Large-Scale Magnetic Field of the Sun and Evolution of Sunspot Activity

Мордвинов, А. В.; Grigoryev, V. M.; Peshcherov, V. S.

doi:10.1007/s11207-012-0020-y

Cited by 8 publications

(5 citation statements)

References 12 publications

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“…In general, such reconstructions require a knowledge of theB r andB φ components of the axisymmetric magnetic field. In the past, vector global magnetic field components were reconstructed via various approaches (Pevtsov & Latushko 2000;Ulrich & Boyden 2005;Lo et al 2010;Mordvinov et al 2012).…”

Section: Discussionmentioning

confidence: 99%

Magnetic Helicity of the Global Field in Solar Cycles 23 and 24

Пипин

Pevtsov

2014

ApJ

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For the first time we reconstruct the magnetic helicity density of global axisymmetric field of the Sun using method proposed by Brandenburg et al. (2003) and Pipin et al. (2013b).To determine the components of the vector potential, we apply the gauge which is typically employed in mean-field dynamo models. This allows for a direct comparison of reconstructed helicity with the predictions from the mean-field dynamo models. We apply the method to two different data sets: the synoptic maps of line-of-sight (LOS) magnetic field from the Michelson Doppler Imager (MDI) on board of Solar and Heliospheric Observatory (SOHO) and vector magnetic field measurements from Vector Spectromagnetograph (VSM) on Synoptic Optical Long-term Investigations of the Sun (SOLIS) system. Based on the analysis of MDI/SOHO data, we find that in solar cycle 23 the global magnetic field had positive (negative) magnetic helicity in the northern (southern) hemisphere. This hemispheric sign asymmetry is opposite to helicity of solar active regions, but it is in agreement with the predictions of mean-field dynamo models. The data also suggest that the hemispheric helicity rule may have reversed its sign in early and late phases of cycle 23. Furthermore, the data indicate an imbalance in magnetic helicity between the northern and southern hemispheres.This imbalance seem to correlate with the total level of activity in each hemisphere in cycle 23. Magnetic helicity for rising phase of cycle 24 is derived from SOLIS/VSM data, and qualitatively, its latitudinal pattern is similar to the pattern derived from SOHO/MDI data for cycle 23.

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Section: Discussionmentioning

confidence: 99%

Magnetic Helicity of the Global Field in Solar Cycles 23 and 24

Пипин

Pevtsov

2014

ApJ

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“…This magnetic flux rises up from the convection zone via a process known as magnetic buoyancy (Parker, 1955 ). Sunspots are generated in their highest number around an equatorial band – where the toroidal field is assumed to be strongest (a consequence of meridional flow) (Mordvinov, Grigoryev, and Peshcherov, 2012 ). Sunspots will typically appear as dark spots on the photosphere, with temperatures between 3000 – 4500 K, in contrast with the surrounding material at a temperature of .…”

Section: Introductionmentioning

confidence: 99%

Magnetic Helicity as a Predictor of the Solar Cycle

Hawkes

Berger

2018

Sol Phys

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It is well known that the polar magnetic field is at its maximum during solar minima, and that the behaviour during this time acts as a strong predictor of the strength of the following solar cycle. This relationship relies on the action of differential rotation (the Omega effect) on the poloidal field, which generates the toroidal flux observed in sunspots and active regions. We measure the helicity flux into both the northern and the southern hemispheres using a model that takes account of the Omega effect, which we apply to data sets covering a total of 60 years. We find that the helicity flux offers a strong prediction of solar activity up to five years in advance of the next solar cycle. We also hazard an early guess as to the strength of Solar Cycle 25, which we believe will be of similar amplitude and strength to Cycle 24.

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“…It was first used to study large scale solar magnetic fields by Howard (1974) and Duvall et al (1979), and subsequently by many others. Global synoptic maps based on this method have been made by Grigoryev et al (1986), Grigor'ev & Latushko (1992, Pevtsov & Latushko (2000), Ulrich et al (2002), Wang & Zhang (2010), and Mordvinov et al (2012). Such synoptic maps have also been combined over long time periods to construct butterfly diagrams of the components of the magnetic field (e.g., Ulrich & Boyden 2005;Vecchio et al 2012;Mordvinov et al 2012;Ulrich & Tran 2013).…”

Section: Estimating Radial Magnetic Flux Densitymentioning

confidence: 99%

“…Global synoptic maps based on this method have been made by Grigoryev et al (1986), Grigor'ev & Latushko (1992, Pevtsov & Latushko (2000), Ulrich et al (2002), Wang & Zhang (2010), and Mordvinov et al (2012). Such synoptic maps have also been combined over long time periods to construct butterfly diagrams of the components of the magnetic field (e.g., Ulrich & Boyden 2005;Vecchio et al 2012;Mordvinov et al 2012;Ulrich & Tran 2013). We attempted to use this method with our chromospheric measurements but were unable to get good solutions for all three vector components due to noise, evolution of the magnetic field vector, and the small change of Earth's heliocentric latitude during one rotation.…”

Section: Estimating Radial Magnetic Flux Densitymentioning

confidence: 99%

Synoptic Mapping of Chromospheric Magnetic Flux

Jin

Harvey

Pietarila

2013

ApJ

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We used daily full-disk Ca ii 854.2 nm magnetograms from the Synoptic Optical Long Term Investigations of the Sun (SOLIS) facility to study the chromospheric magnetic field from 2006 April through 2009 November. We determined and corrected previously unidentified zero offsets in the SOLIS magnetograms. By tracking the disk passages of stable unipolar regions, the measured net flux densities were found to systematically decrease from the disk center to the limb by a factor of about two. This decrease was modeled using a thin flux tube model with a difference in signal formation height between the center and limb sides. Comparison of photospheric and chromospheric observations shows that their differences are largely due to horizontal spreading of magnetic flux with increasing height. The north polar magnetic field decreased nearly linearly with time during our study period while the south polar field was nearly constant. We used the annual change in the viewing angle of the polar regions to estimate the radial and meridional components of the polar fields and found that the south polar fields were tilted away from the pole. Synoptic maps of the chromospheric radial flux density distribution were used as boundary conditions for extrapolation of the field from the chromosphere into the corona. A comparison of modeled and observed coronal hole boundaries and coronal streamer positions showed better agreement when using the chromospheric rather than the photospheric synoptic maps.

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Large-Scale Magnetic Field of the Sun and Evolution of Sunspot Activity

Cited by 8 publications

References 12 publications

Magnetic Helicity of the Global Field in Solar Cycles 23 and 24

Magnetic Helicity of the Global Field in Solar Cycles 23 and 24

Magnetic Helicity as a Predictor of the Solar Cycle

Synoptic Mapping of Chromospheric Magnetic Flux

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