太阳活动高年上电离层中O^+—H^+离子过渡高度的特征

THE HEIGHT OF O+-H+ TRANSITION IN THE TOPSIDE IONOSPHERE AT SOLAR MAXIMUM

本文用日本电离层探测卫星ISS-b的资料,假设F_2层峰顶以上电离层中各类离子随高度呈扩散平衡分布,得到了太阳活动高年(1978年8月—1979年8月)确定顶外电离层电子密度剖面形状的一个重要参数,即O^+—H^+离子过渡高度h_T的一些变化特征.指出h_T的日变化特性主要受电离层中O^+离子的产生与复合作用的控制.太阳活动高年在不同纬度和所有经度区域,平均说来日间h_T为大约1500—2500km变化,而夜间位于800—1400km,冬夜甚至接近中性氢、氧原子的化学平衡高度.过渡高度也表现出明显的纬度关系,在接近±20°的磁赤道地区,h_T基本上不随纬度变化;但在大于±30°磁纬区域h_T随纬度很快增加.义中还就h_T随时间和地磁(或地理)纬度变化的机制作了简要讨论.

In this paper, the data of Ionosphere Sounding Satellite-b(ISS-b) in Japan during the sun-spot maximum from August 1978 to August 1979 were examined. Some features of transition height, hT, an important paramter controlling profile shape of electron denstity in the topside ionosphere are given under the assumption that the ion densities vary in height with diffusive equilibrium. It is shown that the diurnal variations of transition height are dominated primarily by the production and loss of oxygen ions(O +) in the ionosphere. On average, at solar maximum, daytime transition heights vary from about 1500km to 2500km and nighttime transition heights lie in a range 800-1400 km at different latitudes for the whole longitudes. In the winter night, transition height would occur near the height for chemical equilibrium of neutral oxygen and hydrogen. The transition height shows a pronounced latitude dependence. In low latitudes near ±20°, transition heights are approximately independent of latitude, but above geomagnetic latitude ±30°, transition height increases rapidly with latitude. The mechanism of variation in hT with time and geomagnetic (or geographic) latitude and longitude is briefly discussed.