Studies of Solar Wind and Coronal Turbulence via Radioastronomical Observations

University Of Iowa, Iowa City IA

Investigators

Abstract

The investigators will study the plasma of the outer solar corona and inner solar wind using radioastronomical instrumentation and techniques. The instruments are the Very Large Array (VLA) radiotelescope in central New Mexico, and the Very Long Baseline Array (VLBA) array of radiotelescopes distributed throughout the United States. Both instruments are facilities of the National Radio Astronomy Observatory. The research program utilizes observations of extragalactic radio sources whose lines of sight pass close to the Sun, and thus probe the corona and solar wind at distances from 4 to 35 times the solar radius. The study will make use of two types of measurements, which have proven successful in past experiments: (1) Faraday rotation measurements, and (2) measurement of turbulence-induced fluctuations in the phases of the VLBA interferometer. Among the scientific goals of the research program are (1) mapping of the coronal Faraday rotation against an extended, polarized, background radio source, to measure or constrain the global coronal magnetic field and coronal turbulence, (2) tomography of the turbulence in the inner heliosphere by observations of a constellation of extragalactic radio sources at different distances and orientations relative to the Sun, (3) the use of magnetohydrodynamic (MHD) simulations of the solar wind at the time of the observations to illuminate the physical characteristics along the lines of sight, and separately determine high speed and low speed solar wind turbulence conditions, (4) study of the anisotropy of the inertial range plasma turbulence responsible for the phase scintillation phenomena, and (5) continuation of a program to remotely determine the heliocentric distance dependence of the intensity of turbulent density fluctuations. The long-term goal of this program of research is to determine the intensity and plasma physical properties of turbulence in the inner heliosphere, so as to better assess the role this turbulence plays in coronal and solar wind dynamics. In addition, this research is closely related to that of the interstellar medium, including the study of the origin of the cosmic rays associated with supernova remnants.