Spectral analysis of short period of K indices registered in Huancayo   Geomagnetic Observatory
  Wavelet spectral analysis is applied to the daily indices K (SK) registered in Huancayo geomagnetic observatory from 2000.0 to 2015.0, it has become possible to identify predominant periodic components with a confidence level of 95%. In particular we have investigated the periodicity of 27.0 days and its 13.5, 9.0 and 6.8 harmonics, related to the fundamental period of solar rotation effects. A special analysis registered on periods of 59.0 days might be related to the double period of 29.53 days corresponding to the synodic month. The manifestation of the periods of 182.6, 365 and 730 days corresponding to the harmonics of the seasonal variation of the annual cycle is also observed. An important observation is that the global predominant periods registered 6.8 and 9.0 days, in the years 2009, 2013 and 2014 its effect is too small or null, those periods corresponds to the minimum and maximum solar activity. On the other hand, it is observed that the order of predominance of the harmonic period solar rotation are different for each solar cycle (Solar Cycle 23: 9.0, 13.5, 27.0 and 6.8 days; solar cycle 24: 27.0, 13.5, 9.0 and 6.8 days), and it is weaker contribution in the solar cycle 24 with respect to the solar cycle 23. 
Domingo Rosales, Erick Vidal
astro-ph.IM physics.geo-ph