Solar Orbiter Observations of Proton and Alpha Particle Kinetic Signatures Related to the Presence of Switchbacks in the Inner Heliosphere: A Case Study

We investigate how ions, namely protons and alpha particles, kinetically react to the presence of strong deflections in the magnetic field, the so-called switchbacks, in the first stream of slow Alfv & eacute;nic wind observed by Solar Orbiter at the heliocentric distance of 0.64 au. We focus on an isolated, large-scale switchback, and we study in detail ion kinetic properties. Beyond the expected correlation between the magnetic deflection and ion velocity related to the Alfv & eacute;nic nature of the switchbacks, we find that, within the switchback, proton and alpha particle densities increase, suggesting ongoing wave activity. Very interestingly, we observe a clear correlation between the magnetic deflection and alpha particle temperature, while no correlation has been found with proton temperature. This is an indication of a possible role played by switchbacks in preferentially heating heavy ions. Our results suggest that the presence of switchbacks can induce a deformation of the proton velocity distribution function, while the preferential heating of alpha particles could be due to a denser secondary beam and a smaller relative drift speed between the beam and core.