Coronal holes as sources of solar wind

Nolte, J. T.; Krieger, A. S.; Timothy, A. F.; Gold, R. E.; Roelof, E. C.; Vaiana, G. S.; Lazarus, A. J.; Sullivan, J. D.; McIntosh, P. S.

doi:10.1007/bf00149859

Cited by 347 publications

(234 citation statements)

References 15 publications

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“…It was discovered during the 1970s from Skylab data that high-speed solar wind streams originate from large coronal holes (Krieger et al, 1973;Nolte et al, 1976;Zirker, 1977). Wang and Sheeley Jr (1990) investigated the empirical relationship between solar wind speed patterns and the magnetic field structure at the solar wind source location.…”

Section: Relationship Between Coronal Hole Structure and Solar Wind Smentioning

confidence: 99%

“…Crucially, a strong correlation was found between the average unsigned photospheric field strength in open-field regions and the solar wind speed at 1 AU. Nolte et al (1976) had demonstrated that the areas of large equatorial coronal holes are correlated with the maximum speeds of the associated solar wind streams, a pattern that Levine et al (1977) interpreted in terms of expanding flux tubes: high-speed winds originate from the centers of large holes because flux tube expansion is minimal there. This suggested that the solar wind flow could be treated in a manner similar to de Laval nozzle theory, in which con- Blue and yellow shading denote positive and negative polarities, respectively.…”

Section: Relationship Between Coronal Hole Structure and Solar Wind Smentioning

confidence: 99%

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Solar Magnetism in the Polar Regions

Petrie

2015

Living Rev. Sol. Phys.

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This review describes observations of the polar magnetic fields, models for the cyclical formation and decay of these fields, and evidence of their great influence in the solar atmosphere. The polar field distribution dominates the global structure of the corona over most of the solar cycle, supplies the bulk of the interplanetary magnetic field via the polar coronal holes, and is believed to provide the seed for the creation of the activity cycle that follows. A broad observational knowledge and theoretical understanding of the polar fields is therefore an essential step towards a global view of solar and heliospheric magnetic fields. Analyses of both high-resolution and long-term synoptic observations of the polar fields are summarized. Models of global flux transport are reviewed, from the initial phenomenological and kinematic models of Babcock and Leighton to present-day attempts to produce time-dependent maps of the surface magnetic field and to explain polar field variations, including the weakness of the cycle 23 polar fields. The relevance of the polar fields to solar physics extends far beyond the surface layers from which the magnetic field measurements usually derive. As well as discussing the polar fields' role in the interior as seed fields for new solar cycles, the review follows their influence outward to the corona and heliosphere. The global coronal magnetic structure is determined by the surface magnetic flux distribution, and is dominated on large scales by the polar fields. We discuss the observed effects of the polar fields on the coronal hole structure, and the solar wind and ejections that travel through the atmosphere. The review concludes by identifying gaps in our knowledge, and by pointing out possible future sources of improved observational information and theoretical understanding of these fields. Article RevisionsLiving Reviews supports two ways of keeping its articles up-to-date:Fast-track revision. A fast-track revision provides the author with the opportunity to add short notices of current research results, trends and developments, or important publications to the article. A fast-track revision is refereed by the responsible subject editor. If an article has undergone a fast-track revision, a summary of changes will be listed here.Major update. A major update will include substantial changes and additions and is subject to full external refereeing. It is published with a new publication number.For detailed documentation of an article's evolution, please refer to the history document of the article's online version at http://dx

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Section: Relationship Between Coronal Hole Structure and Solar Wind Smentioning

confidence: 99%

Section: Relationship Between Coronal Hole Structure and Solar Wind Smentioning

confidence: 99%

Solar Magnetism in the Polar Regions

Petrie

2015

Living Rev. Sol. Phys.

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“…Because of the strong association between coronal holes and high-speed solar wind streams which has been known since the 1970s (see, e.g., Krieger, Timothy, and Roelof, 1973;Neupert and Pizzo, 1974;Nolte et al, 1976;Zirker, 1977), and because of the detection of blue shift within coronal holes in coronal and transition region lines indicating outflow (see, e.g., Hassler et al, 1999;Peter and Judge, 1999;Xia, Marsch, and Curdt, 2003;Aiouaz, Peter, and Lamaire, 2005) coronal holes are usually identified as the sources of the fast wind from where the wind flows out in the corona and is accelerated in expanding magnetic funnels (Tu et al, 2005). However, in coronal models, the term coronal holes is often used to more generally indicate the foot-points of the magnetic field lines "open" to the heliosphere.…”

Section: Coronal Holesmentioning

confidence: 99%

Evolution of Coronal Holes and Implications for High-Speed Solar Wind During the Minimum Between Cycles 23 and 24

Toma

2010

Sol Phys

118

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We analyze coronal holes present on the Sun during the extended minimum between Cycles 23 and 24, study their evolution, examine the consequences for the solar wind speed near the Earth, and compare it with the previous minimum in 1996. We identify coronal holes and determine their size and location using a combination of EUV observations from SOHO/EIT and STEREO/EUVI and magnetograms. We find that the long period of low solar activity from 2006 to 2009 was characterized by weak polar magnetic fields and polar coronal holes smaller than observed during the previous minimum. We also find that large, low-latitude coronal holes were present on the Sun until 2008 and remained important sources of recurrent high-speed solar wind streams. By the end of 2008, these low-latitude coronal holes started to close down, and finally disappeared in 2009, while smaller, midlatitude coronal holes formed in the remnants of Cycle 24 active regions shifting the sources of the solar wind at the Earth to higher latitudes.

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“…HSSs originate from coronal holes (CHs) on the Sun (Krieger, Timothy, and Roelof, 1973). Since the 1970s, CHs are known for being long-lived and rigidly rotating phenomena in the solar corona (Krieger, Timothy, and Roelof, 1973;Neupert and Pizzo, 1974;Nolte et al, 1976), magnetically "open" to interplanetary space, allowing the solar wind particles to escape from the Sun (Tsurutani et al, 1995;Gosling and Pizzo, 1999;Cranmer, 2009). The plasma temperature and density in CHs is low compared to their surroundings, and thus they appear as dark areas in the corona (Munro and Withbroe, 1972;Cranmer, 2009).…”

Section: Introductionmentioning

confidence: 99%

Real-Time Solar Wind Prediction Based on SDO/AIA Coronal Hole Data

et al. 2015

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We present an empirical model based on the visible area covered by coronal holes close to the central meridian in order to predict the solar wind speed at 1 AU with a lead time up to four days in advance with a 1-h time resolution. Linear prediction functions are used to relate coronal hole areas to solar wind speed. The function parameters are automatically adapted by using the information from the previous 3 Carrington Rotations. Thus the algorithm automatically reacts on the changes of the solar wind speed during different phases of the solar cycle. The adaptive algorithm has been applied to and tested on SDO/AIA-193Å observations and ACE measurements during the years 2011 − 2013, covering 41 Carrington Rotations. The solar wind speed arrival time is delayed and needs on average 4.02 ± 0.5 days to reach Earth. The algorithm produces good predictions for the 156 solar wind high speed streams peak amplitudes with correlation coefficients of cc ≈ 0.60. For 80% of the peaks, the predicted arrival matches within a time window of 0.5 days of the ACE in situ measurements. The same algorithm, using linear predictions, was also applied to predict the magnetic field strength from coronal hole areas but did not give reliable predictions (cc ≈ 0.2).

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Coronal holes as sources of solar wind

Cited by 347 publications

References 15 publications

Solar Magnetism in the Polar Regions

Solar Magnetism in the Polar Regions

Evolution of Coronal Holes and Implications for High-Speed Solar Wind During the Minimum Between Cycles 23 and 24

Real-Time Solar Wind Prediction Based on SDO/AIA Coronal Hole Data

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