High-latitude plasma convection from Cluster EDI: variances and solar wind correlations
High-latitude plasma convection from Cluster EDI: variances and solar wind correlations
复制标题
来自 Cluster EDI 的高纬度等离子体对流：方差和太阳风相关性
DOI：
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发表时间：
2007
期刊：
影响因子：
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通讯作者：
C. Kletzing
中科院分区：
文献类型：
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作者：
M. Förster;G. Paschmann;S. Haaland;J. Quinn;R. Torbert;H. Vaith;C. Kletzing
基于2001年对Cluster上EDI仪器的漂移速度测量，2006年，我们建立了一个高纬度电离层对流速度及相关太阳风和磁层活动参数数据库。在早期的论文（Haaland等人，2007年），我们已经描述了该方法，包括一个改进的技术，用于计算选定的太阳风监测器（ACE）和地球的磁层之间的传播延迟，过滤足够稳定的IMF方向的数据，并映射EDI测量从他们的高海拔位置电离层高度。本论文扩展了这项研究，通过查看对流速度方差的空间模式作为IMF方向的函数，并根据GSM y-z平面中的IMF幅度对数据进行排序，|B yz IMF|估计的重联电场Er，sw，太阳风动压Pdyn，季节以及表征环电流Dst和尾部活动的指数ASYM-H。高纬对流的变化表现出特征性的空间格局，即在北方和南半球之间相对于IMF B y分量呈镜像对称。最高变率带的纬度范围随IMF B z的变化与极光椭圆形范围相似。对流标准差的量级与对流量级相同，甚至更大。发现极帽活动与|B yz IMF|尤其是E r、sw。对于小幅度的E r，sw，严格的线性增加开始偏离到约2 mV/m以上的平坦增加。与P dyn也有弱的正相关。在非常小的P dyn值，出现第二个最大值，这是更明显的太阳风质子密度的相关性。在高的夜侧活动增强的夜侧对流的证据。
Based on drift velocity measurements of the EDI instruments on Cluster during the years 2001?2006, we have constructed a database of high-latitude ionospheric convection velocities and associated solar wind and magnetospheric activity parameters. In an earlier paper (Haaland et al., 2007), we have described the method, consisting of an improved technique for calculating the propagation delay between the chosen solar wind monitor (ACE) and Earth's magnetosphere, filtering the data for periods of sufficiently stable IMF orientations, and mapping the EDI measurements from their high-altitude positions to ionospheric altitudes. The present paper extends this study, by looking at the spatial pattern of the variances of the convection velocities as a function of IMF orientation, and by performing sortings of the data according to the IMF magnitude in the GSM y-z plane, | B yz IMF |, the estimated reconnection electric field, E r,sw , the solar wind dynamic pressure, P dyn , the season, and indices characterizing the ring current ( D st ) and tail activity (ASYM-H). The variability of the high-latitude convection shows characteristic spatial patterns, which are mirror symmetric between the Northern and Southern Hemispheres with respect to the IMF B y component. The latitude range of the highest variability zone varies with IMF B z similar to the auroral oval extent. The magnitude of convection standard deviations is of the same order as, or even larger than, the convection magnitude itself. Positive correlations of polar cap activity are found with | B yz IMF | and with E r,sw , in particular. The strict linear increase for small magnitudes of E r,sw starts to deviate toward a flattened increase above about 2 mV/m. There is also a weak positive correlation with P dyn . At very small values of P dyn , a secondary maximum appears, which is even more pronounced for the correlation with solar wind proton density. Evidence for enhanced nightside convection during high nightside activity is presented.