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Authors: Perrone, Loredana* 
Mikhailov, A.* 
Cesaroni, Claudio* 
Alfonsi, Lucilla* 
De Santis, Angelo* 
Pezzopane, Michael* 
Scotto, Carlo* 
Title: Long-term variations of the upper atmosphere parameters on Rome ionosonde observations and their interpretation
Issue Date: 27-Sep-2017
Series/Report no.: /7(2017)
DOI: 10.1051/swsc/2017021
Keywords: long-term trend
Subject Classification01.02. Ionosphere 
Abstract: A recently proposed self-consistent approach to the analysis of thermospheric and ionospheric long-term trends has been applied to Rome ionosonde summer noontime observations for the (1957–2015) period. This approach includes: (i) a method to extract ionospheric parameter long-term variations; (ii) a method to retrieve from observed foF1 neutral composition (O, O2, N2), exospheric temperature, Tex and the total solar EUV flux with λ<1050 Å; and (iii) a combined analysis of the ionospheric and thermospheric parameter long-term variations using the theory of ionospheric F-layer formation. Atomic oxygen, [O] and [O]/[N2] ratio control foF1 and foF2 while neutral temperature, Tex controls hmF2 long-term variations. Noontime foF2 and foF1 long-term variations demonstrate a negative linear trend estimated over the (1962–2010) period which is mainly due to atomic oxygen decrease after ∼1990. A linear trend in (δhmF2)11y estimated over the (1962–2010) period is very small and insignificant reflecting the absence of any significant trend in neutral temperature. The retrieved neutral gas density, ρ atomic oxygen, [O] and exospheric temperature, Tex long-term variations are controlled by solar and geomagnetic activity, i.e. they have a natural origin. The residual trends estimated over the period of ∼5 solar cycles (1957–2015) are very small (<0.5% per decade) and statistically.
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