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On the dependency between the peak velocity of high-speed solar wind streams near Earth and the area of their solar source coronal holes

Journal Contribution - Journal Article

The relationship between the peak velocities of high-speed solar wind streams near Earth and the areas of their solar source regions, i.e., coronal holes, is known since the 1970s, but still physically not well understood. We perform 3D MHD simulations us- ing the EUHFORIA code to show that this empirical relationship forms during the propagation phase of high-speed streams from the Sun to Earth. For this purpose, we neglect the acceleration phase of high-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. The velocity, temperature, and density in the cross-section of the corresponding high-speed streams at 0:1AU are set to constant, homogeneous values. Finally, we propagate the associated high-speed streams through the inner heliosphere using the EUHFORIA code. The simulated high-speed stream peak velocities at Earth reveal a linear dependence on the area of their source coronal holes. The slopes of the rela- tionship decrease with increasing latitudes of the coronal holes, and the peak velocities saturate at a value of about 730km s􀀀1, similar to the observations. These ndings imply that the empirical relationship between the coronal hole areas and high-speed stream peak velocities does not describe the acceleration phase of high-speed streams, but is a result of the high-speed stream propagation from the Sun to Earth.
Journal: Astrophysical journal letters
ISSN: 2041-8205
Issue: 1
Volume: 897
Publication year:2020
BOF-keylabel:yes
IOF-keylabel:yes
BOF-publication weight:3
CSS-citation score:1
Authors:International
Authors from:Government, Higher Education
Accessibility:Open