Abstract
630.0 nm all-sky imaging data are used to detect airglow depletions associated with equatorial spread F. Pairs of imagers located at geomagnetically conjugate locations in the American sector at low and mid-latitudes provide information on the occurrence rate and zonal motion of airglow depletions. Airglow depletions are seen extending to magnetic latitudes as high as 25°. An asymmetric extension is observed with structures in the northern hemisphere reaching higher latitudes. By tracking the zonal motion of airglow depletions, zonal plasma drifts in the thermosphere can be inferred and their simultaneous behavior in both hemispheres investigated. Case studies using El Leoncito and Mercedes imagers in the southern hemisphere, and the respective magnetically conjugate imagers at Villa de Leyva and Arecibo, provide consistent evidence of the influence of the South Atlantic Magnetic Anomaly on the dynamics and characteristics of the thermosphere–ionosphere system at low and mid-latitudes.
Highlights
The equatorial and low latitude ionospheric region hosts a variety of processes, including the occurrence of ionospheric irregularities, commonly known as equatorial spread F (ESF), as well as the enhancements in the neutral temperature near the local midnight—the midnight temperature maximum (MTM)
This study will investigate the occurrence of ESF-related airglow depletions at Arecibo and will compare magnetically conjugate observations using the imagers at Arecibo and Mercedes and, to the compare magnetically conjugate observations using the imagers at Arecibo and Mercedes and, to the west, at El Leoncito and Villa de Leyva
The main conclusion from the Arecibo–Mercedes simultaneous measurements is that the conjugate behavior of the ESF-related airglow depletions is always observed at these mid-latitude sites, with structures showing very strong similarities in morphology and characteristics; we have found cases when the large-scale ESF structures are not symmetric, meaning that they are not observed at similar magnetic latitudes, in particular when they have apex heights higher than ~2000 km
Summary
The equatorial and low latitude ionospheric region hosts a variety of processes, including the occurrence of ionospheric irregularities, commonly known as equatorial spread F (ESF), as well as the enhancements in the neutral temperature near the local midnight—the midnight temperature maximum (MTM). Implies that an need to be processed in order to assign a latitude and longitude to every pixel This implies that emission height needs to be assumed, and during low solar activity, 250 km is typically used. ~25 locations of the Mercedes and Arecibo ASIs are poleward from the crests of the equatorial ionization and Arecibo poleward from the crests ofatthe anomalysites and the anomaly andASIs the are processes typically observed theequatorial equatorialionization and low-latitude This study will investigate the occurrence of ESF-related airglow depletions at Arecibo and will compare magnetically conjugate observations using the imagers at Arecibo and Mercedes and, to the compare magnetically conjugate observations using the imagers at Arecibo and Mercedes and, to the west, at El Leoncito and Villa de Leyva.
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