TY JOUR TI TEC Observations as a Tool for the Study of ULF Wave Interaction with the Ionosphere: A Review KW Ionosphere KW GNSS KW TEC KW ULF waves KW Pc5 pulsations KW TCV KW SSC KW MHD waves JO Russian Journal of Earth Sciences AU Pilipenko, V.A. AU Meng, X.. AU Belakhovskiy, V.B. AU Kostina, P.. PY 2026 IS 26 PB Geophysical Center of the Russian Academy of Sciences