Drift Orbit Bifurcations and Cross-Field Transport in the Outer Radiation Belt: Global MHD and Integrated Test-Particle Simulations
Drift Orbit Bifurcations and Cross-Field Transport in the Outer Radiation Belt: Global MHD and Integrated Test-Particle Simulations
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DOI：
10.1029/2021ja029802
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发表时间：
2021-10-01
影响因子：
2.8
通讯作者：
Chittenden, J. P.
中科院分区：
文献类型：
--
作者：
Desai, R. T.;Eastwood, J. P.;Chittenden, J. P.
外磁层中的高能粒子通量对建模工作提出了重大挑战，因为它们可以根据太阳风驱动条件的数量级而变化。在这项研究中，我们证明了通过全球磁流体动力学（MHD）模拟传播测试粒子的能力，以高精度，并使用它来映射与相对论电子进行漂移轨道分叉（DOBs）相关的交叉场径向运输。模拟预测DOB主要发生在磁层顶损失锥的地球半径内，并且对于向南和向北的行星际磁场方向出现显着不同。第二个不变的变化表现为一个辍学的粒子通量与俯仰角接近90度，并表明DOB是一个原因的蝴蝶俯仰角分布在夜间部门。对流电场，不包括在以前的DOB的研究，被发现有显着的影响所产生的长期运输，和磁层顶和大气层的损失被确定为一个潜在的方法，将DOB在福克-普朗克运输模型。
Energetic particle fluxes in the outer magnetosphere present a significant challenge to modeling efforts as they can vary by orders of magnitude in response to solar wind driving conditions. In this study, we demonstrate the ability to propagate test particles through global magnetohydrodynamic (MHD) simulations to a high level of precision and use this to map the cross-field radial transport associated with relativistic electrons undergoing drift orbit bifurcations (DOBs). The simulations predict DOBs primarily occur within an Earth radius of the magnetopause loss cone and appear significantly different for southward and northward interplanetary magnetic field orientations. The changes to the second invariant are shown to manifest as a dropout in particle fluxes with pitch angles close to 90 degrees and indicate DOBs are a cause of butterfly pitch angle distributions within the night-time sector. The convective electric field, not included in previous DOB studies, is found to have a significant effect on the resultant long-term transport, and losses to the magnetopause and atmosphere are identified as a potential method for incorporating DOBs within Fokker-Planck transport models.