Solar activity and recurrences in magnetic-field distribution

Bumba, V.; Howard, Robert

doi:10.1007/bf00148402

Cited by 119 publications

(39 citation statements)

References 8 publications

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“…This poleward drift of the weak, decayed magnetic flux appears in Figure 17 as plumes of one dominant polarity, the trailing sunspot polarity, at high latitudes between about 40 ∘ and 65 ∘ , sometimes referred to as a "rush to the poles". Such patterns were first reported by Bumba and Howard (1969) who named them unipolar magnetic regions. The dominant polarity of the poleward plumes is of opposite sign in each hemisphere, and it alternates from cycle to cycle.…”

Section: Chromospheric Synoptic Maps and Potential-field Extrapolationsmentioning

confidence: 73%

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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Section: Chromospheric Synoptic Maps and Potential-field Extrapolationsmentioning

confidence: 73%

Solar Magnetism in the Polar Regions

Petrie

2015

Living Rev. Sol. Phys.

100

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“…ARs tend to emerge in the immediate vicinity or within the boundaries of an existing AR (Bumba and Howard, 1969). Liggett and Zirin (1985) and later Harvey and Zwaan (1993) showed that there is a 10 to 22-fold higher emergence rate within existing ARs than in the quiet sun.…”

Section: Clustering or Nesting Tendency Of Flux Emergencementioning

confidence: 97%

Evolution of Active Regions

Driel-Gesztelyi

Green

2015

Living Rev. Sol. Phys.

266

131

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The evolution of active regions (AR) from their emergence through their long decay process is of fundamental importance in solar physics. Since large-scale flux is generated by the deepseated dynamo, the observed characteristics of flux emergence and that of the subsequent decay provide vital clues as well as boundary conditions for dynamo models. Throughout their evolution, ARs are centres of magnetic activity, with the level and type of activity phenomena being dependent on the evolutionary stage of the AR. As new flux emerges into a pre-existing magnetic environment, its evolution leads to re-configuration of small-and large-scale magnetic connectivities. The decay process of ARs spreads the once-concentrated magnetic flux over an ever-increasing area. Though most of the flux disappears through small-scale cancellation processes, it is the remnant of large-scale AR fields that is able to reverse the polarity of the poles and build up new polar fields. In this Living Review the emphasis is put on what we have learned from observations, which is put in the context of modelling and simulation efforts when interpreting them. For another, modelling-focused Living Review on the sub-surface evolution and emergence of magnetic flux see Fan (2009). In this first version we focus on the evolution of dominantly bipolar ARs. 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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“…gions over one solar cycle, but not from one cycle to the next. Bumba and Howard [1969] demonstrated rigid rotation of low-latitude (+20 ø ) patterns in the solar magnetic field which persisted for several months. On a longer timescale, Bogart [1982] found a persistence of 27-day modulations of daily suns?ot numbers over a period of 128 years, consistent with long-lived active longitudes.…”

Section: Introductionmentioning

confidence: 99%