The origin of slow Alfv’enic solar wind at solar minimum. (arXiv:1907.02646v1 [physics.space-ph])
<a href="http://arxiv.org/find/physics/1/au:+Stansby_D/0/1/0/all/0/1">D. Stansby</a>, <a href="http://arxiv.org/find/physics/1/au:+Matteini_L/0/1/0/all/0/1">L. Matteini</a>, <a href="http://arxiv.org/find/physics/1/au:+Horbury_T/0/1/0/all/0/1">T. S. Horbury</a>, <a href="http://arxiv.org/find/physics/1/au:+Perrone_D/0/1/0/all/0/1">D. Perrone</a>, <a href="http://arxiv.org/find/physics/1/au:+DAmicis_R/0/1/0/all/0/1">R. D'Amicis</a>, <a href="http://arxiv.org/find/physics/1/au:+Bercic_L/0/1/0/all/0/1">L. Berčič</a>
Although the origins of slow solar wind are unclear, there is increasing
evidence that at least some of it is released in a steady state on
over-expanded coronal hole magnetic field lines. This type of slow wind has
similar properties to the fast solar wind, including a high degree of
Alfv’enicity. In this study a combination of proton, alpha particle, and
electron measurements are used to investigate the kinetic properties of a
single interval of slow Alfv’enic wind at 0.35 AU. It is shown that this slow
Alfv’enic interval is characterised by high alpha particle abundances,
pronounced alpha-proton differential streaming, strong proton beams, and large
alpha to proton temperature ratios. These are all features observed
consistently in the fast solar wind, adding evidence that at least some
Alfv’enic slow solar wind also originates in coronal holes. Observed
differences between speed, mass flux, and electron temperature between slow
Alfv’enic and fast winds are explained by differing magnetic field geometry in
the lower corona.
Although the origins of slow solar wind are unclear, there is increasing
evidence that at least some of it is released in a steady state on
over-expanded coronal hole magnetic field lines. This type of slow wind has
similar properties to the fast solar wind, including a high degree of
Alfv’enicity. In this study a combination of proton, alpha particle, and
electron measurements are used to investigate the kinetic properties of a
single interval of slow Alfv’enic wind at 0.35 AU. It is shown that this slow
Alfv’enic interval is characterised by high alpha particle abundances,
pronounced alpha-proton differential streaming, strong proton beams, and large
alpha to proton temperature ratios. These are all features observed
consistently in the fast solar wind, adding evidence that at least some
Alfv’enic slow solar wind also originates in coronal holes. Observed
differences between speed, mass flux, and electron temperature between slow
Alfv’enic and fast winds are explained by differing magnetic field geometry in
the lower corona.
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