P.F. Denisenko, I.I. Ivanov, V.M. Novikov, A.A. Khomyakov, M.Yu. Kotov
The characteristics of the TID in the topside ionosphere are investigated during weak geomagnetic disturbances according to data of the ionospheric sounding from the board of «Kosmos-1809» at mid-latitudes in the altitude range 400-900 km. Harmonic components of the electron density variations were identified, their amplitudes, wavelengths, wave surfaces were obtained. It was found that normal to the wave surface is constant in one or two fixed altitudes during the entire measurement interval along the orbit of satellite.