Proton Core Behaviour inside Magnetic Field Switchbacks

Abstract:

Magnetic field switchbacks are ubiquitous in the near-Sun solar wind and persist across many different streams, yet their origins and many of their properties are still unknown. Here we use SPC measurements to compare ion velocity distribution functions (VDFs) inside and outside of nearly full magnetic field reversals. We show that the ion VDFs inside switchbacks are consistent with a rigid phase space rotation of the background plasma and that the proton core parallel temperature is not distinctly different inside and outside of these structures. As a consequence, flow speed enhancements associated with these large field reversals do not follow a typical solar wind T-V relation. We conclude that switchbacks are consistent with large amplitude Alfvén pulses propagating along open magnetic field lines and discuss their possible sources. We also address the behaviour of the radial Poynting flux associated to these structures, showing that there is no obvious link between larger kinetic energies and radial Poynting flux enhancements.