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Features of Magnetic Field Switchbacks in Relation to the Local-field Geometry of Large-amplitude Alfv\ enic Oscillations: Wind and PSP Observations
| Author | Bourouaine, Sofiane; Perez, Jean; Raouafi, Nour; Chandran, Benjamin; Bale, Stuart; Velli, Marco; |
| Keywords | Parker Data Used; Heliosphere; Solar wind; 711; 1534; Astrophysics - Solar and Stellar Astrophysics; Physics - Space Physics |
| Abstract | In this Letter, we report observations of magnetic switchback (SB) features near 1 au using data from the Wind spacecraft. These features appear to be strikingly similar to the ones observed by the Parker Solar Probe mission closer to the Sun: namely, one- sided spikes (or enhancements) in the solar-wind bulk speed V that correlate/anticorrelate with the spikes seen in the radial- field component B $_ R $. In the solar-wind streams that we analyzed, these specific SB features near 1 au are associated with large-amplitude Alfv\ enic oscillations that propagate outward from the Sun along a local background (prevalent) magnetic field B $_0$ that is nearly radial. We also show that, when B $_0$ is nearly perpendicular to the radial direction, the large-amplitude Alfv\ enic oscillations display variations in V that are two sided (i.e., V alternately increases and decreases depending on the vector \ensuremath\Delta B = B - B $_0$). As a consequence, SBs may not always appear as one-sided spikes in V, especially at larger heliocentric distances where the local background field statistically departs from the radial direction. We suggest that SBs can be well described by large-amplitude Alfv\ enic fluctuations if the field rotation is computed with respect to a well-determined local background field that, in some cases, may deviate from the large-scale Parker field. |
| Year of Publication | 2022 |
| Journal | \apjl |
| Volume | 932 |
| Number of Pages | L13 |
| Section | |
| Date Published | jun |
| ISBN | |
| URL | |
| DOI | 10.3847/2041-8213/ac67d9 |
