Switchbacks in the Solar Magnetic Field: Their Evolution, Their Content, and Their Effects on the Plasma

Author
Keywords
Abstract
<p>Switchbacks (rotations of the magnetic field) are observed on the Parker Solar Probe. Their evolution, content, and plasma effects are studied in this paper. The solar wind does not receive a net acceleration from switchbacks that it encountered upstream of the observation point. The typical switchback rotation angle increased with radial distance. Significant Poynting fluxes existed inside, but not outside, switchbacks, and the dependence of the Poynting flux amplitude on the switchback radial location and rotation angle is explained quantitatively as being proportional to (B sin(θ))<sup>2</sup>. The solar wind flow inside switchbacks was faster than that outside due to the frozen-in ions moving with the magnetic structure at the Alfv\ en speed. This energy gain results from the divergence of the Poynting flux from outside to inside the switchback, which produces a loss of electromagnetic energy on switchback entry and recovery of that energy on exit, with the lost energy appearing in the plasma flow. Switchbacks contain 0.3-10 Hz waves that may result from currents and the Kelvin-Helmholtz instability that occurs at the switchback boundaries. These waves may combine with lower frequency magnetohydrodynamic waves to heat the plasma.</p>
Year of Publication
2020
Journal
The Astrophysical Journal Supplement Series
Volume
246
Number
Number of Pages
68
Date Published
02/2020
URL
https://iopscience.iop.org/article/10.3847/1538-4365/ab7196
DOI
10.3847/1538-4365/ab7196