<i>ACE</i>/SWICS OBSERVATIONS OF HEAVY ION DROPOUTS WITHIN THE SOLAR WIND

Weberg, M. J.; Zurbuchen, T. H.; Lepri, S. T.

doi:10.1088/0004-637x/760/1/30

Cited by 28 publications

(29 citation statements)

References 36 publications

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“…The observational evidence from a large number of Hinode data analyses indicates that the continuous expansion of active regions and its interaction with nearby open field can lead to the process of interchange reconnection, and therefore such outflows represent a possible contribution to the SSW2 (see Section 2.1.1). Blobs flowing along streamer stalks (e.g., Sheeley et al, 1997) and depleted elemental abundances near the heliospheric current sheet (Suess et al, 2009;Weberg et al, 2012) support the idea of streamer material released by field pinching at the top of the streamer cusp/current sheet (SSW3 scenario).…”

Section: Discussionmentioning

confidence: 82%

Slow Solar Wind: Observations and Modeling

et al. 2016

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While it is certain that the fast solar wind originates from coronal holes, where and how the slow solar wind (SSW) is formed remains an outstanding question in solar physics even in the post-SOHO era. The quest for the SSW origin forms a major objective for the planned future missions such as the Solar Orbiter and Solar Probe Plus. Nonetheless, results from spacecraft data, combined with theoretical modeling, have helped to investigate many aspects of the SSW. Fundamental physical properties of the coronal plasma have been derived from spectroscopic and imaging remote-sensing data and in situ data, and these results have provided crucial insights for a deeper understanding of the origin and acceleration of the SSW. Advanced models of the SSW in coronal streamers and other structures have been developed using 3D MHD and multi-fluid equations. However, the following questions remain open: What are the source regions and their contributions to the SSW? What is the role of the magnetic topology in the corona for the origin, acceleration and energy deposition of the SSW? What are the possible acceleration and heating mechanisms for the SSW? The aim of this review is to present insights on the SSW origin and formation gathered from the discussions at the International Space Science Institute (ISSI) by the Team entitled "Slow solar wind sources and acceleration mechanisms in the corona" held in Bern (Switzerland) in March 2014 and 2015.

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Section: Discussionmentioning

confidence: 82%

Slow Solar Wind: Observations and Modeling

et al. 2016

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“…Interestingly enough, Feldman & Widing further indicate that there are cases where Ne is enhanced over the photosphere, consistent with our interpretation. In contrast, large-scale loops near coronal boundaries, as identified by an elemental composition that reflects gravitational settling, routinely and repeatedly become sources of solar wind plasma (Weberg et al 2012), as predicted by the S-web theory. Our results also imply that the slow wind must be released from loops whose lifetimes are of intermediate timescale, long enough to build up a significant FIP effect but not as long as the several-day lifetime of active region loops.…”

Section: Discussionmentioning

confidence: 99%

Composition of Coronal Mass Ejections

Zurbuchen

Weberg

Steiger

et al. 2016

ApJ

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We analyze the physical origin of plasmas that are ejected from the solar corona. To address this issue, we perform a comprehensive analysis of the elemental composition of interplanetary coronal mass ejections (ICMEs) using recently released elemental composition data for Fe, Mg, Si, S, C, N, Ne, and He as compared to O and H. We find that ICMEs exhibit a systematic abundance increase of elements with first ionization potential (FIP) < 10 eV, as well as a significant increase of Ne as compared to quasi-stationary solar wind. ICME plasmas have a stronger FIP effect than slow wind, which indicates either that an FIP process is active during the ICME ejection or that a different type of solar plasma is injected into ICMEs. The observed FIP fractionation is largest during times when the Fe ionic charge states are elevated above Q Fe > 12.0. For ICMEs with elevated charge states, the FIP effect is enhanced by 70% over that of the slow wind. We argue that the compositionally hot parts of ICMEs are active region loops that do not normally have access to the heliosphere through the processes that give rise to solar wind. We also discuss the implications of this result for solar energetic particles accelerated during solar eruptions and for the origin of the slow wind itself.

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“…For solar wind plasma compositions, various processes in the low coronal can affect the abundance of ions, based on their ionization, gravitational settling and transport histories. Examples of fractionation processes at work are collisional coupling (especially for He), First Ionization Potential (FIP) fractionation (Hovestadt et al 1973;Bochsler 2000) presumably operating in the low solar atmosphere, and gravitational settling (Geiss et al 1970;Weberg et al 2012).…”

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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ACE/SWICS OBSERVATIONS OF HEAVY ION DROPOUTS WITHIN THE SOLAR WIND

Cited by 28 publications

References 36 publications

Slow Solar Wind: Observations and Modeling

Slow Solar Wind: Observations and Modeling

Composition of Coronal Mass Ejections

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

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