A Comparison of the Midlatitude Nickel and Sodium Layers in the Mesosphere: Observations and Modeling

Abstract

The layer of nickel (Ni) atoms in the upper mesosphere and lower thermosphere (MLT) as well the layers of other metals (Fe, Na, Mg, Ca, and K) produced by meteoric ablation provide a unique means of observing the physics and chemistry of the atmosphere between 75 and 110 km (Plane, 2003;Plane et al., 2015). Although the Ni layer was only observed for the first time in 2012 (Collins et al., 2015), much progress in understanding the characteristic features of the layer has been made in the past 5 years. This has been achieved through a combination of further observations (

First Simultaneous Lidar Observations of Thermosphere‐Ionosphere Sporadic Ni and Na (TISNi and TISNa) Layers (∼105–120 km) Over Beijing (40.42°N, 116.02°E)

“…The main Ni and Na layers peak around 85 and 92 km, respectively, and main [Ni]/[Na] ratios are ∼0.1, consistent with the results of Jiao et al. (2022). The probable explanations include the more efficient ablation of Na from cosmic dust than Ni, the more rapid neutralization of Na + than Ni + between 90 and 100 km, and the significant differences in the neutral chemistries of these two metals below 90 km (Jiao et al., 2022).…”

“…However, these oxide ions also react with O, reducing them back to Ni + and this process competes with dissociative recombination, thereby slowing the conversion of Ni + to Ni. Thus, the relative electron to O concentrations control the rate of dissociative recombination (Bones et al., 2020; Jiao et al., 2022).…”

“…(2022). The probable explanations include the more efficient ablation of Na from cosmic dust than Ni, the more rapid neutralization of Na + than Ni + between 90 and 100 km, and the significant differences in the neutral chemistries of these two metals below 90 km (Jiao et al., 2022). In contrast, the TISNi and TISNa layers have strikingly similar morphologies with temporal‐spatial correlations of nearly 1 and [TISNi]/[TISNa] ratios close to 1.…”

“…TISNi and TISNa have similar column abundance in 105–120 km, ranging from ∼5 × 10 7 to ∼5 × 10 8 cm −2 (see Tables S1 and S2 in Supporting Information ). The mean column abundance of the main Ni and Na layers in May–June is respectively ∼2.6 × 10 8 and ∼3.9 × 10 9 cm −2 (Jiao et al., 2022). Therefore, the [TISNi]/[TISNa] ratios are ∼10 times of the main layer [Ni]/[Na] ratios.…”

“…One of the dye lasers was frequency doubled to 341.5744 nm (in vacuum) while another one was tuned to 589.1583 nm to excite resonance fluorescence from the Ni( 3 D 3 ↔ 3 F 4 ) and Na D 2 transitions, respectively. Details can be found in Jiao et al (2015Jiao et al ( , 2022 and Wu et al (2021). The raw data were taken at time and vertical resolutions of 33 s and 96 m. The Ni and Na densities were then retrieved with integrated resolutions of 30 min and 960 m, but with an over-sampling step size of 15 min.…”