Occurrence rates (%) of Pc1 pulsations during the storm (blue) and non-storm (red) periods depend on ellipticity of the pulsations. The ellipticities are tangent values (tan β) and are divided into 200 bins from −1 to 1. The occurrence rates were obtained by dividing the number of time segments which belong to each of ellipticity bins into the total number of time segments of all valid wave events and multiplying by 100 to gain per cent values.