Imaging science at El Leoncito, Argentina

Abstract. Thermospheric and mesospheric structures are studied using an all-sky imager located at El Leoncito, Argentina (31.8° S, 69.3° W, –18° mag lat). This site has relatively high geographic latitude for a location under the crest of the equatorial ionization anomaly (EIA), and thus observations can be used to study the intrusion of several equatorial processes into the midlatitude domain. In addition, it has a conjugate point close to the field of view of our companion imager at Arecibo, PR, allowing for the study of inter-hemispheric effects. Four types of phenomena were studied using 630.0 nm and 777.4 nm observations: (1) highly-structured airglow depletions associated with the Rayleigh-Taylor instability/equatorial spread-F (RTI/ESF) process, (2) brightness waves (BW) associated with the midnight temperature maximum (MTM), (3) strong airglow enhancements associated with the positive phase of ionospheric storms, and (4) simple (non-structured) bands of airglow depletions with characteristics matching a Perkins-like instability. Using 557.7 nm mesospheric observations, a fifth category of study deals with gravity waves probably generated by lower atmospheric disturbances, and mesospheric bores related to strong vertical temperature gradients.

While ESF depletions and BW events are detected fairly frequently, the mid-latitude bands are not, and thus their successful imaging at El Leoncito offers the first example of the coupling from mid-latitudes to low-latitudes in the South American longitude sector. Preliminary results on these features are presented in this paper. Taken together, these five types of optical structures offer the opportunity to investigate coupling, both in altitude and latitude, of aeronomic processes at low latitudes in an under-sampled longitude sector in the Southern Hemisphere.