Solar Wind Charge Exchange Soft X-Ray Emissions in the Magnetosphere during an Interplanetary Coronal Mass Ejection Compared to Its Driven Sheath

Abstract

Soft X-ray emissions from solar wind charge exchange (SWCX) are applied in a recently developed approach to study the magnetosphere using panoramic soft X-ray imaging. This study represents the first attempt to distinguish magnetospheric SWCX emissions observed by XMM-Newton during the impact of an interplanetary coronal mass ejection (ICME) and its driven sheath on Earth. In addition, data from the Advanced Composition Explorer (ACE) were available during this same observational period, which is rare in previous studies. Results showed that SWCX emissions peaked during the ICME at approximately 2.3 times the mean of the observation period, although the solar wind flux decreased to a much lower level. A comparison of spectral results with ion data probed by ACE revealed that high ionization states in the ICME effectively enhanced line emission intensity for heavy ions (e.g., Ne, Mg, and Al). Thus, despite a low proton flux, elevated high-valence ion abundance in the ICME favors magnetospheric soft X-ray observations. Furthermore, the fitted X-ray flux of ion line emissions was consistent with elemental abundance ratios determined in situ by ACE, particularly for C5+, C6+, Ne9+, Mg11+, and Mg12+. This confirms the viability of spectral diagnosis of SWCX emissions as a new method for remotely analyzing high-state ion distributions in solar wind. A time-correlated or two-stage efficiency factor is further suggested to better estimate X-ray intensity during an ICME impact, which was ∼1.7 times higher in the ICME than in the sheath.

The Effect of Fast Solar Wind on Ion Distribution Downstream of Earth’s Bow Shock

“…Soft X-ray emission due to charge exchange processes also arises near the Earth's magnetopause (Sibeck et al 2018). This emission can be affected by different heavy ion abundances in ejecta (Zhang et al 2022b;Zhou et al 2023), slow and fast solar wind (Whittaker & Sembay 2016). Different local soft X-ray emission in the quasi-parallel and quasi-perpendicular sheath might arise due to different thermal velocities in both regions (discussed in Sibeck et al 2018) or by jets indenting the magnetopause (Yang et al 2024).…”

Dynamical Response of Solar Wind Charge Exchange Soft X-Ray Emission in Earth’s Magnetosphere to the Solar Wind Proton Flux

“…Here, to avoid the influence of signals other than the particle background, the energy band of 2.5-12.0 keV was used for the MOS, and the same energy band excluding 7.2-10 keV was used for the pn. After removing the first three backgrounds, we finally obtained a soft X-ray signal consisting of the target time-varying magnetospheric SWCX emission and last four stable backgrounds (Carter et al 2010;Zhang et al 2022).…”

“…Many previous works have conducted observational studies of the correlation between the magnetospheric SWCX emission intensity and the solar wind proton flux. In the case studies, this correlation was sometimes good and sometimes bad (Snowden et al 2004;Fujimoto et al 2007;Carter et al 2010;Ezoe et al 2010Ezoe et al , 2011Ishikawa et al 2013;Ishi et al 2019;Asakura et al 2021;Ishi et al 2022;Zhang et al 2022). In statistical studies, such a correlation was often weak or even nonexistent (Snowden et al 1997;Carter & Sembay 2008;Kuntz & Snowden 2008;Henley & Shelton 2010;Carter et al 2011Carter et al , 2012Henley & Shelton 2012;Kuntz et al 2015;Whittaker et al 2016).…”

Hybrid-Vlasov simulation of soft X-ray emissions at the Earth’s dayside magnetospheric boundaries

“…While there have been no wide-field-of-view soft X-ray observations of the geospace, the existence of near-Earth SWCX soft X-ray emissions has been studied in various works using data from the XMM and ROSAT astrophysics missions (e.g. Carter et al, 2010Carter et al, , 2011Cravens et al, 2001;Snowden et al, 2004;Connor & Carter, 2019;Jung et al, 2022;Zhang et al, 2022). Subsequently, modeling efforts were undertaken to understand the soft X-ray emissions detected by the ROSAT mission (Snowden et al, 1995) and to quantify the contributions of various source mechanisms (e.g., Cox, 1998;Cravens et al, 2001).…”