Imaging science at El Leoncito, Argentina

Abstract

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 interhemispheric effects. Four types of phenomena were studied using 630.0 nm and 777.4 nm observations: (1) highlystructured airglow depletions associated with the RayleighTaylor 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.

Climatology of nighttime medium-scale traveling ionospheric disturbances (MSTIDs) in the Central Pacific and South American sectors

“…It should be noted that the Shiokawa et al (2003a) Another feature of our data is the relatively low occurrence rates recorded in Cerro Tololo, Chile, compared with the instrumentation in Hawaii. Low occurrence rates were also found by Martinis et al (2006) in El Leoncito, Argentina (−31.8 • N, 290.7 • E, dip = −31.5 • ), which is approximately 230 km southeast of Cerro Tololo. Analogous to CNFI and CASI located in Hawaii, the narrow field view of PICASSO observes lower geomagnetic latitudes compared to the allsky imager used in the Martinis et al (2006) study.…”

“…Low occurrence rates were also found by Martinis et al (2006) in El Leoncito, Argentina (−31.8 • N, 290.7 • E, dip = −31.5 • ), which is approximately 230 km southeast of Cerro Tololo. Analogous to CNFI and CASI located in Hawaii, the narrow field view of PICASSO observes lower geomagnetic latitudes compared to the allsky imager used in the Martinis et al (2006) study. In their study, Martinis et al (2006) observed MSTIDs in less than 5 % of the nights between 2000 and 2005.…”

“…Analogous to CNFI and CASI located in Hawaii, the narrow field view of PICASSO observes lower geomagnetic latitudes compared to the allsky imager used in the Martinis et al (2006) study. In their study, Martinis et al (2006) observed MSTIDs in less than 5 % of the nights between 2000 and 2005. Our complete data set from PICASSO includes 44 MSTID counts out of 939 usable nights, which gives a total occurrence rate of 4.7 %.…”

“…The study by Martinis et al (2006) was performed primarily during solar maximum with the F10.7A reaching a maximum value of ∼ 220 SFU in October 2001. Due to these solar conditions, it is expected that the occurrence rate would be relatively low.…”

Wave activity at ionospheric heights above the Andes Mountains detected from FORMOSAT‐3/COSMIC GPS radio occultation data

“…Observations of electron density and minor constituent fluctuations may be detected by various instruments like incoherent scatter radar, ionosondes, all-sky airglow imagers, Global Positioning System (GPS) receivers, on site measurements, and satellite remote sensing [e.g., Nicolls et al, 2004;Brunini et al, 2004;Miró Amarante et al, 2004;Martinis et al, 2006;Earle et al, 2008;Wickert et al, 2009;Scheer and Reisin, 2010]. Near the Andes, at the El Leoncito Observatory (Argentina) (31.8°S, 69.3°W) where the main sources of GWs in the lower and middle atmosphere are found [Fritts and Alexander, 2003], Smith et al [2009] reported for the first time imaging observations of stationary mesospheric gravity waves in the nightglow emissions of OH, from all-sky images.…”