China-Brazil Joint Laboratory for Space Weather, Chinese Academy of Sciences
Pekin, China
Pekin, China
Pekin, China
Uhan', China
Uhan', China
A double-laser beam lidar to measure potassium (K) layer at Beijing (40.5° N, 116.2° E) was successfully developed in 2010. The parameters of sporadic Ks layers and their distributions were given. The seasonal distribution of Ks occurrence frequency was obtained, with two maxima in July and January. The seasonal distributions of sporadic Es layer occurrence frequency over Beijing differ from those of Ks. However, the good correlation between Es and Ks in the case-by-case studies supports the mechanism of neutralization of metal ions in a descending Es layer.
lidar, sporadic potassium layers, sporadic E layers
1. INTRODUCTION
Meteoric metal (Na, K, Ca, Mg, etc.) layers between 80 and 110 km originate from meteor ablation [Plane, 1991; Kane et al., 2001]. Lidar observations and studies of metal layers have been carried out for about 40 years, promoting better understanding of chemical and dynamic processes in the mesopause region. Sporadic or narrow metal layers (Ns) were often observed in lidar data.
There are fewer lidar observations of the K layer than the sodium (Na) one. This is because the density of the K layer is approximately two orders of magnitude lower than that of the Na layer [Megie et al., 1978]. While several lidar observations of K layers over dif-ferent regions were made [Eska, Hoffner, 1988; Eska et al., 1998; von Zahn et al., 1999; Friedman et al., 2002], reports on Ks layers were limited in number: two dif-ferent sporadic layer events were analyzed by Delgado et al. [2012], and the Ks layers were observed in both neutral K and Ca+ layers with a lidar. A temperature-dependent chemical model was also developed to simulate the observations: one event that occurred be-tween June 12 and 13, 2002 was successfully reproduced. Raizada et al. [2004] found that sudden increases in both K and Ca densities were often observed during early morning hours or at night when meteor showers occurred.
Among many mechanisms for interpreting the Ns formation, the most promising is the neutralization of ions, as evidenced by the high temporal and spatial correlation between enhanced metal atoms and Es layers [Gardner et al., 1993; Friedman et al., 2000; Williams et al., 2007; Delgado et al., 2012; Dou et al., 2012]. However, no reports examined the relationship between the Ks and Es layers.
In this paper, using lidar and digital ionosonde observations from the newly launched Meridian Project, the aim of which is to help researchers better understand and predict space weather conditions over China, we statistically analyzed the Ks and Es layer events at Beijing. The observational data were obtained by the Na-K lidar at Beijing from November 2010 to October 2011 and from May 2013 to April 2014.
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