Turbulent Properties of Interplanetary Coronal Mass Ejections Observed by Solar Orbiter in the Inner Heliosphere

TL;DR

This study analyzes the turbulent properties of 12 ICMEs observed by Solar Orbiter, revealing distinct turbulence regimes in ICMEs versus the solar wind and identifying effective diagnostics for ICME boundaries.

Contribution

It provides the first detailed turbulence analysis of ICMEs across different distances, highlighting differences in spectral properties and Alfvénicity compared to the solar wind.

Findings

ICME sheaths are the most turbulent regions.

ICME substructures exhibit Kolmogorov-like spectra.

Spectral break frequencies are higher in ICMEs.

Abstract

We investigate the turbulent properties of 12 interplanetary coronal mass ejections (ICMEs) observed by Solar Orbiter between 0.29 and 1.0 AU. We analyze fluctuation power, spectral indices, break scales, and correlations between magnetic and velocity fluctuations (v-b) to quantify differences between ICME substructures (sheath and magnetic ejecta (ME)) and the surrounding solar wind. The ICME sheath is consistently the most turbulent region at all distances. In the solar wind, Alfv\'enicity influences inertial-range scaling, resulting in either single power laws near f^-3/2 or f^-5/3, or a coexistence of both, whereas ICME substructures consistently exhibit Kolmogorov-like f^-5/3 spectra. Alfv\'enicity is reduced within ICMEs, particularly in the ejecta, indicating more balanced Alfv\'enic fluctuations than in the solar wind. Spectral breaks shift to higher frequencies in ICME regions, with average break frequencies of 0.53 +/- 0.35 Hz (solar wind), 1.87 +/- 1.46 Hz (sheath), and 1.46 +/- 1.28 Hz (ME), reflecting differences in underlying microphysical scales. Our findings highlight distinct turbulence regimes in ICMEs compared to the solar wind and support the use of fluctuation power, spectral breaks, and v-b correlations as effective diagnostics for identifying ICME boundaries.