Helium abundance and speed difference between helium ions and protons in the solar wind from coronal holes, active regions, and quiet Sun

Fu, Hui; Madjarska, M. S.; Li, Bo; Xia, Lidong; Huang, Zhaoqin

doi:10.1093/mnras/sty1211

Cited by 26 publications

(28 citation statements)

References 102 publications

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“…From our study, it is not clear which of these theories is most consistent with PSP observations, but recent work by Fu et al (2018) suggests that these two mechanisms can work in parallel, with the open field line mechanism being more important within coronal holes. A more complicated framework for solar wind release and acceleration has been proposed by Viall & Borovsky (2020) to address observed cases that are not easily resolved by these theories.…”

Section: Low α-Particle Abundancecontrasting

confidence: 57%

Plasma properties, switchback patches, and low α-particle abundance in slow Alfvénic coronal hole wind at 0.13 au

Woolley

Matteini

McManus

et al. 2021

Monthly Notices of the Royal Astronomical Society

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The Parker Solar Probe (PSP) mission presents a unique opportunity to study the near-Sun solar wind closer than any previous spacecraft. During its fourth and fifth solar encounters, PSP had the same orbital trajectory, meaning that solar wind was measured at the same latitudes and radial distances. We identify two streams measured at the same heliocentric distance (∼0.13au) and latitude (∼-3.5○) across these encounters to reduce spatial evolution effects. By comparing the plasma of each stream, we confirm that they are not dominated by variable transient events, despite PSP’s proximity to the heliospheric current sheet. Both streams are consistent with a previous slow Alfvénic solar wind study once radial effects are considered, and appear to originate at the Southern polar coronal hole boundary. We also show that the switchback properties are not distinctly different between these two streams. Low α-particle abundance (∼ 0.6 %) is observed in the encounter 5 stream, suggesting that some physical mechanism must act on coronal hole boundary wind to cause α-particle depletion. Possible explanations for our observations are discussed, but it remains unclear whether the depletion occurs during the release or the acceleration of the wind. Using a flux tube argument, we note that an α-particle abundance of ∼ 0.6 % in this low velocity wind could correspond to an abundance of ∼ 0.9 % at 1 au. Finally, as the two streams roughly correspond to the spatial extent of a switchback patch, we suggest that patches are distinct features of coronal hole wind.

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Section: Low α-Particle Abundancecontrasting

confidence: 57%

Plasma properties, switchback patches, and low α-particle abundance in slow Alfvénic coronal hole wind at 0.13 au

Woolley

Matteini

McManus

et al. 2021

Monthly Notices of the Royal Astronomical Society

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“…Moreover, this type of wind usually has a relatively steady alpha particle abundance, and the alpha particles often stream faster than protons with a differential velocity comparable to the local Alfvén velocity (Marsch et al 1982b;Fu et al 2018). The SBO wind refers to the plasma originating from either the edge of a coronal hole near a streamer belt or the edge of an open streamer, while the SRR wind involves the plasma from the tip of the open streamer where a magnetic sector reversal exists (Gosling et al 1981;Antonucci et al 2005;Marsch 2006;Foullon et al 2009).…”

Section: Data and Analysis Methodsmentioning

confidence: 99%

“…Both the SBO and SRR winds contribute to the slow solar wind with a speed often 400 km s −1 (Schwenn 2006;Xu & Borovsky 2015). Compared with the CHO wind, they are more variable and filamentary, and have a low proton temperature, high plasma density, low alpha particle abundance, and small alpha−proton differential velocity (Schwenn 2006;Fu et al 2018). The ejecta concerns the transient wind denoted as coronal mass ejections that may prevail during the solar maximum (Schwenn 2006;Chen 2011).…”

Section: Data and Analysis Methodsmentioning

confidence: 99%

“…However, this deduction, to the best our knowledge, has not been examined by any in situ observation. Moreover, the presence of V d with a direction toward the Sun is possible, especially for the slow solar wind (e.g., Fu et al 2018). In this regard, some investigation on the occurrence of ECWs with various directions of V d should be desirable.…”

Section: Introductionmentioning

confidence: 99%

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Effects of Alpha–Proton Differential Flow on Proton Temperature Anisotropy Instabilities in the Solar Wind: Wind Observations

Zhao

Feng

et al. 2019

ApJ

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Plasma kinetic waves and alpha−proton differential flow are two important subjects on the topic of evolution of the solar wind. Based on the Wind data during 2005−2015, this paper reports that the occurrence of electromagnetic cyclotron waves (ECWs) near the proton cyclotron frequency significantly depends on the direction of alpha−proton differential flow V d . As V d rotates from anti-Sunward direction to Sunward direction, the occurrence rate of ECWs as well as the percentage of left-handed (LH) polarized ECWs decreases considerably. In particular, it is shown that the dominant polarization changes from LH polarization to right-handed polarization during the rotation. The investigation on proton and alpha particle parameters ordered by the direction of V d further illustrates that large kinetic energies of alpha−proton differential flow correspond to high occurrence rates of ECWs. These results are well consistent with theoretical predictions for effects of alpha−proton differential flow on proton temperature anisotropy instabilities.

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“…Solar wind is a stream of charged particles released from the corona, and can be divided into fast and slow streams taking speed as criterion. It is generally accepted that fast wind originates from coronal holes, and slow wind can emanate from active regions and/or quiet-Sun regions (e.g., Zhao et al 2017;Fu et al 2018). Two classes of models have been proposed to explain the origin of solar wind, including the wave-turbulence-driven (WTD) models, which suggest the solar wind being released along open magnetic field lines directly (Hollweg 1986;Cranmer et al 2007;Verdini et al 2009), and the reconnection loop opening (RLO) models, which propose the stream escaping through magnetic reconnections between open and closed magnetic field lines (Fisk et al 1999;Fisk 2003;Woo et al 2004) and work for solar wind originating from closed-field region.…”

Section: Introductionmentioning

confidence: 99%

Comparison of Helium Abundance between ICMEs and Solar Wind near 1 AU

Song,

Cheng,

et al. 2021

Preprint

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The Helium abundance, defined as A He = n He /n H × 100, is ∼8.5 in the photosphere and seldom exceeds 5 in fast solar wind. Previous statistics have demonstrated that A He in slow solar wind correlates tightly with sunspot number. However, less attention is paid to the solar cycle dependence of A He within interplanetary coronal mass ejections (ICMEs) and comparing the A He characteristics of ICMEs and solar wind. In this paper we conduct a statistical comparison of Helium abundance between ICMEs and solar wind near 1 AU with observations of Advanced Composition Explorer from 1998 to 2019, and find that the ICME A He also exhibits the obvious solar cycle dependence. Meanwhile, we find that the A He is obviously higher within ICMEs compared to solar wind, and the means within 37% and 12% of ICMEs exceed 5 and 8.5, respectively. It is interesting to answer where and how the high Helium abundance originates. Our statistics demonstrate that 21% (3%) of ICME (slow wind) A He data points exceed 8.5 around solar maximum, which decreases dramatically near minimum, while no such high A He values appear in the fast wind throughout the whole solar cycle. This indicates that the high A He (e.g., >8.5) emanates from active regions as more ICMEs and slow wind originates from active regions around maximum, and supports that both active regions and quiet-Sun regions are the sources of slow wind. We suggest that the high A He from active regions could be explained by means of the magnetic loop confinement model and/or photoionization effect.

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Helium abundance and speed difference between helium ions and protons in the solar wind from coronal holes, active regions, and quiet Sun

Cited by 26 publications

References 102 publications

Plasma properties, switchback patches, and low α-particle abundance in slow Alfvénic coronal hole wind at 0.13 au

Plasma properties, switchback patches, and low α-particle abundance in slow Alfvénic coronal hole wind at 0.13 au

Effects of Alpha–Proton Differential Flow on Proton Temperature Anisotropy Instabilities in the Solar Wind: Wind Observations

Comparison of Helium Abundance between ICMEs and Solar Wind near 1 AU

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