Verification of large-scale rapid transport in the lower thermosphere: Tracking the exhaust plume of STS-107 from launch to the Antarctic

摘要

New analysis of the Doppler shift of O_2 airglow spectra recorded by the TIMED Doppler Interferometer (TIDI) and the High Resolution Doppler Imager (HRDI) have provided conclusive evidence that the shuttle main engine exhaust plume generated in the lower thermosphere by the launch of STS-107 and imaged by the Global Ultraviolet Imager (GUVI) instrument on TIMED was transported to the Antarctic in ～80h, supporting a key inference from the initial study by Stevens et al. (2005). These new results were aided by improved knowledge of the effects of instrumental and satellite artifacts imposed on the Doppler spectra. STS-107 launched on 16 January 2003, and the neutral wind near its launch trajectory and nearby volume was sampled within minutes by TIDI. These initial observations suggested that the northernmost end of the shuttle's exhaust plume would move northeast and that the southern end would move southeast, motions that were identified in imagery acquired during the next orbit of TIMED. The direction and magnitude of plume motion inferred from GUVI images obtained 12, 26, and 50 h after launch were again confirmed by TIDI and HRDI. The appearance of the plume over the Antarctic ～80 h after launch, inferred from earlier work by the appearance of iron ablated from the shuttle's main engines, was consistent with neutral winds measured by the satellite Doppler instruments over the Antarctic. The transport of the plume from the coast of Florida to the Antarctic was aided by the favorable phase and strong amplitude of a 2 day planetary wave of wave number three in the southern hemisphere on 18 January 2003. The existence of the 2 day wave was deduced from zonally averaged and combined TIDI and HRDI neutral wind observations. We conclude that the existence of strong and sustained winds in the MLT, significantly greater than expected from empirical and theoretical models, is indisputable and provides compelling evidence supporting the global-scale nature of thermospheric winds with magnitude greater than 100 m/s observed by Larsen (2002) from 40 years of sounding rocket chemical release experiments.