Longitudinal Difference of Equatorial Thermospheric Zonal Wind’s Reversal Time and Speed
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摘要: 使用CHAMP卫星观测资料和TIEGCM模拟数据，研究了太阳活动低年春秋分季节赤道地区热层纬向风的反转时间和风速在经度分布上的差异，重点分析了离子拖曳力在不同地磁场构型下对纬向风速地理经度分布的影响。研究发现，纬向风一般在清晨时段由东向转为西向，下午时段由西向转为东向，但反转时间存在明显的经度差异，最大经度差异可达1.8 h，这主要是由于低层大气非迁移潮汐波的影响。非迁移潮汐波使下午时段的风场反转时间提前约2 h，更符合卫星观测结果；但其对清晨时段风场反转时间的影响不明显，从而使模拟结果与观测结果有较大差异。纬向风的经度四波结构主要来源于低层大气潮汐，但离子拖曳力对不同地磁场构型下的纬向风四波结构有一定的影响。分析发现，除低层大气非迁移潮汐波的作用外，离子拖曳力对纬向风四波结构的贡献约为25%，白天时段的贡献高于夜晚时段，在理想偶极子磁场时的贡献高于真实地磁场。Abstract: Based on the Challenging Minisatellite Payload (CHAMP) satellite observations and Thermosphere Ionosphere Electrodynamics General Circulation Model (TIEGCM) simulations, the longitudinal variation of the reversal local time of the equatorial thermospheric zonal wind and its speed at equinoxes during solar minimum period are investigated. It is found that the zonal wind generally turns from eastward to the westward in the morning and from westward to the eastward in the afternoon. However, there are obvious longitudinal differences in the reversal time, with the maximum longitudinal difference of 1.8 h. This is mainly due to the upward-propagating non-migrating tide in the lower atmosphere. The tide can advance the reversal time about 2 h in the afternoon, which is more consistent with the observation. However, it has no obvious effect on the reversal time in the morning, which makes the simulation result different from the observation. The longitudinal wave-4 structure of the zonal wind mainly comes from the non-migrating tide, but the ion drag contributes to the wave-4 structure of the zonal wind. The quantitative analysis shows that the contribution of ion drag to the wave-4 structure is about 25%. The ion drag effect is larger in the daytime than the nighttime, and larger in the frame of the idea dipole field than the real IGRF field.
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Key words:
- Longitudinal difference of zonal wind /
- Ion drag /
- CHAMP /
- TIEGCM
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图 1 赤道地区纬向风反转时间的经度分布。
$\Delta {\rm{LT}}$ 为反转时间在不同经度的最大差异Figure 1. Longitudinal variation of the reversal time of the equatorial zonal wind.
$\Delta {\rm{LT}} $ is the maximum differences in the reversal time in different longitude
图 2 在IGRF地磁场下利用TIEGCM模拟赤道地区纬向风的经度分布
Figure 2. Longitudinal variations of equatorial zonal winds simulated by TIEGCM under IGRF configuration
图 3 在偶极子磁场中利用TIEGCM模拟的赤道地区纬向风经度分布
Figure 3. Longitudinal variations of equatorial zonal winds simulated by TIEGCM in the dipole field
图 4 在IGRF地磁场中白天和夜晚两个时段赤道地区纬向风的经度平均分布
Figure 4. Longitudinal variations of zonal winds during the daytime and nighttime under IGRF configuration
图 5 在Dipole地磁场中白天和夜晚两个时段赤道地区纬向风的经度平均分布
Figure 5. Longitudinal variations of zonal winds during the daytime and nighttime in the Dipole field
表 1 离子拖曳力对纬向风四波经度分布影响的定量分析结果
Table 1. Quantitative analysis of the influence of ion drag on the longitudinal variation of the zonal wind
10:00－12:00 LT 20:00－22:00 LT IGRF 26.4% 25.3% Dipole 31.1% 26.7% 
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