Interhemispheric transport of metallic ions within ionospheric sporadic E layers by the lower thermospheric meridional circulation

Abstract

Abstract. Long-lived metallic ions in the Earth's atmosphere/ionosphere have been investigated for many decades. Although the seasonal variation in ionospheric sporadic E layers was first observed in the 1960s, the mechanism driving the variation remains a long-standing mystery. Here we report a study of ionospheric irregularities using scintillation data from COSMIC satellites and identify a large-scale horizontal transport of long-lived metallic ions, combined with the simulations of the Whole Atmosphere Community Climate Model with the chemistry of metals and ground-based observations from two meridional chains of stations from 1975–2016. We find that the lower thermospheric meridional circulation influences the meridional transport and seasonal variations of metallic ions within sporadic E layers. The winter-to-summer, meridional velocity of ions is estimated to vary between −1.08 and 7.45 m/s at altitudes of 107–118 km between 10°–60° N latitude. Our results not only provide strong support for the lower thermospheric meridional circulation predicted by a whole atmosphere chemistry-climate model, but also emphasise the influences of this winter-to-summer circulation on the large-scale interhemispheric transport of composition in the thermosphere/ionosphere.

Occurrences of Regional Strong Es Irregularities and Corresponding Scintillations Characterized Using a High‐Temporal‐Resolution GNSS Network

“…However, both ionosondes and VHF radars suffer from a scarcity of site distribution that cannot form a dense network for routinely monitoring of E s with a high spatial resolution. On the other hand, the technique of Global Navigation Satellite System (GNSS) radio occultation (RO) is employed in E s detection benefitting from its global coverage (e.g., Chu et al., 2014; Yeh et al., 2014; Yue et al., 2015; Yu et al., 2021). But the incontinuity of RO measurement makes it difficult to monitor E s over specific regions continuously, thus is more favorable for E s investigation on a climatologic sense (e.g., Chu et al., 2014).…”

Occurrence and Variations of Middle and Low Latitude Sporadic E Layer Investigated With Longitudinal and Latitudinal Chains of Ionosondes

“…Recently, Yu et al. (2021a) simulated the global horizontal transport of metallic ions and found that seasonal dependence of the Es is consistent with the interhemispheric transport of long‐lived metallic ions by the winter‐to‐summer lower thermospheric meridional circulation. Thus, the seasonal dependence of the Es is the combined effect of different mechanisms and is still mysterious.…”

“…Recently, Yu et al. (2021) found that the 27‐day and 13.5‐day oscillations in the high‐latitude Es layers correlated well with the geomagnetic activity Dst and Ap indices. Thus, it is necessary to analyze the disturbances of the geomagnetic and solar activities.…”

“…also calculated the global distribution of the vertical ion convergence and found that local and seasonal variations of neutral wind shear is an important factor in determining the geographical and seasonal variation in Es occurrence rate. Recently,Yu et al (2021a) simulated the global horizontal transport of metallic ions and found that seasonal dependence of the Es is consistent with the interhemispheric transport of long-lived metallic ions by the winter-to-summer lower thermospheric meridional circulation. Thus, the seasonal dependence of the Es is the combined effect of different mechanisms and is still mysterious.…”

“…Recently, Yu et al. (2021) found that the formation and seasonal variations of Es layers are significantly influenced by the interhemispheric horizontal transport of metallic ions caused by the lower thermospheric meridional circulation in the three‐dimensional wind shear theory. The horizontal magnetic field is weak and the vertical magnetic field is strong in the north America region.…”