Acoustic Gravity Wave (AGW) generation during the barium injection experiments

Abstract

Abstract The main objective of the recent wavelike ionosphere disturbance dynamics studies is to obtain information about the source of the disturbance generation. As a rule in practice either generator type or its precise location are unknown. There is a reason to believe that active space experiments with artificial injection are of interest in respect to this problem. The results of spectral analysis of artificial wavelike ionosphere disturbances generated by barium orbital injection in the CRRES - Caribbean campaign experiments are presented here. Plasma density variations at the F2 peak height were registered by an ionosonde over Havana (Cuba), a long way up to 2500 km off the injection point. Exact coordinates of the injection and the time delay between the injection moment and 10 min period of the spectral component of the density variation have been used to estimate a wavelike disturbance propagation velocity of 323–390 m/s, which depends on the particular injection conditions for all five experiments. In each experiment the effective propagation velocity in the terminator zone was correlated with the length of the sunlit part of the signal trace. Energy estimation was made and the conformity of space-time scales of the barium cloud development to the wavelike disturbance parameters registered over Havana was obtained. In this case the orbital CRRES injections were the most likely the reason for the appearance of wavelike ionospheric disturbances. Terminator passage can produce wavelike disturbances of the same parameters but they usually propagate from west to east (in our experiment they propagate in opposite direction, from east to west). Natural wavelike disturbances of such periods are connected with acoustic-gravity waves propagating in neutral atmosphere. Orbital injection of artificial barium clouds appears to be the effective source of acoustic gravity waves generation at upper ionosphere heights. If so, we have to deal with unique case of wave generation and propagation when the parameters of acoustic gravity waves source and its location are accurately known and situated at high altitudes of the ionosphere.