Day-night ratio for auroral absorption events associated with negative magnetic bays

An examination of solar illumination effects for auroral absorption events centered over the 27.6-Mc/s riometer antenna pattern at College, Alaska, shows that the daynight absorption ratio is essentially unity. This finding indicates that electron-positive ion recombination far outweighs electron attachment processes in auroral absorption regions and is consistent with present knowledge of the electron bombardment as well as ionic-molecular processes at the 90-100-km level. Further implications of this result are discussed.