The mesospheric sodium airglow emission occurs when the sodium atom decays from the excited level ²P to the level ²S, emitting at the line D in lambda = 589.3 nm. Measurements of the emission's nocturnal intensity has been carried by a multichannel photometer installed in São João do Cariri (7,38ºS; 36,54ºw) since 1998. This work analyzed a data set corresponding to a period from 1998 to 2003, in order to study the emission's seasonal comportment. The analyses showed a strong seasonal variation. The results are in accordance to other studies completed at equatorial regions. The relationship between solar activity and NaD emission showed a correspondence during ascension and descension of the solar activity, but discrepancies arise during peak of the solar activity. On the other hand, the NaD and OH (6-2) showed similar aspects in their respective seasonal variation.
mesospheric sodium; airglow; OH; solar activity
