Connection of Turbulence with Polytropic Index in the Solar Wind Proton Plasma

Livadiotis Livadiotis

doi:10.3390/e21111041

Abstract

This paper improves our understanding of the interplay of the proton plasma turbulent heating sources of the expanding solar wind in the heliosphere. Evidence is shown of the connections between the polytropic index, the rate of the heat absorbed by the solar wind, and the rate of change of the turbulent energy, which heats the solar wind in the inner and outer heliosphere. In particular, we: (i) show the theoretical connection of the rate of a heat source, such as the turbulent energy, with the polytropic index and the thermodynamic process; (ii) calculate the effect of the pick-up protons in the total proton temperature and the relationship connecting the rate of heating with the polytropic index; (iii) derive the radial profiles of the solar wind heating in the outer and inner heliosphere; and (iv) use the radial profile of the turbulent energy in the solar wind proton plasma in the heliosphere, in order to show its connection with the radial profiles of the polytropic index and the heating of the solar wind.

Highlights

Solar wind protons flow throughout the supersonic heliosphere under expansive cooling and turbulent heating
The purpose of this paper is to show the connection between the polytropic index and the turbulent energy rate in the solar wind proton plasma, by comparing their corresponding radial profiles in the outer and inner heliosphere
The paper improved the understanding of the interplay and partition of the sources of proton plasma turbulent heating of the expanding solar wind in the inner and outer heliosphere

Summary

Introduction

Solar wind protons flow throughout the supersonic heliosphere under expansive cooling and turbulent heating. Since the turbulent heating affects the solar wind thermodynamic process and polytropic index value, we may ask: Are the radial profiles of polytropic index γ(R) and the rate of change of the turbulent energy dEt /dt related to each other? The purpose of this paper is to show the connection between the polytropic index and the turbulent energy rate in the solar wind proton plasma, by comparing their corresponding radial profiles in the outer and inner heliosphere. We show the connection between the radial profiles of the polytropic index and the turbulent heating of the solar wind in the outer and inner heliosphere.

Thermodynamics of Polytropes

Effect of Pick-up Ions

Polytropic Index Versus Turbulent Energy

Conclusions