Local Proton Heating at Magnetic Discontinuities in the Alfvénic and Non-Alfvénic Solar Wind

Understanding how the solar wind is heated while it expands in the

inner heliosphere remains an open fundamental question. Plasma tem-

perature enhancements have been commonly associated with inter-

mittent structures or magnetic discontinuities. However, solar wind

streams differ by the type of fluctuations and turbulence, and which

mechanism that lead to proton heating are favored in different solar

wind conditions remains to be understood. Here we investigate lo-

cal proton energization at magnetic structures/discontinuities and the

corresponding kinetic signatures in velocity phase space in Alfv´enic

(high cross helicity) and non-Alfvénic (low cross helicity) wind, by us-

ing Parker Solar Probe observations at distances 0.07 <R<0.263 AU.

We complement our data analysis with 2.5 hybrid-kinetic simulations

to understand what processes are likely to contribute to the observed

proton heating and temperature anisotropy in the two types of wind.

We compare the local kinetic features and temperature enhancements 

found in Alfvénic and non-Alfvénic streams and discuss to what extent

they can be explained in terms of wave-like vs 2D turbulence dynamics.