New Evidence on the Origin of Solar Wind Microstreams/Switchbacks. (arXiv:2305.06914v1 [astro-ph.SR])
<a href="http://arxiv.org/find/astro-ph/1/au:+Kumar_P/0/1/0/all/0/1">Pankaj Kumar</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Karpen_J/0/1/0/all/0/1">Judith T. Karpen</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Uritsky_V/0/1/0/all/0/1">Vadim M. Uritsky</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Deforest_C/0/1/0/all/0/1">Craig E. Deforest</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Raouafi_N/0/1/0/all/0/1">Nour E. Raouafi</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+DeVore_C/0/1/0/all/0/1">C. Richard DeVore</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Antiochos_S/0/1/0/all/0/1">Spiro K. Antiochos</a>
Microstreams are fluctuations in the solar wind speed and density associated
with polarity-reversing folds in the magnetic field (also denoted switchbacks).
Despite their long heritage, the origin of these microstreams/switchbacks
remains poorly understood. For the first time, we investigated periodicities in
microstreams during Parker Solar Probe (PSP) Encounter 10 to understand their
origin. Our analysis was focused on the inbound corotation interval on 2021
November 19-21, while the spacecraft dove toward a small area within a coronal
hole (CH). Solar Dynamics Observatory remote-sensing observations provide rich
context for understanding the PSP in-situ data. Extreme ultraviolet images from
the Atmospheric Imaging Assembly reveal numerous recurrent jets occurring
within the region that was magnetically connected to PSP during intervals that
contained microstreams. The periods derived from the fluctuating radial
velocities in the microstreams (approximately 3, 5, 10, and 20 minutes) are
consistent with the periods measured in the emission intensity of the jetlets
at the base of the CH plumes, as well as in larger coronal jets and in the
plume fine structures. Helioseismic and Magnetic Imager magnetograms reveal the
presence of myriad embedded bipoles, which are known sources of
reconnection-driven jets on all scales. Simultaneous enhancements in the PSP
proton flux and ionic ($^3$He, $^4$He, Fe, O) composition during the
microstreams further support the connection with jetlets and jets. In keeping
with prior observational and numerical studies of impulsive coronal activity,
we conclude that quasiperiodic jets generated by interchange/breakout
reconnection at CH bright points and plume bases are the most likely sources of
the microstreams/switchbacks observed in the solar wind.
Microstreams are fluctuations in the solar wind speed and density associated
with polarity-reversing folds in the magnetic field (also denoted switchbacks).
Despite their long heritage, the origin of these microstreams/switchbacks
remains poorly understood. For the first time, we investigated periodicities in
microstreams during Parker Solar Probe (PSP) Encounter 10 to understand their
origin. Our analysis was focused on the inbound corotation interval on 2021
November 19-21, while the spacecraft dove toward a small area within a coronal
hole (CH). Solar Dynamics Observatory remote-sensing observations provide rich
context for understanding the PSP in-situ data. Extreme ultraviolet images from
the Atmospheric Imaging Assembly reveal numerous recurrent jets occurring
within the region that was magnetically connected to PSP during intervals that
contained microstreams. The periods derived from the fluctuating radial
velocities in the microstreams (approximately 3, 5, 10, and 20 minutes) are
consistent with the periods measured in the emission intensity of the jetlets
at the base of the CH plumes, as well as in larger coronal jets and in the
plume fine structures. Helioseismic and Magnetic Imager magnetograms reveal the
presence of myriad embedded bipoles, which are known sources of
reconnection-driven jets on all scales. Simultaneous enhancements in the PSP
proton flux and ionic ($^3$He, $^4$He, Fe, O) composition during the
microstreams further support the connection with jetlets and jets. In keeping
with prior observational and numerical studies of impulsive coronal activity,
we conclude that quasiperiodic jets generated by interchange/breakout
reconnection at CH bright points and plume bases are the most likely sources of
the microstreams/switchbacks observed in the solar wind.
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