New Findings Relating Tidal Variability and Solar Activity in the Low Latitude MLT Region

Abstract

Mesospheric winds have been measured by meteor radar at Cachoeira Paulista (22.7°S; 45°W) since April 1999. The tidal components were analyzed over about 21 years of available data exhibiting an annual and semi‐annual variation. Amplitudes of meridional diurnal (semidiurnal) tide are on averaged 30% (28%) and the zonal ones are 14% (20%) stronger at solar minimum than at solar maximum. The anticorrelation between F10.7 cm solar flux and amplitudes of the semiannual oscillation of diurnal and semidiurnal tides is presented. Additionally, the sporadic E (Es) layers occurrence has an anti‐correlation with solar activity due to the tidal wind variation. A discussion about the physical mechanism is performed in terms of the particle precipitation during High‐Speed Stream (HSS) events according to the solar cycle. Finally, a superposed epoch analysis of the tidal amplitudes during the HSS events in 2018 is presented. And a slight increase in all tidal components is seen when the structure reached the Earth and in the following days showing that indeed the electron precipitation during HSS events affect the tidal amplitudes.

Blanketing Sporadic‐E Layer Occurrences Over Santa Maria, a Transition Station From Low to Middle Latitude in the South American Magnetic Anomaly (SAMA)

“…This anticorrelation between the occurrence of Es layers and solar activity was also found by Andrioli et al. (2022) when the tidal amplitudes were studied during the solar cycle minimum (2018) and maximum (2015) in Cachoeira Paulista (22.7°S, 45.0°W, GL = 14.5°S), a low‐latitude station in Brazil.…”

“…Moreover, the Es b layers are anticorrelated with solar activity. This anticorrelation between the occurrence of Es layers and solar activity was also found by Andrioli et al (2022) when the tidal amplitudes were studied during Therefore, in this work we present the first study of the Es b occurrences from a Digisonde Portable Sounder (DPS-4D) measurements that started operation in Santa Maria (29.7°S, 53.8°W, GL = 20.5°S), Brazil, in 2017. Santa Maria is located in the central region of the SAMA.…”

“…The occurrences of Es b layers have been studied on a global scale using satellite data (Arras & Wickert, 2018; Chu et al., 2014; Luo et al., 2021; Wu et al., 2005; Yu et al., 2019; Yue et al., 2016) and overhead at some ionospheric stations with ground‐based radar such as ionosondes (Abdu et al., 1996; Andrioli et al., 2022; Conceição‐Santos et al., 2019; Jo et al., 2019; Pignalberi et al., 2014; Resende et al., 2017b; Yadav et al., 2017; Zhou et al., 2017).…”

Seasonal and Interannual Variations of Global Tides in the Mesosphere and Lower Thermosphere Neutral Winds: I. Diurnal Tides

“…Utilizing TIMED/TIDI data, Dhadly et al (2018) and Oberheide et al (2009) found that DW1 and DE3 have no clear solar cycle dependences in the MLT. Recently, Andrioli et al (2022) demonstrated that the SAO amplitudes of diurnal tide were anticorrelated with solar cycle at Cachoeira Paulista (22.7°S, 45.0°W).…”

Seasonal and Interannual Variations of Global Tides in the Mesosphere and Lower Thermosphere Neutral Winds: II. Semidiurnal and Terdiurnal Tides

“…The response of the semidiurnal tides to the solar cycle were studied by for example, Andrioli et al (2022), de Araújo et al (2020), Fraser et al (1989, Guharay et al (2019), Iimura et al (2010), Keuer et al (2007), Namboothiri et al (1993), Sridharan et al (2010). The response is weak and negative at middle latitudes (e.g., Fraser et al, 1989;Keuer et al, 2007;Namboothiri et al, 1993).…”