A high charge state Coronal Mass Ejection seen through solar wind charge exchange emission as detected by XMM-Newton

TL;DR

This paper analyzes XMM-Newton observations of variable diffuse X-ray emission caused by solar wind charge exchange during a CME, revealing detailed spectral signatures and linking them to solar wind data.

Contribution

It provides the first detailed spectral analysis of a CME-related SWCX event with rich emission lines, connecting X-ray data to solar wind measurements.

Findings

Detection of prominent OVIII emission line in SWCX spectrum

Observation of highly ionized silicon and iron indicating CME origin

Correlation of X-ray emission with solar wind flux increase from ACE and Wind

Abstract

We present the analysis of an observation by XMM-Newton that exhibits strongly variable, low-energy diffuse X-ray line emission. We reason that this emission is due to localised solar wind charge exchange (SWCX), originating from a passing cloud of plasma associated with a Coronal Mass Ejection (CME) interacting with neutrals in the Earth's exosphere. This case of SWCX exhibits a much richer emission line spectrum in comparison with previous examples of geocoronal SWCX or in interplanetary space. We show that emission from OVIII is very prominent in the SWCX spectrum. The observed flux from oxygen ions of 18.9 keV cm-2 s-1 sr-1 is consistent with SWCX resulting from a passing CME. Highly ionised silicon is also observed in the spectrum, and the presence of highly charged iron is an additional spectral indicator that we are observing emission from a CME. We argue that this is the same event detected by the solar wind monitors ACE and Wind which measured an intense increase in the solar wind flux due to a CME that had been released from the Sun two days previous to the XMM-Newton observation.