On the Sources of the Ionospheric Variability in the South American Magnetic Anomaly During Solar Minimum

Abstract

We investigate for the first time the variability of the F2 layer critical frequency (foF2), its peak height (hmF2), the thickness parameter B0, and the E region critical frequency (foE) over Santa Maria (29.7° S, 53.7° W, dip angle = −37°), a station located in the central region of the South American Magnetic Anomaly. The selected ionospheric parameters were obtained from ionograms recorded by a recent Digisonde Portable Sounder 4‐D. The time period covers 309 days from 1 September 2017 to 30 August 2018. The diurnal analyses revealed a large day‐to‐day ionospheric variability, with some peculiarities as a strong semiannual pattern superimposed to expected ionospheric behavior. Furthermore, the results show significant differences between the averaged foF2 in December and June solstices, revealing a possible presence of the annual asymmetry. The coefficient of variation (CV) is used as a quantitative description of the variability of each parameter versus time and season. Considering low solar flux and geomagnetically quiet days only, we note that CV is smaller during the daytime and larger during nighttime for all parameters. The least variable ionospheric parameter in our study is foE, while the most variable one is B0. Regarding the F2 layer parameters, we observe that foF2 is much more variable than hmF2. We attribute the observed CV to the neutral atmosphere source over Santa Maria. The ionospheric variability is in general enhanced during geomagnetically disturbed periods. The estimated CV is higher over Santa Maria than Wuhan, China (30.5° N, 114.4° E, dip angle = 46°), a station with no influence of the South American Magnetic Anomaly.

Different Sporadic‐E (Es) Layer Types Development During the August 2018 Geomagnetic Storm: Evidence of Auroral Type (Esa) Over the SAMA Region

“…The SMK29 data are automatically uploaded to the Embrace website and the Digisonde network of the Global Ionosphere Radio Observatory (GIRO) Digital Ionogram DataBase (DIDBase; Reinisch & Galkin, 2011). More details about the Santa Maria Digisonde including the past studies about the variability of the E-region and F-region parameters, and its comparisons with the International Reference Ionosphere (IRI) model during geomagnetic quiet days can be found in Moro et al (2019Moro et al ( , 2020Moro et al ( , 2021. The Es layer parameters used in this work are manually scaled from the ionograms with the SAO Explorer software according to the echo's traces.…”

“…More details about the Santa Maria Digisonde including the past studies about the variability of the E ‐region and F ‐region parameters, and its comparisons with the International Reference Ionosphere (IRI) model during geomagnetic quiet days can be found in Moro et al. (2019, 2020, 2021). The present work is the first one about the Es layers responses over Santa Maria.…”

“…The installation of a new digital ionosonde in Santa Maria, Brazil, in 2017 (Moro et al, 2019) Therefore, the main focus of this work is to investigate the formation mechanism of Es a during the August 2018 geomagnetic storm with a numerical model of the E-region dynamics so-called MIRE (Portuguese acronym for the E-Region Ionospheric Model), which cover the items (a) and (b). However, this study is not limited to this aspect only.…”

Performance of the IRI-2016 at the Brazilian low-latitude ionosphere over the South America Magnetic Anomaly during solar minimum

“…Discussion started: 10 September 2019 c Author(s) 2019. CC BY 4.0 License.variabilities of the F2 and E layers parameters over Santa Maria during the period analysed in the recent work byMoro et al (2019).…”

The role of the inner radiation belt dynamic in the generation of auroral-type sporadic E-layers over south American magnetic anomaly

“…Here, we use the data collected by Digisondes installed in Cachoeira Paulista, Brazil (22.7 °S, 45.0 °W, dip: -35 °, L = 1.13), from the Embrace Network (Denardini et al, 2016), and installed in Santa Maria, Brazil (29.7 °S, 53.8 °W, dip: -37 °, L = 1.16) from the China-Brazil Joint Laboratory for Space Weather (Moro et al, 2019) to monitor the occurrence of Es a layer over the SAMA region. The ionograms are graphs of virtual height versus frequency, which provide the ionospheric profile, and from which the ionospheric parameters, including the sporadic-E layer types, can be obtained.…”