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Grigoryev, V. M.; Ermakova, L. V.

doi:10.1023/a:1016207115843

Cited by 9 publications

(4 citation statements)

References 6 publications

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“…The subtle answer to our initial question seems to hinge on the observational capability to distinguish whether an emerging small-scale flux tube dies by shredding or by annihilation! Additional complications of the not-understood dynamics are upward-propagating acoustic waves in internetwork grains (Hoekzema et al 2002;Rosenthal et al 2002), horizontally undulating moving features (Bernasconi et al 2002), and helicity transport (Chae 2001;Grigoryev & Ermakova 2002).…”

Section: How Do Elementary Flux Tubes Die?mentioning

confidence: 99%

Astrophysics in 2002

Trimble

Aschwanden

2003

PUBL ASTRON SOC PAC

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ABSTRACT. This has been the Year of the Baryon. Some low temperature ones were seen at high redshift, some high temperature ones were seen at low redshift, and some cooling ones were (probably) reheated. Astronomers saw the back of the Sun (which is also made of baryons), a possible solution to the problem of ejection of material by Type II supernovae (in which neutrinos push out baryons), the production of R Coronae Borealis stars (previously-owned baryons), and perhaps found the missing satellite galaxies (whose failing is that they have no baryons). A few questions were left unanswered for next year, and an attempt is made to discuss these as well.

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Section: How Do Elementary Flux Tubes Die?mentioning

confidence: 99%

Astrophysics in 2002

Trimble

Aschwanden

2003

PUBL ASTRON SOC PAC

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“…Numerical simulations have established that a small amount of twist is necessary for a flux tube rising through the convection zone to survive as an entity (Emonet & Moreno-Insertis 1998;Fan, Zweibel, & Lantz 1998). Observations also indicate that the magnetic field emerges carrying a nonzero twist (Leka et al 1996;Portier-Fozzani et al 2001;Grigoryev & Ermakova 2002), which implies that at least some fraction of the photospheric helicity may be generated below the photosphere. Berger & Field (1984) showed that the magnetic helicity flux into the solar atmosphere can be separated into two components, one due to vertical advection of the twisted magnetic field through the photosphere and one due to '' braiding '' of fields by differential rotation or other largescale horizontal motions.…”

Section: Introductionmentioning

confidence: 99%

Helicity Evolution in Emerging Active Regions

Pevtsov

Maleev

Longcope

2003

ApJ

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We study the evolution of twist and magnetic helicity in the coronal fields of active regions as they emerge. We use multiday sequences of Solar and Heliospheric Observatory Michelson Doppler Interferometer magnetograms to characterize the region's emergence. We quantify the overall twist in the coronal field, , by matching a linear force-free field to bright coronal structures in EUV images. At the beginning of emergence, all regions studied have ' 0. As the active region grows, increases and reaches a plateau within approximately 1 day of emergence. The inferred helicity transport rate is larger than differential rotation could produce. Following the 2000 work of Longcope & Welsch, we develop a model for the injection of helicity into the corona by the emergence of a twisted flux tube. This model predicts a ramp-up period of approximately 1 day. The observed time history ðtÞ is fitted by this model assuming reasonable values for the subphotospheric Alfvén speed. The implication is that helicity is carried by twisted flux tubes rising from the convection zone and transported across the photosphere by spinning of the poles driven by magnetic torque.

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“…Latitudinal dependence of a for 466 active regions observed from 1998-2000 by the Haleakala Stokes Polarimeter (HSP, Mickey 1985). The dashed line is a least-square linear best fit.Magnetic flux emerges with non-zero twist(Leka et al Fozzani et al 2001;Grigoryev & Ermakova 2002).…”

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confidence: 99%

Helicity Generation and Signature in Solar Atmosphere

Pevtsov

2005

Highlights astron.

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To fully understand the origin, evolution and topology of solar magnetic fields, one should comprehend their magnetic helicity. Observationally, non-zero helicity reveals itself in the patterns of electric currents inside active regions, superpenumbral sunspot whirls, the shape of coronal loops and the fine structure of chromospheric filaments. Some patterns may bear information about deep sub-photospheric processes (e.g., dynamo, turbulent convection). Others may originate at or near the photosphere. This presentation reviews the observations of magnetic and current helicity on the Sun, discusses the possible mechanisms of helicity generation, and compares them with the observations.

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Cited by 9 publications

References 6 publications

Astrophysics in 2002

Astrophysics in 2002

Helicity Evolution in Emerging Active Regions

Helicity Generation and Signature in Solar Atmosphere

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