Abstract. Simulations of the ionospheric response to solar flux changes driven by the twenty-seven days 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 EUV variations in the model, the ionospheric delay at the solar rotation period is well reproduced and amounts to about 1 day, 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 a primary factor that influences the delay of the ionospheric total electron content (TEC). We observed the peak response time of atomic oxygen to the molecular nitrogen ratio to 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 rates resulting in a decrease of 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, as EUV radiation drives ionization processes that lead to composition changes. Hence, the combined effect of eddy diffusion and solar activity lead to longer delay in the low and mid latitude region.

中文翻译：

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涡流扩散在延迟电离层对太阳通量变化的响应中的作用

摘要。使用基于全局3D耦合热球/电离层等离子层电动力学（CTIPe）的物理模型，已经进行了电离层对由太阳旋转27天驱动的太阳通量变化的响应的模拟。使用F10.7指数代替模型中太阳EUV的变化，可以很好地重现太阳旋转周期的电离层延迟，总计约1天，这与卫星和原位测量一致。从减少和增加涡流扩散的机械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）延迟的主要因素。我们观察到，在涡流扩散增加的过程中，与较弱的涡流扩散相比，原子氧对分子氮比率与太阳能EUV通量的峰值响应时间迅速变化。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的增加。在低纬度地区，由于EUV辐射驱动电离过程导致成分变化，因此太阳活动的影响更大。因此，涡旋扩散和太阳活动的综合作用导致低纬度和中纬度地区的延迟更长。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的增加。在低纬度地区，由于EUV辐射驱动电离过程导致成分变化，因此太阳活动的影响更大。因此，涡旋扩散和太阳活动的综合作用导致低纬度和中纬度地区的延迟更长。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的增加。在低纬度地区，由于EUV辐射驱动电离过程导致成分变化，因此太阳活动的影响更大。因此，涡旋扩散和太阳活动的综合作用导致低纬度和中纬度地区的延迟更长。