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研究了中高度（离地心３－４个地球半径）极隙区上行电子束流和上行氧离子（ｏ＋）锥引起的沿磁力线传播的电磁不稳定性．采用的物理模型假定：上行电子具有单能束流分布函数，而上行氧离子（ｏ＋）锥可用单能环－束分布函数来描述．结果表明，左旋和右旋圆偏振的低频电磁模是不稳定的，激发不稳定性的自由能源主要由上行电子束流提供，而上行氧离子（Ｏ＋）锥因自由能太小只影响频率色散关系，上行粒子（电子和氧离子）与背景等离子体密度比的变化对电磁不稳定性有重要影响．这些结果对解释权隙区纬度地面站低频电磁波观测资料和理解极隙区动力学过程是很有益的．
The electromagnetic instabilities propagating along the lines of magnetic force caused by upward electron beam currents and upward oxygen ion (o +) cones were studied at medium and high polar regions (3-4 earth radii from the earth's center). The physical model used assumes that the upgoing electrons have a monoenergetic beam distribution function and that the upside oxygen (o +) cone can be described by a monoenergetic ring-bundle distribution function. The results show that the low-frequency electromagnetic modes of left-hand and right-hand circular polarizations are unstable and the free energy of excitation instability is mainly provided by the upward electron beam, while the upward oxygen ion (O +) cone only affects the frequency dispersion due to the too small free energy The relationship between the upward particle (electron and oxygen ions) and the background plasma density ratio changes have a significant impact on the electromagnetic instability. These results are very useful to explain the low-frequency electromagnetic wave observation data of the ground station at the latitude of the gap region and to understand the dynamic process of the pole gap region.