Validation of COSMIC ionospheric peak parameters by the measurements of an ionosonde chain in China

Hu, Leyin; Ning, Baiqi; Liu, Libo; Li, G.; Huang, Zhi; Hao, X. Q.; Chang, Shenghai; Wu, Zhensen

doi:10.5194/angeo-32-1311-2014

Cited by 30 publications

(21 citation statements)

References 29 publications

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“…Each occultation event can be inverted into an electron density profile (EDP) using the Abel inversion. Although the assumption used by the Abel inversion leads to some discrepancies between electron densities derived from the COSMIC IRO data and other observations in the lower ionosphere, their morphologies are consistent (Chu et al, 2010;Hu et al, 2014;Lei et al, 2007;Yue et al, 2010). COSMIC data have been used in various researches, including the characteristics of the F 2 layer peak electron density (NmF2), F 2 layer peak height (hmF2), slab thickness, and equatorial dynamics, and obtained reasonable results (Guo et al, 2011;He et al, 2009He et al, , 2011Huang et al, 2016;Lin, Wang, et al, 2007;Liu et al, 2009).…”

Section: Methodsmentioning

confidence: 73%

Transition of Interhemispheric Asymmetry of Equatorial Ionization Anomaly During Solstices

Huang

Liu

et al. 2018

JGR Space Physics

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The magnitudes of the two crests of equatorial ionization anomaly (EIA) vary with local time. During the solstices, EIA crest in the winter hemisphere is larger than that in the summer hemisphere before noon/early afternoon. Whereafter, the crest in the summer hemisphere becomes intensified, and the stronger EIA crest transits to the summer hemisphere. Using Constellation Observing System for Meteorology, Ionosphere, and Climate ionospheric radio occultation data, we examine the longitudinal and altitudinal variations of this interhemispheric transition in four longitudinal sectors and at seven heights under low/high solar activity conditions. The results show that during the June solstice the transition of the stronger EIA peak from the winter to the summer hemisphere is earlier in the sectors where the geomagnetic equator is further away from the subsolar point and the geomagnetic field declination is larger, while during the December solstice the longitudinal variations generally show the opposite compared with that in the June solstice. The distance between the geomagnetic equator and subsolar point and the geomagnetic field configuration control the upward/downward plasma movements in the summer/winter hemisphere, leading to the different transition times in different longitudinal sectors. For both solstices, transition times emerge earlier as height increases, which is mainly caused by the larger effective scale height in the summer hemisphere than in the winter hemisphere, resulting in a smaller electron density difference at higher altitudes with a fast transition. Solar activity alters the transition time below 320 km, whereas it has no evident effect at higher altitudes.

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Section: Methodsmentioning

confidence: 73%

Transition of Interhemispheric Asymmetry of Equatorial Ionization Anomaly During Solstices

Huang

Liu

et al. 2018

JGR Space Physics

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“…However, an extensive pre-processing and data screening was necessary for both the RO and ionosonde data to eliminate disturbances in the data and improve the data reliability. Many authors like Krankowski et al (2011), Hu et al (2014, Wu et al (2009), Yue et al (2010, and Lei et al (2007) evaluated the accuracy of electron density peaks, retrieved from F-3/C data, either on a regional scale by means of selected ionosonde stations allowing for a manual ionogram scaling or even used synthetic data to validate the accuracy under different conditions, e.g., under the influence of varying F10.7 indices. In this work, SPIDR network data based on automatically scaled measurements are taken into account.…”

Section: Discussionmentioning

confidence: 99%

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

Limberger¹,

Hernández‐Pajares

Aragón‐Àngel

et al. 2015

J. Space Weather Space Clim.

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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.

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“…For example, statistical comparisons of the N m F 2 values between GPS/MET retrievals and ionosonde measurements indicate a 20-40% difference between them [Hajj and Romans, 1998;Schreiner et al, 1999;Hajj et al, 2000;Tsai et al, 2001]. The global and long-term comparisons between COSMIC-retrieved and ionosonde-measured N m F 2 values show that their relative differences are within À30% to 30% [Chu et al, 2010a[Chu et al, , 2010bHu et al, 2014]. The mean residual errors in the corrected COSMIC-measured N m E are also in general similar to the IRI model-simulated GPS RO retrieval errors of F region electron density at around 300 km, as shown in Figure 1.…”

Section: Discussionmentioning

confidence: 98%

Improvement of GPS radio occultation retrieval error of E region electron density: COSMIC measurement and IRI model simulation

Chu

2015

JGR Space Physics

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In this article, we use the International Reference Ionosphere (IRI) model to simulate temporal and spatial distributions of global E region electron densities retrieved by the FORMOSAT-3/COSMIC satellites by means of GPS radio occultation (RO) technique. Despite regional discrepancies in the magnitudes of the E region electron density, the IRI model simulations can, on the whole, describe the COSMIC measurements in quality and quantity. On the basis of global ionosonde network and the IRI model, the retrieval errors of the global COSMIC-measured E region peak electron density (N m E) from July 2006 to July 2011 are examined and simulated. The COSMIC measurement and the IRI model simulation both reveal that the magnitudes of the percentage error (PE) and root mean-square-error (RMSE) of the relative RO retrieval errors of the N m E values are dependent on local time (LT) and geomagnetic latitude, with minimum in the early morning and at high latitudes and maximum in the afternoon and at middle latitudes. In addition, the seasonal variation of PE and RMSE values seems to be latitude dependent. After removing the IRI model-simulated GPS RO retrieval errors from the original COSMIC measurements, the average values of the annual and monthly mean percentage errors of the RO retrieval errors of the COSMIC-measured E region electron density are, respectively, substantially reduced by a factor of about 2.95 and 3.35, and the corresponding root-mean-square errors show averaged decreases of 15.6% and 15.4%, respectively. It is found that, with this process, the largest reduction in the PE and RMSE of the COSMIC-measured N m E occurs at the equatorial anomaly latitudes 10°N-30°N in the afternoon from 14 to 18 LT, with a factor of 25 and 2, respectively. Statistics show that the residual errors that remained in the corrected COSMIC-measured N m E vary in a range of À20% to 38%, which are comparable to or larger than the percentage errors of the IRI-predicted N m E fluctuating in a range of À6.5% to 20%.

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Validation of COSMIC ionospheric peak parameters by the measurements of an ionosonde chain in China

Cited by 30 publications

References 29 publications

Transition of Interhemispheric Asymmetry of Equatorial Ionization Anomaly During Solstices

Transition of Interhemispheric Asymmetry of Equatorial Ionization Anomaly During Solstices

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

Improvement of GPS radio occultation retrieval error of E region electron density: COSMIC measurement and IRI model simulation

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