The Fast Solar Wind in the Acceleration Region: Observational Constraints from Interplanetary Scintillation Measurements

The acceleration of the solar wind is still one of the outstanding problems of solar physics. One difficulty is the uncertainty in remote-sensing observations of solar winds outflow speeds when using proxies for solar wind velocity such as the drift velocity of density irregularities it is not always obvious how these drift speeds relate to that of the background solar wind. In particular, there is evidence that the turbulent-scale structures may be boosted above the bulk flow speed by wave action in the fast wind close to the Sun. By combining different types of measurement which are sensitive to different scale sizes of action, improving the accuracy to which the bulk flow speed can be determined and providing information on the wave field in the solar wind.