Millstone Hill incoherent scatter observations of auroral convection over 60° < Λ < 75°: 3. Average patterns versus Kp
Millstone Hill incoherent scatter observations of auroral convection over 60° < Λ < 75°: 3. Average patterns versus Kp
复制标题
Millstone Hill 对 60° < Λ < 75° 范围内极光对流的非相干散射观测：3. 平均模式与 Kp
DOI：
--
复制
发表时间：
1983
期刊：
影响因子：
--
通讯作者：
J. V. Evans
中科院分区：
文献类型：
--
作者：
W. Oliver;J. Holt;R. Wand;J. V. Evans
马萨诸塞州韦斯特福德的Millstone Hill雷达（Λ = 56°）已经升级，通过增加一个150英尺的雷达，用于支持国际磁层研究的观测。直径完全可控天线。该天线允许使用现有的UHF（68厘米波长）雷达测量F区离子漂移，从中可以导出F区电场。本文描述了60°（3 °）极光区平均电场行为的分析模型。每个模型都采用了一个多项式描述的强度与不变的纬度和正弦谐波变化在当地时间与102个自由度的每个垂直电场分量。该模型的系数可供用户进行数值计算。这些领域的表格和计算机程序来计算领域和潜力可从要求的作者。结果与Heppner [1977]发表的模型进行了比较。每个这些平均场模型是一致的两个细胞对流模式具有反向阳等离子体流在极和返回路径向东和向西通过黎明和黄昏子午线。涡旋中心位于观测的远限（Λ = 75°）附近。整个对流模式似乎从名义上的正午到午夜的越极气流方向向更早的当地时间旋转了多达两个小时，尽管这一结论受到我们最不可靠（最高纬度）数据的强烈影响。黄昏细胞是占主导地位的大小和强度，然而，无论是模式旋转和细胞的相异性减少Kp的增加。哈朗间断，这是可识别的个别日子，在很大程度上是缺席的平均模式，大概是由于其位置的变化。尽管如此，我们确实看到了一个残余的，低速的，傍晚突出的黄昏细胞向低纬度地区延伸，增加当地时间，达到0300 LT的低Kp，但只有午夜的高Kp。对于低Kp，我们观察到一个区域的非常小的平均流量从黎明到中午，显然断开的整体对流模式。随着Kp的增加，黎明小区侵入该区域，但是1000-1200 LT扇区即使对于高Kp也保持其低速特性。跨极冠电位随Kp线性变化，V = 10.06 + 14.44 Kp kV，但我们观测中的平滑可能导致这是一个低估。极光电场最有可能穿透中纬度地区，而且在夜晚部分最强。
The Millstone Hill radar, Westford, Massachusetts (Λ = 56°), has been upgraded for observations in support of the International Magnetospheric Study (IMS) by means of the addition of a 150-ft. diameter fully steerable antenna. This antenna allows measurements of F-region ion drifts, from which F-region electric fields can be derived, using the existing UHF (68-cm wavelength) radar. This paper describes analytical models of the mean electric field behavior in the auroral zone over the interval 60° 3o). Each model incorporates a polynomial description of intensity with invariant latitude and a sinusoidal harmonic variation in local time with 102 degrees of freedom for each of the perpendicular electric field components. Coefficients of this model are provided for numerical computation by users. Tabulations of these fields and a computer program to calculate fields and potentials are available on request from the authors. The results are compared with models published by Heppner [1977]. Each of these average field models is consistent with a two-cell convection pattern having antisunward plasma flow over the pole and return paths eastward and westward through the dawn and dusk meridians. The centers of the vortices are near the far limit of observation (Λ = 75°). The entire convection pattern appears to be rotated by as much as two hours toward earlier local times from the nominal noon-midnight over-the-pole flow direction, though this conclusion is influenced strongly by our least reliable (highest latitude) data. The dusk cell is dominant in size and strength; however, both the pattern rotation and cell dissimilarity lessen as Kp increases. The Harang discontinuity, which was recognizable on individual days, is largely absent in the average patterns, presumably as a result of the variability in its position. Nevertheless, we do see a residual, low-speed, late-evening protrusion of the dusk cell extending toward lower latitudes with increasing local time, reaching as far as 0300 LT for low Kp but only to midnight for high Kp. For low Kp, we observe a region of very small average flow from dawn to noon, apparently disconnected from the overall convection pattern. The dawn cell encroaches into this region as Kp increases, but the 1000–1200 LT sector maintains its low-speed character even for high Kp. The cross-polar-cap potential varies linearly with Kp as V = 10.06 + 14.44 Kp kV, but the smoothing in our observations may have caused this to be an underestimate. Penetration of auroral electric fields to mid-latitudes is most likely to occur and to be strongest in the evening sector.