O. A. Laryunin - Ph.D. (Phys.-Math.), Research Scientist, ISTP SB RAS. E-mail: laroleg@inbox.ru
V. I. Kurkin - D.Sc. (Phys.-Math.), Deputy Director, ISTP SB RAS. E-mail: zargano@yandex.ru
А. V. Podlesny - Research Scientist, ISTP SB RAS

The possibility of TID diagnostics from VIS ionograms has been discussed in a number of papers. However, to determine, say, the full vector of TID velocity, we usually need more than one radiophysical instrument, otherwise it is not always possible to determine an azimuth angle of arrival even through the use of indirect methods (experiments are planned in which angles of arrival cannot be measured directly). The use of several ionosondes at a time proves to be more effective and informative. The length of the Usolye-Tory path is 120 km. Geographical coordinates of the points of emanation and reception are 5253΄N, 10316΄E and 5148΄N, 1035΄E respectively. In addition to oblique ionospheric sounding over short paths (OIS), we took vertical sounding (VIS) at the Tory end of the path. Winter day-time VIS and OIS ionograms often contain an additional cusp-shaped trace. The cusp usually moves down turning with time into a bend of the main trace in the. The cusps in the ionograms have been found to be caused by traveling ionospheric disturbances the front of which is inclined to the horizon. A pattern observed in ionograms from one of the ionosondes can be observed several minutes later in ionograms from the second ionosonde. The closest fit between the cusps in the ionograms suggests that the TID was moving from north to south. Notice that in most cases the cusp appeared initially in Usolye-Tory ionograms, and several minutes later, in VIS ionograms. This implies that the said TID direction prevailed during this experiment.