Sunspots with the Strongest Magnetic Fields

Livingston, W.; Harvey, J. W.; Malanushenko, O.; Webster, Leslie T.

doi:10.1007/s11207-006-0265-4

Cited by 100 publications

(119 citation statements)

References 34 publications

Supporting

Mentioning

106

Contrasting

Unclassified

Order By: Relevance

“…However, it appears that one needs to introduce an Evershed flow to eliminate the apparent umbral bright ring in the continuum. Similar work on return-flux sunspot models was undertaken by Osherovich and Lawrence (1983), Osherovich and Garcia (1989), and Liu and Song (1996).…”

Section: Self-similar Fieldsmentioning

confidence: 85%

See 1 more Smart Citation

Modeling the Subsurface Structure of Sunspots

et al. 2010

View full text Add to dashboard Cite

While sunspots are easily observed at the solar surface, determining their subsurface structure is not trivial. There are two main hypotheses for the subsurface structure of sunspots: the monolithic model and the cluster model. Local helioseismology is the only means by which we can investigate subphotospheric structure. However, as current linear inversion techniques do not yet allow helioseismology to probe the internal structure with sufficient confidence to distinguish between the monolith and cluster models, the development of physically realistic sunspot models are a priority for helioseismologists. This is because they are not only important indicators of the variety of physical effects that may influence helioseismic inferences in active regions, but they also enable detailed assessments of the validity of helioseismic interpretations through numerical forward modeling. In this article, we provide a critical review of the existing sunspot models and an overview of numerical methods employed to model wave propagation through model sunspots. We then carry out a helioseismic analysis of the sunspot in Active Region 9787 and address the serious inconsistencies uncovered by Gizon et al. (2009aGizon et al. ( , 2009b. We find that this sunspot is most probably associated with a shallow, positive wave-speed perturbation (unlike the traditional two-layer model) and that travel-time measurements are consistent with a horizontal outflow in the surrounding moat.

show abstract

Section: Self-similar Fieldsmentioning

confidence: 85%

“…Ringnes and Jensen, 1960;Brants and Zwaan, 1982;Kopp and Rabin, 1992;Collados et al, 1994;Livingston, 2002;. The field strength drops steadily toward the sunspot's periphery, becoming 700 -1000 G at the edge of the visible sunspot (e.g.…”

Section: Field Strength and Orientationmentioning

confidence: 98%

Modeling the Subsurface Structure of Sunspots

et al. 2010

View full text Add to dashboard Cite

show abstract

“…Typically, magnetic field strengths of about 1 kG are found in penumbrae while the maximum umbral field strengths usually range between 2 and 4 kG (Title et al 1993;Lites et al 1993;Schad 2013). In extreme cases, values as large as 6 kG have been reported (Livingston et al 2006). Only recently, van Noort et al (2013) reported ≈7 kG in a sunspot, although surprisingly not in the umbral area but near the outer edge of the penumbra, in a strong downflow region.…”

Section: Temporal Evolution Of the Magnetic Fieldmentioning

confidence: 99%

The magnetic field in the solar atmosphere

Wiegelmann

Thalmann

Solanki

2014

Astron Astrophys Rev

176

125

View full text Add to dashboard Cite

This publication provides an overview of magnetic fields in the solar atmosphere with the focus lying on the corona. The solar magnetic field couples the solar interior with the visible surface of the Sun and with its atmosphere. It is also responsible for all solar activity in its numerous manifestations. Thus, dynamic phenomena such as coronal mass ejections and flares are magnetically driven. In addition, the field also plays a crucial role in heating the solar chromosphere and corona as well as in accelerating the solar wind. Our main emphasis is the magnetic field in the upper solar atmosphere so that photospheric and chromospheric magnetic structures are mainly discussed where relevant for higher solar layers. Also, the discussion of the solar atmosphere and activity is limited to those topics of direct relevance to the magnetic field. After giving a brief overview about the solar magnetic field in general and its global structure, we discuss in more detail the magnetic field in active regions, the quiet Sun and coronal holes.

show abstract

“…Livingston et al (2006), who searched historical measurements from Mt Wilson and Rome observatories covering many decades for spots with particularly strong fields, found that only 0.2% of all spots have field strengths larger than 4 kG, with the strongest umbral field ever measured being 6.1 kG. The values in excess of 7 kG measured in the downflows would therefore make these candidates for the strongest fields ever measured on the Sun.…”

Section: Strong Magnetic Fieldsmentioning

confidence: 99%

Peripheral downflows in sunspot penumbrae

Noort

Lagg

Tiwari

et al. 2013

A&A

128

View full text Add to dashboard Cite

Context. Sunspot penumbrae show high-velocity patches along the periphery. Aims. The high-velocity downflow patches are believed to be the return channels of the Evershed flow. We aim to investigate their structure in detail using Hinode SOT/SP observations. Methods. We employ Fourier interpolation in combination with spatially coupled height dependent LTE inversions of Stokes profiles to produce high-resolution, height-dependent maps of atmospheric parameters of these downflows and investigate their properties. Results. High-speed downflows are observed over a wide range of viewing angles. They have supersonic line-of-sight velocities, some in excess of 20 km s −1 , and very high magnetic field strengths, reaching values of over 7 kG. A relation between the downflow velocities and the magnetic field strength is found, in good agreement with MHD simulations. Conclusions. The coupled inversion at high resolution allows for the accurate determination of small-scale structures. The recovered atmospheric structure indicates that regions with very high downflow velocities contain some of the strongest magnetic fields that have ever been measured on the Sun.

show abstract

Sunspots with the Strongest Magnetic Fields

Cited by 100 publications

References 34 publications

Modeling the Subsurface Structure of Sunspots

Modeling the Subsurface Structure of Sunspots

The magnetic field in the solar atmosphere

Peripheral downflows in sunspot penumbrae

Contact Info

Product

Resources

About