2-STATION AURORAL INFRASONIC WAVE OBSERVATIONS

The morphologies of auroral infrasonic wave substorms are compared for two stations, College and Palmer, Alaska, that are 368 km apart and approximately on the same magnetic meridian. During an 11-month period of simultaneous operation, five times more auroral infrasonic waves were received at College, the northernmost station, than at Palmer. When Palmer was closest to the equatorward edge of the average auroral oval (1100-1400 UT), very few signals were received there, probably because of an acoustical skip-zone effect. A model for the intersection of the auroral infrasonic shock surface with the ground plane is developed in order to examine marked differences in the characteristics of infrasonic wave packets observed successively at College and Palmer. These differences are related to the positions of the observing sites with respect to two regions in the model, defined as the front shock region and the side shock region. © 1969.