Magnetic switchbacks are rapid high amplitude reversals of the radial magnetic field in the solar wind that do not involve a heliospheric current sheet crossing. First seen sporadically in the seventies in Mariner and Helios data, switchbacks were later observed by the Ulysses spacecraft beyond 1 au and have been recently identified as a typical component of solar wind fluctuations in the inner heliosphere by the Parker Solar Probe spacecraft. Here we provide a simple yet predictive theory for the formation of these magnetic reversals: the switchbacks are produced by the shear of circularly polarized Alfv\'en waves by a transversely varying radial wave propagation velocity. We provide an analytic expression for the magnetic field variation, establish the necessary and sufficient conditions and show that the mechanism works in a realistic solar wind scenario.
@article{arxiv.2301.02572,
title = {Formation of Magnetic Switchbacks Observed by Parker Solar Probe},
author = {Gabor Toth and Marco Velli and Bart van der Holst},
journal= {arXiv preprint arXiv:2301.02572},
year = {2023}
}