Sounding of Sporadic E layers by the GPS-COSMIC radio occultation experiment

The GPS radio occultation technique is sensitive for layered structures at the Earth's limb, which provides ideal observation on ionospheric vertical structures such as Sporadic E (Es) layers. This paper reports the comparison between the SNR measurements of L1 C/A code at 50-Hz sampling rate obtained from the GPS-COSMIC radio occultation experiment and the simultaneous observations of the Australia ionosonde chain. The results show that Es structures did exist over the ionosonde as denoted by the ionosonde observations when large SNR fluctuations were observed at ionospheric E-region heights during GPS-COSMIC radio occultation which occurred in the vicinity of the ionosonde. Therefore, GPS-COSMIC radio occultation measurements provide a means of sounding Es structures on a global basis, which can not be done using traditional ground-based monitoring techniques.