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首页> 外文期刊>Journal of Geophysical Research, A. Space Physics: JGR >A survey of quiet auroral arc orientation and the effects of the interplanetary magnetic field
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A survey of quiet auroral arc orientation and the effects of the interplanetary magnetic field

机译：安静的极光弧的调查方向和行星际磁场的影响

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Using data from the THEMIS All-Sky Imager array, we have carried out an extensive study of the orientation of quiet auroral arcs relative to the magnetic east-west direction. We used over 7500 images of quiet auroral arcs that were collected during extended solar minimum and at various geomagnetic latitudes and longitudes. For each arc, we determined its “tilt” (the angle the arc makes with the local magnetic east-west direction) and its “multiplicity” (whether or not the arc was part of a multiple-arc system). We have found that at more equatorward latitudes, arc tilts are within σ_(SD) = ±7.7?. We determined that both single- and multiple-arc systems tend to tilt a few degrees to the south-east prior to 23 magnetic local time (MLT) and to the north-east afterward. This tilt appears to be more prominent at higher latitudes. We compared the auroral arc orientations to the mapping of equatorial contours of constant magnetic field strength into the ionosphere, where we used the T87 and T89 magnetic field models for quiet (K_p = 1,3) conditions for the mappings and to determine the constant equatorial magnetic field strength contours. We found that the MLT trends of the tilts are such that arc alignment appears to follow the constant magnetic field strength contours as projected into the ionosphere. We assert that the systematic dependencies of the orientation of auroral arcs indicate that arc morphology is governed by the large-scale structure of the magnetosphere as opposed to localized processes within the ionosphere. In addition, we studied the effects of the interplanetary magnetic field (IMF) on the location in MLT of the reversal of the arc tilts. We found that negative IMF B_x and B_y conditions cause the reversal location to shift duskward of 23 MLT. Alternately, a positive IMF B_x, coupled with a negative B_y, results in a shift in reversal location toward magnetic midnight. This behavior is consistent with that found in studies of the MLT distribution of substorm onsets.
机译：忒弥斯全天成像仪使用数据数组,我们已经进行了广泛的研究极光弧相对取向的安静磁性东西方向。安静的图片收集的极光弧在扩展太阳能最低和在不同地磁纬度,也构成经度。弧,我们确定它的“倾斜”(角弧与当地的磁性的东西方向)及其“多样性”(是否弧是一个多重弧系统的一部分)。发现更多阻碍纬度,内弧倾斜是σ_ (SD) =±7.7 ?。确定单一和多重弧系统倾向于倾斜几度东南亚之前,当地时间23日磁(MLT)和东北。似乎在高纬度地区更加突出。我们比较了极光弧的方向映射的赤道轮廓不变磁场强度电离层,我们使用T87和T89磁场在哪里安静的模型(K_p = 1, 3)条件映射和确定常数赤道磁场强度轮廓。MLT倾斜的趋势,使电弧对齐似乎遵循恒定磁场作为投射到磁场强度轮廓电离层。极光弧的方向的依赖性表明电弧形态是由大型结构的磁气圈反对在本地化过程电离层。行星际磁场(IMF)的位置在MLT的逆转弧倾斜。我们发现的话-国际货币基金组织提出的条件引起的位置将duskward逆转23匝。消极的话,结果在一个转变反转的位置向磁午夜。行为是一致的,研究中发现的亚暴MLT分布的发作。

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