Frequency of Forbush effects as an index of solar activity Belov, A. V. ; Buetikofer, R. ; Eroshenko, E. A. ; Flueckiger, E. O. ; Gushchina, R. T. ; Oleneva, V. A. ; Yanke, V. G. Abstract Publication: 29th International Cosmic Ray Conference (ICRC29), Volume 1 Pub Date: 2005 Bibcode: 2005ICRC....1..375B