Japan-US Multi-Instrument Study of Ionospheric Sporadic-E

在中纬度电离层E区，VHF雷达经常观测到来自场向不规则体的强回波。在irregulaties中，我们发现了“准周期（QP）”结构，显示间歇性出现的回波周期为5-10分钟，空间波长为10-20公里。1996年8月在日本九州成功地进行了一次观测活动SEEK（九州上空的零星E试验），以广泛研究QP结构。从内浦发射了两枚探空火箭，而在种子岛的频率捷变雷达（FAR）观测了QP结构。探空火箭观测了电场波动、电子密度分布和波动。中性风也通过TMA（三甲基铝酸盐）尾迹测量。在火箭发射的同时进行了几次地面观测，包括FAR、MU和中李/台湾甚高频雷达、中频雷达、电离层探测仪、多普勒成像仪和法布里-珀罗多普勒干涉仪。从TMA实验中发现，在Es层附近的中性风中有一个非常大的垂直切变。现场电场强度超过10 mV/m，在海拔100-120 km处波动较大。FAR在Eslayr的高度附近接收到最强烈的回波，那里的电场波动最大。看来，不规则性产生在陡峭的密度梯度两侧的Es层。

Intense echoes from field-aiegned irregularities are often observed by VHF radars in the mid-latitude ionospheric E-region. In the iregulaties we have found "quasi-periodic (QP)" structures that show intermittent appearance of echoes with periods of 5-10 minutes and with spatial wavelengths of 10-20 km. An observation campaign SEEK (Sporadic-E Exper iment over Kyushu) was conducted successfully for an extensive study of the QP structure conducted in Kyushu, Japan in August 1996. Two sounding rockets were launched from Uchinoura while QP structure was observed by the frequency agile radar (FAR) in Tane-gashima. The sounding rockets observed electric field fluctuations, electron density profiles and fluctuations. Neutral winds were also measured by a TMA (Trimethyl Aluminate) trail. Several ground-based observations were conducted concurrently with the rocket launching, including FAR,MU and Chung-Li/Taiwan VHF radars, MF radar, ionosondes, multicolor imager and Fabry Perot Doppler interferometer. From the TMA experiment, a very large vertical shear in the neutral wind was found near the Es layr. The in-situ electric field strengths exceeded 10 mV/m with large fluctuations at altitudes around 100-120 km. FAR received the most intense echoes around the altitude of the Eslayr, where fluctuations in the electric fields were the maximum. It seems that the irregularities were generated at steep density gradients on both sides of the Es layr.