Abstract: The occurrence rate, intensity and density of field-aligned currents measured in the earth's inner magnetosphere by ISEE-1 and ISEE-2 are examined for four levels of geomagnetic activity: very quiet, quiet, active and very disturbed. It was found that the occurrence rate, current intensity and density increase with an increasing level of geomagnetic activity. The occurrence rate is only 8.9% at the lowest level, while 73.2% of events occurred above active level. Most events are accompanied with substorm in the night. These results indicate that field-aligned currents are presumably generated by interaction between solar wind, IMF and magnetosphere.

Key words: field aligned currents, AL index, substorm

摘要： 检验了场向电流与地磁和亚暴活动的相关性。按极光电集流指数AL的大小，地磁活动被分为4个水平，即|AL|<=50，50<|AL|<=150，150<|AL|<=300和|AL|>300分别相应于非常平静、平静、扰动和强烈扰动。统计结果表明，场向电流的发生率、强度和密度都随地磁活动的增加而增大。在最低活动水平，发生率只有8.9%，而73.2%的事件发生在扰动水平以上。对于夜间的场向电流，65.5%的事件伴随着磁层亚暴。

关键词: 场向电流, AL指数, 亚暴