Elemental Abundances for the 1996 Streamer Belt

Uzzo, M.; Ko, YK; Raymond, J. C.; Würz, Peter; Ipavich, F. M.

doi:10.1086/346132

Cited by 37 publications

(51 citation statements)

References 29 publications

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“…Even so, oxygen appears to be depleted with respect to its photospheric abundance [log N (O) phot ¼ 8:82; Allen 1973], an effect that can easily be explained if we envisage the quiet plasma ahead of and behind the CS to be the remnant of the streamer that has been partially disrupted by the CME event. An oxygen depletion in streamers has been found by many authors (see, e.g., Raymond et al 1997;Uzzo et al 2003;Bemporad et al 2003); hence, we can interpret the present underabundance to be a signature of the streamer origin of the plasma that is being sampled.…”

Section: Elemental Abundances In the Current Sheet And Adjacent Regionssupporting

confidence: 75%

Current Sheet Evolution in the Aftermath of a CME Event

Бемпорад

Poletto

Suess

et al. 2006

ApJ

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We report on SOHO UVCS observations of the coronal restructuring following a coronal mass ejection (CME) on 2002 November 26, at the time of a SOHO-Ulysses quadrature campaign. Starting about 1.5 hr after a CME in the northwest quadrant, UVCS began taking spectra at 1.7 R , covering emission from both cool and hot plasma. Observations continued, with occasional gaps, for more than 2 days. Emission in the 974.8 8 line of [Fe xviii], indicating temperatures above 6 ; 10 6 K, was observed throughout the campaign in a spatially limited location. Comparison with EIT images shows the [Fe xviii] emission to overlie a growing post-flare loop system formed in the aftermath of the CME. The emission most likely originates in a current sheet overlying the arcade. Analysis of the [Fe xviii] emission allows us to infer the evolution of physical parameters in the current sheet over the entire span of our observations: in particular, we give the temperature versus time in the current sheet and estimate its density. At the time of the quadrature, Ulysses was directly above the location of the CME and intercepted the ejecta. High ionization state Fe was detected by the Ulysses SWICS throughout the magnetic cloud associated with the CME, although its rapid temporal variation suggests bursty, rather than smooth, reconnection in the coronal current sheet. The SOHOUlysses data set provided us with the unique opportunity of analyzing a current sheet structure from its lowest coronal levels out to its in situ properties. Both the remote and in situ observations are compared with predictions of theoretical CME models.

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Section: Elemental Abundances In the Current Sheet And Adjacent Regionssupporting

confidence: 75%

Current Sheet Evolution in the Aftermath of a CME Event

Бемпорад

Poletto

Suess

et al. 2006

ApJ

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“…Once heated by lower hybrid waves, the enhanced electron temperature would lead the elemental charge states to a higher level. However, this would be different for a slow solar wind because the slow solar wind is believed to accumulate in closed loops for hours to days before releasing into the heliosphere (e.g., Uzzo et al 2003). The ions execute sufficient heating in the loops and become almost isotropic.…”

Section: Resultsmentioning

confidence: 99%

Solar wind elemental abundances related to the Sun's open magnetic flux

Wang¹,

Klecker²,

Würz³

2009

A&A

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Context. We present an investigation of the effects of solar magnetic field on the elemental abundance ratios of heavy ions in the solar wind. Aims. We compare the elemental abundance ratios Fe/O, Si/O, Mg/O, Ne/O, and C/O over the 23rd solar cycle, attention being given to the varying fraction of open magnetic flux on the visible side of the solar disc. Methods. We use ACE solar wind data, the current sheet source surface (CSSS) model of the corona, and SoHO/MDI data to relate solar wind compositional properties with the fraction of open magnetic flux on the Sun. We include both a quasi-stationary and intermittent solar wind. Results. For the six investigated solar wind speed ranges, the elemental composition shows a similar FIP-bias of the quasi-stationary solar wind composition with respect to the photosphere but with three plateaus separating low-, mid-, and high-FIP elements. The average enrichment factor for the low-FIP element group (Mg, Fe, Si) with respect to the photospheric values is between 1.67 and 2.47 when the fraction of open magnetic flux on the visible side of the solar disc is above 14%, and it ranges from 2.78 to 4.15 when this fraction is less than 7%. They are close to the enrichment of low-FIP elements with respect to the photospheric values in quasistationary fast-and slow-solar wind, which implies similar fractionation mechanisms for the stationary solar wind and the intermittent solar wind. In the low alpha (<7%) case (alpha is the fraction of open magnetic flux on the visible side of the solar disc), the enrichment of heavy elements for the fast solar wind is well correlated with the high fraction of CMEs. In addition, both the charge state ratios and the elemental abundance ratios exhibit a lower dependence on alpha in a slow solar wind than in a fast solar wind. The dependence of the charge state ratios on alpha is correlated with FIP, which implies that solar magnetic effects play a non-negligible role in the elemental fractionation of the solar wind. We suggest that lower hybrid waves play an important role in the possible linkage between solar magnetic field and elemental fractionation.

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“…Even though many recent works made it evident that a link exists between streamers and the slow solar wind (see, e.g., Noci et al 1997;Habbal et al 1997;Woo & Martin 1997;Wang et al 1998;Uzzo et al 2003), it is not yet clear from which regions within these structures the particle flux originates. Outflow (e.g., Habbal et al 1997;Strachan et al 2002;Uzzo et al 2006Uzzo et al , 2007 and abundance (e.g., Raymond et al 1997;Antonucci et al 2006;Uzzo et al 2007) measurements have shown that potential sources of the slow solar wind might be the streamer regions where a transition from closed to open magnetic field lines exists, i.e.…”

Section: Introductionmentioning

confidence: 99%

Physical parameters along the boundaries of a mid-latitude streamer and in its adjacent regions

Susino¹,

Ventura

Spadaro

et al. 2008

A&A

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Context. Coronal streamers appear to be strictly associated with the generation of the slow solar wind, even if a firm identification of the sources of the particle flux within these structures is still an unresolved issue. Aims. The purpose of this work is to contribute to a better knowledge of the physical characteristics of streamers and of their surroundings in a wide range of heliocentric distances and at both high radial and latitudinal resolutions. Methods. The analysis is based on spectral observations of a narrow, mid-latitude streamer performed with UVCS/SOHO during one week in May 2004: H i Lyα and O vi resonance doublet line intensities and profiles were obtained at different heliocentric distances and latitudes. In addition, white-light polarized brightness images were taken in the same days of observation, through the LASCO/SOHO C2 coronagraph.Results. The radial variations in electron density and temperature, H i and O vi kinetic temperatures, and outflow velocities were derived from the observed line intensities, profiles, and O vi line intensity ratios between 1.6 and 5.0 R , in two regions, 2-3 arcmin wide, located along the boundaries and in a narrow strip (5-10 arcmin) outside the streamer structure. Significantly high kinetic temperatures and outflow velocities were found in the out-of-streamer region above 3.0 R for the O vi ions and, for the first time, H i atoms, compared to those obtained along the streamer boundaries. Moreover, the O vi kinetic temperatures and velocities turn out much higher than the H i ones at any heliocentric distance in all the observed regions. A higher anisotropy is also noticed for the O vi kinetic temperature in the region flanking the streamer. Conclusions. The slow coronal wind is found to flow with significantly different speeds and kinetic temperatures along the boundaries of the streamer and in the out-of-streamer regions at all heights, above 3.0-3.5 R . This fact, consistent with previous studies, indicates that two components of slow wind probably form in the observed regions: one originates just above the streamer cusp and flows with velocities a little higher than 100 km s −1 , while the other flows along the open magnetic field lines flanking the streamer with velocities slightly lower than the slow wind asymptotic heliospheric value of ∼400 km s −1 , around 5.0 R .

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Elemental Abundances for the 1996 Streamer Belt

Cited by 37 publications

References 29 publications

Current Sheet Evolution in the Aftermath of a CME Event

Current Sheet Evolution in the Aftermath of a CME Event

Solar wind elemental abundances related to the Sun's open magnetic flux

Physical parameters along the boundaries of a mid-latitude streamer and in its adjacent regions

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