The east–west component of the geomagnetic field (Y-component) at the Trivandrum (TRD) station, an equatorial site, is used to investigate the characteristics of Inter-Hemispheric Field-Aligned Currents (IHFACs) in the Indian sector during solar cycles 21 and 22. The observations reveal an annual variation of IHFAC in the dawn/noon sector with positive/negative peaks around northern summer. Furthermore, it is noted that IHFAC amplitudes are modulated by solar activity, superimposed with seasonal effects, with consistently higher amplitudes during the northern summer months. The dusk-time IHFAC also shows a pattern modulated by seasons and solar cycles, with negative peaks around northern summer only during the low solar active years. The seasonal pattern of IHFAC shows a similar trend from April to September, where dawn/noon IHFAC is south/north directed, and for the remaining months, both are northward directed. The dusk-side IHFAC is mostly south-directed irrespective of the season. Moreover, it is demonstrated that the seasonal pattern of dawn and noon-time IHFAC amplitudes show a strong to moderate correlation with amplitudes of Sq asymmetries between two hemispheres, but dusk-time IHFAC does not follow this trend. The IHFAC directions at TRD follow the Fukushima model for May to September during the dawn-noon sector for 70%–95% of the days and less than 50% of the days for remaining months. The noon-dusk sector shows Fukushima model-type polarity for ∼60% of days in June–July and less than 50% for remaining months. The global analysis of IHFAC, using monthly averages of hourly values from eight observatories spanning Asia, Africa, and America, reveals spatial differences in amplitude and directions. The directions of noon-time IHFAC in the Indian-East Asian and East-African sectors follow similar trends, and the amplitude variations of noon-time IHFAC can be explained by DE-3 tidal effects. The IHFAC from the South American and West African sectors show intense southward and northward currents compared to other sites, indicating the influence of the South Atlantic Anomaly (SAA).

中文翻译：

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半球间场对齐电流的变化：地面地磁测量的观测

赤道特里凡得琅 (TRD) 站的地磁场东西向分量（Y 分量）用于研究太阳周期期间印度扇区的半球间场对准电流 (IHFAC) 的特征21 和 22。观测结果揭示了黎明/中午区域 IHFAC 的年度变化，在北半球夏季左右出现正/负峰值。此外，值得注意的是，IHFAC 振幅受到太阳活动的调节，叠加季节性影响，在北方夏季月份中振幅始终较高。黄昏时的 IHFAC 还显示出受季节和太阳周期调节的模式，只有在太阳活动较少的年份，北夏季前后才会出现负峰值。从 4 月到 9 月，IHFAC 的季节模式显示出类似的趋势，其中黎明/中午 IHFAC 向南/向北，而在其余月份，两者都向北。无论季节如何，黄昏一侧的 IHFAC 大部分都朝南。此外，研究表明，黎明和中午 IHFAC 振幅的季节模式与两个半球之间 Sq 不对称性的振幅表现出强到中度的相关性，但黄昏时 IHFAC 并不遵循这种趋势。TRD 的 IHFAC 方向遵循 5 月至 9 月黎明至中午时段的福岛模式，其中 70%–95% 的天数和其余月份的不到 50% 的天数。6 月至 7 月约 60% 的天数中，正午-黄昏扇区显示出福岛模型型极性，而其余月份的天数则低于 50%。IHFAC 使用亚洲、非洲和美洲八个观测站每小时值的月平均值进行的全球分析揭示了幅度和方向的空间差异。印度-东亚和东非扇区正午IHFAC的方向遵循相似的趋势，正午IHFAC的幅度变化可以用DE-3潮汐效应来解释。与其他地点相比，南美和西非地区的 IHFAC 显示出强烈的南向和北向洋流，表明受到南大西洋异常 (SAA) 的影响。