ANOMALOUS CHARACTERISTICS OF S_q IN EAST ASIA

The magnetic records of the world station network during IGY/IGC with additional data at Changchun, Beijing, Shanghai and Lahsa of China have been used to study the characteristics of S_q in East Asia magnetic anomaly region. The results show that the principal harmonics (lst and 2nd harmonics) of S_q have special features different from those in other regions. The amplitudes of Xcomponent in the anomaly region are larger than those at other stations of similar latitude. The latitude of minimums amplitude is lower by 20° , and the minimum value is also smaller. The current intensity caculated on the basis of the data in East Asia region is similar to that from other regions data. However, the geomagnetic latitude of the current focus is lower by 10°. The S_q dynamo current depends on the earth's magnetic field and ionospheric conductivity structure, and the latter is affected by the magnetic field. Consequently, the above-mentioned features of S_q in East Asia region can be attributed to effects of magnetic field on ionospheric dynamo process.Numerial simulations show that the combined effects of the geomagnetic axis tiltand the magnetic anomaly in this region can explain these features of S_q. It is suggested from this study that the magnetic anomaly remarkably affects the electromagnetic environment of the near-earth space.