Predicting Lower Band Chorus With Autoregressive‐Moving Average Transfer Function (ARMAX) Models
Predicting Lower Band Chorus With Autoregressive‐Moving Average Transfer Function (ARMAX) Models
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DOI：
10.1029/2019ja026726
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发表时间：
2019-07
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通讯作者：
L. Simms;M. Engebretson;C. Rodger;J. Gjerloev;G. Reeves
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作者：
L. Simms;M. Engebretson;C. Rodger;J. Gjerloev;G. Reeves
我们使用每日和每小时的自回归-移动平均传递函数(ARMAX)方程对来自Demeter卫星的低频带合唱观测进行建模。ARMAX模型可以解释在时间上测量接近的观测值之间的序列自相关性，并且可以用于根据响应变量的过去行为预测响应变量，而不需要最近的数据。在描述大合唱的每日ARMAX模型中，辐射带源电子的不稳定分布(数十keV)和被认为注入这些电子的亚暴活动(来自SuperMAG阵列的Smed)都是具有统计意义的解释变量。来自该模型的预测与坚持测试数据集中的观察结果具有很好的相关性(验证相关性为0.675)。当观测来自同一天或合唱测量的前一天时，源电子通量的影响最大，随着时间的推移，影响迅速衰减。亚暴在前几天发生时影响更大，可能是因为它们从等离子体片中注入了源电子。以行星际磁场|B|、行星际磁场BZ和太阳风压作为输入的日ARMAX模型，而不是上面给出的模型，对合唱的预测能力较差(r=0.611)。仅有太阳风和国际货币基金组织投入的每小时ARMAX模型的成功程度更低，验证相关性为0.502。
We model lower band chorus observations from the DEMETER satellite using daily and hourly autoregressive‐moving average transfer function (ARMAX) equations. ARMAX models can account for serial autocorrelation between observations that are measured close together in time and can be used to predict a response variable based on its past behavior without the need for recent data. Unstable distributions of radiation belt source electrons (tens of keV) and the substorm activity (SMEd from the SuperMAG array) that is thought to inject these electrons were both statistically significant explanatory variables in a daily ARMAX model describing chorus. Predictions from this model correlated well with observations in a hold‐out test data set (validation correlation of 0.675). Source electron flux was most influential when observations came from the same day or the day before the chorus measurement, with effects decaying rapidly over time. Substorms were more influential when they occurred on previous days, presumably due to their injecting source electrons from the plasma sheet. A daily ARMAX model with interplanetary magnetic field (IMF)|B|, IMF Bz, and solar wind pressure as inputs instead of those given above was somewhat less predictive of chorus (r=0.611). An hourly ARMAX model with only solar wind and IMF inputs was even less successful, with a validation correlation of 0.502.