Source-dependent properties of two slow solar wind states. (arXiv:2102.06568v1 [astro-ph.SR])
<a href="http://arxiv.org/find/astro-ph/1/au:+Griton_L/0/1/0/all/0/1">Léa Griton</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Rouillard_A/0/1/0/all/0/1">Alexis P. Rouillard</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Poirier_N/0/1/0/all/0/1">Nicolas Poirier</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Issautier_K/0/1/0/all/0/1">Karine Issautier</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Moncuquet_M/0/1/0/all/0/1">Michel Moncuquet</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Pinto_R/0/1/0/all/0/1">Rui Pinto</a>
Two states of the slow solar wind are identified from in-situ measurements by
Parker Solar Probe (PSP) inside 50 solar radii from the Sun. At such distances
the wind measured at PSP has not yet undergone significant transformation
related to the expansion and propagation of the wind. We focus in this study on
the properties of the quiet solar wind with no magnetic switchbacks. The two
states differ by their plasma beta, flux and magnetic pressure. PSP’s magnetic
connectivity established with Potential Field Source Surface (PFSS)
reconstructions, tested against extreme ultraviolet (EUV) and white-light
imaging, reveals the two states correspond to a transition from a streamer to
an equatorial coronal hole. The expansion factors of magnetic field lines in
the streamer are 20 times greater than those rooted near the center of the
coronal hole. The very different expansion rates of the magnetic field result
in different magnetic pressures measured by PSP in the two plasma states. Solar
wind simulations run along these differing flux tubes reproduce the slower and
denser wind measured in the streamer and the more tenuous wind measured in the
coronal hole. Plasma heating is more intense at the base of the streamer field
lines rooted near the boundary of the equatorial hole than those rooted closer
to the center of the hole. This results in a higher wind flux driven inside the
streamer than deeper inside the equatorial hole.
Two states of the slow solar wind are identified from in-situ measurements by
Parker Solar Probe (PSP) inside 50 solar radii from the Sun. At such distances
the wind measured at PSP has not yet undergone significant transformation
related to the expansion and propagation of the wind. We focus in this study on
the properties of the quiet solar wind with no magnetic switchbacks. The two
states differ by their plasma beta, flux and magnetic pressure. PSP’s magnetic
connectivity established with Potential Field Source Surface (PFSS)
reconstructions, tested against extreme ultraviolet (EUV) and white-light
imaging, reveals the two states correspond to a transition from a streamer to
an equatorial coronal hole. The expansion factors of magnetic field lines in
the streamer are 20 times greater than those rooted near the center of the
coronal hole. The very different expansion rates of the magnetic field result
in different magnetic pressures measured by PSP in the two plasma states. Solar
wind simulations run along these differing flux tubes reproduce the slower and
denser wind measured in the streamer and the more tenuous wind measured in the
coronal hole. Plasma heating is more intense at the base of the streamer field
lines rooted near the boundary of the equatorial hole than those rooted closer
to the center of the hole. This results in a higher wind flux driven inside the
streamer than deeper inside the equatorial hole.
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