Birkeland current system key parameters derived from Iridium observations: Method and initial validation results
Birkeland current system key parameters derived from Iridium observations: Method and initial validation results
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伯克兰电流系统关键参数源自铱星观测：方法和初步验证结果
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发表时间：
2002
期刊：
影响因子：
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通讯作者：
B. A. Toth
中科院分区：
文献类型：
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作者：
B. Anderson;Kazue Takahashi;T. Kamei;C. Waters;B. A. Toth
[1] 铱星卫星位于高度 780 公里的圆极轨道上，通过工程磁力计数据对伯克兰洋流系统进行持续的全球监测。这些数据已用于表征全局场对准电流 (FAC) 的基本特征，时间窗口为 45 分钟，时间步长为 15 分钟。 3 sigma 磁力计数据噪声阈值平均为 93 nT。高于噪声的测量值分数用于提供极光 FAC 位置的一种测量。还提出了区域 1/区域 2 FAC 系统的平均纬度和赤道/极地范围的测量值。区域 1/区域 2 FAC 的赤道纬度与 Kp 反相关，r = 0.68。与 AE、AU 和 AL 指数类比，给出了北（南）半球向东（向西）磁扰动的净 FAC 强度指数。铱星系统指数在个别情况下和统计上都显示出与快速查看极光电射流指数的高度相关性，其对数之间的 r = +0.73。结果显示了两次风暴的结果，1999 年 9 月 22 日至 23 日，Dst 最小值约为 160 nT，以及 1999 年 10 月 21 日至 22 日，Dst 最小值约为 230 nT，反映了全球 FAC 的强化和向赤道扩展是对南向 IMF 的响应。增强的动压促进了更快速的赤道扩张，9 月份的风暴在 1.5 小时内扩张了 10°，在 IMF 向南转向时动压增强了 15-20 nPa，而 10 月份的情况则在 8 小时内扩张了 13°，向南转向发生在标称动压 5 nPa 期间。在这两次风暴中，当国际货币基金组织转向北或接近水平时，在风暴恢复开始时，当前强度会在一小时内降低到风暴前的水平。关键参数是访问铱星系统数据进行初步分析的有用手段，初步结果为未来的分析提供了动力，以量化源自铱星系统数据的产品的准确性和可靠性。索引术语：2708 磁层物理：当前系统 (2409)； 2736 磁层物理学：磁层/电离层相互作用； 2407 电离层：极光电离层（2704）； 2794 磁层物理：仪器和技术； 2788 磁层物理：风暴和亚暴；关键词: 铱星星座, 伯克兰场对准电流
[1] The Iridium satellites in 780 km altitude, circular polar orbits provide continuous global monitoring of the Birkeland current system via engineering magnetometer data. These data have been used to characterize basic features of the global field-aligned currents (FACs) with a time window of 45 min and a time step of 15 min. The three sigma magnetometer data noise threshold is 93 nT on average. The fraction of measurements above the noise is used to provide one measure of the location of the auroral FACs. Measures are also presented for the mean latitude and equatorward/poleward extent of the region 1/region 2 FAC system. The equatorward latitude of region 1/region 2 FACs is anticorrelated with Kp, r = 0.68. Indices are presented for the net FAC intensity in terms of the eastward (westward) magnetic perturbation in the northern (southern) hemisphere by analogy with the AE, AU, and AL indices. The Iridium system indices show high correlation with the quick look auroral electrojet indices both in individual cases and statistically, r = +0.73 between their logarithms. Results are presented for two storms, 22–23 September 1999, Dst minimum approximately 160 nT, and 21–22 October 1999, Dst minimum approximately 230 nT, reflecting that intensification and equatorward expansion of the global FACs occur in response to southward IMF. Enhanced dynamic pressure promotes more rapid equatorial expansion, 10� in 1.5 hours for the September storm, for which the dynamic pressure was enhanced, 15–20 nPa, at southward IMF turning, as opposed to the October case, 13� over 8 hours, for which the southward turning occurred during nominal dynamic pressure, 5 nPa. In both storms the current intensity decreases to prestorm levels within an hour when the IMF turns northward or nearly horizontal, at the beginning of storm recovery. The key parameters are a useful means of accessing the Iridium system data for preliminary analyses, and the initial results provide motivation for future analyses to quantify the accuracy and reliability of products derived from the Iridium system data. INDEX TERMS: 2708 Magnetospheric Physics: Current systems (2409); 2736 Magnetospheric Physics: Magnetosphere/ionosphere interactions; 2407 Ionosphere: Auroral ionosphere (2704); 2794 Magnetospheric Physics: Instruments and techniques; 2788 Magnetospheric Physics: Storms and substorms; KEYWORDS: Iridium constellation, Birkeland field-aligned currents