TY JOUR TI ULF wave power index for space weather and geophysical applications: A review KW ULF waves KW space weather KW substorms KW magnetic storms KW earthquake precursors KW geomagnetically induced currents KW discrete mathematical analysis JO Russian Journal of Earth Sciences AU Pilipenko, V.A. AU Kozyreva, O.V. AU Engebretson, M.J. AU Soloviev, A.A. PY 2017 IS 17 PB Geophysical Center of the Russian Academy of Sciences