AURORAL KILOMETRIC RADIATION AND THE AURORAL ELECTROJET INDEX FOR THEJANUARY 1997 MAGNETIC CLOUD EVENT

Auroral kilometric radiation (AKR) observations by Polar and Geotail a re compared with the auroral electrojet index for the January 1997 mag netic cloud event. These two-spacecraft measurements are complementary in covering the AKR emission cones throughout the event and, together , reasonably represent the auroral electrojet AE index. We point out, however, limitations of both the AKR index and the AE index in providi ng truly global measurements of substorm activity.