A. Guharay

A case study on occurrence of an unusual structure in the sodium layer over Gadanki, India

The height-time-concentration map of neutral sodium (Na) atoms measured by a Na lidar during the night of 18 to 19 March 2007 over Gadanki, India (13.5° N, 79.2° E) reveals an unusual structure in the Na layer for around 30 min in the altitude range of 92 to 98 km which is similar to the usual ‘C’ type structures observed at other locations. In order to understand the physical mechanism behind the generation of this unusual event, an investigation is carried out combining the data from multiple instruments that include the meteor wind radar over Thiruvananthapuram, India (8.5° N, 77° E) and the SABER instrument onboard the TIMED satellite. The temperature and wind profiles from the data set provided by these instruments allow us to infer the Richardson number which is found to be noticeably less than the canonical threshold of 0.25 above 92 km over Thiruvananthapuram suggesting the plausible generation of Kelvin-Helmholtz (KH) billows over southwestern part of the Indian subcontinent. Based on the average wind speed and direction over Thiruvananthapuram, it is proposed that the KH-billow structure was modified due to the background wind and was advected with it in nearly ‘frozen-in’ condition (without significant decay) in the northeastward direction reaching the Na lidar location (Gadanki). This case study, therefore, presents a scenario wherein the initially deformed KH-billow structure survived for a few hours (instead of a few minutes or tens of minutes as reported in earlier works) in an apparently ‘frozen-in’ condition under favorable background conditions. In this communication, we suggest a hypothesis where this deformed KH-billow structure plays crucial role in creating the abovementioned unusual structure observed in the Na layer over Gadanki.

Erratum to: A case study on occurrence of an unusual structure in the sodium layer over Gadanki, India

Erratum After publication, it was found in the text that the words ‘Figure 6’ and ‘Figure 7’ were printed in the reverse order in several places of the article by Sarkhel et al. (2015). The details are as follows: Page 7, Right column, Last paragraph, Line 8: ‘Figure 6a’ should be read as ‘Figure 7a’ Page 9, Left column, Last paragraph, Line 11: ‘Figure 7’ should be read as ‘Figure 6’ Page 9, Right column, Last paragraph, Line 1: ‘Figure 6’ should be read as ‘Figure 7’ Page 10, Left column, Line 6: ‘Figure 6a’ should be read as ‘Figure 7a’ Page 10, Left column, Line 25: ‘Figure 6a’ should be read as ‘Figure 7a’ Page 10, Left column, Line 33: ‘Figure 6a’ should be read as ‘Figure 7a’ Page 10, Left column, Line 37: ‘Figure 6b’ should be read as ‘Figure 6’ Page 10, Right column, Line 15: ‘Figure 6a’ should be read as ‘Figure 7a’ Page 10, Right column, Line 19: ‘Figure 6b’ should be read as ‘Figure 7b’ Page 11, Left column, Section: Role of sporadic-E activity, Line 12: ‘Figure 6a’ should be read as ‘Figure 7a’