Dependence of sporadic-E layer and lower thermosphere dynamics on solar activity

On the influence of solar activity on the mid-latitude sporadic E layer

“…With regard to the comparison between foEsð365Þ 12LT and " F ð365Þ, a greater normalized slope (À0.01444 vs. À0.00899) indicates that, besides the solar activity, also some other physical mechanism concurs to the decrease of foEs. It is interesting to highlight that the decreasing trend characterizing foEs was noticed also by Maksyutin et al (2001), who used a data set of three solar cycles, as we did in this work; however, it is worth noting that the two data sets are shifted of about 20 years (1955-1988 vs. 1976-2009), which underlines that this decrease is a feature that has characterized the foEs trend since more than half a century.…”

“…1). Our analyses, which are essentially based on foEsð365Þ 12LT and fbEsð365Þ 12LT , and on the 365 days running mean of the daily values of F 10.7 , " F ð365Þ, are then much less rough than those carried out by Bossolasco & Elena (1963), and Maksyutin et al (2001), which are based on yearly averages of foEs and the sunspot number.…”

“…The analyses described in this paper, that are based on foEs and fbEs time series and not on Es occurrence percentages, are much more refined than those performed by Bossolasco & Elena (1963), and by Maksyutin et al (2001), and show unambiguously that the solar variability affects the Es layer.…”

“…Bossolasco & Elena (1963) used data recorded at several mid-latitude stations between 1958 and 1962 to show that higher yearly mean values of foEs occur generally with higher yearly mean sunspot numbers, and they proposed a basic analytical relation between these two quantities. Also Maksyutin et al (2001), referring to data recorded at Moscow during three solar cycles, found that daytime yearly mean values of foEs are positively correlated with yearly mean sunspot numbers.…”

“…Pietrella et al (2014), by using the same data set of Pietrella & Bianchi (2009), showed also that, regardless of the solar activity, Es develops concurrently over extended regions in space, instead of being a spatially limited layer. Instead of considering the Es occurrence, Bossolasco & Elena (1963) and Maksyutin et al (2001) investigated this issue by analysing simply the foEs values. Bossolasco & Elena (1963) used data recorded at several mid-latitude stations between 1958 and 1962 to show that higher yearly mean values of foEs occur generally with higher yearly mean sunspot numbers, and they proposed a basic analytical relation between these two quantities.…”