Analysis of the effectiveness of ground‐based VLF wave observations for predicting or nowcasting relativistic electron flux at geostationary orbit
Analysis of the effectiveness of ground‐based VLF wave observations for predicting or nowcasting relativistic electron flux at geostationary orbit
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DOI：
10.1002/2014ja020337
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发表时间：
2015-03
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影响因子：
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通讯作者：
L. Simms;M. Engebretson;A. Smith;M. Clilverd;V. Pilipenko;G. Reeves
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作者：
L. Simms;M. Engebretson;A. Smith;M. Clilverd;V. Pilipenko;G. Reeves
风暴后地球同步轨道上的相对论电子通量增强与卫星现场观测的甚低频（VLF）波有一定的相关性。然而，我们之前的研究发现，在南极洲哈雷的地面仪器测量的电子通量和VLF之间几乎没有相关性。在这里，我们探讨了这种低相关性的几种可能的解释。使用220个风暴（1992-2002），我们以前的工作开发了一个预测模型的风暴后通量在地球同步轨道上的解释变量测量前一两天的通量增加。在临近预报模型中，我们使用的平均值的变量从时间段时，磁通量在恢复阶段的磁暴和限制的VLF（1.0 kHz）测量哈雷黎明期间（09：00-12：00 UT）上升。这改善了VLF波强度与通量的简单相关性，尽管VLF在总体多元回归中的影响仍然远小于其他因子。当季节和行星际磁场（IMF）Bz方向分别进行分析时，VLF超过其他因素的影响，只有在冬季几个月时，IMF Bz是在一个平均的北向方向。
Poststorm relativistic electron flux enhancement at geosynchronous orbit has shown correlation with very low frequency (VLF) waves measured by satellite in situ. However, our previous study found little correlation between electron flux and VLF measured by a ground‐based instrument at Halley, Antarctica. Here we explore several possible explanations for this low correlation. Using 220 storms (1992–2002), our previous work developed a predictive model of the poststorm flux at geosynchronous orbit based on explanatory variables measured a day or two before the flux increase. In a nowcast model, we use averages of variables from the time period when flux is rising during the recovery phase of geomagnetic storms and limit the VLF (1.0 kHz) measure to the dawn period at Halley (09:00–12:00 UT). This improves the simple correlation of VLF wave intensity with flux, although the VLF effect in an overall multiple regression is still much less than that of other factors. When analyses are performed separately for season and interplanetary magnetic field (IMF) Bz orientation, VLF outweighs the influence of other factors only during winter months when IMF Bz is in an average northward orientation.