On a possible control mechanism for solar wind outflow velocity from coronal holes
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In this paper we give an explanation for a control mechanism for velocityV of solar wind (SW) streams for coronal holes (CHs) based on the idea suggested by Rudenko and Fainshtein (1993). In accordance with that idea, the difference of values ofV in high-speed SW streams from different CHs is due to the spread in magnitude of magnetic fieldBa in the region of acceleration of such streams near the Sun. In this case, with increasing magnitude ofBa, there is an increase in velocity of the high-speed stream.
Through calculations of the coronal magnetic field (potential-field approximation) it is shown that on the source surface the magnetic field 〈Bs〉, averaged over the cross-section of the magnetic tube from a CH, can vary for different tubes over a wide range and correlates quite well with the area of this tube's base as well as depending on the radial component of the magnetic field at the base of the tube on the source surface 〈Bor〉.
It is found that the value of superradial divergence of the magnetic tube from a CH depends not only on the area of its base (as shown in prior work) but also on 〈Bor〉. A positive correlation at the Earth's orbit between velocityV of the high-speed SW and the radial component of the magnetic field in the region of this stream is detected, which agrees indirectly with theV-control mechanism under discussion.
KeywordsMagnetic Field Solar Wind Control Mechanism Prior Work Coronal Hole
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