Distribution of Radar Auroras Over Alaska

Abstract

Analysis of data collected by five auroral radars located in Alaska shows the distribution of ionospheric disturbances as a function of time and location. The radars were operated during the IGY and were located in a nearly straight line running magnetically north-south across Alaska; these locations made it possible to observe disturbances continuously in the range, from 60 to 80 degrees geomagnetic latitude, which includes the visual auroral zone. An apparent radar auroral zone with a maximum at 67 degrees geomagnetic latitude is indicated by this study. The decrease in occurrence to the south of this maximum is verified, but the decrease to the north can not be accurately defined as the roll of aspect sensitivity is not fully understood. The radar auroral zone spreads to the south during increased magnetic disturbance, and some indication is found of a lessening of activity well north of the visual auroral zone. A conclusion is also reached that the layer causing radio wave absorption during aurora is not uniform but contains "holes" or regions of low absorption. The diurnal occurrence curves indicate two principal maxima. One is observed at all stations at times near local midnight. The time of the other maximum depends on the latitude of observation; it is later in the morning at the more northern locations. These two echoes exhibit differing degrees of aspect sensitivity, the morning echoes having a narrower scattering polar diagram.