Science. 1966 Oct 14;154(3746):228-34. doi: 10.1126/science.154.3746.228.
Over the past few years, the satellite topside sounders have significantly contributed to the understanding of the upper ionosphere. A great quantity of radio echo data has been accumulated, from which the ionospheric electrondensity distribution can be determined. The topside measurements of electron density essentially agree with similar measurements from the ground, except for an occasional 10-percent discrepancy near the peak of the ionosphere. While horizontal non-uniformity is a likely cause, this discrepancy has not yet been adequately explained. The electron-density scale heights measured at a constant altitude indicate both a higher temperature and a heavier mean ion mass at high latitudes. At low latitudes the topside measurements have shown the detailed latitudinal structure of the equatorial anomaly, demonstrating control by the geomagnetic field. A variety of electron-density irregularities have been studied. Most are greatly elongated along the magnetic field, and produce echoes either by lateral scattering, if they are thin, or by longitudinal ducting, if they are thick. Some of the thick irregularities are continuous between the hemispheres and support conjugate echo propagation. The topside sounders have revealed the complex structure of the ionosphere near the auroral zone and at higher latitudes. At night an east-west trough of greatly reduced electron density occurs equatorward of the auroral zone. At the auroral zone itself the electron density is high and quite variable, both in space and time. The electron density at the polar cap within the auroral zone is often uniform and smooth. Ionospheric irregularities are common in the area of the trough and the auroral zone. Among other satellites, the topside sounders have been used in various plasma studies involving the excitation and propagation of waves. These studies suggest that the ionosphere is an appropriate region for future plasma physics investigations, especially with rocket and satellite payloads designed specifically for that purpose.
在过去的几年中，卫星顶部探测器极大地促进了对高层电离层的理解。已经积累了大量的无线电回波数据，从中可以确定电离层电子密度分布。顶部测量的电子密度基本上与地面类似测量结果一致，除了在电离层峰值附近偶尔出现 10%的差异。虽然水平不均匀性可能是一个原因，但这个差异尚未得到充分解释。在恒定高度测量的电子密度标度高度表明，在高纬度地区，温度更高，平均离子质量更重。在低纬度地区，顶部测量结果显示了赤道异常的详细纬度结构，证明了磁场的控制。已经研究了各种电子密度不规则性。大多数不规则性沿着磁场极大地拉长，如果它们很薄，则通过横向散射产生回波，如果它们很厚，则通过纵向导管产生回波。一些厚的不规则性在半球之间连续，支持共轭回波传播。顶部探测器揭示了极光带和高纬度地区附近电离层的复杂结构。在夜间，极光带以南的赤道地区会出现电子密度大大降低的东西向槽。在极光带本身，电子密度很高，并且在空间和时间上都非常不稳定。极光带内的极盖区的电子密度通常是均匀和平滑的。在槽区和极光带区域，电离层不规则性很常见。在其他卫星中，顶部探测器已用于涉及波的激发和传播的各种等离子体研究。这些研究表明，电离层是未来等离子体物理研究的合适区域，特别是对于那些专门为此目的设计的火箭和卫星有效载荷。
