On polar substorms as the source of large-scale traveling ionospheric disturbances

The present study shows that it is possible to relate the occurrence of large-scale traveling ionospheric disturbances (TID's) observed at midlatitudes with polar substorms on a statistical basis. In addition under favorable conditions (relatively low geomagnetic activity) it is possible to show a connection between the occurrence of the TID's and substorms on a one-to-one basis. Columnar electron content measurements were used to detect the TID's and magnetograms from several high-latitude geomagnetic observatories were used to study the substorms. The results strongly support the theory that large-scale TID's originate during polar substorms. It was also possible to determine the location of the source of a number of individual TID's. These locations lie primarily in the evening sector of the auroral oval.