IMPULSE-RESPONSE OF GEOMAGNETIC INDEXES TO INTER-PLANETARY MAGNETIC-FIELD

The impulse response of the geomagnetic indices (Dst, AL, AU and AE) to the interplanetary magnetic field southward component (IMF-BZ) is calculated on the assumption that the magnetosphere acts as a linear system. Hourly data for 300 days are used in this analysis. The main results obtained are as follows: (1) Using interplanetary data, a fairly large portion of geomagnetic disturbances may be predicted with the assumption of a linear system. (2) The response of the Dst index and the AL index develops at two steps or has an oscillating property with a period of several hours. (3) The response of the AU index is rather different from that of the other indices. These results may suggest that the disturbances represented by the Dst and AL indices have a common origin associated with the interplanetary magnetic or electric field, whereas those indicated by the AU index have an origin somewhat different from it. © 1979, Society of Geomagnetism and Earth, Planetary and Space Sciences. All rights reserved.