Relationship between Pi2 in Beijing and AE indexes
北京地区Pi2脉动和地磁AE指数的关系

We analyze the characteristics of Pi2s in Beijing from January 1 to March 26 in 1998 and from April 24 to June 13 in 1998, and compare them with AE indexes. In Beijing near the noon time, the occurrence rate of Pi2 is less and the amplitudes of Pi2s smaller. Not all substorms can excite the cavity oscillation modes. The amplitudes of Pi2 usually increase with the growth of AE index. However there remain some exceptions which may be due to the fact that Beijing is sometimes very far from the substorm current wedge. Pi2s in Beijing are throughout the whole substorm stages. However for some substorms, no Pi2 is found in Beijing. The AE indexes of these substorms range from 200 nT to 800 nT. Although Beijing is classified as a low lattitude region, the characteristics of Pi2s in Beijing are more analogous to that of the Pi2s in middle latitude regions. So it is not very credible to use the Pi2s in Beijing to predict and monitor substorms.