Characteristics and applications of interplanetary coronal mass ejection composition

TL;DR

This review discusses how in situ measurements of ICME composition, including elemental abundances and charge states, enhance understanding of CME origins and eruption processes, complementing remote sensing data.

Contribution

It provides a comprehensive overview of ICME composition analysis and demonstrates its applications in studying CME origins and eruption mechanisms.

Findings

Elemental abundance ratios diagnose CME plasma origin.

Charge state ratios reveal CME electron temperatures.

ICME composition helps understand filament plasma and flux rope eruptions.

Abstract

In situ measurements of interplanetary coronal mass ejection (ICME) composition, including elemental abundances and charge states of heavy ions, open a new avenue to study coronal mass ejections (CMEs) besides remote-sensing observations. The ratios between different elemental abundances can diagnose the plasma origin of CMEs (e.g., from the corona or chromosphere/photosphere) due to the first ionization potential (FIP) effect, which means elements with different FIP get fractionated between the photosphere and corona. The ratios between different charge states of a specific element can provide the electron temperature of CMEs in the corona due to the freeze-in effect, which can be used to investigate their eruption process. In this review, we first give an overview of the ICME composition and then demonstrate their applications in investigating some important subjects related to CMEs, such as the origin of filament plasma and the eruption process of magnetic flux ropes. Finally, we point out several important questions that should be addressed further for better utilizing the ICME composition to study CMEs.