A statistical study of the plasma and composition distribution inside magnetic clouds: 1998-2011

Abstract

A comprehensive analysis of plasma and composition characteristics inside magnetic clouds (MCs) observed by the Advanced Composition Explorer (ACE) spacecraft from 1998 February to 2011 August is presented. The results show that MCs have specific interior structures, and MCs of different speeds show differences in composition and structure. Compared with the slow MCs, fast MCs have enhanced mean charge states of iron, oxygen, silicon, magnesium, ${\mathrm{O}}^{7+}/{\mathrm{O}}^{6+}$, ${\mathrm{C}}^{6+}/{\mathrm{C}}^{5+}$, ${\mathrm{C}}^{6+}/{\mathrm{C}}^{4+}$ and $\mathrm{F}{\mathrm{e}}^{\ge 16+}/F{\mathrm{e}}_{\mathrm{total}}$ values. For ionic species in fast MCs, a higher atomic number represents a greater enhancement of mean charge state than slow MCs. We also find that both the fast and slow MCs display bimodal structure distribution in the mean iron charge state ($⟨\mathrm{Q}⟩\mathrm{Fe}$), which suggests that the existence of flux rope prior to the eruption is common. Furthermore, the $⟨\mathrm{Q}⟩\mathrm{Fe}$, $\mathrm{F}{\mathrm{e}}^{\ge 16+}/F{\mathrm{e}}_{\mathrm{total}}$, and ${\mathrm{O}}^{7+}/{\mathrm{O}}^{6+}$ ratio distribution inside fast MCs have the feature that the posterior peak is higher than the anterior one. This result agrees with the "standard model" for CME/flares, by which magnetic reconnection occurs beneath the flux rope, thereby ionizing the ions of the posterior part of flux rope sufficiently by high-energy electron collisions or by direct heating in the reconnection region.

arXiv comment11 pages,3 figures

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Cited by in corpus (7)

• Characteristics and applications of interplanetary coronal mass ejection composition
• Solar Cycle Dependence of ICME Composition
• Comparison of Helium Abundance between ICMEs and Solar Wind near 1 AU
• Comparative Analyses of Plasma Properties and Composition in Two Types of Small-Scale Interplanetary Flux-ropes
• Composition Comparison between ICMEs from Active Regions and Quiet-Sun Regions
• The Inhomogeneity of Composition along the Magnetic Cloud Axis
• Drop of solar wind at the end of the 20th century