Solar Wind Helium Abundance as a Function of Speed and Heliographic Latitude: Variation through a Solar Cycle

Kasper, J. C.; Stevens, Michael L.; Lazarus, A. J.; Steinberg, J. T.; Ogilvie, K. W.

doi:10.1086/510842

Cited by 173 publications

(253 citation statements)

References 36 publications

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“…Labels indicate the velocity bin in km/s corresponding to the data points. The ordering of the helium abundances according to velocities corresponds to expectations for a Coulomb drag model, and long-range averages of He/H abundance ratios observed by Aellig et al (2001) and by Kasper et al (2007). The large scatter of data points in the higher velocity bins could possibly be caused by an admixture of CME-ejecta.…”

Section: H I Given Insupporting

confidence: 71%

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Solar abundances of oxygen and neon derived from solar wind observations

Bochsler¹

2007

A&A

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Context. Recently, a revision of the solar abundances of C, N, and O to substantially lower values has led to a controversy on solar opacities in the solar standard model and to the suggestion to revise the solar abundance of neon upward by as much as a factor of 1.6 leading to enhanced solar neon/oxygen abundance ratios by a factor of 3. Neon and oxygen are neighboring elements with easily defined charged states in the solar wind, and they have been well identified and measured for over two decades in the solar wind under many circumstances and with several instruments. The solar wind Ne/O ratio is 0.14 with a conservative error estimate of ±0.03, consistent with the coronal value derived from solar energetic particle measurements. Aims. We investigate, whether solar wind observations are consistent with the newly proposed elemental solar abundances of neon and oxygen. Methods. The solar helium abundance has been derived from helioseismological observations. Helium and neon abundances in the solar wind have been well determined with the Apollo Foil experiments and, more recently, confirmed with the Genesis sample return mission. With these observations and the neon/oxygen solar wind abundance ratio determined by in-situ mass-spectrometry and using a simple theoretical model of Coulomb-drag fractionation for the solar wind, we estimate solar abundances for neon and oxygen. Results. From the variability of the helium/oxygen and the helium/neon ratio in the solar wind and from theoretical considerations, we conclude that the helium/neon ratio in the outer solar convective zone is 900 ± 110. Our best estimates of the solar neon and oxygen abundances in logarithmic dex-units are [Ne] = 7.96 ± 0.13, and [O] = 8.87 ± 0.11. Conclusions. Our solar neon/oxygen abundance ratio is consistent with the ratio derived from EUV-spectra from SOHO/CDS. However, our absolute abundance for oxygen is only marginally compatible with the newly derived value for oxygen, and our neon value is clearly incompatible with the recently proposed enhancement of the solar neon abundance.

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Section: H I Given Insupporting

confidence: 71%

“…Substantial observational evidence indicates that this mechanism operates in the context of variably diverging open magnetic flux tubes (see Kasper et al 2007, for a more extensive discussion).…”

Section: Coulomb Drag Versus Fip-effectmentioning

confidence: 99%

Solar abundances of oxygen and neon derived from solar wind observations

Bochsler¹

2007

A&A

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“…Finally, when |δv αp | > δv c αp , strong heating is restricted to the high energy tail of the He 2+ VDF. By virtue of the fact that H + far outnumbers He 2+ [34], the H + will absorb the majority of the wave power in this regime. T ⊥α /T ⊥p will be lower still in this regime, while T ⊥p /T p will be elevated as the H + ions experience cyclotron resonant heating.…”

Section: For δV Cmentioning

confidence: 99%

“…We followed previously documented procedures to select the subset of measurements for this study [34]. That work also examined solar wind conditions as a function of the Coulomb collision frequency.…”

Section: For δV Cmentioning

confidence: 99%

Sensitive Test for Ion-Cyclotron Resonant Heating in the Solar Wind

et al. 2013

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Plasma carrying a spectrum of counter-propagating field-aligned ion-cyclotron waves can strongly and preferentially heat ions through a stochastic Fermi mechanism. Such a process has been proposed to explain the extreme temperatures, temperature anisotropies, and speeds of ions in the solar corona and solar wind. We quantify how differential flow between ion species results in a Doppler shift in the wave spectrum that can prevent this strong heating. Two critical values of differential flow are derived for strong heating of the core and tail of a given ion distribution function. Our comparison of these predictions to observations from the Wind spacecraft reveals excellent agreement. Solar wind helium that meets the condition for strong core heating is nearly seven times hotter than hydrogen on average. Ion-cyclotron resonance contributes to heating in the solar wind, and there is a close link between heating, differential flow, and temperature anisotropy. Introduction.-The solar corona and solar wind are so tenuous that wave-particle interactions can dominate over fluid or collisional processes, resulting in highly nonthermal plasma as seen by spacecraft in interplanetary space. Heavier ions escape from the Sun at higher speeds than the ionized hydrogen (H + ) that dominates the solar wind. Within a given solar wind stream, different species flow through one another at speeds of up to several hundred km s −1 [1,2]. This differential flow appears to be stable as long as it is aligned with the local magnetic field B and below the Alfvén wave speed C A [3,4]. Heavier ions are also often much hotter than H + , with temperatures reaching and often exceeding mass proportionality [5][6][7][8]. These non-thermal properties can be used to identify the role wave-particle interactions play in heating the corona and solar wind [9][10][11]. If we can understand the underlying physics, we will be able to predict the relative heating of ions and electrons in the solar wind, the corona and other magnetized plasmas.

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“…In the second column typical slow solar wind values are shown for comparison. As /p abundance varies as a function of solar wind velocity and solar cycle (Kasper et al 2007 and references therein), we use the observed coronal value of 4% for comparison. In the third column are the averages for each parameter for all large flare associated events.…”

Section: Icme Parameter Dependence On Source Longitude and Associatedmentioning

confidence: 99%

Analysis of Interplanetary Coronal Mass Ejection Parameters as a Function of Energetics, Source Location, and Magnetic Structure

Reinard

2008

ApJ

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We describe a study of how ICME parameters vary as function of source location, associated flare magnitude, and magnetic structure. The strongest compositional enhancements are found to occur in events originating in central longitudes of the Sun, those with large associated flares, and those that are identified as magnetic clouds. In situ velocity is highest for events associated with large flares. Density has a strong negative correlation with associated flare size, but no strong trend with source longitude or magnetic cloud structure. Temperature is lower than expected for events originating in central longitudes, events associated with large flares, and for magnetic clouds. Total magnetic field is highest for events originating in central longitudes and for magnetic clouds. Combining these results, we suggest that ICMEs may have a basic structure consisting of a core (or cores) of magnetic cloud plasma and compositional signatures that are modulated by CME energetics, surrounded by an envelope with weaker signatures. If this core/envelope scenario is proven to be valid, that suggests that a larger percentage of energetic ICMEs may contain enhanced composition that is not detected by the current single track observations.

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Solar Wind Helium Abundance as a Function of Speed and Heliographic Latitude: Variation through a Solar Cycle

Cited by 173 publications

References 36 publications

Solar abundances of oxygen and neon derived from solar wind observations

Solar abundances of oxygen and neon derived from solar wind observations

Sensitive Test for Ion-Cyclotron Resonant Heating in the Solar Wind

Analysis of Interplanetary Coronal Mass Ejection Parameters as a Function of Energetics, Source Location, and Magnetic Structure

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