Characterising the large-scale structure and plasma properties of the inner corona is crucial to understand the source and subsequent expansion of the solar wind and related space weather effects .
Here we apply a new coronal rotational tomography method , along with a method to narrow streamers and refine the density estimate , to COR2A/STEREO observations from a period near solar minimum and maximum , gaining density maps for heights between 4 and 8 R _ { \odot } .
The coronal structure is highly radial at these heights , and the streamers are very narrow , in some regions only a few degrees in width .
The mean densities of streamers is almost identical between solar minimum and maximum .
However , streamers at solar maximum contain around 50 % more total mass due to their larger area .
By assuming a constant mass flux , and constraints on proton flux measured by Parker Solar Probe ( PSP ) , we estimate an outflow speed within solar minimum streamers of 50-120 km s ^ { -1 } at 4 R _ { \odot } , increasing to 90-250 km s ^ { -1 } at 8 R _ { \odot } .
Accelerations of around 6 m s ^ { -2 } are found for streamers at a height of 4 R _ { \odot } , decreasing with height .
The solar maximum slow wind shows a higher acceleration to extended distances compared to solar minimum .
To satisfy the solar wind speeds measured by PSP , there must be a mean residual acceleration of around 1-2 m s ^ { -2 } between 8 and 40 R _ { \odot } .
Several aspects of this study strongly suggest that the coronal streamer belt density is highly variable on small scales , and that the tomography can only reveal a local spatial and temporal average .