Radial evolution of switchbacks in the inner heliosphere: observations from PSP to Ulysses
Abstract
We have analyzed magnetic field data from the first six encounters of Parker Solar Probe, three fast streams observed by Helios 1 and 2, and two Ulysses south polar passes to determine the radial evolution of switchbacks in the range of heliocentric distances 0.1 < R < 3 au. We have compared the radial evolution of the magnetic field variances with that of the mean square amplitudes of switchbacks. In addition, we have calculated the occurrence rate of switchbacks at various radial distances. We find that the radial amplitudes of switchbacks decrease faster than that of the overall turbulent fluctuations, following the radial decrease of the mean (radial) magnetic field. This result is consistent with the expected saturation of amplitudes, a condition that must be satisfied by fluctuations like switchbacks that display a constant total magnetic field strength. Furthermore, we find that the occurrence of switchbacks in the solar wind is scale-dependent: the fraction of longer duration switchbacks increases with radial distance, whereas the fraction of shorter switchbacks decreases with radial distance. Our results show that switchbacks decay and re-form in the inner heliosphere. We confirm that they can be generated in-situ by the expansion, although other types of switchbacks, forming closer to the sun, cannot be ruled out.
- Publication:
-
AGU Fall Meeting Abstracts
- Pub Date:
- December 2021
- Bibcode:
- 2021AGUFMSH35C2092T