A nearly universal solar wind-magnetosphere coupling function inferred from 10 magnetospheric state variables
A nearly universal solar wind-magnetosphere coupling function inferred from 10 magnetospheric state variables
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DOI：
10.1029/2006ja012015
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发表时间：
2007-01-12
影响因子：
2.8
通讯作者：
Rich, F. J.
中科院分区：
文献类型：
--
作者：
Newell, P. T.;Sotirelis, T.;Rich, F. J.
[1]我们研究了是否一个或几个耦合函数可以代表最好的太阳风和磁层之间的相互作用，在各种各样的磁层活动。研究了表征磁层状态的十个变量。从地面磁力计中选择了五个指数，即Dst，Kp，AE，Au和AL，以及其他来源的五个指数，即极光功率（极地UVI），尖点纬度（sin（Lambda（c），b2 i（两个DMSP），地球同步磁倾角（GOES）和极帽大小（SuperDARN）。这些指数与20多个候选太阳风耦合函数相关。一个函数，代表率磁通量是开放的磁层顶，相关性最好的10个指标的磁层活动。这是d Phi（MP）/dt = v（4/3）B（T）（2/3）sin（8/3）（theta（c）/2），由（IMF磁力线接近磁层顶的速率，类似于v）（合并的IMF磁力线的百分比，sin（8/3）（theta（c）/2））（行星际磁场强度，B-T）（合并线长度，类似于（B-MP/B-T）（1/3））计算得出。合并线的长度是基于太阳风和偶极子场之间的通量匹配，并同意叠加IMF的真空偶极子。国际货币基金组织的时钟角度的依赖性相匹配的合并率报告（尽管有限的统计数据）在高海拔。当绘制指数的平均值、散点图和d Phi（MP）/dt的上级相关性时，磁层对BT和v的响应的非线性是明显的。我们的研究结果表明，各种各样的磁层现象可以预测合理的精度（r > 0.80，在几种情况下）从头算，即没有目标指数的时间历史，由一个单一的功能，估计向阳面合并率。在研究的所有状态变量（包括难以预测的AL和难以测量的极帽大小）中，d Phi（MP）/dt约占方差的57.2%，而E-KL为50.9%，vBs为48.8%。所有数据集都包含了多年来至少数千个点，最多两个太阳活动周期，只有两个参数拟合，因此相关性是稳健的。与d Phi（MP）/dt的相关性不佳的唯一指标是Dst，其与p（1/2）d Phi（MP）/dt的相关性最佳（r = 0.87）。如果将这一成功归功于d Phi（MP）/dt，则其平均分数会更高。
[1] We investigated whether one or a few coupling functions can represent best the interaction between the solar wind and the magnetosphere over a wide variety of magnetospheric activity. Ten variables which characterize the state of the magnetosphere were studied. Five indices from ground-based magnetometers were selected, namely Dst, Kp, AE, AU, and AL, and five from other sources, namely auroral power ( Polar UVI), cusp latitude ( sin(Lambda(c))), b2i (both DMSP), geosynchronous magnetic inclination angle (GOES), and polar cap size (SuperDARN). These indices were correlated with more than 20 candidate solar wind coupling functions. One function, representing the rate magnetic flux is opened at the magnetopause, correlated best with 9 out of 10 indices of magnetospheric activity. This is d Phi (MP)/dt = v(4/3)B(T)(2/3) sin(8/3)(theta(c)/2), calculated from (rate IMF field lines approach the magnetopause, similar to v)(% of IMF lines which merge, sin(8/3)(theta(c)/2))( interplanetary field magnitude, B-T)(merging line length, similar to(B-MP/B-T)(1/3)). The merging line length is based on flux matching between the solar wind and a dipole field and agrees with a superposed IMF on a vacuum dipole. The IMF clock angle dependence matches the merging rate reported (albeit with limited statistics) at high altitude. The nonlinearities of the magnetospheric response to BT and v are evident when the mean values of indices are plotted, in scatterplots, and in the superior correlations from d Phi(MP)/dt. Our results show that a wide variety of magnetospheric phenomena can be predicted with reasonable accuracy (r > 0.80 in several cases) ab initio, that is without the time history of the target index, by a single function, estimating the dayside merging rate. Across all state variables studied (including AL, which is hard to predict, and polar cap size, which is hard to measure), d Phi(MP)/dt accounts for about 57.2% of the variance, compared to 50.9% for E-KL and 48.8% for vBs. All data sets included at least thousands of points over many years, up to two solar cycles, with just two parameter fits, and the correlations are thus robust. The sole index which does not correlate best with d Phi(MP)/dt is Dst, which correlates best (r = 0.87) with p(1/2)d Phi(MP)/dt. If d Phi(MP)/dt were credited with this success, its average score would be even higher.