Satelite low-frequency radio measurments have shown that an intense radio emission from the earth's auroral regions called auroral kilometric radition is closely associated with auroral and magnetic disturbances. In this paper we present a detailed investigation of this relationship, using the auroral electrojet (AE) index as an indicator of auroral magnetic disturbances and radio measurements from the Imp 6 spacecraft. This study indicates that the mean power flux of the 178-kHz radiation tends to be proportional to (AE)1.2 for AE>100&ggr; and, with less certainly, to (AE)2 for AE<100&ggr;. The correlation coefficient between log AE and the logarithm of the power flux is 0.514. Occasionally, a kilometric radiation event is detected which is not detected by the ground magnetometer stations, even though an auroral substorm is in progress. This study shows that the remote detection of kilometric radio emissions from the earth can be used as a reasonably reliable indicator of auroral substorm activity.