Mid‐Latitude Thermosphere‐Ionosphere Na (TINa) Layers Observed With High‐Sensitivity Na Doppler Lidar Over Boulder (40.13°N, 105.24°W)

Abstract

We report the first lidar observations of regular occurrence of mid-latitude thermosphereionosphere Na (TINa) layers over Boulder (40.13°N, 105.24°W), Colorado. Detection of tenuous Na layers (∼0.1-1 cm −3 from 150 to 130 km) was enabled by high-sensitivity Na Doppler lidar. TINa layers occur regularly in various months and years, descending from ∼125 km after dusk and from ∼150 km before dawn. The downward-progression phase speeds are ∼3 m/s above 120 km and ∼1 m/s below 115 km, consistent with semidiurnal tidal phase speeds. One or more layers sometimes occur across local midnight. Elevated volume mixing ratios above the turning point (∼105-110 km) of Na density slope suggest in situ production of the dawn/dusk layers via neutralization of converged Na + layers. Vertical drift velocity of TINa + calculated with the Ionospheric Connection Explorer Hough Mode Extension tidal winds shows convergent ion flow phases aligned well with TINa, supporting this formation hypothesis.

First Lidar Profiling of Meteoric Ca+ Ion Transport From ∼80 to 300 km in the Midlatitude Nighttime Ionosphere

“…where 𝐴𝐴 𝐴𝐴𝐷𝐷 is the dip angle of geomagnetic field line ( 𝐴𝐴 𝐴𝐴𝐷𝐷 = 64.34° at Beijing), 𝐴𝐴 𝐴𝐴 is the ratio of ion-neutral collision frequency to the gyro frequency of ions, and 𝐴𝐴 𝐴𝐴𝑛𝑛 is the neutral winds in geomagnetic zonal (x), meridional (y), and vertical (z) coordinates (Chu et al, 2021). Neutral winds at altitudes of 250, 96, and 87 km were concurrently measured with a FPI from three airglow emission wavelengths (OI 630.0, OI 557.7, and OH 892.0 nm) at Xinglong Station (40.23°N, 117.34°E) (Yuan et al, 2010), ∼130 km away from Yanqing.…”

“…Above the main metal layers, thermosphere‐ionosphere metal (TIMt) layers were recently discovered in Antarctica (Chu et al., 2011) and then detected globally with lidars up to ∼200 km (e.g., Chu et al., 2020, 2021; Friedman et al., 2013; Gao et al., 2015; Raizada et al., 2020; Tsuda et al., 2015; Xun et al., 2019). Following the terminology in Chu et al.…”

On the force of vertical winds in the upper atmosphere: consequences for small biological particles

“…This led the authors to suggest that the origins of the winds were not related to auroral activity. There are also new observations that show unexpected signatures of metallic ion layers at altitudes as high as 180-200 km [20]. These observations indicate that non-auroral activity might be involved in the transport of particles deeper into the thermosphere in a combination of both neutral vertical winds and geomagnetic Lorentz forcing [20].…”

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)

“…By now TIMt layers have been observed by lidars for the metallic species Fe, Na, K, and Ca + extending to ∼200 km for neutrals and ∼300 km for Ca + (e.g., Chu et al., 2011, 2020, 2021; Friedman et al., 2013; Gao et al., 2015; Jiao et al., 2021; Liu et al., 2016; Lübken et al., 2011; Raizada et al., 2015, 2020; Tsuda et al., 2015; Xun et al., 2019). Most of the neutral TIMt layers exhibit clear signatures of gravity or tidal waves, showing fast downward phase progression (e.g., Chu et al., 2011, 2020, 2021; Gao et al., 2015; Lübken et al., 2011).…”

“…After nearly a century of ground‐based observations of the (permanent) main metal layers (∼75–105 km) (e.g., Bernard, 1938; Bowman et al., 1969; Chu & Papen, 2005; Plane, 1991), thermosphere‐ionosphere metal (TIMt) layers above the main layers were first discovered in Fe species by lidar observations in Antarctica (Chu et al., 2011) and then observed globally at all latitudes. By now TIMt layers have been observed by lidars for the metallic species Fe, Na, K, and Ca + extending to ∼200 km for neutrals and ∼300 km for Ca + (e.g., Chu et al., 2011, 2020, 2021; Friedman et al., 2013; Gao et al., 2015; Jiao et al., 2021; Liu et al., 2016; Lübken et al., 2011; Raizada et al., 2015, 2020; Tsuda et al., 2015; Xun et al., 2019). Most of the neutral TIMt layers exhibit clear signatures of gravity or tidal waves, showing fast downward phase progression (e.g., Chu et al., 2011, 2020, 2021; Gao et al., 2015; Lübken et al., 2011).…”