content (TEC) that is estimated from the excess phases of the GPS L1 and L2 frequencies only to delete the questionable profiles, instead of relying on any model and other observations. A systematic criterion has been developed based on the statistics to relinquish the so-called questionable density profiles. The computed gradients and fluctuations of the topside ionosphere electron density profiles have shown a few important features including, solar activity dependency and pronounced variations in between around +40° and −40° latitudes. After the removal of questionable profiles, both peak densities and heights of the ionosphere F layer are presented globally in different seasons of years during 2007 and 2012 that revealed several important features. 出版者： Elsevier Ltd 出版日期： 2016-06-15 出處： Advances in space research, 2016-06, Vol.57 (12), p.2452-2463 資源來源： ScienceDirect 版權： 2016 COSPAR 識別號： ISSN: 0273-1177 識別號： EISSN: 1879-1948 識別號： DOI: 10.1016/j.asr.2016.03.034
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