J. Space Weather Space Clim.
Volume 7, 2017
|Number of page(s)||11|
|Published online||27 September 2017|
Long-term variations of the upper atmosphere parameters on Rome ionosonde observations and their interpretation
Istituto Nazionale di Geofisica e Vulcanologia (INGV),
Via di Vigna Murata 605,
2 Pushkov Institute of Terrestrial Magnetism, Ionosphere and Radio Wave Propagation (IZMIRAN), Troitsk, Moscow 142190, Russia
* Corresponding author: firstname.lastname@example.org
Accepted: 13 August 2017
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 insignificant.
Key words: long-term trend / ionosphere / thermosphere
© L. Perrone et al., Published by EDP Sciences 2017
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