A Measure of Alfvenic Turbulence during PSP encounters 6, 7, and 8

Authors: Michael Terres (The University of Alabama in Huntsville), Gang Li (The University of Alabama in Huntsville)

The solar wind is a superposition of various wave modes and structures that fully develop a turbulent cascade that permeates throughout the entire heliosphere. Alfv\'{e}n waves facilitate the cascading of the solar wind turbulence, and at the MHD scale counter-propagating Alfv\'{e}n waves are necessary for the cascading process to operate. A Kraichnan $k^{-3/2}$ spectrum can naturally develop in this scenario. However, observations from Helios, Wind, and more recently PSP, have shown that there is a predominant outward expulsion of Alfv\'{e}n waves preventing the full development of an Alfv\'{e}nic cascade. Using observations from the Parker Solar Probes encounters 6, 7, and 8, we investigate the Alfv\'{e}nic nature and magnetic structures for periods of low cross helicity and negative residual energy (i.e. $\sigma_c \sim 0$ and $\sigma_r \sim -1$). We separate magnetic structures from Alfven waves to obtain the true power from Alfv\'{e}nic turbulence. Our results will have various implications on our understanding of solar wind turbulence.