Long-term studies of photospheric magnetic fields on the Sun

Pevtsov, Alexei A.; Bertello, L.; Nagovitsyn, Yu. A.; Tlatov, A. G.; Пипин, В. В.

doi:10.1051/swsc/2020069

Cited by 15 publications

(6 citation statements)

References 167 publications

(185 reference statements)

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“…In the southern hemisphere, the A • B evolves in the opposite way. A very similar pattern is found in the solar observations (Pevtsov et al 2021).…”

Section: Magnetic Helicity Evolutionsupporting

confidence: 88%

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On effects of surface bipolar magnetic regions on the convection zone dynamo

Pipin

2021

Preprint

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We investigate the effect of the surface tilted bipolar magnetic regions (BMR) on the large-scale dynamo distributed in the bulk of the convection zone. The study employs the nonlinear 3D mean-field dynamo model. The emergence of the BMR on the surface is modeled by means of the nonaxisymmetric magnetic buoyancy effect which acts on the large-scale toroidal magnetic field in the upper half of the convection zone. The nonaxisymmetric magnetic field which results from this mechanism is shallow. At the surface the effect of the BMR on the magnetic field generation is dominant. However, because of the shallow BMR distribution, its effect on the global dynamo is moderate. The most dynamo effect of the surface BMR is due to their evolution and the convective zone α effect. The fluctuations of the BMR's tilt affect the equatorial symmetry of the dynamo-generated magnetic field. In agreement with the solar observations, the emerging BMRs result in the negative magnetic helicity density of the large-scale nonaxisymmetric magnetic fields in the northern hemisphere of the star.

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“…In the southern hemisphere, the A • B evolves in the opposite way. A very similar pattern is found in the solar observations (Pevtsov et al 2021).…”

Section: Magnetic Helicity Evolutionsupporting

confidence: 88%

“…The results for the total magnetic helicity (Fig. 8a) are in the qualitative agreement with the solar observation (see, e.g., Lund et al 2020 andPevtsov et al 2021). The evolution of the small-scale helicity density, χ , which is produced by the dynamo follows the Eq(17).…”

Section: Magnetic Helicity Evolutionsupporting

confidence: 83%

On effects of surface bipolar magnetic regions on the convection zone dynamo

Pipin

2021

Preprint

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“…This work suggests several future research directions. For example, spatially resolved magnetogram measurements from the Mount Wilson Observatory (MWO) extend back to the early 1970's (Pevtsov et al, 2021) and our histogram analysis could be applied to these data to create a much longer magnetic proxy time series. Addition- ally, the skill of flux transport models in forecasting solar activity needs to be compared with simpler, statistical methods (e.g., Warren et al (2017)).…”

Section: Summary and Discussionmentioning

confidence: 99%

A Multicomponent Magnetic Proxy for Solar Activity

2021

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It has long been recognized that the Sun's radiative output is strongly correlated with the magnetic field (Gurman et al., 1974), which has been measured extensively over the past 50 years using both ground based and space based instruments. Furthermore, almost all of these measurements are spatially resolved, yielding information on the distribution of magnetic flux on the solar surface. Finally, the evolution of the surface magnetic field is well described by models, which provide a physics-based framework for forecasting solar activity. Surprisingly, there

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“…Stanford University began providing daily full-disk maps in 1976 and observations are still underway at the Wilcox Solar Observatory (WSO, Scherrer et al 1977). The National Solar Observatory (NSO) at Kitt Peak (KP) and the Mount Wilson observatory (MWO) have also created long continuous series of maps of the photospheric magnetic field at a higher spatial resolution than WSO (for a review of early full-disk magnetographic observations, see Pevtsov et al (2021)). Space-based instruments, such as SOHO/MDI and SDO/HMI, later emerged to provide observations without interference from the Earth's atmosphere.…”

Section: Introductionmentioning

confidence: 99%

Reconstructing solar magnetic fields from historical observations

Virtanen

Pevtsov

Bertello

et al. 2022

A&A

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Context. We apply our recently developed method to reconstruct synoptic maps of the photospheric magnetic field from observations of chromospheric plages and the magnetic polarity of sunspots. Here, we apply the method to an extended time interval from 1915 to 1985. Aims. Systematic magnetographic observations of the solar photospheric magnetic field were initiated as recently as the 1970s and the lack of earlier observations limits our ability to study and understand the long-term evolution of the Solar global field. This study is aimed at creating synoptic maps of magnetic fields for the pre-magnetograph era and using these maps as input for modern simulation models to investigate the long-term (centennial) evolution of the Sun's global magnetic fields. Methods. We reconstructed active Solar regions by identifying chromospheric plages from Ca II K line synoptic maps and assigning magnetic polarities based on the observed polarity of sunspots. We used a surface flux transport (SFT) model to simulate the evolution of the photospheric magnetic field from the reconstructed active regions. We used the potential field source surface (PFSS) model to determine the amount of open magnetic flux from the reconstruction and from magnetographic observations. We also reconstructed the coronal field during two eclipses and compared the result with eclipse drawings. Results. We successfully reconstructed the photospheric magnetic field from 1915 to 1985. The number and total magnetic flux of the reconstructed active regions shows a realistic cyclic behavior that mostly follows the evolution of the sunspot number, even on relatively short timescales. The polar field strengths of cycles 19 and 20 do not reflect the evolution of the sunspot number very accurately, which may be related to problems related to the calcium data during cycle 19 and the long data gap during cycle 20. The polarity of polar fields and the amount of open field both at high and low latitudes all demonstrate the expected cyclic behaviour. The agreement of the modeled coronal structure with eclipse drawings in 1922 and 1923 is fair.

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Long-term studies of photospheric magnetic fields on the Sun

Cited by 15 publications

References 167 publications

On effects of surface bipolar magnetic regions on the convection zone dynamo

On effects of surface bipolar magnetic regions on the convection zone dynamo

A Multicomponent Magnetic Proxy for Solar Activity

Reconstructing solar magnetic fields from historical observations

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