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The relationship between the peak velocities of high-speed solar wind streamsnear Earth and the areas of their solar source regions, i.e., coronal holes,has been known since the 1970s, but it is still physically not well understood.We perform 3D magnetohydrodynamic (MHD) simulations using the EuropeanHeliospheric Forecasting Information Asset (EUHFORIA) code to show that thisempirical relationship forms during the propagation phase of high-speed streamsfrom the Sun to Earth. For this purpose, we neglect the acceleration phase ofhigh-speed streams, and project the areas of coronal holes to a sphere at 0.1au. We then vary only the areas and latitudes of the coronal holes. Thevelocity, temperature, and density in the cross section of the correspondinghighspeed streams at 0.1 au are set to constant, homogeneous values. Finally,we propagate the associated high-speed streams through the inner heliosphereusing the EUHFORIA code. The simulated high-speed stream peak velocities atEarth reveal a linear dependence on the area of their source coronal holes. Theslopes of the relationship decrease with increasing latitudes of the coronalholes, and the peak velocities saturate at a value of about 730 km/s, similarto the observations. These findings imply that the empirical relationshipbetween the coronal hole areas and high-speed stream peak velocities does notdescribe the acceleration phase of high-speed streams, but is a result of thehigh-speed stream propagation from the Sun to Earth.

On the Dependency between the Peak Velocity of High-speed Solar Wind Streams near Earth and the Area of Their Solar Source Coronal Holes