Relationship between Pi2 Pulsations in Beijing and AE Indexes of Geomagnetism

We analyze the characteristics of Pi2 pulsations in Beijing from January 1 to March 26 of 1998 and from April 24 to June 13 of 1998, and compare them with AE indexes of geomagnetism. In Beijing near the noon time, the less the occurrence rate of Pi2 is, the smaller the amplitudes of Pi2s are. 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 can occur throughout the whole substorm stages, though for some substorms no Pi2 is found in Beijing. The AE indexes of theses substorms range from 200nT to 800nT. Although Beijing is classified as a low latitude 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.