Dynamic Properties of a Sporadic Sodium Layer Revealed by Observations Over Zhongshan, Antarctica: A Case Study

Abstract

A sodium Doppler lidar system with three‐directional measurements of sodium density, atmospheric wind field, and temperature was established at Zhongshan (69.4°S, 76.4°E), Antarctica. On November 14, 2019, a sporadic sodium layer (SSL) was observed at an altitude range of 93–103 km. The temporal/spatial sodium density variations of this SSL are associated with a strong sporadic E (Es) layer at nearly the same height, which is modulated by the convective electric field. By considering the structures and the time lags of the SSL's growth at three positions, the SSL appears to have a horizontal advection in an approximately westward direction with a velocity of the order of 80 m/s. This is consistent with the zonal wind velocity derived from the lidar system itself. The temporal/spatial sodium density variations strongly indicate that the formation and perturbation of SSLs are related to the evolution of ES layers due to varied electric fields and atmospheric gravity waves, while it is advected by the horizontal wind.

Simultaneous Observations of a Polar Cap Sporadic‐E Layer by Twin Incoherent Scatter Radars at Resolute

“…Moreover, the multiple electron density profiles provide a large number of important information. Regarding the formation of the polar cap Es layer, the initial section of the polar cap Es layer is usually connecting to the lower F region (>150 km), presenting a piece of direct and firm evidence to prove the postulate of Chen et al (2021). This peculiar manner instructively inspires the possible generation mechanism.…”

“…In literature, several models have been proposed to explain the Es layer at high latitudes (e.g., Bristow & Watkins, 1991; Kirkwood & Collis, 1989; MacDougall & Jayachandran, 2005; MacDougall et al., 2000b; Nygrén et al., 2006), here some of which will be discussed in detail. First, the high‐frequency appearance of the Es layer over a “cusp latitude” station is reasonably explained by the two‐step mechanisms, including the horizontal convergence of ionization by the electric field of convection reversal at first, and then vertical convergence of these ionizations by the electric field in the polar cap (e.g., Chen et al., 2021; MacDougall & Jayachandran, 2005). However, as pointed out by the authors, it can only be suitable to a very narrow strip at high latitudes due to the strictly required terms of the electric field.…”

“…As a consequence, we present a peculiar evidence for the first time to greatly enrich our knowledge on the polar cap Es layer, showing us a new insight on it. radio-occultation techniques, as well as GPS receivers (e.g., Bristow & Watkins, 1993;Chen et al, 2021;Fukao et al, 1998;Larsen et al, 2007;MacDougall et al, 2000a;Maeda & Heki, 2014;2015;Maeda et al, 2016;Sun et al, 2018Sun et al, , 2020Sun et al, , 2021Wu et al, 2005;Yeh et al, 2014). Recently, at middle latitudes, Maeda and Heki (2014); Maeda et al (2016) and Maeda and Heki (2015) attempted to fundamentally illustrate the horizontal structure of the Es layer by 2-dimensional Total Electron Content maps drawn from the dense GPS receivers over Japan, generally concluding that the Es layer was spanning over ∼150 km in length and ∼30 km in width and was propagating in different directions.…”

“…In decades, the studies dealing with the characteristics of thin Es layers have been continued, which were carried out by using a large number of instruments, such as ionosondes, incoherent scatter radars, high‐frequency radars, radio‐occultation techniques, as well as GPS receivers (e.g., Bristow & Watkins, 1993; Chen et al., 2021; Fukao et al., 1998; Larsen et al., 2007; MacDougall et al., 2000a; Maeda & Heki, 2014; 2015; Maeda et al., 2016; Sun et al., 2018, 2020, 2021; Wang, Jayachandran, et al., 2021; Wu et al., 2005; Yeh et al., 2014). Recently, at middle latitudes, Maeda and Heki (2014); Maeda et al.…”

“…Chen et al. (2021) inferred that the Es layer over Antarctica was in the form of bands along a specific direction but without directly observation evidence. As a consequence, it is still a long way to study the polar cap Es layer in detail, compared with the abundant investigations at middle latitudes.…”