Document Type

Article

Publication Date

3-23-2006

Publication Title

Annales Geophysicae

Department

Department of Physics and Astronomy

Abstract

The thermospheric midnight temperature maxi-

mum (MTM) is a highly variable, but persistent, large scale

neutral temperature enhancement which occurs at low lati-

tudes. Its occurrence can impact many fundamental upper

atmospheric parameters such as pressure, density, neutral

winds, neutral density, and F-region plasma. Although the

MTM has been the focus of several investigations employ-

ing various instrumentation including photometers, satellites,

and Fabry-Perot interferometers, limited knowledge exists

regarding the latitude extent of its influence on the upper at-

mosphere. This is largely due to observational limitations

which confined the collective geographic range to latitudes

within ±23◦. This paper investigates the MTM’s latitudi-

nal extent through all-sky imaging observations of its 6300 A ̊

airglow signature referred to by Colerico et al. (1996) as

the midnight brightness wave (MBW). The combined field

of view of three Southern Hemisphere imaging systems lo-

cated at Arequipa, Peru, and Tucuman and El Leoncito, Ar-

gentina, for the first time extends the contiguous latitudinal

◦◦

range of imager observations to 8 S–39 S in the American sector. Our results highlight the propagation of MBW events

◦

throughthecombinedfieldsofviewpast39 Slatitude,pro- viding the first evidence that the MTM’s effect on the up- per atmosphere extends into mid-latitudes. The observations presented here are compared with modeled 6300 A ̊ emis- sions calculated using the NCAR thermosphere-ionosphere- electrodynamic general circulation model (TIEGCM) in con- junction with an airglow code. We report that at this time TIEGCM is unable to simulate an MBW event due to the model’s inability to reproduce an MTM of the same mag- nitude and occurrence time as those observed via FPI mea- surements made from Arequipa.

DOI

10.5194/angeo-24-503-2006

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