Parker Solar Probe In-Situ Observations of Magnetic Reconnection Exhausts During Encounter 1. (arXiv:2001.06048v1 [astro-ph.SR])

Parker Solar Probe In-Situ Observations of Magnetic Reconnection Exhausts During Encounter 1. (arXiv:2001.06048v1 [astro-ph.SR])
<a href="http://arxiv.org/find/astro-ph/1/au:+Phan_T/0/1/0/all/0/1">T. D. Phan</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Bale_S/0/1/0/all/0/1">S. D. Bale</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Eastwood_J/0/1/0/all/0/1">J. P. Eastwood</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Lavraud_B/0/1/0/all/0/1">B. Lavraud</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Drake_J/0/1/0/all/0/1">J. F. Drake</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Oieroset_M/0/1/0/all/0/1">M. Oieroset</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Shay_M/0/1/0/all/0/1">M. A. Shay</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Pulupa_M/0/1/0/all/0/1">M. Pulupa</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Stevens_M/0/1/0/all/0/1">M. Stevens</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+MacDowall_R/0/1/0/all/0/1">R. J. MacDowall</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Case_A/0/1/0/all/0/1">A. W. Case</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Larson_D/0/1/0/all/0/1">D. Larson</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Kasper_J/0/1/0/all/0/1">J. Kasper</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Whittlesey_P/0/1/0/all/0/1">P. Whittlesey</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Szabo_A/0/1/0/all/0/1">A. Szabo</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Korreck_K/0/1/0/all/0/1">K. E. Korreck</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Bonnell_J/0/1/0/all/0/1">J. W. Bonnell</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Wit_T/0/1/0/all/0/1">T. Dudok de Wit</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Goetz_K/0/1/0/all/0/1">K. Goetz</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Harvey_P/0/1/0/all/0/1">P. R. Harvey</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Horbury_T/0/1/0/all/0/1">T. S. Horbury</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Livi_R/0/1/0/all/0/1">R. Livi</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Malaspina_D/0/1/0/all/0/1">D. Malaspina</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Paulson_K/0/1/0/all/0/1">K. Paulson</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Raouafi_N/0/1/0/all/0/1">N. E. Raouafi</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Velli_M/0/1/0/all/0/1">M. Velli</a>

Magnetic reconnection in current sheets converts magnetic energy into
particle energy. The process may play an important role in the acceleration and
heating of the solar wind close to the Sun. Observations from Parker Solar
Probe provide a new opportunity to study this problem, as it measures the solar
wind at unprecedented close distances to the Sun. During the 1st orbit, PSP
encountered a large number of current sheets in the solar wind through
perihelion at 35.7 solar radii. We performed a comprehensive survey of these
current sheets and found evidence for 21 reconnection exhausts. These exhausts
were observed in heliospheric current sheets, coronal mass ejections, and
regular solar wind. However, we find that the majority of current sheets
encountered around perihelion, where the magnetic field was strongest and
plasma beta was lowest, were Alfv’enic structures associated with bursty
radial jets and these current sheets did not appear to be undergoing local
reconnection. We examined conditions around current sheets to address why some
current sheets reconnected, while others did not. A key difference appears to
be the degree of plasma velocity shear across the current sheets: The median
velocity shear for the 21 reconnection exhausts was 24% of the Alfv’en
velocity shear, whereas the median shear across 43 Alfv’enic current sheets
examined was 71% of the Alfv’en velocity shear. This finding could suggest
that large, albeit sub-Alfv’enic, velocity shears suppress reconnection. An
alternative interpretation is that the Alfv’enic current sheets are isolated
rotational discontinuities which do not undergo local reconnection.

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