Embedded Coherent Structures from Magnetohydrodynamics to Sub-ion Scales in Turbulent Solar Wind at 0.17 au

We study intermittent coherent structures in solar wind turbulence from MHD to kinetic plasma scales using Parker Solar Probe data during its first perihelion (at 0.17 au) in the highly Alfv & eacute;nic slow solar wind. We detect coherent structures using Morlet wavelets. For the first time, we apply a multiscale analysis in physical space. At MHD scales within the inertial range, times scales tau is an element of (1, 102) s, we find (i) current sheets including switchback boundaries and (ii) Alfv & eacute;n vortices. Within these events are embedded structures at smaller scales: typically Alfv & eacute;n vortices at ion scales, tau is an element of (0.08, 1) s, and compressible vortices at sub-ion scales, tau is an element of 8(10-3, 10-2) s. The number of coherent structures grows toward smaller scales: we observe similar to 200 events during a 5 hr time interval at MHD scales, similar to 103 at ion scales, and similar to 104 at sub-ion scales. In general, there are multiple structures of ion and sub-ion scales embedded within one MHD structure. There are also examples of ion and sub-ion scale structures outside MHD structures. To quantify the relative importance of different types of structures, we do a statistical comparison of the observed structures with the expectations of models of the current sheets and vortices. The results show the dominance of Alfv & eacute;n vortices at all scales in contrast to the widespread view of the dominance of current sheets. This means that Alfv & eacute;n vortices are important building blocks of Alfv & eacute;nic solar wind turbulence.