Composition of Coronal Mass Ejections

Zurbuchen, T. H.; Weberg, M. J.; Steiger, R. von; Mewaldt, R. A.; Lepri, S. T.; Antiochos, S. K.

doi:10.3847/0004-637x/826/1/10

Cited by 59 publications

(50 citation statements)

References 53 publications

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“…It is possible, and indeed likely, that an important systematics is still at play, namely that we cannot completely exclude a small amount of residual fractionation in these regions. However, it has been shown that any unaccounted residual fractionation would go in the direction of reducing the measured metallicity, and thus, the derived metallicity Z is actually a lower limit to the photospheric metallicity [17,[21][22][23][24][25]. In view of the recent downward revisions that have led to the "solar modeling problem", such a measurement can provide a very important cross-check to the values of metallicity obtained through spectroscopy.…”

Section: In Situ Solar Wind Measurements Of Metallicitymentioning

confidence: 97%

New Solar Metallicity Measurements

Vagnozzi

2019

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In the past years, a systematic downward revision of the metallicity of the Sun has led to the "solar modeling problem", namely the disagreement between predictions of standard solar models and inferences from helioseismology. Recent solar wind measurements of the metallicity of the Sun, however, provide once more an indication of a high-metallicity Sun. Because of the effects of possible residual fractionation, the derived value of the metallicity Z = 0.0196 ± 0.0014 actually represents a lower limit to the true metallicity of the Sun. However, when compared with helioseismological measurements, solar models computed using these new abundances fail to restore agreement, owing to the implausibly high abundance of refractory (Mg, Si, S, Fe) elements, which correlates with a higher core temperature and hence an overproduction of solar neutrinos. Moreover, the robustness of these measurements is challenged by possible first ionization potential fractionation processes. I will discuss these solar wind measurements, which leave the "solar modeling problem" unsolved.

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Section: In Situ Solar Wind Measurements Of Metallicitymentioning

confidence: 97%

New Solar Metallicity Measurements

Vagnozzi

2019

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“…Among all solar wind samples in the heliosphere, solar wind from polar coronal holes (PCHs) is the least fractionated of all samples of steady state of transient solar wind flows (Zurbuchen 2007;Zurbuchen et al 2012;Zurbuchen et al 2016). Even in PCH-associated wind, there is still some fractionation, especially of insufficient collisional coupling that affects all of solar wind, but is most evident in He/H (Geiss et al 1970).…”

Section: In Situ Solar Wind Measurements Of Metallicitymentioning

confidence: 99%

Solar Models in Light of New High Metallicity Measurements from Solar Wind Data

Vagnozzi

Freese²,

Zurbuchen

2017

ApJ

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We study the impact of new metallicity measurements, from solar wind data, on the solar model. The "solar modelling problem" refers to the persisting discrepancy between helioseismological observations and predictions of solar models computed implementing state-of-the-art photospheric abundances. We critically reassess the problem, in particular considering the new set of abundances of von Steiger & Zurbuchen 2016, determined through the in situ collection of solar wind samples from polar coronal holes. This new set of abundances indicates a solar metallicity Z ≥ 0.0196 ± 0.0014, significantly higher than the currently established value. The new values hint at an abundance of volatile elements (i.e. C, N, O, Ne) close to previous results of Grevesse & Sauval 1998, whereas the abundance of refractory elements (i.e. Mg, Si, S, Fe) is considerably increased. Using the Linear Solar Model formalism, we determine the variation of helioseismological observables in response to the changes in elemental abundances, in order to explore the consistency of these new measurements with constraints from helioseismology. We find that, for observables that are particularly sensitive to the abundance of volatile elements, in particular the radius of the convective zone boundary (CZB) and the sound speed around the radius of CZB, improved agreement over previous models is obtained. Conversely, the high abundance of refractories correlates with a higher core temperature, resulting in an overproduction of neutrinos and a huge increase in the surface Helium abundance. We conclude that the "solar modelling problem" remains unsolved.

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“…On the other hand, the elemental ratios depend, in a complex way, on chromospheric temperatures, the magnetic field configuration at the origin of the plasma, and the plasma confinement time before the release (e.g., Laming (2015), and references therein). In ICMEs, increased amounts of high charge states of elements such as Fe, Ne, Si, Mg are often observed suggesting extended confinement times (e.g., Lepri et al 2001;Zurbuchen et al 2016).…”

Section: General Icme Signaturesmentioning

confidence: 99%

Coronal mass ejections and their sheath regions in interplanetary space

Kilpua

Koskinen

Pulkkinen

2017

Living Rev Sol Phys

373

360

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Interplanetary coronal mass ejections (ICMEs) are large-scale heliospheric transients that originate from the Sun. When an ICME is sufficiently faster than the preceding solar wind, a shock wave develops ahead of the ICME. The turbulent region between the shock and the ICME is called the sheath region. ICMEs and their sheaths and shocks are all interesting structures from the fundamental plasma physics viewpoint. They are also key drivers of space weather disturbances in the heliosphere and planetary environments. ICME-driven shock waves can accelerate charged particles to high energies. Sheaths and ICMEs drive practically all intense geospace storms at the Earth, and they can also affect dramatically the planetary radiation environments and atmospheres. This review focuses on the current understanding of observational signatures and properties of ICMEs and the associated sheath regions based on five decades of studies. In addition, we discuss modelling of ICMEs and many fundamental outstanding questions on their origin, evolution and effects, largely due to the limitations of single spacecraft observations of these macro-scale structures. We also present current understanding of space weather consequences of these large-scale solar wind structures, including effects at the other Solar System planets and exoplanets. We specially emphasize the different origin, properties and consequences of the sheaths and ICMEs.

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Composition of Coronal Mass Ejections

Cited by 59 publications

References 53 publications

New Solar Metallicity Measurements

New Solar Metallicity Measurements

Solar Models in Light of New High Metallicity Measurements from Solar Wind Data

Coronal mass ejections and their sheath regions in interplanetary space

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