This paper "The Solar Wind and Heliosphere" (PDF) mentions on page 5, regarding the Solar Wind:
An ion’s thermal speed is small (~45 km·s-1) so its bulk speed (~450 km·s-1) determines the time (4 days) it takes to reach Earth.
- What's the difference between thermal speed and bulk speed? (the physics, not numerically)
- Is the thermal speed a component of the bulk speed?
- Or are they measuring different physical properies?