Long-term study of medium-scale traveling ionospheric disturbances using O I 630 nm all-sky imaging and ionosonde over Brazilian low latitudes

Author(s)

Amorim, D. C. M. ; Pimenta, A. A. ; Bittencourt, J. A. ; Fagundes, P. R.

• Document type: Journal article
• Source: JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS; v. 116, p. 7-pg., 2011-06-18.

Abstract

In this paper, we report a long-term study of medium-scale traveling ionospheric disturbance (MSTID) occurrence using all-sky images of O I 630 nm airglow emission. Our study is based on a 10.5 year data series in which 5.5 years compound a new data set. The images were obtained by an all-sky imager installed at Cachoeira Paulista (22.7 degrees S, 45 degrees W, 15 degrees S magnetic latitude). Our results show the greatest occurrence of MSTIDs during solar minimum and a minor occurrence rate during descending and ascending solar activity periods. During solar maximum, we have not detected MSTID signatures on all-sky images. All detected events have occurred during geomagnetically quiet conditions. Simultaneous measurements using both all-sky images and ionograms obtained at the same site show the occurrence of spread F and a sharp rise in the ionospheric F layer at the same time as dark bands are optically registered over the zenith. It is possible that for certain weaker events, the ionosonde may resolve bands that are not sufficiently raised to cause darkening of the all-sky images. In order to investigate this possibility, we have conducted a study using only ionograms for a 1 year period (March 2000-February 2001) during solar maximum, when we have not seen any MSTID events in the all-sky images. As we conjectured, MSTIDs also occur during solar maximum, and the risings of the ionospheric F layer are not able to disturb the airglow layer during such events. (AU)