Assessment of the auroral electrojet index performance under various geomagnetic conditions
Assessment of the auroral electrojet index performance under various geomagnetic conditions
复制标题
DOI：
10.1016/j.jastp.2012.09.017
复制
发表时间：
2013
影响因子：
1.9
通讯作者：
K. Liou;Kazue Takahashi;B. Anderson;M. Nosé;T. Iyemori
中科院分区：
文献类型：
--
作者：
K. Liou;Kazue Takahashi;B. Anderson;M. Nosé;T. Iyemori
在风暴期间，极光电射流（AE）指数的饱和是一种已知但尚未完全理解的现象。为了解决这个难题，我们将（临时）AE指数与净场向电流（Net-dB）指数相关联，净场向电流指数是从铱卫星星座的磁场测量得出的数据产品（安德森等人，2010），假设AE主要测量由Net-dB指数表示的场向电流驱动的对流。Net-dB指数的时间分辨率为1045分钟，目前可从1999年2月18日至2008年5月31日使用。据发现，对于整个数据周期，有一个很好的线性相关性（r=0.74）之间的AE指数，当平均超过净分贝指数的时间网格，和净分贝指数，这表明，统计上约55%的电离层霍尔电流与大规模对流场向电流中所反映的。还发现，在风暴期间的相关性降低，有一个明显的下降趋势，更负的Sym-H。对于大风暴（Sym-H<− 100 nT），相关性变得很弱（r<0.4）。发现了两个相关峰：一个主峰（r=0.73）出现在Sym-H> 30 nT处，一个次峰（r=0.66）出现在Sym-H =-50到-30nT处。进一步的研究表明，AE-Net-dB相关性的变化与进出电离层的场向电流相对于地面磁力计站的位置有关，这是经常预期的，但过去没有证明。
Saturation of the auroral electrojet (AE) index during storm times is a phenomenon that has been known but not fully understood. To address this puzzle, here we correlate the (provisional) AE index with net field-aligned current (Net-dB) index, which is a data product derived with magnetic field measurements from the Iridium satellite constellation (Anderson et al., 2010), with an assumption that AE is largely measuring convection driven by the field-aligned currents represented by the Net-dB index. The Net-dB index has a time resolution of ∼45min and is currently available from February 18, 1999, to May 31, 2008. It is found that, for the entire data period, there is a good linear correlation (r=0.74) between the AE index, when averaging over the Net-dB index time grids, and the Net-dB index, suggesting that statistically ∼55% of the ionospheric Hall currents correlate with large scale convection as reflected in the field-aligned currents. It is also found that the correlation decreases during storm times, with a clear decreasing trend toward a more negative Sym-H. For large storms (Sym-H<−100nT), the correlation becomes weak (r<0.4). Two correlation peaks are identified: a major peak (r=0.73) occurring at Sym-H>30nT and a secondary peak (r=0.66) at Sym-H∼−50 to −30nT. A further study shows that the variations of the AE–Net-dB correlation are associated with the location of the field-aligned currents into and out of the ionosphere relative to the ground magnetometer stations, as expected often but not demonstrated in the past.