Comparison of the characteristics of ionospheric parameters obtained from FORMOSAT-3 and digisonde over Ascension Island

Abstract

Electron density profile data obtained from the FORMOSAT-3 radio occultation (RO) measurements over Ascension Island are used to study the bottomside thickness parameter <I>B0</I> in the International Reference Ionosphere (IRI) model, scale height around the F region peak height, and other F2 region parameters. The RO data were collected when the radio occultation occurred at Ascension Island (345.6° E, 8.0° S) during the solar minimum activity period from May 2006 to April 2008. Results show that the <I>B0</I> values are in moderate agreement with the ground-based observations in the equinox period (correlation coefficient <I>r</I> = 0.682) and winter (<I>r</I> = 0.570), with a strong correlation in summer (<I>r</I> = 0.750). The seasonal and diurnal variations in <I>B0</I> over Ascension Island show peak values during the daytime and in winter. In addition, the <I>B0</I> values were underestimated and overestimated in the RO measurements during the daytime and nighttime, respectively. Moreover, the comparison of scale heights shows that scale heights obtained from the retrieved data and digisonde observations are weakly correlation in all three seasons. Furthermore, although the effective scale height (<I>H</I>_T) values were reverse of those obtained from the RO measurements and are higher during the nighttime than in the daytime, they are in good agreement with those from ground-based observations. This paper also provides a comprehensive discussion of the effect of the asymmetric ionospheric electron density profiles on RO measurements

Long‐term analysis between radio occultation and ionosonde peak electron density and height during geomagnetic storms

“…For example, Krankowski et al [] obtained a correlation ( R ) of 0.986 when validating COSMIC N m F 2 with ionosonde data over European midlatitude region during 2008, while R values of 0.96 [ Chu et al , ] and 0.92 [ Habarulema et al , ] were reported for global and African sector studies using 2006 and 2008 data, respectively. Furthermore, single station [e.g., Chuo et al , ] and global simulation [e.g., Yue et al , ] studies have also reported R values (0.96 and 0.95) in the same range. Comparing GPS/MET‐derived N m F 2 with collocated ionosonde observations, Hajj and Romans [] reported an agreement to within 20% at 1 σ level.…”

“…Thus, some comparative studies between RO and ground‐based observations preferred analyses during geomagnetically quiet conditions [e.g., Chu et al , ; Wu et al , ] to avoid errors related to the occurrence of ionospheric electron density irregularities. However, other studies have done validation case studies on one storm period [e.g., Krankowski et al , ], while significant literature that exists performs statistics based on large data sets without necessarily doing any isolation based on geomagnetic activity or occurrence of ionospheric irregularities [e.g., Yue et al , ; Chuo et al , ; Pedatella et al , , and references therein]. These studies give an indication that RO data may be able to follow ionospheric dynamics even during geomagnetic storms, although not in a detailed quantitative sense.…”

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

“…Chuo et al, 2011). Comparison of characteristics of ionospheric parameters obtained from COSMIC and a digisonde over Ascension Island also illustrates similar diurnal variation and high correlation for both NmF2 (> 0.91) and hmF2 (> 0.72) in the equinox, summer and winter periods (Chuo et al, 2013). Comparison between RO EDPs from the COSMIC satellites with digisonde data over the Brazilian region shows generally good correlation for NmF2 (0.92) and hmF2 (0.78) (Ely et al, 2012).…”

“…Statistical comparisons of ionospheric peak parameters (NmF2 and hmF2) measured by COSMIC satellites and ionosondes indicate that there are considerable high correlations between COS-MIC and ionosonde ionospheric parameters (Lei et al, 2007;Chu et al, 2010;Chuo et al, 2011Chuo et al, , 2013Ely et al, 2012;Krankowski et al, 2011;J.-Y. Liu et al, 2010;Hu et al, 2014).…”

Unusual behavior of quiet-time zonal and vertical plasma drift velocities over Jicamarca during the recent extended solar minimum of 2008

“…The impacts of the recent deep and prolonged solar minimum on the electron density, temperature, spread F, and total electron content, as well as the vertical and zonal plasma drifts, over the equatorial and low-latitude ionosphere have been studied using different types of observational data, such as digisondes (Liu Libo et al, 2011;Candido et al, 2011;Chuo et al, 2013;Solomon et al, 2013;Narayanan et al, 2014), satellites (Solomon et al, 2011;Huang et al, 2010Huang et al, , 2012Chuo et al, 2013;Fejer et al, 2013) and incoherent scatter radar (Aponte et al, 2013;Kotov et al, 2015;Santos et al, 2016a). During the period of June 2008 the mean monthly F10.7 radio index reached an extremely low value of ∼ 65.7 × 10 −22 W m −2 Hz −1 , which represented a solar extreme ultraviolet (EUV) irradiance that was lower than during previous solar cycles.…”