Statistical study of MHD turbulence straddling the Alfven surface.
Abstract
Driven by the internal dynamics of the Sun, the solar wind expands into the interplanetary medium to fill the increasing volume of the heliosphere. A point of fundamental physical significance during the expansion is the locus at which the radial solar wind speed V_{SW} equals the Alfven speed V_{A}, distinguishing the magnetically dominated sub-Alfvenic, coronal flow M_{A} ≡ V_{sw}/V_{A} ≪ 1 from the super-Alfvenic solar wind plasma by dynamical means, namely the "Alfven region". During its latest perihelia, the Parker Solar Probe mission has encountered several extended sub-Alfvenic regions providing us with unprecedented in-situ measurements in the vicinity of the Alfven-zone. These observations will ultimately enable us to explore the consequences of the Alfven-zone in processes such as the heating of the solar corona, as well as the generation and subsequent acceleration of the solar wind. In this work, a statistical study comparing the properties of turbulence straddling the Alfven surface during encounters E_{8}, E_{9} & E_{10} of Parker Solar Probe is presented. The degree of intermittency of the magnetic and velocity field, as well as the Alfvenicity of the fluctuations, magnetic compressibility, wavevector anisotropy, are examined.
- Publication:
-
44th COSPAR Scientific Assembly. Held 16-24 July
- Pub Date:
- July 2022
- Bibcode:
- 2022cosp...44.1474S