Turbulent density fluctuations in the solar wind

Abstract

Measurements of density electric field magnetic field in the solar wind haverevealed fluctuations in these quantities spanning a large range of scales indicative of turbulence The nature of turbulence in the solar wind has beenthe subject of intense research as it plays an essential role in several aspects ofplasma behavior such as solar wind acceleration and heating of the extendedsolar corona and solar wind While considerable progress has been made thenature of turbulent dissipation especially in the extended solar corona andthe role of density turbulence therein remains a significant unsolved problem This thesis is concerned with the nature of density turbulence in the extendedsolar corona especially near the inner dissipation scale Electromagnetic waves traversing the solar wind experience scatteringdue to turbulent density fluctuations which leads to a wide variety of observedphenomena such as intensity scintillations angular broadening pulsesmearing etc These observations provide useful constraints on the quantitiescharacterizing density turbulence Chapter 2 provides an overview of thephenomenon of angular broadening Treatments of the radio scattering due to density turbulence in the solarwind typically employ asymptotic approximations to the phase structurefunction In chapter 3 we use a general structure function GSF that straddlesthe asymptotic limits and quantify the relative error introduced by theapproximations We show that the regimes where GSF predictions are accuratethan those of its asymptotic approximations is not only of practicalrelevance but are where inner scale effects influence the estimate of thescatter broadening Thus we propose that GSF should henceforth be usedfor scatter broadening calculations and estimates of quantities characterizingdensity turbulence in the solar corona and solar wind In the next part of this newline newline