The solar wind composition throughout the solar cycle: A continuum of dynamic states

Zurbuchen, T. H.; Fisk, L. A.; Gloeckler, G.; Steiger, R. von

doi:10.1029/2001gl013946

Cited by 178 publications

(179 citation statements)

References 28 publications

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“…Observations of the quietSun corona find that the f Si /f Fe ratio remains close to 1 Zurbuchen et al 2002;Bryans et al 2009). Laming (2009) presents a model in which the FIP effect is caused by the ponderomotive force generated by Alfvén waves propagating through the chromosphere and being transmitted or reflected within coronal loops.…”

Section: Iron and Siliconmentioning

confidence: 99%

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Properties of a Polar Coronal Hole During the Solar Minimum in 2007

Hahn

Bryans

Landi

et al. 2010

ApJ

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We report measurements of a polar coronal hole during the recent solar minimum using the Extreme Ultraviolet Imaging Spectrometer on Hinode. Five observations are analyzed that span the polar coronal hole from the central meridian to the boundary with the quiet-Sun corona. We study the observations above the solar limb in the height range of 1.03-1.20 R . The electron temperature T e and emission measure (EM) are found using a geometric mean emission measure method. The EM derived from the elements Fe, Si, S, and Al are compared in order to measure relative coronal-to-photospheric abundance enhancement factors. We also studied the ion temperature T i and the non-thermal velocity v nt using the line profiles. All these measurements are compared to polar coronal hole observations from the previous (1996-1997) solar minimum and to model predictions for relative abundances. There are many similarities in the physical properties of the polar coronal holes between the two minima at these low heights. We find that the electron density, T e , and T i are comparable in both minima. T e shows a comparable gradient with height. Both minima show a decreasing T i with increasing charge-to-mass ratio q/M. A previously observed upturn of T i for ions above q/M > 0.25 was not found here. We also compared relative coronal-to-photospheric elemental abundance enhancement factors for a number of elements. These ratios were ∼1 for both the low first ionization potential (FIP) elements Si and Al and the marginally high FIP element S relative to the low FIP element Fe, as is expected based on earlier observations and models for a polar coronal hole. These results are consistent with no FIP effect in a polar coronal hole.

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Section: Iron and Siliconmentioning

confidence: 99%

“…This is referred to as the FIP effect and the amount of the enhancement is called the FIP factor. Based on previous observations and theoretical models, coronal holes are expected to have a small FIP effect with FIP factors of ≈1-2 compared to ≈3-4 in the quiet-Sun corona Zurbuchen et al 2002;Bryans et al 2009;Laming 2009). …”

Section: Fip Factorsmentioning

confidence: 99%

Properties of a Polar Coronal Hole During the Solar Minimum in 2007

Hahn

Bryans

Landi

et al. 2010

ApJ

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“…4) : Crooker et al 2004;Zurbuchen et al 2002), between closed magnetic fields lines (generating helical fields) and between open field lines of opposite polarities (Einaudi et al 1999;Wang et al 2007;Linton et al 2009) have all been invoked as the different mechanisms which could trigger the formation and release of such streamer blobs. In addition to serving as a potential source of the slow solar wind, these reconnection processes have a bearing on questions as diverse as the formation and evolution of the HPS/HCS, the heliospheric magnetic flux budget, the solar-cycle evolution of the coronal field, and the rigid rotation of coronal holes.…”

Section: Science Question 2: 'How Do the Observed Structures In The Cmentioning

confidence: 99%

The Wide-Field Imager for Solar Probe Plus (WISPR)

et al. 2015

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mission designed to orbit as close as 7 million km (9.86 solar radii) from Sun center. WISPR employs a 95 • radial by 58 • transverse field of view to image the fine-scale structure of the solar corona, derive the 3D structure of the large-scale corona, and determine whether a dust-free zone exists near the Sun. WISPR is the smallest heliospheric imager to date yet it comprises two nested wide-field telescopes with large-format (2 K × 2 K) APS CMOS detectors to optimize the performance for their respective fields of view and to minimize the risk of dust damage, which may be considerable close to the Sun. The WISPR electronics are very flexible allowing the collection of individual images at cadences up to 1 second at perihelion or the summing of multiple images to increase the signal-to-noise when the spacecraft is further from the Sun. The dependency of the Thomson scattering emission of the corona on the imaging geometry dictates that WISPR will be very sensitive to the emission from plasma close to the spacecraft in contrast to the situation for imaging from Earth orbit. WISPR will be the first 'local' imager providing a crucial link between the large-scale corona and the in-situ measurements.

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“…(2) Understand Which Heating Mechanisms Dominate as a Function of Distance from the Sun Numerous models to describe the heating and acceleration mechanisms of the Hollweg (2008), Cranmer (2000), Hollweg and Isenberg (2002), Isenberg (2001a), Galinsky and Shevchenko (2000), Marsch and Tu (2001), Kasper et al (2008 b Matthaeus et al (1999), Dmitruk et al (2002), Cranmer et al (2007), Chandran et al (2009) c Bruner (1978), Ulmschneider (1985) d Parker (1979Parker ( , 1987, Sturrock (1999), Priest et al (2002), Axford and McKenzie (1992), Cargill and Klimchuk (2004), Schrijver et al (1997), Zurbuchen et al (2002) e Scudder (1994), Pierrard and Lamy (2003) solar corona and wind have been advanced with varying degrees of success, but none is universally accepted and possibly many are valid in some subset of plasma conditions. With the correct measurements SPP can determine the relative contribution of these mechanisms in the solar wind and understand which are most important.…”

Section: Heating the Corona And Solar Windmentioning

confidence: 99%

Solar Wind Electrons Alphas and Protons (SWEAP) Investigation: Design of the Solar Wind and Coronal Plasma Instrument Suite for Solar Probe Plus

et al. 2015

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The Solar Wind Electrons Alphas and Protons (SWEAP) Investigation on SolarProbe Plus is a four sensor instrument suite that provides complete measurements of the electrons and ionized helium and hydrogen that constitute the bulk of solar wind and coronal plasma. SWEAP consists of the Solar Probe Cup (SPC) and the Solar Probe Analyzers (SPAN). SPC is a Faraday Cup that looks directly at the Sun and measures ion and electron fluxes and flow angles as a function of energy. SPAN consists of an ion and electron electrostatic analyzer (ESA) on the ram side of SPP (SPAN-A) and an electron ESA on the anti-ram side (SPAN-B). The SPAN-A ion ESA has a time of flight section that enables it to sort particles by their mass/charge ratio, permitting differentiation of ion species. SPAN-A and -B are rotated relative to one another so their broad fields of view combine like the seams on a baseball to view the entire sky except for the region obscured by the heat shield and covered by SPC. Observations by SPC and SPAN produce the combined field of view and measurement capabilities required to fulfill the science objectives of SWEAP and Solar Probe Plus. SWEAP measurements, in concert with magnetic and electric fields, energetic particles, and white light contextual imaging will enable discovery and understanding of solar wind acceleration and formation, coronal and solar wind heating, and particle acceleration in the inner heliosphere of the solar system. SPC and SPAN are managed by the SWEAP Electronics Module (SWEM), which distributes power, formats onboard data products, and serves as a single electrical interface to the spacecraft. SWEAP data products include ion and electron velocity distribution functions with high energy and angular resolution. Full resolution data are stored within the SWEM, enabling high resolution observations of structures such as shocks, reconnection events, and other transient structures to be selected for download after the fact. This paper describes the implementation of the SWEAP Investigation, the driving requirements for the suite, expected performance of the instruments, and planned data products, as of mission preliminary design review.

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The solar wind composition throughout the solar cycle: A continuum of dynamic states

Cited by 178 publications

References 28 publications

Properties of a Polar Coronal Hole During the Solar Minimum in 2007

Properties of a Polar Coronal Hole During the Solar Minimum in 2007

The Wide-Field Imager for Solar Probe Plus (WISPR)

Solar Wind Electrons Alphas and Protons (SWEAP) Investigation: Design of the Solar Wind and Coronal Plasma Instrument Suite for Solar Probe Plus

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