Climatology of the inter-hemispheric field-aligned currents system over the Nigeria ionosphere
Climatology of the inter-hemispheric field-aligned currents system over the Nigeria ionosphere
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尼日利亚电离层半球间场对准电流系统的气候学
DOI：
10.1016/j.jastp.2012.07.008
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发表时间：
2012
影响因子：
1.9
通讯作者：
K
中科院分区：
文献类型：
--
作者：
Bolaji;OS;Rabiu;AB;Oyeyemi;EO;Yumoto;K
这项工作使用了伊洛林大学磁数据采集系统设施2009年的偏角(D)磁场数据记录。根据D分量的分钟值，推算出D分量的每小时值(Sq(Qd))来估计其日(Sq(D))值，其中最安静的五天被识别出来。研究了最安静的5天的月平均(MSQ(D))及其季节变化(SSQ(D))。半球间场向电流(IHFAC)在Sq(D)、MSQ(D)和SSQ(D)变化的所有局部时间都表现为一对向下和向上的半球间场向薄层电流。从这些变化中可以观察到，IHFAC在正午和黄昏时段从冬半球流向夏半球，而在黎明时段流向相反的方向。5月、6月、8月、9月观测到的Sq(D)变率与1月、2月、3月和11月的扰动变率相比平缓。正值(∼1.7arcmin)和负值(∼−2.7arcmin)最大值分别出现在8月份的黎明时段和中午时段。这些值表明，8月份的IHFACs在黎明和中午分别为强南向(正)和强北向(负)。正如Magdas观测到的那样，黄昏侧的IHFAC在所有季节都是弱北行的。IHFAC的方向不是在秋分时反转，而是在6月和11月，而不是在至日变大，而是在8月。观测到的IHFACs具有明显的经向变异性，这表明在正午时段，冬至至夏季IHFACs的振幅(北向/负IHFAC)大于12月至日(南向/正IHFACs)。
Records of the declination (D) magnetic field data for the year 2009 from the Magnetic Data Acquisition System (MAGDAS) facilities at University of Ilorin were employed for this work. From the minutes value of the D-component, the deduced hourly values of the D-component (Sq(QD)) were used to estimate its diurnal (Sq(D)) values with the most five quietest days identified. The monthly mean (MSq(D)) of the most five quietest days and their seasonal (SSq(D)) variabilities were investigated. The inter-hemispheric field aligned currents (IHFACs) exhibit downward and upward inter-hemispheric field-aligned sheet current that appears as a pair at all local times of the Sq(D), MSq(D), and SSq(D) variations. From these variabilities, the IHFACs were observed to flow from the winter to summer hemisphere during noon and dusk sector and flowing in opposite direction during the dawn sector. The Sq(D) variability patterns that were observed in May, June, August September are gentle compared to the disturbed variabilities in January, February, March and November. The highest positive (∼1.7arc-min) and negative (∼−2.7arcmin) MSq(D) maxima values were observed in August during the dawn and noon sectors respectively. These values indicated that the IHFACs flow in August is strongly southbound (positive) and northbound (negative) in the dawn and noon sectors respectively. Dusk-side IHFACs as can be observed by MAGDAS are weakly northbound in all the seasons. The direction of IHFACs does not flip at the equinoxes but in June and November and does not become largest at solstices but in August. The IHFACs was observed to exhibit longitudinal variability, which indicated that larger amplitude of winter-to-summer IHFACs is observed to be greater in June solstice (northbound/negative IHFACs) than in the December solstice (southbound/positive IHFACs) during the noon sector.