Role of eddy diffusion in the delayed ionospheric response to solar flux changes
Role of eddy diffusion in the delayed ionospheric response to solar flux changes
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DOI：
10.5194/angeo-39-641-2021
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发表时间：
2021-07
影响因子：
1.9
通讯作者：
Rajesh Vaishnav;C. Jacobi;J. Berdermann;M. Codrescu;Erik Schmölter
中科院分区：
文献类型：
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作者：
Rajesh Vaishnav;C. Jacobi;J. Berdermann;M. Codrescu;Erik Schmölter
抽象的。使用全球 3-D 耦合热层电离层等离子体层电动力学 (CTIPe) 基于物理的数值模型模拟了 27 d 太阳自转驱动的电离层对太阳通量变化的响应。使用 F10.7 指数作为模型中太阳极紫外 (EUV) 变化的代理，太阳自转周期的电离层延迟得到了很好的再现，约为 1 d，这与卫星和现场测量结果一致。从涡流扩散减少和增加的机制 CTIPe 研究中，我们得出结论，涡流扩散是影响电离层总电子含量 (TEC) 延迟的重要因素。我们观察到，与较弱的涡流扩散相比，在涡流扩散增加的过程中，原子氧与分子氮的比率对太阳 EUV 通量的峰值响应时间变化很快。这些结果表明，涡流扩散的增加导致更快的传输过程和增加的损失率，从而导致电离层时间延迟的减少。此外，我们发现太阳活动的增加导致电离层延迟增强。在低纬度地区，太阳活动的影响更强，因为极紫外辐射会驱动电离过程，从而导致成分变化。因此，涡扩散和太阳活动的共同作用导致低纬度和中纬度地区的延迟时间更长。
Abstract. Simulations of the ionospheric response to solar flux changes driven by the 27 d solar rotation have been performed using the global 3-D Coupled Thermosphere Ionosphere Plasmasphere electrodynamics (CTIPe) physics-based numerical model. Using the F10.7 index as a proxy for solar extreme ultraviolet (EUV) variations in the model, the ionospheric delay at the solar rotation period is well reproduced and amounts to about 1 d, which is consistent with satellite and in situ measurements. From mechanistic CTIPe studies with reduced and increased eddy diffusion, we conclude that the eddy diffusion is an important factor that influences the delay of the ionospheric total electron content (TEC). We observed that the peak response time of the atomic oxygen to molecular nitrogen ratio to the solar EUV flux changes quickly during the increased eddy diffusion compared with weaker eddy diffusion. These results suggest that an increase in the eddy diffusion leads to faster transport processes and an increased loss rate, resulting in a decrease in the ionospheric time delay. Furthermore, we found that an increase in solar activity leads to an enhanced ionospheric delay. At low latitudes, the influence of solar activity is stronger because EUV radiation drives ionization processes that lead to compositional changes. Therefore, the combined effect of eddy diffusion and solar activity leads to a longer delay in the low-latitude and midlatitude region.