Solar Wind Turbulence Around Mars: Relation Between The Energy Cascade Rate And The Proton Cyclotron Waves Activity

TL;DR

This study estimates the energy cascade rate in the plasma upstream of Mars using MAVEN data, revealing a slight increase in cascade activity when proton cyclotron waves are present, and characterizes the nature of turbulent fluctuations.

Contribution

First estimation of the MHD-scale energy cascade rate around Mars using MAVEN data and an exact MHD turbulence relation, highlighting the influence of proton cyclotron waves.

Findings

Energy cascade rate is slightly higher with proton cyclotron waves.

Turbulent fluctuations are mainly Alfvénic and non-Alfvénic in magnetic dominant regimes.

Presence of both Alfvénic and non-Alfvénic fluctuations in the plasma.

Abstract

The first estimation of the incompressible energy cascade rate at magnetohydrodynamic (MHD) scales is obtained in the plasma upstream of the Martian bow shock, using MAVEN observations and an exact relation derived for MHD turbulence. The energy cascade rate is computed for events with and without proton cyclotron wave (PCW) activity, for time intervals when MAVEN was in the solar wind with no magnetic connection to the bow shock. It is shown that the nonlinear cascade of energy at the MHD scales is slightly amplified when PCWs are present in the plasma. The analysis of the normalized cross helicity and residual energy for the turbulent fluctuations shows the presence of Alfv\'enic and non-Alfv\'enic fluctuations in a magnetic dominant regime for the majority of the cases.