Solar sources of the interplanetary magnetic field and solar wind

Levine, Randolph H.; Altschuler, Martin D.; Harvey, J. W.

doi:10.1029/ja082i007p01061

Cited by 189 publications

(101 citation statements)

References 6 publications

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“…The wind speed is estimated at the source surface radius first. Solar wind speeds are known to correlate with the amount of field line divergence (Levine et al 1977;Wang & Sheeley 1990). Wang & Sheeley (1991) showed that such a correlation is plausible provided that the amount of Alfven wave energy flux is constant within open flux tubes.…”

Section: Stellar Windmentioning

confidence: 99%

Time-scales of close-in exoplanet radio emission variability

See

Jardine

Farès

et al. 2015

Monthly Notices of the Royal Astronomical Society

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We investigate the variability of exoplanetary radio emission using stellar magnetic maps and 3D field extrapolation techniques. We use a sample of hot Jupiter hosting stars, focusing on the HD 179949, HD 189733 and τ Boo systems. Our results indicate two time-scales over which radio emission variability may occur at magnetised hot Jupiters. The first is the synodic period of the star-planet system. The origin of variability on this time-scale is the relative motion between the planet and the interplanetary plasma that is co-rotating with the host star. The second time-scale is the length of the magnetic cycle. Variability on this time-scale is caused by evolution of the stellar field. At these systems, the magnitude of planetary radio emission is anticorrelated with the angular separation between the subplanetary point and the nearest magnetic pole. For the special case of τ Boo b, whose orbital period is tidally locked to the rotation period of its host star, variability only occurs on the time-scale of the magnetic cycle. The lack of radio variability on the synodic period at τ Boo b is not predicted by previous radio emission models, which do not account for the co-rotation of the interplanetary plasma at small distances from the star.

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Section: Stellar Windmentioning

confidence: 99%

Time-scales of close-in exoplanet radio emission variability

See

Jardine

Farès

et al. 2015

Monthly Notices of the Royal Astronomical Society

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“…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%

Solar Magnetism in the Polar Regions

Petrie

2015

Living Rev. Sol. Phys.

100

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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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“…Studies in the 1970s using Skylab data suggested that regions with low areal expansion corresponded well with high-speed streams observed at Earth (Kopp & Holzer 1976;Levine et al 1977). Nearly two decades later, Wang and Sheeley (WS) established an empirical inverse relationship between the inecliptic solar wind speed (SWS) and the expansion rates of magnetic flux tubes (FTEs) defined as where B(phot) and B(ss) are the photospheric and the source surface magnetic fields at radii R e and R ss .…”

Section: Introductionmentioning

confidence: 99%

Controlling Influence of Magnetic Field on Solar Wind Outflow: An Investigation Using Current Sheet Source Surface Model

Poduval

2016

ApJL

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This Letter presents the results of an investigation into the controlling influence of large-scale magnetic field of the Sun in determining the solar wind outflow using two magnetostatic coronal models: current sheet source surface (CSSS) and potential field source surface. For this, we made use of the Wang and Sheeley inverse correlation between magnetic flux expansion rate (FTE) and observed solar wind speed (SWS) at 1 au. During the period of study, extended over solar cycle23 and beginning of solar cycle24, we found that the coefficients of the fitted quadratic equation representing the FTE-SWS inverse relation exhibited significant temporal variation, implying the changing pattern of the influence of FTE on SWS over time. A particularly noteworthy feature is an anomaly in the behavior of the fitted coefficients during the extended minimum, 2008-2010 (CRs 2073 -2092, which is considered due to the particularly complex nature of the solar magnetic field during this period. However, this variation was significant only for the CSSS model, though not a systematic dependence on the phase of the solar cycle. Further, we noticed that the CSSS model demonstrated better solar wind prediction during the period of study, which we attribute to the treatment of volume and sheet currents throughout the corona and the more accurate tracing of footpoint locations resulting from the geometry of the model.

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Solar sources of the interplanetary magnetic field and solar wind

Cited by 189 publications

References 6 publications

Time-scales of close-in exoplanet radio emission variability

Time-scales of close-in exoplanet radio emission variability

Solar Magnetism in the Polar Regions

Controlling Influence of Magnetic Field on Solar Wind Outflow: An Investigation Using Current Sheet Source Surface Model

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