Influence of heavy ions on the high‐speed solar wind

Li, Xing; Esser, Ruth; Habbal, Shadia Rifai; Hu, Youqiu

doi:10.1029/97ja01448

Cited by 38 publications

(30 citation statements)

References 28 publications

(14 reference statements)

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“…The faster O vi outflow velocity, together with the O vi kinetic temperatures that are much higher than the hydrogen temperatures (see above), suggest that the absorption of Alfvén waves at the ion cyclotron frequency, as proposed by several authors (e.g., Li et al 1997Li et al , 1999Tu & Marsch 1997;Cranmer et al 1999aCranmer et al , 1999bHu & Habbal 1999) to explain both the high kinetic temperatures and the high ion outflow velocities observed in coronal holes, might also occur inside streamers, at least above a certain height.…”

Section: Diagnostics Of Physical Parametersmentioning

confidence: 94%

Physical parameters of a mid-latitude streamer during the declining phase of the solar cycle

Spadaro

Susino

Ventura

et al. 2007

A&A

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Context. Investigating the physical properties of solar coronal streamers is important for understanding their role in the global magnetic structure of the extended solar atmosphere, as well as in the generation of the slow solar wind. Aims. We hope to contribute as completely as possible to the ongoing SOHO instruments campaign devoted to the study of the physical characteristics of coronal streamers at various heliocentric distances. Results. Electron densities and temperatures, H i and O vi kinetic temperatures, and outflow velocities were derived from the line intensities and widths, as well as from the O vi line intensity ratio in the 1.6−5 R range of heights, limited to the central region of the streamer. To our knowledge, the H i outflow velocities obtained in this work are the first ones determined inside a streamer structure. They are significantly lower than those of the O vi ions. This, together with the O vi kinetic temperatures that are much higher than the H i ones, suggest that the absorption of Alfvén waves at the ion cyclotron frequency might also occur inside streamers. Methods. We analyzed ultraviolet H iConclusions. In comparison with other streamers described in the literature, the structure examined in this work generally exhibits lower electron density and neutral hydrogen kinetic temperature. Conversely, the O vi kinetic temperature and outflow velocity radial profiles are consistent with the results for the other examined streamers.

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Section: Diagnostics Of Physical Parametersmentioning

confidence: 94%

Physical parameters of a mid-latitude streamer during the declining phase of the solar cycle

Spadaro

Susino

Ventura

et al. 2007

A&A

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“…A high T p is a genuine property of these models, and thus flow velocities of up to 800 km s −1 are readily obtained within 10 R by a deposition of heat or momentum within a fraction of a solar radius above the Sun's surface. Li et al (1997) recently studied the influence of heavy ions on the fast wind in a three-fluid model in detail. They concluded that preferential heating of heavy ions, in particular of α particles, has an impact on the bulk flow that must be considered in wind models.…”

Section: Models With Hot Ions In the Inner Coronamentioning

confidence: 99%

Observations of the Sun at Vacuum-Ultraviolet Wavelengths from Space. Part II: Results and Interpretations

et al. 2007

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In Part I of this review, the concepts of solar vacuum-ultraviolet (VUV) observations were outlined together with a discussion of the space instrumentation used for the investigations. A section on spectroradiometry provided some quantitative results on the solar VUV radiation without considering any details of the solar phenomena leading to the radiation. Here, in Part II, we present solar VUV observations over the last decades and their interpretations in terms of the plasma processes and the parameters of the solar atmosphere, with emphasis on the spatial and thermal structures of the chromosphere, transition region and corona of the quiet Sun. In addition, observations of active regions, solar flares and prominences are included as well as of small-scale events. Special sections are devoted to the elemental composition of the solar atmosphere and theoretical considerations on the heating of the corona and the generation of the solar wind.

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“…In addition, the heavy ions are deduced to be significantly hotter and faster than the protons (Li et al 1997).…”

Section: Introductionmentioning

confidence: 99%

Sensitivity of solar off-limb line profiles to electron density stratification and the velocity distribution anisotropy

Raouafi¹,

Solanki²

2005

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The effect of the electron density stratification on the intensity profiles of the H i Ly-α line and the O vi and Mg x doublets formed in solar coronal holes is investigated. We employ an analytical 2-D model of the large scale coronal magnetic field that provides a good representation of the corona at the minimum of solar activity. We use the mass-flux conservation equation to determine the outflow speed of the solar wind at any location in the solar corona and take into account the integration along the line of sight (LOS). The main assumption we make is that no anisotropy in the kinetic temperature of the coronal species is considered. We find that at distances greater than 1 R from the solar surface the widths of the emitted lines of O vi and Mg x are sensitive to the details of the adopted electron density stratification. However, Ly-α, which is a pure radiative line, is hardly affected. The calculated total intensities of Ly-α and the O vi doublet depend to a lesser degree on the density stratification and are comparable to the observed ones for most of the considered density models. The widths of the observed profiles of Ly-α and Mg x are well reproduced by most of the considered electron density stratifications, while for the O vi doublet only few stratifications give satisfying results. The densities deduced from SOHO data result in O vi profiles whose widths and intensity ratio are relatively close to the values observed by UVCS although only isotropic velocity distributions are employed. These density profiles also reproduce the other considered observables with good accuracy. Thus the need for a strong anisotropy of the velocity distribution (i.e. a temperature anisotropy) is not so clear cut as previous investigations of UVCS data suggested. However, these results do not rule completely out the existence of some degree of anisotropy in the corona. The results of the present computations also suggest that the data can also be reproduced if protons, heavy ions and electrons have a common temperature, if the hydrogen and heavy-ion spectral lines are also non-thermally broadened by a roughly equal amount.

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Influence of heavy ions on the high‐speed solar wind

Cited by 38 publications

References 28 publications

Physical parameters of a mid-latitude streamer during the declining phase of the solar cycle

Physical parameters of a mid-latitude streamer during the declining phase of the solar cycle

Observations of the Sun at Vacuum-Ultraviolet Wavelengths from Space. Part II: Results and Interpretations

Sensitivity of solar off-limb line profiles to electron density stratification and the velocity distribution anisotropy

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