A new view of the origin of the solar wind

Woo, Richard; Habbal, Shadia Rifai

doi:10.1063/1.58719

Cited by 4 publications

(4 citation statements)

References 13 publications

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“…Results from these coordinated measurements also reinforce those obtained from comparing intensity scintillation and solar wind speed measurements (Woo & Martin 1997), i.e., low levels of Doppler scintillation observed away from streamer stalks -9are a proxy for the fast wind. The use of Doppler scintillation as a proxy for wind speed is particularly important because its high sensitivity to changes in electron density over small distances makes it a measurement of high spatial resolution (Woo 1996).…”

Section: Radio Occultation Measurementsmentioning

confidence: 99%

Origins of the Slow and the Ubiquitous Fast Solar Wind

Habbal

Woo

Fineschi

et al. 1997

The Astrophysical Journal

123

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We present in this Letter the first coordinated radio occultation measurements and ultraviolet observations of the inner corona below 5.5R s , obtained during the Galileo solar conjunction in 1997 January, to establish the origin of the slow solar wind. Limits on the flow speed are derived from the Doppler dimming of the resonantly scattered component of the oxygen 1032 and 1037.6 Å lines as measured with the ultraviolet coronagraph spectrometer (UVCS) on the Solar and Heliospheric Observatory (SOHO). White light images of the corona from the large-angle spectroscopic coronagraph (LASCO) on SOHO taken simultaneously are used to place the Doppler radio scintillation and ultraviolet measurements in the context of coronal structures. These combined observations provide the first direct confirmation of the view recently proposed by Woo & Martin that the slow solar wind is associated with the axes, also known as stalks, of streamers. Furthermore, the ultraviolet observations also show how the fast solar wind is ubiquitous in the inner corona and that a velocity shear between the fast and slow solar wind develops along the streamer stalks.

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Section: Radio Occultation Measurementsmentioning

confidence: 99%

Origins of the Slow and the Ubiquitous Fast Solar Wind

Habbal

Woo

Fineschi

et al. 1997

The Astrophysical Journal

123

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“…Woo & Habbal (2003) (and further references therein) found observational evidence being in favor of radial outflow from the quiet sun. It seems as if the solar wind during solar minimum can also originate from solar sources at middle and low latitudes, where the quiet Sun regions usually appear.…”

Section: Introductionmentioning

confidence: 99%

Can the solar wind originate from a quiet Sun region?

He¹,

Tu²,

Marsch³

2007

A&A

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Context. It is well known that the fast solar wind originates from coronal holes (CHs). However, the question whether it can also originate from quiet Sun regions has not yet been answered. Aims.To study this problem we analyze SOHO data obtained from observations made in a quiet Sun area. The data set includes far-ultraviolet data from SUMER, magnetic field data from MDI, and extreme-ultraviolet data from EIT. Methods. We make a potential-field extrapolation of the coronal magnetic field and calculate the field lines from the photosphere up to 80 Mm height. Those field lines which can be traced from the bottom to the top of the extrapolation box are called (locally) open field lines. By a combined analysis of the coronal magnetic field structures inferred from MDI data, the flows indicated by the Ne viii Doppler shifts in the SUMER data, and the Fe xii radiance images from EIT, it is possible to study this problem in depth. Results. We find that most of the sites with plasma outflow, which can be recognized by the Ne viii blue shift, are not located in regions with an open magnetic field. Most likely, these outflows just correspond to plasma being delivered to magnetic loops. It is further found that, in a cross-section plane located at a height of 25 Mm, the pattern of open field lines intersecting that plane is consistent with the dark pattern of low radiance in the image of the Fe xii 19.5 nm line. Usually, small dark regions are considered to represent small CHs, and thus are assumed to be sources of the solar wind. However, since here the source of the low emission appears to be located at a height of only 25 Mm, it seems more likely that this radiation originates near the foot points of large coronal loops. Conclusions. Previous results obtained at middle latitudes on the quiet Sun indicated that sizable outflow velocities occur at the intersections of the network boundaries. This finding is also confirmed here. However, we could not identify most of these intersections as sources of the solar wind. Only a few small outflow regions might be sources. Yet, one dark area that we found on the EIT map seems to be connected with open field lines, and therefore it could be a source of the solar wind.

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“…Further support for this scenario comes from the fact that the white light images of the Sun at total eclipses, when properly processed, exhibit a rich set of filamentary structures that extend almost radially from the solar surface (see fig. 1 in Woo & Habbal 2003). Supposing these fine structures trace the magnetic field lines, this would suggest that some coronal magnetic field lines penetrate the dome-shaped streamer base.…”

Section: Introductionmentioning

confidence: 98%

“…Given the importance of addressing the origin of the open magnetic flux of the heliosphere, it is surprising to see that while the traditional scenario has been extensively incorporated into numerical studies originated by Pneuman & Kopp (1971) (also see Lionello et al 2009, and references therein), the scenario proposed by Woo & Habbal (2003) has not been modeled quantitatively. Here we wish to implement this scenario in a numerical model, thereby testing it against two fundamental constraints that the traditional scenario can readily satisfy: one is the appearance of a dome-shaped bright feature in the pB images, and the other is the fact established by Ulysses measurements that the radial magnetic field strength B r is nearly uniform with latitude beyond 1 AU (Smith & Balogh 1995;Smith et al 2001).…”

Section: Introductionmentioning

confidence: 99%

Interpretation of the coronal magnetic field configuration of the Sun

Li¹,

Li²,

Yu³

2012

Res. Astron. Astrophys.

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The origin of the heliospheric magnetic flux on the Sun, and hence the origin of the solar wind, is a topic of hot debate. While the prevailing view is that the solar wind originates from outside coronal streamer helmets, there also exists the suggestion that the open magnetic field spans a far wider region. Without the definitive measurement of the coronal magnetic field, it is difficult to resolve the conflict between the two scenarios without doubt. We present two 2-dimensional, Alfvénic-turbulence-based models of the solar corona and solar wind, one with and the other without a closed magnetic field region in the inner corona. The purpose of the latter model is to test whether it is possible to realize a picture suggested by polarimetric measurements of the corona using the Fe XIII 10747Å line, where open magnetic field lines seem to penetrate the streamer base. The boundary conditions at the coronal base are able to account for important observational constraints, especially those on the magnetic flux distribution. Interestingly, the two models provide similar polarized brightness (pB) distributions in the field of view (FOV) of SOHO/LASCO C2 and C3 coronagraphs. In particular, a domeshaped feature is present in the C2 FOV even for the model without any closed magnetic field.Moreover, both models fit equally well the Ulysses data scaled to 1 AU. We suggest that: 1)The pB observations cannot be safely taken as a proxy for the magnetic field topology, as often implicitly assumed. 2) The Ulysses measurements, especially the one showing a nearly uniform distribution with heliocentric latitude of the radial magnetic field, do not rule out the ubiquity of open magnetic fields on the Sun.

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A new view of the origin of the solar wind

Cited by 4 publications

References 13 publications

Origins of the Slow and the Ubiquitous Fast Solar Wind

Origins of the Slow and the Ubiquitous Fast Solar Wind

Can the solar wind originate from a quiet Sun region?

Interpretation of the coronal magnetic field configuration of the Sun

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