Capturing Uncertainty in Magnetospheric Ultralow Frequency Wave Models
Capturing Uncertainty in Magnetospheric Ultralow Frequency Wave Models
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DOI：
10.1029/2018sw002102
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发表时间：
2019-04
期刊：
影响因子：
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通讯作者：
S. Bentley;C. Watt;I. J. Rae;M. Owens;K. Murphy;M. Lockwood;J. K. Sandhu
中科院分区：
文献类型：
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作者：
S. Bentley;C. Watt;I. J. Rae;M. Owens;K. Murphy;M. Lockwood;J. K. Sandhu
我们开发并测试了一个经验模型，该模型预测了超低频（ULF，1-20 mHz）波功率在一系列频率，纬度和MLT扇区中的地面观测。这是参数化的瞬时太阳风速度vsw，在质子数密度var（Np）的变化，和行星际南向磁场Bz。超低频波功率的概率模型将使我们能够解决径向扩散系数的不确定性，从而提高地球外辐射带径向传输的扩散模型。我们的模型可以用两种方式来再现波功率：通过从条件概率分布函数中采样和通过使用平均值（期望值）。我们推导出一种方法，用于测试质量的参数化和测试的能力，该模型再现超低频波功率时间序列。采样是一种更好的方法，可以在延长的时间段内重现功率，因为它保持相同的总体分布，而平均值更适合预测时间序列中的功率。该模型预测时间序列中的每一个小时都比假设电力从前一个小时持续存在要好。最后，我们回顾了扩散系数不确定性的其他来源。虽然这个波模型主要是为了改进径向扩散系数的目标而设计的，以包括在基于外辐射带扩散的建模中，但我们预计我们的模型也可以用于研究整个磁层中ULF波的发生，从而研究ULF波产生和传播的物理学。
We develop and test an empirical model predicting ground‐based observations of ultralow frequency (ULF, 1–20 mHz) wave power across a range of frequencies, latitudes, and MLT sectors. This is parameterized by instantaneous solar wind speed vsw, variance in proton number density var(Np), and interplanetary southward magnetic field Bz. A probabilistic model of ULF wave power will allow us to address uncertainty in radial diffusion coefficients and therefore improve diffusion modeling of radial transport in Earth's outer radiation belt. Our model can be used in two ways to reproduce wave power: by sampling from conditional probability distribution functions and by using the mean (expectation) values. We derive a method for testing the quality of the parameterization and test the ability of the model to reproduce ULF wave power time series. Sampling is a better method for reproducing power over an extended time period as it retains the same overall distribution, while mean values are better for predicting the power in a time series. The model predicts each hour in a time series better than the assumption that power persists from the preceding hour. Finally, we review other sources of diffusion coefficient uncertainty. Although this wave model is designed principally for the goal of improved radial diffusion coefficients to include in outer radiation belt diffusion‐based modeling, we anticipate that our model can also be used to investigate the occurrence of ULF waves throughout the magnetosphere and hence the physics of ULF wave generation and propagation.