Abstract
Abstract. This work presents new results about sporadic E-layers (Es layers) using GPS (global positioning system) radio occultation (RO) measurements obtained from the FORMOSAT-3/COSMIC satellites and digisonde data. The RO profiles are used to study the Es layer occurrence as well as its intensity of the signal-to-noise ratio (SNR) of the 50 Hz GPS L1 signal. The methodology was applied to identify the Es layer on RO measurements over Cachoeira Paulista, a low-latitude station in the Brazilian region, in which the Es layer development is not driven tidal winds only as it is at middle latitudes. The coincident events were analyzed using the RO technique and ionosonde observations during the year 2014 to 2016. We used the electron density obtained using the blanketing frequency parameter (fbEs) and the Es layer height (h'Es) acquired from the ionograms to validate the satellite measurements. The comparative results show that the Es layer characteristics extracted from the RO measurements are in good agreement with the Es layer parameters from the digisonde. Keywords. Ionosphere (ionosphere–atmosphere interactions)
Highlights
Sporadic layers (Es) are electron density enhancements which appear in the lower ionospheric E region at heights between 90 and 130 km with a typical thickness of less than 5 km
The study is based on data collected by the digisonde located in Cachoeira Paulista and coinciding GPS radio occultation measurements provided by the FORMOSAT-3/COSMIC mission between 2014 and 2016
In this work we use the electron density profiles known as ionograms provided by a DPS4D (4D digital portable sounder), which is a high-frequency radar with variable operational frequency that consists of transmitter, receiver and antennae installed at Cachoeira Paulista, Brazil, to collect the Es parameters
Summary
Sporadic layers (Es) are electron density enhancements which appear in the lower ionospheric E region at heights between 90 and 130 km with a typical thickness of less than 5 km. In the Brazilian low-latitude region, which is under the influence of the South American Magnetic Anomaly, the Es layer occurrence and its characteristics are highly variable is due to their formation mechanism, tidal winds, electric fields or particle precipitation (Batista and Abdu, 1977; Resende et al, 2013). Resende et al.: Low-latitude Es layers based on GPS RO measurements tion process at low latitudes This agrees with the results in Pancheva et al (2003), in which the authors demonstrated that the largest amplitudes of semidiurnal tide are found at middle and high latitudes, whereas the diurnal tide is dominating the wind field at low latitudes. Some outliers can be linked to the electric field influence in the Es layer formation in this region
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