Statistical Study on Daytime Es Observed by Ground-ionosonde and RO-COSMIC S4 Index in Magnetic Equator Region in 2010

The previous studies show that scintillations under 150 km height shown by radio occultation (RO) of COSMIC are considered to be associated with ionospheric sporadic E (Es) layer. In this paper, we perform a statistical study on daytime Es observed by ground-ionosonde at five stations in magnetic Equator region in 2010, and make a comparison between foEs and S4 index from RO-COSMIC within 6 degree of each station. The results show that the foEs and S4 index had similar distributions. The agreement between scintillation occurrence and extreme Es cases showed that the Es had a significant contribution to the S4 index in daytime. It implies the satellite RO data could be used to study ionospheric structures/irregularities. The results also showed that the Es had more contribution at Sao Luis/Ilorin than that at Jicamarca/Kwajalein. However, the Es contribution to the S4 index during daytime need to be further studied in detail.