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首页> 外文期刊>Journal of Geophysical Research, A. Space Physics: JGR >Principal components of quiet time temporal variability of equatorial and low-latitude geomagnetic fields
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Principal components of quiet time temporal variability of equatorial and low-latitude geomagnetic fields

机译：安静的时间时间的主要组件可变性的赤道和低纬度地磁场

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摘要

Diurnal variations of the horizontal component of the geomagnetic field ΔH on International Quiet days of 1999–2012, measured hourly at two stations in the same longitude zone in the Northern Hemisphere, near and away from the dip equator, have been subjected to principal component analysis. This technique is also applied to the difference ΔH_(EEJ) of ΔH at these two stations, which is attributed to the equatorial electrojet (EEJ). The first three principal components, PC1–PC3, account for 91–96% of the variances in the data. Maximum contribution to the quiet day variations in ΔH around its peak in the morning hours at both the stations, and in the EEJ, comes from the day-to-day variation of the amplitude of PC1. Patterns of day-to-day variations of PC1 amplitudes for the equatorial station and the EEJ are essentially semiannual modulated by solar EUV flux, superimposed on a longer timescale solar EUV flux-dependent trend. Contributions from PC2 and to a lesser extent from PC3 are seen to be responsible for the absence of semiannual variations in ΔH in the afternoon hours at the equatorial station. Distribution of amplitudes of PC2 and PC3 for ΔH_(EEJ) for weak electrojet days shows seasonal features in accordance with greater occurrence of afternoon (morning) counter electrojet during June (December) solstice. During the extended solar minimum, PC3 amplitudes for ΔH at the equatorial station and for the EEJ display annual variation. Possible sources for these seasonal features in the variations of equatorial ΔH are discussed.
机译：水平分量的昼夜变化在国际安静的地磁场ΔH1999 - 2012年,在两个测量每小时站在同一经度区北半球,附近,远离倾斜赤道,遭受本金成分分析。应用于不同ΔH_ (EEJ)ΔH在这些两个站,这是归因于赤道电喷流(EEJ)。主要组件、PC1-PC3占91 - 96%方差的数据。贡献安静一天变化ΔH大约在早上高峰小时站,EEJ,来自日常PC1振幅的变化。PC1的日常变化的模式赤道站和EEJ振幅本质上是由太阳能EUV半年度调制通量,叠加在一个更长的时间尺度太阳能EUV flux-dependent趋势。和在较小程度上的生物负责半年的缺失ΔH在下午时间的变化赤道。PC2和生物ΔH_ (EEJ)弱电喷流天显示了按照季节性特征更大的下午(上午)计数器电喷流在6月冬至(12月)。在扩展的太阳活动极小期,生物振幅在赤道车站ΔH和EEJ显示年变化。这些季节性特征的变化讨论了赤道ΔH。

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