Characterization of medium-scale traveling ionospheric disturbances in the brazilian low latitude sector - Statistical Analysis of All-Sky Images of oi 630 nm airglow emission

In order to characterize the phenomenon known as Medium-Scale Traveling Ionospheric Disturbances (MSTIDs), we present in this paper the resultsobtained from the statistical analysis of 10.5 years all-sky images of OI 630 nm airglow emission over the Brazilian low latitude sector. The images, which were obtainedby an all-sky imager installed at Cachoeira Paulista (22.7◦S, 45◦W), show dark band structures propagating from southeast to northwest with velocities of 50-200 m/s.Our results show the greatest occurrence of MSTIDs during solar minimum and a minor occurrence rate during descending and ascending solar activity periods. Duringsolar maximum activity we have not detected MSTIDs signatures on all-sky images. In relation to seasonality, the greatest frequency of occurrence is during local winter.All detected events have occurred during geomagnetically quiet conditions (Kp<3). Possible mechanisms of generation of this phenomenon are discussed.