摘  要

　　　Elsasser于1950年對(duì)磁流體方程引入新變量后Goldreich 和 Shirida于1995年提出臨界平衡理論假設(shè)。并將理論應(yīng)用于太陽(yáng)風(fēng)湍流中得到功率譜各向異性特征和功率譜的譜指標(biāo)特征。

　　　本文的主要目的是做出速度場(chǎng)的功率譜，進(jìn)一步檢驗(yàn)臨界平衡理論假設(shè)的正確性與適用性。文中采用了安裝在WIND衛(wèi)星上的磁場(chǎng)探測(cè)器MFI和三維等離子體探測(cè)器3DP在1995年1月31日所采集到的總磁場(chǎng)和等離子體速度場(chǎng)數(shù)據(jù)。并且采用基于小波變換的功率譜分析，做出速度場(chǎng)功率譜密度函數(shù)圖和磁場(chǎng)功率譜密度函數(shù)圖。其中橫軸為局部磁場(chǎng)和太陽(yáng)徑向向外方向的夾角；縱軸為時(shí)間尺度。通過(guò)功率譜密度函數(shù)圖的分析可以得出功率譜隨角度變化的分布特征。

　　　通過(guò)計(jì)算機(jī)的計(jì)算結(jié)果表明：當(dāng)天的速度場(chǎng)功率譜顯式出各向同性的特征，同時(shí)磁場(chǎng)的功率譜也同樣顯示出了各向同性的特征。這說(shuō)明臨界平衡理論假設(shè)并不是普遍適用的。

　　　從原始數(shù)據(jù)看，由于速度擾動(dòng)和速度化磁場(chǎng)擾動(dòng)高度相關(guān)，筆者認(rèn)為這可能是產(chǎn)生各向同性的原因之一。遺憾的是本文只針對(duì)1995年1月31日的數(shù)據(jù)進(jìn)行了考察，無(wú)法同其他明顯存在阿爾文波時(shí)間段的功率譜進(jìn)行比較。同時(shí)當(dāng)功率譜為各向同性時(shí)，功率譜譜指標(biāo)特征也有待進(jìn)一步探究。

　　

　　　關(guān)鍵詞：臨界平衡；太陽(yáng)風(fēng)湍流；功率譜；小波分析；各向異性；

Abstract

　　　 Goldreich and Shirida in 1995, propose a critical balance of theoretical assumptions. After Elsasser interoduce a new varibles in the MHD equation in 1950. The theory can be applied to the solar wind turbulence characteristics of the anisotropy power spectrum and characteristics of the power spectrum spectral index.

　　　The main purpose of this paper is to make the power spectrum of the velocity field, Further test the accuracy and applicability of the critical balance of theoretical assumptions. This paper uses a magnetic field and plasma velocity field data on January 31, 1995. collected by MFI and 3DP which installed on the WIND spacecraft. And based on wavelet transform power spectrum analysis, to make the power spectral density of the velocity field maps and magnetic field power spectral density map. Where the horizontal axis is the angle between the local magnetic field and solar radial outward direction, the longitudinal axis is the time scale. By the power spectral density maps can be easily observed power spectrum changes with the angle distribution characteristics.

　　　Computational results show that day the velocity field power spectrum shows isotropic characteristics of the magnetic field power spectrum also shows isotropic characteristics. This shows that the theoretical assumptions of the critical balance is not generally applicable.

　　　From the data, highly correlated to the velocity disturbance and the speed of the magnetic field disturbance, I think this may be one of the reasons to produce isotropic. Unfortunately, this paper only examined data for January 31, 1995, can not be compared with other power spectrum when the Alfven waves is apparent existence. And when the power spectrum is isotropic, the characteristics of the power spectrum spectral index also needs further exploration.

　　　

Key words: Critical balance; solar wind turbulence; power spectrum; wavelet analysis; anisotropy;

目    錄

  前  言 1

    1      背景介紹 2

 1．1   太陽(yáng)大氣與太陽(yáng)風(fēng) 2

 1．2   太陽(yáng)風(fēng)及湍流 3

 1．3   阿爾文波 4

 1．4   臨界平衡 5

 1．5   太陽(yáng)風(fēng)湍流功率譜的各向異性 8

 1．6   衛(wèi)星介紹. 10

2      數(shù)據(jù)及數(shù)據(jù)處理原理 13

 2．1   數(shù)據(jù)來(lái)源及處理過(guò)程 13

 2．2   小波分析數(shù)據(jù)原理 13

        2．2．1  小波分析原理 13

    2．2．2  實(shí)際工作中小波分析的運(yùn)用 14

    2．2．3  功率譜密度PSD 15

 2．3   功率譜隨角度的分布 16

3      數(shù)據(jù)處理及處理結(jié)果 18

 3．1   太陽(yáng)風(fēng)中的時(shí)間序列 18

 3．2   磁場(chǎng)數(shù)據(jù)處理 19

 3．3   速度場(chǎng)數(shù)據(jù)處理 20

結(jié)  論 21

致  謝 22

參考文獻(xiàn) 23

附 錄 一 24

附 錄 二 32

附 錄 三 36