Joint Physics Dept.–Inst. for Space Weather Sci. Colloquium

September 16, Thursday (** SPECIAL DAY**)

Turbulence and the Heating of the Solar Corona

Prof. Gary Zank, Univ. of Alabama

(Solar & Terrestrial Physics, Host: Wang)

**SPECIAL TIME: 1pm - 2pm, door opening at 12:45pm

Room: ECE 202

A primary goal of the Parker Solar Probe and the Solar Orbiter missions is to determine the heating mechanism that accounts for the very high temperature of the plasma in the solar corona. Various heating mechanisms have been suggested but one that is gaining increasing credence is associated with the dissipation of low frequency magnetohydrodynamic (MHD) turbulence. However, the MHD turbulence models come in several flavors. Two basic MHD turbulence transport models have been developed, one in which outwardly propagating Alfvén waves experience reflection from the large-scale flow and density gradients associated with the solar corona, and the resulting counter-propagating Alfvén waves couple nonlinearly to produce quasi-2D turbulence that dissipates and heats the corona. The second approach eschews a dominant outward flux of Alfvén waves but argues instead that quasi-2D turbulence dominates the lower coronal plasma, is generated in the constantly upwelling magnetic carpet, experiencing dissipation as it is advected through the corona, leading to temperatures in the corona that exceed a million degrees. We discuss the two theoretical turbulence models and describe the basic modeling that has been done. We will relate current Parker Solar Probe observations to the basic predictions of both models but perhaps even more interesting, since protons in the outer solar corona remain coupled to neutral hydrogen (via photoionization, collisional ionization, radiative recombination, and charge-exchange), Metis measurements will characterize the electron and the proton components in a unique and important way at distances not accessible to in situ Parker Solar Probe or in situ Solar Orbiter plasma measurements. We present some recent results of a Solar Orbiter – Parker Solar Probe quadrature that illustrate these opportunities.