Parameter tuning for a multi-fidelity dynamical model of the magnetosphere
Parameter tuning for a multi-fidelity dynamical model of the magnetosphere
复制标题
磁层多保真动力学模型的参数调整
DOI：
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复制
发表时间：
2013
期刊：
影响因子：
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通讯作者：
D. Bingham
中科院分区：
文献类型：
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作者：
Stephan;R.;Sain;Matthew;J.;Heaton;M. Wiltberger;C.;S. Reese;D. Bingham
地磁暴在空间天气物理学中发挥着关键作用，可能造成深远的经济影响，包括电网中断、空中交通改道、卫星损坏和GPS中断。LFM-MIX是能够模拟磁暴的最先进的磁层-电离层耦合模型。该模型包含了将磁流体动力学状态参数转化为进入电离层的电子的能量和通量的物理方程，其中包含一组输入参数。这些输入参数在模型中的确切值是未知的，我们试图量化这些参数的不确定性时，模型输出与观察比较。该模型可在不同的保真度：较低的保真度，这是更快的运行，和更高的保真度，但更计算密集的版本。模式输出和观测数据都是大的时空系统，传统的计算机实验设计和分析方法无法科普这种涉及多个模式输出的大数据集。我们开发了一种方法，这个逆问题的大型时空数据集，采用了两个不同版本的物理模型。在初步设计之后，我们提出了一个基于预期改进的序贯设计。对于LFM-MIX，预期改进建议的额外运行通过排除后验模式和缩小后验分布的宽度来减少后验不确定性。我们还说明了我们的方法，使用Lorenz '96系统的简化大气方程，使用已知的输入参数。对于Lorenz '96系统，在基于预期改进执行顺序运行之后，后验模式收敛到真值，并且后验可变性减小。
Geomagnetic storms play a critical role in space weather physics with the potential for far reaching economic impacts including power grid outages, air traffic rerouting, satellite damage and GPS disruption. The LFM-MIX is a state-of-the-art coupled magnetospheric-ionospheric model capable of simulating geomagnetic storms. Imbedded in this model are physical equations for turning the magnetohydrodynamic state parameters into energy and flux of electrons entering the ionosphere, involving a set of input parameters. The exact values of these input parameters in the model are unknown, and we seek to quantify the uncertainty about these parameters when model output is compared to observations. The model is available at different fidelities: a lower fidelity which is faster to run, and a higher fidelity but more computationally intense version. Model output and observational data are large spatiotemporal systems; the traditional design and analysis of computer experiments is unable to cope with such large data sets that involve multiple fidelities of model output. We develop an approach to this inverse problem for large spatiotemporal data sets that incorporates two different versions of the physical model. After an initial design, we propose a sequential design based on expected improvement. For the LFM-MIX, the additional run suggested by expected improvement diminishes posterior uncertainty by ruling out a posterior mode and shrinking the width of the posterior distribution. We also illustrate our approach using the Lorenz `96 system of equations for a simplified atmosphere, using known input parameters. For the Lorenz `96 system, after performing sequential runs based on expected improvement, the posterior mode converges to the true value and the posterior variability is reduced.
DOI：
10.1002/9780470685853
发表时间：
1994
期刊：
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影响因子：
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作者：
L. Biegler;G. Biros;O. Ghattas;M. Heinkenschloss;D. Keyes;B. Mallick;Y. Marzouk;L. Tenorio;B. V. B. Waanders-B.-V.-B.-Waanders-1863062;K. Willcox
通讯作者：
L. Biegler;G. Biros;O. Ghattas;M. Heinkenschloss;D. Keyes;B. Mallick;Y. Marzouk;L. Tenorio;B. V. B. Waanders-B.-V.-B.-Waanders-1863062;K. Willcox