| Summary: | 碩士 === 國立中央大學 === 太空科學研究所 === 83 === Pc型地磁微脈動可分為Pc1 、Pc2 、Pc3 、Pc4 、Pc5 ，用FFT的技巧，
可以將地磁微脈動的頻譜分析出來，再用極化分析的方法研究這些頻帶的
極化主軸偏向與極化方向。今由觀測資料得知：磁暴發生後，微脈動周期
有變長(Pc4 - Pc5)及變短(Pc2) 的現象，而寧靜時期的微脈動大致上為
Pc3 。在理論方面，根據 HASEGAWA 及 CHEN 的理論，再配合實際觀測資
料（午前、午後的極化主軸大都在二、四象限）得知：上午電離層的電子
密度往下漸增，而下午電離層的電子密度往下漸減。中壢地區屬於地磁特
低緯地區，地磁微脈動會受電離層之影響，並且不同於中、高緯地區微脈
動之特性，有其研究價值。
Continuous magnetic pulsations are classified as Pc1,Pc2, Pc3,
Pc4, and Pc5. We use fast Fourier transform (FFT) to get the
spectra of geomagnetic micropulations. By the method of
polarization analysis, we obtain the orientation of major axis
and the sense of polarization. From the data analysis, it is
found that the pulsations of Pc4 - Pc5 and Pc2 after the
occurrence of geomagnetic storm are observed. Pulsations are
within the Pc3 band during quiet time. The observed major axis
lies in the second-fourth quadrants in both the morning side
and the evening side. Based on the theory of Hasegawa and Chen,
the density gradient of the electrons in ionosphere is positive
and negative toward the ground in the morning and in the
evening, respectively. The area of Chung-Li is at geomagnetic
very low latitude, therefore, the pulsations are influenced by
the ionosphere. The characteristics of pulsation of this area
are different from that of middle and high geomagnetic
latitudes.
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