Effects of different geomagnetic field models on the motion of high-energy charged particles in space
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摘要: 以蒙特卡罗软件Geant4中的MAGNETOCOSMIC程序为基础，通过计算模拟不同地磁场模型和地理位置发射时的粒子损失过程，探讨了地球磁场对人工辐射带中粒子运动和俘获的影响规律。首先，模拟了10MeV电子在不同经度和L值（ L是赤道面上的空间映射点距地心距离与地球半径的比值） 下的发射，分析了在中心偶极子、偏心偶极子和国际地磁参考场（IGRF）三种地磁模型下电子的运动轨迹、损失锥角和俘获条件。结果显示：中心偶极子模型中电子的漂移轨迹相对规则且对称，而偏心偶极子模型则出现了不对称性，而 IGRF 模型则因其更精细的参数和更高的精度，展现了更复杂、不规则且更接近实际的轨迹；损失锥角随L值的变化关系中，IGRF模型下损失锥角最大，电子更难被地磁场俘获。其次，探讨了电子发射经度对损失过程的影响，尤其是在南大西洋异常区（SAA区）的损失过程。结果表明，当电子运动到靠近SAA中心的位置时会更容易发生漂移损失。
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关键词:
- 人工辐射带 /
- 损失锥 /
- 南大西洋异常区(SAA区) /
- 国际地磁参考场 /
- 绝热不变运动
Abstract:Background The motion and trapping of high-energy charged particles in the radiation belts are significantly influenced by the structure of Earth's magnetic field. Utilizing different geomagnetic models in simulations can lead to varying understandings of particle loss mechanisms in artificial radiation belts.Purpose This study aims to simulate and compare the trajectories and loss processes of 10 MeV electrons injected at different longitudes and L-values under the centered dipole, eccentric dipole, and International Geomagnetic Reference Field (IGRF) models, to elucidate the influence of geomagnetic field models on particle trapping and loss, particularly within the South Atlantic Anomaly (SAA) region.Methods The particle loss processes during injection were simulated using the MAGNETOCOSMIC program within the Geant4 Monte Carlo software. Simulations were conducted for 10 MeV electrons at various longitudes and L-values. The trajectories, loss cone angles, and trapping conditions were analyzed and compared among the three geomagnetic models.Results The centered dipole model yielded relatively regular and symmetric electron drift trajectories. asymmetry was observed in the eccentric dipole model. The IGRF model produced the most complex and irregular trajectories, best reflecting the actual variability of Earth's magnetic field. Regarding the relationship between loss cone angle and L-value, the IGRF model exhibited the largest loss cone angles, indicating the most stringent conditions for particle trapping. Furthermore, injection longitude significantly influenced loss processes, with electrons approaching the center of the SAA being most susceptible to drift loss.Conclusions The choice of geomagnetic model critically impacts the simulation of particle dynamics in artificial radiation belts. The IGRF model, offering the most detailed field representation, predicts the strictest trapping conditions and most realistic loss patterns, especially within the SAA. These findings enhance the understanding of particle trapping mechanisms and are significant for space environment research and applications. -
图 3 三种地磁场模型下电子的漂移轨迹
Figure 3. The electron drift trajectories under the three geomagnetic models
图 4 发生回弹与漂移损失前的电子轨迹图
Figure 4. Electron Trajectory Diagram Prior to Rebound and Drift Loss
图 5 三种地磁场模型下损失锥角和L值的关系
Figure 5. Relationship between the loss cone angle and the L value under three magnetic field models
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