Long-term variations of the upper atmosphere parameters on Rome ionosonde observations and their interpretation

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 period. This approach includes: (i) a method to extract ionospheric parameter long-term variations; (ii) a method to retrieve from observed f o F 1 neutral composition (O, O 2 , N 2 ), exospheric temperature, Tex and the total solar EUV flux with l < 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] period which is mainly due to atomic oxygen decrease after ∼1990. A linear trend in (dh m F 2 ) 11y estimated over the period is very small and insignificant reflecting the absence of any significant trend in neutral temperature. The retrieved neutral gas density, r 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 are very small (<0.5% per decade) and statistically.

Reply to Comment by Zhang et al. on the Paper “Long‐Term Variations of Exospheric Temperature Inferred From foF1 Observations: A Comparison to ISR Ti Trend Estimates” by Perrone and Mikhailov

“…The spatial and temporal (relative) variations of all thermospheric parameters are from the MSIS‐86 model. The validity of this assumption is confirmed by a comparison of the retrieved neutral gas density to the excellent CHAMP/STAR observations (Mikhailov & Perrone, ; Perrone et al, ) as well as by a good agreement with the EUV flux model for aeronomic calculations model (Mikhailov & Perrone, ) the latter having nothing common with the retrieval process. If this assumption were absolutely wrong, we could hardly get such testing results (section 2.3). P&M retrieve exospheric temperature (Tex) from f o F 1 but assume without justification that the other two MSIS thermospheric temperature parameters (temperature at 120 km and shape factor) are correct .…”

Evidence of vertical coupling: meteorological storm Fabienne on 23 September 2018 and its related effects observed up to the ionosphere

“…The perturbations can be detected at the ground level, for instance by magnetometers. Disturbances associated with such enhanced solar energy inputs are in general called geomagnetic storms (Gonzales et al, 1994;Buonsanto, 1999) or geospheric storms (Prölss, 2004). Different types of solar agents that are mainly responsible for geomagnetic disturbances have been analyzed with respect to their geoeffectiveness by Kakad et al (2019), Georgieva et al (2006), Fenrich and Luhmann (1998), Leamon et al (2002), Prölss (2004) and many others.…”

“…During night time electron concentration decreases at all heights due to recombination processes and a lack of ionizing radiation. It leads to practical disappearance of all ion pairs below the F layer that remains present due to slow recombination processes at its height (Davies, 1990;Rishbeth, 1998;Prölss, 2004, among many others). As a measure of the ability of the Earth's atmosphere to absorb incoming solar radiation, we can consider the maximum electron concentration NmF2 in the highest ionospheric level F or F2 if present.…”

“…However, the relationship is not linear and is the subject of a large investigation. The link between ionospheric variability and both solar and geomagnetic indices was analyzed for instance by Clilverd et al (2003), Cnossen et al (2014), Forbes et al (2000), Roux et al (2012), Koucká Knížová et al (2018, and Perrone et al (2017). Understanding of the relation between solar activity and the corresponding ionospheric and/or atmospheric behavior is crucial for instance in the estimation of the trends and potential human impact on the atmosphere and ionosphere (Roininen et al, 2015;Laštovička et al, 2012;Laštovička, 2012;Georgieva et al, 2012).…”

“…Their matching can be explained by a dominant contribution of the F2 layer's electron content contribution to the TEC and a much lower contribution of the E layer's variability during the studied days, even during the Fabienne event. The effect of electron concentration decrease on the ionosphere can be attributed to the geomagnetic disturbance observed as a negative storm effect (Prölss, 2004) related to the decrease in the atomic oxygen leading to a decrease in production of oxygen ions and the increase in molecular nitrogen density leading to the increase in the loss rate of ion species. Both processes lead to electron-ion concentration decrease.…”