The Analysis of Periodic Structure of Solar Wind Velocity

Three kinds of spectrum analysis method are performed in order to study the regularities of distribution of solar wind. The first one is the general log power spectrum from which it can be seen that there is a overweighted 13-day period during the descending and minimum phases of the sunspot cycle, but in the ascending and maximum phases of the sunspot cycle, the spectrum is random. It seems that solar wind is in disorder during these periods. The second kind of spectrum analysis used is the maximum entropy spectrum which has better spectrum resolution. This gives out a different situation that the solar wind in the years of ascending and maximum phases of this sunspot cycle also possesses the 13-day period which far overweight the other periods. In order to verify further that there is really the same regularity of distribution of solar wind in ascending and maximum phases of the sunspot cycle as that in descending and minimum phases, a kind of filtering technique is performed, which is called cross-correlation filter. The third kind of spectrum is the power spectrum of filtered sequence. It is shown that solar wind in the years during which it would seem in disorder both in general power spectrum and in maximum entropy spectrum now possesses the overweighted 13-day period after being filtered. >