太阳终端激发的电离层波包的MHD性质
The MHD nature of ionospheric wave packets excited by the solar terminator
摘要：
首次获得了电离层中尺度波包（MSTWP）磁流体动力学（MHD）性质的实验证据。我们使用的总电子含量（TEC）的测量数据在密集的日本网络GPS/GEONET（1220站）在2008-2009年。我们发现，周日，季节和光谱MSTWP的特点是指定的太阳终结者（ST）动力学。MSTWP是窄带TEC振荡的链，单个包的持续时间约为1-2小时，振荡周期为10-20分钟。它们的总持续时间约为4- 6小时。MSTWP的空间结构的特点是高度的各向异性和相干的距离超过10个波长。MSTWP行进方向的特征在于不受季节影响的高方向性。白天MSTWPs的发生率在冬季和春分期间较高。夜间MSTIDS的发病率以夏季为高峰。这些功能是一致的，与以前的MS旅行电离层扰动（TID）的统计数据，从630 nm的气辉成像观测在日本。在冬季，北半球的MSTWP在早晨ST通过后3-4小时被观测到。在夏季，MSTWP被检测到1.5-2小时之前，晚上ST发生在观测点，在晚上ST通过磁共轭点的时刻。在观测点和磁共轭区，振荡系统的高Q因子以及MSTWP的出现与日珥通过的同步性都证明了ST激发MSTWP产生的MHD性质。所得结果是ST产生离子声波假说的第一个实验证据。
英文摘要：
We obtained the first experimental evidence for the magnetohydrodynamic (MHD) nature of ionospheric medium-scale travelling wave packets (MSTWP). We used data on total electron content (TEC) measurements obtained at the dense Japanese network GPS/GEONET (1220 stations) in 2008-2009. We found that the diurnal, seasonal and spectral MSTWP characteristics are specified by the solar terminator (ST) dynamics. MSTWPs are the chains of narrow-band TEC oscillations with single packet's duration of about 1-2 hours and oscillation periods of 10-20 minutes. Their total duration is about 4--6 hours. The MSTWP spatial structure is characterized by a high degree of anisotropy and coherence at the distance of more than 10 wavelengths. The MSTWP direction of travelling is characterized by a high directivity regardless of seasons. Occurrence rate of daytime MSTWPs is high in winter and during equinoxes. Occurrence rate of nighttime MSTIDs has its peak in summer. These features are consistent with previous MS travelling ionosphere disturbance (TID) statistics obtained from 630-nm airglow imaging observations in Japan. In winter, MSTWPs in the northern hemisphere are observed 3-4 hours after the morning ST passage. In summer, MSTWPs are detected 1.5-2 hours before the evening ST occurrence at the point of observations, at the moment of the evening ST passage in the magneto-conjugate point. Both the high Q-factor of oscillatory system and synchronization of MSTWP occurrence with the solar terminator passage at the point of observations and in the magneto-conjugate area testify the MHD nature of ST-excited MSTWP generation. The obtained results are the first experimental evidence for the hypothesis of the ST-generated ion sound waves.
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