Dependence of ground-based Pc5 ULF wave power on F10.7 solar radio flux and solar cycle phase

Utilising fifteen (1990–2005) years of ground-based magnetometer data from four magnetometer stations, we characterise the statistical dependence of the Pc5 ULF wave power spectra on variations in F10.7 solar radio flux and on solar cycle phase. We show that the median Pc5 ULF wave power spectra can be characterised as a power-law with a localised Gaussian centred at a specific frequency superimposed on the power-law spectrum. Further, we demonstrate that the location of the Gaussian in frequency systematically varies with both solar cycle phase and F10.7 and is more pronounced during high-speed solar wind intervals. We postulate that the localised power spectrum enhancement (or Gaussian) is a manifestation of the local eigenfrequency of field line resonances in the Earth's magnetosphere and that the variation in the location of the Gaussian occurs as a result of increased ionospheric outflow during periods of enhanced F10.7 and active solar activity.

► We present a statistical characterisation of Pc5 wave power. ► We show that Pc5 power is the characteristic of a Gaussian superimposed onto a power-law. ► The dependence of Pc5 wave power on solar radio flux (F10.7) is discussed. ► The dependence of Pc5 wave power and solar cycle phase is discussed.