Interhemispheric transport of metallic ions within ionospheric sporadic <i>E</i> 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, combining 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. Our results not only provide strong support for the lower thermospheric meridional circulation predicted by a whole atmosphere chemistry–climate model, but also emphasize the influences of this winter-to-summer circulation on the large-scale interhemispheric transport of composition in the thermosphere–ionosphere.

Self-consistent global transport of metallic ions with WACCM-X

“…1. Since the metallic ions are the main reservoir for neutral metal atoms in the lower thermosphere , this is in good agreement with the summer peak occurrence of lower thermospheric neutral Na layers observed by mid-latitude lidars (Wang et al, 2012;Dou et al, 2013;Yuan et al, 2014;Xun et al, 2020).…”

“…There are a number of interesting findings: (1) a clear seasonal cycle is found in the monthly averaged global distributions of Mg + , in good agreement with the SCIAMACHY measurements (Langowski et al, 2015), although the peak height and peak density are about 5 km and 35 % lower than the observations, respectively. (2) Uplift of metal ions in the summer hemisphere at mid-latitudes (∼ 40 • ±10 • ), driven by the vertical ion velocity due to the neutral wind, appears to explain the summer peak occurrence of lower thermospheric neutral Na layers observed by mid-latitude lidars (Wang et al, 2012;Dou et al, 2013;Yuan et al, 2014;Xun et al, 2020). (3) Upward transport of metallic ions by E × B forcing is generally consistent with the fountain effect.…”

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).…”

Sporadic E Layer with a Structure of Double Cusp in the Vertical Sounding Ionogram

“…The examples of phenomena associated with sporadic layers presented in Figures 6 and 7 show that unusual traces on ionograms, similar to those shown in Figure 2, can be con-sidered as a manifestation of the process of the interaction between the E and F layers, including the propagation of atmospheric waves [2,17,[35][36][37][38][39][40][41][42]. Many studies considered the interaction of regions E and F during the propagation of medium-scale traveling ionospheric disturbances (TIDs), as well as the influence of solar thermal tidal motions that cause the appearance of the so-called descending intermediate E s layers [1][2][3][4][5]8,15,19].…”