太阳F10.7指数准27天振荡的小波分析

利用1956—2003年的F10．7日均值数据,采用Morlet小波变换方法,分析了准27天振荡的特征及与太阳活动11年周期(Schwabe周期)的关系．结果表明, F10．7的准27天振荡的幅度和周期存在明显的短期变化现象,不同年里变化的程度差别很大,有些年里起伏非常剧烈,在几天到几十天的很短时间里,幅度变化达十几倍,周期可变化数天,甚至发生十几天的突变;有些年里,幅度变化很大但起伏很小,周期也比较稳定．准27天振荡的年平均幅度存在明显的逐年变化,与太阳活动显著相关．一般说来,F10．7越高,准27天振荡的幅度就越大,然而在太阳活动19周峰年, F10．7比其他活动周的值都高,但准27天振荡的幅度却比其他活动周低．准27天振荡的周期也有明显的逐年变化,除了个别年(如1987年),年平均周期在24至31天之间变化,与太阳活动周期没有明显的关系．48年的平均周期为27．3天．从总体看,周期有逐渐缩短的趋势,48年里周期大约减少了1．5天．造成准27天振荡起伏的因素非常复杂,有待深入研究．

Wavelet Analysis of Quasi-27-Day Oscillations in the Solar Index F10.7

Using the daily averaged values of the F10.7 for years 1956-2003, the Morlet Wavelet Transform is used to analyze the characteristics of quasi-27-day period oscillation and the relation between the oscillation and the solar 11-year cycle (Schwabe cycle). The result shows: The amplitude and period of quasi-27-day period oscillation have obvious short-term fluctuations. The change has very large difference in different years. In some years, the amplitude changes more than ten times and the period changes several days, even changes suddenly more than ten days during several days to tens of the day. In other years, the amplitude is large, but the fluctuation is small and the period was steady. The yearly averaged quasi-27-day oscillation amplitude has obvious change year after year and it is correlated with the solar 11-year cycle observably. Generally, the quasi-27-day oscillation amplitude is larger when yearly averaged F10.7 is bigger. But in the solar cycle 19 maximum years, the quasi-27-day oscillation amplitudes is smaller than maximum years of other cycles, although yearly averaged F10.7 of cycle 19 maximum years is bigger than other cycles. The quasi-27-day oscillation amplitude has obvious change year after year except some years (for example 1987), and the yearly averaged period change range is 24-31 days and is not correlated with the solar cycle. The averaged period of 48 years is 27.3 days. On the whole, the period trends shorter gradually, the period decreases about 1.5 days during 1956-2003. The reasons that conduces to the fluctuations of quasi-27-day oscillation is very complicated, it needs to be studied in the future.