Characteristics of the Equatorial Electrojet determined from an array of magnetometers in N-NE Brazil
Characteristics of the Equatorial Electrojet determined from an array of magnetometers in N-NE Brazil
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由巴西东北部磁力计阵列确定的赤道电喷射的特征
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发表时间：
1999
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通讯作者：
A. Padilha
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作者：
A. Rigoti;F. Chamalaun;N. Trivedi;A. Padilha
从1990年11月至1991年3月，在巴西东北部使用了一个由29个矢量磁力计组成的阵列。我们对16个选定的平静日进行了分析，其中Sq和EEJ的等效电流分布的简单模型拟合正午观测到的日变化的最大幅度。在赤道地区，Sq场的精确纬度剖面被EEJ掩盖。这种不确定性可以通过假设EEJ（从日范围中减去Sq后得到）为西向东洋流呈现0.3的比率来解决。在此约束条件下，利用Sq和EEJ的非线性最小二乘组合反演方法估计Onwumechili EEJ电流分布模型的参数。同时反演了16天EEJ的H、Z分量，计算值与观测值吻合较好。在16个安静日中，EEJ的主要参数平均值为：总正电流强度为67±20 (103 A)，日范围为M4（或80±20 (103 A)），半宽度为403±67 km。EEJ中心位于倾角赤道以南21±16 km处。Sq是由几个永久观测站估计出来的，发现它的中心平均纬度为南纬5.5±2度。
An array of 29 vector magnetometers was operated in N-NE Brazil from November 1990 until March 1991. We present the analysis of 16 selected quiet days, for which a simple model of an equivalent current distribution for the Sq and EEJ, fits the observed maximum amplitude of the daily variation at midday.In equatorial regions the precise latitude profile of the Sq field is masked by the EEJ. This uncertainty is resolved by assuming that the EEJ, obtained after subtracting the Sq from the daily ranges, should present a ratio of 0.3 for the westward to eastward current. With this constraint, a combined non-linear least squares inversion of Sq and EEJ was used to estimate the parameters of Onwumechili’s model of the EEJ current distribution. The H and Z components of the EEJ are jointly inverted and good agreement obtained between the calculated and observed data for all 16 days.The EEJ’s main parameters averaged for 16 quiet days were: A total positive current intensity equal to 67 ± 20 (103 A) for diurnal range M4 (or 80 ± 20 (103 A) for M3) and a half-width of 403 ± 67 km. The EEJ centre was located at 21 ± 16 km south of the dip equator. The Sq was estimated from several permanent observatories and found to be centred at a mean latitude of 5.5 ± 2 degrees south.