Proton/electron temperature ratio in the magnetotail

A V Artemyev,W Baumjohann,I Dandouras,R Nakamura,A Fazakerley,A A Petrukovich

doi:10.5194/angeo-29-2253-2011

Abstract

Abstract. We study the temperature ratio of protons and electrons based on statistics of Cluster observations in the Earth's magnetotail from 2001 to 2004. During these years, from June to November, the Cluster spacecraft visited the plasma sheet at the distance r~−19 RE. We use proton and electron moments collected in the central region of the plasma sheet (|Z|<5 RE). We find an average ratio of proton and electron temperatures ⟨Tp/Te ⟩ &amp;approx; 3.5. The dependence of Tp on Te can be approximated by the power-law function: Tp &amp;approx; 11Te0.62, where Tp and Te are measured in MK. A previous reported ratio ⟨Tp/Te ⟩ ~ 7 is limited to small electron temperatures <20 MK. The observations with the high electron temperature correspond to smaller values of the electron density and larger values of the proton and electron bulk velocities. A correlation between Te and curlometer current density is not found.

Highlights

IntroductionThe proton and electron temperature ratio Tp/Te in the Earth magnetotail is controlled by the relationship between various mechanisms of acceleration (and thermalization) of solar wind and ionospheric plasma
We study the temperature ratio of protons and electrons based on statistics of Cluster observations in the Earth’s magnetotail from 2001 to 2004
We find an average ratio of proton and electron temperatures Tp/Te ≈ 3.5

Summary

Introduction

The proton and electron temperature ratio Tp/Te in the Earth magnetotail is controlled by the relationship between various mechanisms of acceleration (and thermalization) of solar wind and ionospheric plasma. This ratio is important for understanding of the general energy transport in the magnetosphere. The authors showed that the proton temperature grows linearly with the electron one This result was obtained with data collected by the AMPTE/IRM spacecraft. Kaufmann et al (2005) obtained Tp/Te ≈ 6–8 using eight years of Geotail observations with approximately the same maximum Te. We use Cluster data for a similar analysis and in particular demonstrate how the ratio Tp/Te changes with taking into account electrons with temperature Te > 10 MK

Cluster observation

Findings

Conclusions