Artificial Aurora Experiment: Ground-based optical observations

Abstract

Ground-based image-orthicon television systems detected five raylike artificial auroras produced by electron beams with maximum energy of 8.7 kev directed downward from a rocket-borne accelerator flown January 26, 1969, from Wallops Island, Virginia. Four rays produced by 1-sec 8.7-kev pulses were observed at two stations separated enough to enable the spatial coordinates of the rays to be determined by triangulation. The lower ends of the observed rays were located at altitudes of approximately 104 to 106 km; the upper ends, ranging from altitudes of 122 to 132 km, were not so well defined. Widths of the artificial auroral rays (130±50 meters) and altitudes of the lower ends are in agreement with calculations of Berger et al. (1970), for which Coulomb scattering in a standard model atmosphere with a magnetic dip angle of 69° is assumed. The observed ray positions were within 0.1° of arc, or approximately 400 meters, of the positions predicted from knowledge of the rocket trajectory and the direction of the local geomagnetic field. From the observed durations of three of these auroras and from other data, it is concluded that the ratio of N2+ first negative to O I 5577 emission was between 3 and 7. The observations show no delay in the arrival of the electron beams and indicate that most or all of the energy entered the atmosphere in a well-confined beam.