Significance of Bernoulli Integral Terms for the Solar Wind Protons at 1 au

Georgios Nicolaou,Mihir I Desai,George Livadiotis

doi:10.3390/app11104643

Abstract

The Bernoulli integral describes the energy conservation of a fluid along specific streamlines. The integral is the sum of individual terms that contain the plasma density, speed, temperature, and magnetic field. Typical solar wind analyses use the fluctuations of the Bernoulli integral as a criterion to identify different plasma streamlines from single spacecraft observations. However, the accurate calculation of the Bernoulli integral requires accurately determining the plasma polytropic index from the analysis of density and temperature observations. To avoid this complexity, we can simplify the calculations by keeping only the dominant terms of the integral. Here, we analyze proton plasma and magnetic field observations obtained by the Wind spacecraft at 1 au, during 1995. We calculate the Bernoulli integral terms and quantify their significance by comparing them with each other. We discuss potential simplifications of the calculations in the context of determining solar wind proton thermodynamics using single spacecraft observations.

Highlights

We investigate the significance of the Bernoulli integral terms in solar wind proton plasma
Our analysis shows that the second term of the non-isothermal Bernoulli integral and its uncertainty may become significant for values γ → 1
We examine the significance of the thermal term against the dynamic term as calculated for the solar wind protons at ~1 au assuming γ = 5/6 and γ = 5/4, respectively

Summary

Introduction

Sci. 2021, 11, The solar wind is a very dynamic system, with plasma and electromagnetic field fluctuations occurring in a wide range of scales (e.g., [1], and references therein). Plasma and field measurements should be analyzed properly in order to understand the mechanisms that govern solar wind and space plasmas in general. Certain dynamical processes need to be investigated along specific streamlines. If plasma observations are obtained in different streamlines, plasmas with entirely different properties may end up being analyzed, regardless of the mechanisms acting on them. Different streamlines in the solar wind may contain plasmas that originated in vastly different structures of the Sun. if we do not analyze specific streamlines separately, the observed plasma variations may reflect the different plasma sources and not the effects of interesting dynamical processes

Results

Discussion

Conclusion