Empirically derived particle outflow speeds over the solar poles in
late 1996 and early 1997.  The yellow region denotes the range of
hydrogen speeds able to reproduce observational data from UVCS, and
the blue region denotes the corresponding range of speeds for ionized
oxygen (O 5+). The black lines denote the proton outflow speed derived
from mass flux conservation: for a time-steady flow, the product of
the density, speed, and flow-tube area should be constant, and we use
density and polar flow-tube information, as well as in-situ mass flux
data from Ulysses, to define the constant.

(Kohl et al. 1998, Astrophys. J., 501, L127; Cranmer et al. 1999,
Astrophys. J., 511, 481)