author = "Sarkhel, S. and Mathews, J. D. and Raizada, S. and Sekar, R. and 
                         Chakrabarty, D. and Guharay, Amitava and Jee, G. and Kim, J-H. and 
                         Kerr, R. B. and Ramkumar, G. and Sridharan, S. and Wu, Q. and 
                         Mlynczak, M. G. and Russell, J. M.",
          affiliation = "{Pennsylvania State University} and {Pennsylvania State 
                         University} and SRI International, Arecibo and {Physical Research 
                         Laboratory} and {Physical Research Laboratory} and {Instituto 
                         Nacional de Pesquisas Espaciais (INPE)} and {Korea Polar Research 
                         Institute} and {Korea Polar Research Institute} and SRI 
                         International, Arecibo and {Vikram Sarabhai Space Centre} and 
                         National Atmospheric Research Laboratory, India and {National 
                         Center for Atmospheric Research} and {NASA Langley Research 
                         Center} and {Hampton University}",
                title = "A case study on occurrence of an unusual structure in the sodium 
                         layer over Gadanki, India",
              journal = "Earth, Planets and Space",
                 year = "2015",
               volume = "67",
               number = "1",
             abstract = "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.",
                  doi = "10.1186/s40623-015-0183-5",
                  url = "http://dx.doi.org/10.1186/s40623-015-0183-5",
                 issn = "1343-8832",
             language = "en",
           targetfile = "Sarkhel_case.pdf",
        urlaccessdate = "04 dez. 2020"