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Ann. Geophys., 24, 1375-1385, 2006
www.ann-geophys.net/24/1375/2006/
© European Geosciences Union 2006
Imaging science at El Leoncito, Argentina
C. Martinis1, J. Baumgardner1, S. M. Smith1, M. Colerico1,*, and M. Mendillo1
1Center for Space Physics-Boston, Boston, MA 02215, USA
*now at: MIT Haystack Observatory, Westford, MA, USA
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.
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