极光区电离层扰动的两种类型

本文从ＥＩＳＣＡＴ探测资料分析确认，沉降粒子对极光区电离层的电离生成率有极重要的作用，但高能和低能粒子的有效电离高度范围完全不同，另一方面，磁层对流的增强却常使Ｆ层电子密度Ｎ下降，１９８５年１月２８～２９日期间出现Ｎ（Ｅ层）Ｎ（Ｆ层），且１４７ｋｍ以上Ｎ随高度增加而下降的典型扰动剖面。这是高能粒子和强磁层对流共同作用的结果。１９９３年２月１６～１７日期间，中午前后ＮｍＦ异常地增大，而Ｎ（Ｅ层）却无明显变化。这是与前者特征不同的另一类典型剖面。磁层内低能粒子（能量小于１ｋｅＶ）从极隙区沉降直抵电离层是使Ｆ层电子密度剧增的物理机制

TWO TYPES OF IONOSPHERIC DISTURBANCE IN THE AURORAL REGION

The EISCAT data are used to confirm the important role of precipitation particles in the ionization rate in the auroral region. The height range of the effective ionization is quite different for particles with different energies. On the other hand,an enhancement of magnetospheric convection often results in decreasing of electron density, N, in the F layer. During 28～29 January, 1985, the disturbed profile of N was very typical, in which N(E layer)N(F layer) and N decreased with height above 147km.This phenomenon was caused by both energetic particles and intensive convection.During the period of 16～17 February, 1993, however, the N(F layer) increased extremely, while N(E layer) remained low. This is also a typical profile, but is opposite to that of the former one. In this case, the particles with lower energy( < 1keV) in the magnetosheath entered directly the high latitude ionosphere through the cusp, and can contribute significantly to the F layer ionization content.