Field Of Sunspots Research Articles

Evaluation of a Magnetic Field Inversion Method Using Only Stokes I

We compare a method for inferring the photospheric vector magnetic field using only spectroscopy to a conventional method based on polarimetry. The magnetic field strength B and inclination angle can be inferred from the Zeeman splitting using only Stokes I. We applied this method to a sunspot observed with the Vacuum Tower Telescope and compared the results to vector magnetograms from the Helioseismic and Magnetic Imager on the Solar Dynamics Observatory, which used a polarimetric inversion. The spectroscopic inversion tends to show higher values in B compared to the polarimetric data. In quiet regions the discrepancy in B was typically a factor of two. In the strong sunspot fields, the differences averaged ≈22%. These discrepancies are significant, but comparable to those typically found among magnetograms from different instruments. Our results support the use of the spectroscopic inversion technique to provide a fast and reasonable estimate of B.

Classification of circular polarization Stokes profiles in a sunspot using k-means clustering

The magnetic and velocity fields in sunspots are highly structured on small spatial scales which are encoded in the Stokes profiles. The Stokes profiles are in turn, derived from a sequence of polarization modulations on the incoming light that are imaged using an analyser-detector combination. Our aim is to identify Stokes profiles in a sunspot which exhibit spectral characteristics that deviate from those associated with the Evershed flow and their corresponding spatial distribution. To that end, we employ the k-means clustering routine to classify Stokes V spectra in the penumbra of a regular, unipolar sunspot, that also comprises a granular and a filamentary light bridge. We find that 75% of the penumbral region, corresponding to about 93500 pixels, is dominated by profiles comprising two, nearly anti-symmetric lobes, while 21% of the area is occupied by three-lobed profiles that are associated with the Evershed flow returning to the solar photosphere. The remaining 4% of the penumbral area is dominated by four groups/families of profiles - Group 1: three-lobed profiles in which both the rest and strong downflowing (sometimes supersonic) component have the same polarity as the host sunspot and seen exclusively in the filamentary light bridge. Group 2: single, red-lobed profiles occupying an area of about 2% located at the outer penumbra in discrete patches that possibly signify the downflowing leg of an Ω-loop. Group 3: three-lobed or highly asymmetric profiles, in which the rest component and the strong downflowing component have an opposite polarity as the sunspot. These occupy about 1.4% of the penumbra’s area and are seen in conspicuous, elongated structures or isolated patches in the outer penumbra and at the penumbra-quiet Sun boundary. Group 4: three lobed-profiles, in which the rest component has the same polarity as the sunspot and a weaker, upflowing component with a polarity opposite that of the sunspot. These profiles are located close to the entrance of the filamentary light bridge and are found in only 0.12% of the penumbral area. These minority groups of profiles could be related to dynamic phenomena that could also affect the overlying chromosphere. The simplicity and speed of k-means can be utilized to identify such anomalous profiles in larger data sets to ascertain their temporal evolution and the physical processes responsible for these inhomogeneities.

TO THE QUESTION OF THE LOCALIZATION OF CME GENERATION ON THE SUN

The localization of CME occurrence zones on the Sun from November 2006 to February 2007 was studied using the SOHO catalog. A method is described for comparing such zones with active regions (ARs) both in the visible and invisible hemispheres of the Sun. It is shown that a simple linear continuation of the projections of the CME trajectory on the Sun in many cases passes by the AO. 63.5% of CMEs managed to be tied to ARs, 19% failed, and for 17.5% a choice must be made between ARs and flare sites, where spots were observed 1–3 rotations of the Sun earlier. The hypothesis is discussed that the displacement of the beginning of the CME trajectory from the AR centroid is associated with the asymmetry of the location of the magnetic rope, on the basis of which the CME is formed, with respect to the AO: one base of the rope is located near the strong magnetic fields of sunspots, the second is in the region of weak fields on the periphery or outside the AO.

On the Magnetic Nature of Quiet-Sun Chromospheric Grains

Ca ii K grains, i.e., intermittent, short-lived (about 1 minute), periodic (2–4 minutes), pointlike chromospheric brightenings, are considered to be the manifestations of acoustic waves propagating upward from the solar surface and developing into shocks in the chromosphere. After the simulations of Carlsson and Stein, we know that hot shocked gas moving upward interacting with the downflowing chromospheric gas (falling down after having been displaced upward by a previous shock) nicely reproduces the spectral features of the Ca ii K profiles observed in such grains, i.e., a narrowband emission-like feature at the blue side of the line core. However, these simulations are one-dimensional and cannot explain the location or the pointlike shape of the grains. Here, we report on the magnetic nature of these events. Furthermore, we report on similar events occurring at the largest flux concentrations, though they are longer-lived (up to 8 minutes) and exhibit the typical signature of steep velocity gradients traveling across the atmosphere. The spectral signatures of the studied events resemble their counterparts in sunspots, the umbral flashes. We then propose that magnetohydrodynamical waves are not only channeled through the magnetic field in sunspots, but they pervade the whole atmosphere. The propagation along magnetic fields can explain the pointlike appearance of the calcium grains observed in the quiet chromosphere.

Dynamics of Photospheric Magnetic Flux Distribution and Variations in Solar RVs: A Study Using HARPS-N Solar and SDO Observations

The distribution and evolution of photospheric magnetic fields in sunspots, plages, and network, and variations in their relative flux content, play key roles in radial velocity (RV) fluctuations observed in Sun-as-a-star spectra. Differentiating and disentangling such magnetic contributions to RVs help in building models to account for stellar activity signals in high-precision RV exoplanet searches. In this work, as earlier authors, we employ high-resolution images of the solar magnetic field and continuum intensities from SDO/HMI to understand the activity contributions to RVs from HARPS-N solar observations. Using well-observed physical relationships between strengths and fluxes of photospheric magnetic fields, we show that the strong fields (spots, plages, and network) and the weak inter-network fields leave distinguishing features in their contributions to the RV variability. We also find that the fill factors and average unsigned magnetic fluxes of different features correlate differently with the RVs and hence warrant care in employing either of them as a proxy for RV variations. In addition, we examine disk-averaged UV intensities at 1600 and 1700 Å wavelength bands imaged by SDO/AIA and their performances as proxies for variations in different magnetic features. We find that the UV intensities provide a better measure of contributions of plage fields to RVs than the Ca ii H-K emission indices, especially during high activity levels when the latter tend to saturate.

АСТРОНОМІЧНА ОБСЕРВАТОРІЯ КИЇВСЬКОГО НАЦІОНАЛЬНОГО УНІВЕРСИТЕТУ ІМЕНІ ТАРАСА ШЕВЧЕНКА У 2023 р.

In 2023, the Astronomical Observatory employed 67 employees, including 48 full-time and 19 part-time workers, 35 scientists (9 doctors of science and 15 candidates of science). During the year, 5 budget topics were implemented. Main scientific results. The cosmological and astrophysical manifestations of F(R) gravity, as an inflationary theory and as a candidate for dark matter, were studied. It is shown that a modified theory of gravity, with a different expression for the action, can have observable manifestations that are interpreted as manifestations of the existence of dark matter. The mechanisms of the acceleration of cosmic rays at the fronts of relativistic shock waves in the relativistic jets of active galactic nuclei (AGN) were considered, the expected fluxes and spectra of cosmic rays of non-thermal and neutrino radiation from them were calculated, and the prospects of registering these fluxes with the detectors of the STA and IceCube Cherenkov telescopes were assessed. On the basis of photometric, polarimetric and spectral observations, non-stationary processes in the short-period comet 67P/Churyumov– Gerasimenko, the hyperbolic comet C/2013 X1, the active asteroid 2005 QN173 and the centaur 174P/Echeclus were studied. Morphological, optical, physical and chemical characteristics of the researched chewed objects were obtained. Based on data from the “Rosetta” space mission to comet 67P/C-G, a new method for direct determination of the volume distribution of dust in the coma by nuclear shadow photometry is proposed. For the first time, the formation of an unstable atmosphere around the nucleus during an outburst was recorded. New observational data have been obtained that confirm the existence of strong magnetic fields (up to 105 Gs) in powerful solar flares – 2 orders of magnitude stronger than the well-known magnetic fields in sunspots. Based on the study of the growth curves of solar activity in the previous 24 cycles, the forecast of the current 25th cycle was calculated and it was concluded that the amplitude of the smoothed numbers of sunspots in the current cycle is expected to be within 150 ± 30 units. Based on the results of research, 2 monographs, 2 textbooks, 75 scientific articles, 89 reports at scientific conferences were published.

Clarifying Physical Properties of Magnetic Fields in Sunspots

We demonstrate that the radial magnetic-field component at the outer boundary of the sunspot penumbra is about 550 Mx cm$^{-2}$ independent of the sunspot area and the maximum magnetic field in the umbra. The mean magnetic-field intensity in sunspots grows slightly as the sunspot area increases up to 500 -- 1000 millionth of visual hemisphere (m.v.h.) and may reach about 900 -- 2000 Mx cm$^{-2}$. The total magnetic flux weakly depends on the maximum field strength in a sunspot and is determined by the spottedness, i.e. the sunspot number and the total sunspot area; however, the relation between the total flux and the sunspot area is substantially nonlinear. We suggest an explicit parametrization for this relation. The contribution of the magnetic flux associated with sunspots to the total magnetic flux is small, not achieving more than 20% even at the maximum of the solar activity.

Magnetic Field Re-configuration Associated With a Slow Rise Eruptive X1.2 Flare in NOAA Active Region 11944

Using multi-wavelength observations, we analysed magnetic field variations associated with a gradual X1.2 flare that erupted on January 7, 2014 in active region (AR) NOAA 11944 located near the disk center. A fast coronal mass ejection (CME) was observed following the flare, which was noticeably deflected in the south-west direction. A chromospheric filament was observed at the eruption site prior to and after the flare. We used SDO/HMI data to perform non-linear force-free field extrapolation of coronal magnetic fields above the AR and to study the evolution of AR magnetic fields prior to the eruption. The extrapolated data allowed us to detect signatures of several magnetic flux ropes present at the eruption site several hours before the event. The eruption site was located under slanted sunspot fields with a varying decay index of 1.0-1.5. That might have caused the erupting fields to slide along this slanted magnetic boundary rather than vertically erupt, thus explaining the slow rise of the flare as well as the observed direction of the resulting CME. We employed sign-singularity tools to quantify the evolutionary changes in the model twist and observed current helicity data, and found rapid and coordinated variations of current systems in both data sets prior to the event as well as their rapid exhaustion after the event onset.

Long-term studies of photospheric magnetic fields on the Sun

We briefly review the history of observations of magnetic fields on the Sun, and describe early magnetograps for full disk measurements. Changes in instruments and detectors, the cohort of observers, the knowledge base etc may result in non-uniformity of the long-term synoptic datasets. Still, such data are critical for detecting and understanding the long-term trends in solar activity. We demonstrate the value of historical data using studies of active region tilt (Joy’s law) and the evolution of polar field and its reversal. Using the longest dataset of sunspot field strength measurements from Mount Wilson Observatory (1917-present) supplemented by shorter datasets from Pulkovo (1956–1997) and Crimean (1956-present) observatories we demonstrate that the magnetic properties of sunspots did not change over the last hundred years. We also show that the relationship between the sunspot area and its magnetic flux can be used to extend the studies of magnetic field in sunspots to periods with no direct magnetic field measurements. Finally, we show how more recent full disk observations of the vector magnetic field can be used to study the long-term (solar cycle) variations in magnetic helicity on the Sun.

Sunspot magnetic fields: a comparison between the CrAO and SDO/HMI data

We performed a digitization of maximum magnetic field measurements in sunspots. The original data were acquired as drawings at the Crimean Astrophysical Observatory of the Russian Academy of Sciences (CrAO RAS). About 1000 sunspots observed in 2014 have been analyzed. The data were compared to the corresponding measurements from the SDO/HMI instrument (with both the line-of-sight magnetic field Bz(HMI) and the modulus of the magnetic field vector B(HMI)). For the same sunspot, the maximum modulus of the magnetic field derived at CrAO was compared to the corresponding value from HMI. The Crimean data and the space-based data (of both types) were found to be in direct proportion to each other. A linear approximation over the entire range of measurements (1–4) kilogauss (kG) shows a Pearson correlation coefficient of 0.71 (with the 95 % confidence boundaries of 0.68–0.74) and a slope of linear regression of 0.65±0.02 for both types of the space-based data. A linear approximation over the range of strong fields B(CrAO) > 1.8 kG gives a similar correlation, however the slope of linear regression is far closer to unity and constitutes 0.90 for the relationship (Bz(HMI) vs B(CrAO)) and 0.84 for the relationship (B(HMI) vs B(CrAO)). In the range of weak fields B(CrAO) < 1.8 kG, a non-linear deviation (exceeding) of the space-based data is observed. Non-linearity can be explained, in part, by a specific routine of the magnetic field measurements at CrAO, however further investigations are needed to explore sources of possible non-linearity in the HMI data. The Crimean measurements of the maximum magnetic field in sunspots are concluded to be in good agreement with the corresponding SDO/HMI measurements, and therefore they can be used for scientific purposes.

Detection of Opposite Magnetic Polarity in a Light Bridge: Its Emergence and Cancellation in Association with LB Fan-shaped Jets

Abstract Light bridges (LBs) are relatively bright structures that divide sunspot umbrae into two or more parts. Chromospheric LBs are known to be associated with various activities including fan-shaped jet-like ejections and brightenings. Although magnetic reconnection is frequently suggested to be responsible for such activities, not many studies present firm evidence to support the scenario. We carry out magnetic field measurements and imaging spectroscopy of an LB where fan-shaped jet-like ejections occur with co-spatial brightenings at their footpoints. We study LB fine structure and magnetic field changes using TiO images, Near-InfraRed Imaging Spectropolarimeter, and Hα data taken by the 1.6 m Goode Solar Telescope. We detect magnetic flux emergence in the LB that is of opposite polarity to that of the sunspot. The new magnetic flux cancels with the pre-existing flux at a rate of 5.6 × 1018 Mx hr−1. Both the recurrent jet-like ejections and their base brightenings are initiated at the vicinity of the magnetic flux cancellation, and show apparent horizontal extension along the LB at a projected speed of up to km s−1 to form a fan-shaped appearance. Based on these observations, we suggest that the fan-shaped ejections may have resulted from slipping reconnection between the new flux emerging in the LB and the ambient sunspot field.

THE ROLE OF MACROSCOPIC TURBULENT DIAMAGNETISM IN ENSURING LONG-TERM STABILITY OF SUNSPOTS

We investigated the role of macroscopicturbulent diamagnetism in ensuring the long-term stabilityof the equilibrium state of the sunspots. The physicalmeaning of macroscopic diamagnetism of turbulentplasma is expulsion of a large-scale magnetic field fromareas with increased turbulence intensity to areas withreduced turbulence. We follow the idea of Krause &Rüdiger (1975) that a strong magnetic field of a sunspotmodifies the structure of turbulence in spot umbra, so itbecomes two-dimensional. In addition, we take into accountthe strong magnetic suppression of turbulence in the spot,where it becomes less intense than the turbulent convectionaround the spot. As a result, a relatively thin transitionalvertical layer of permeable convection (convective overshotlayer) should be formed between these sections, in whichthe intensity of turbulent pulsations decreases noticeablyin the transverse direction during the transition from theconvection section to the spot. In this permeable convectionlayer, the effect of turbulent diamagnetic displacement ofthe magnetic field from the convection region to the sunspotoccurs. Owing to the two-dimensional turbulent diffusion,the magnetic field of the spot spreads outwards, while theintense turbulent pulsations in the convection region returnthe magnetic field in the opposite direction, back to thespot. Therefore, these two oppositely directed processes ofmagnetic field transfer in the horizontal plane competewith each other. As a result, the magnetic fields that aretransferred due to turbulent diffusion outward from thesunspot will be thrown backward into the spot due to strongexternal turbulent convection. In our opinion, this effectshould ensure long-term stability of the equilibrium stateof the magnetic field of sunspots and support them in theform of isolated vertical unipolar magnetic force tubes.

Formation of superstrong horizontal magnetic field in delta-type sunspot in radiation magnetohydrodynamic simulations

ABSTRACT We perform a series of radiative magnetohydrodynamic simulations to understand the amplification mechanism of the exceptionally strong horizontal magnetic field in delta-type sunspots. In the simulations, we succeed in reproducing the delta-type sunspot and resulting strong magnetic field exceeding 6000 G in a light bridge between the positive and negative polarities. Our conclusions in this study are summarized as follows: (1) The essential amplification mechanism of the strong horizontal magnetic field is the shear motion caused by the rotation of two spots. (2) The strong horizontal magnetic field remains the force-free state. (3) The peak strength of the magnetic fields does not depend on the spatial resolution, top boundary condition, or Alfvén speed limit. The origin of the rotating motion is rooted in the deep convection zone. Therefore, the magnetic field in the delta-spot light bridge can be amplified to the superequipartition values in the photosphere.

Connecting the Wilson depression to the magnetic field of sunspots

Context. In sunspots, the geometric height of continuum optical depth unity is depressed compared to the quiet Sun. This so-called Wilson depression is caused by the Lorentz force of the strong magnetic field inside the spots. However, it is not understood in detail yet how the Wilson depression is related to the strength and geometry of the magnetic field or to other properties of the sunspot. Aims. We aim to study the dependence of the Wilson depression on the properties of the magnetic field of the sunspots and how exactly the magnetic field contributes to balancing the Wilson depression with respect to the gas pressure of the surroundings of the spots. Methods. Our study is based on 24 spectropolarimetric scans of 12 individual sunspots performed with Hinode. We derived the Wilson depression for each spot using both a recently developed method that is based on minimizing the divergence of the magnetic field and an approach that was developed earlier, which enforces an equilibrium between the gas pressure and the magnetic pressure inside the spot and the gas pressure in the quiet Sun, thus neglecting the influence of the curvature force. We then performed a statistical analysis by comparing the Wilson depression resulting from the two techniques with each other and by relating them to various parameters of the sunspots, such as their size or the strength of the magnetic field. Results. We find that the Wilson depression becomes larger for spots with a stronger magnetic field, but not as much as one would expect from the increased magnetic pressure. This suggests that the curvature integral provides an important contribution to the Wilson depression, particularly for spots with a weak magnetic field. Our results indicate that the geometry of the magnetic field in the penumbra is different between spots with different strengths of the average umbral magnetic field.

Магнитные поля солнечных пятен: сравнение данных КрАО и SDO/HMI

Переведены в цифровой формат данные об измерении максимального магнитного поля в солнечных пятнах, полученные в Крымской астрофизической обсерватории Российской академии наук (КрАО РАН) в виде зарисовок. Исследовано около 1000 пятен, наблюдавшихся в 2014 году. Эти данные были сопоставлены с данными SDO/HMI (значениями магнитного поля по лучу зрения Bz(HMI) и значениями модуля полного вектора магнитного поля B(HMI)). Сравнивались максимальные значения модуля поля в одних и тех же пятнах. Показано, что имеет место прямо пропорциональная зависимость между крымскими данными и космическими данными обоих типов. Линейная аппроксимация для всего интервала измерений поля (1–4) килогаусс (kG) показывает коэффициент корреляции Пирсона 0.71 (95 % доверительный интервал: 0.68–0.74) и наклон линейной регрессии 0.65 ± 0.02 для обоих типов космических данных. Линейная аппроксимация в области сильных полей B(CrAO) > 1.8 kG показывает примерно тот же коэффициент корреляции, но значительно более близкий к единице наклон линейной регрессии: 0.90 для (Bz(HMI) vs B(CrAO)) и 0.84 для (B(HMI) vs B(CrAO)). При слабых полях B(CrAO) < 1.8 kG наблюдается нелинейное отклонение (завышение) космических данных. Характер нелинейности частично можно объяснить особенностями крымской методики измерений, однако этот вопрос требует дальнейшего исследования возможных источников нелинейности в космических данных. Сделан вывод о том, что данные по измерению магнитного поля в КрАО показывают хорошее согласие со значениями современного космического аппарата SDO/HMI, поэтому их можно использовать в научных целях.

Reconstructing solar magnetic fields from historical observations

Context. Systematic observations of magnetic field strength and polarity in sunspots began at Mount Wilson Observatory (MWO), USA in early 1917. Except for a few brief interruptions, this historical dataset has continued until the present. Aims. Sunspot field strength and polarity observations are critical in our project of reconstructing the solar magnetic field over the last hundred years. We provide a detailed description of the newly digitized dataset of drawings of sunspot magnetic field observations. Methods. The digitization of MWO drawings is based on a software package that we developed. It includes a semiautomatic selection of solar limbs and other features of the drawing, and a manual entry of the time of observations, measured field strength, and other notes handwritten on each drawing. The data are preserved in an MySQL database. Results. We provide a brief history of the project and describe the results from digitizing this historical dataset. We also provide a summary of the final dataset and describe its known limitations. Finally, we compare the sunspot magnetic field measurements with those from other instruments, and demonstrate that, if needed, the dataset could be continued using modern observations such as, for example, the Vector Stokes Magnetograph on the Synoptic Optical Long-term Investigations of the Sun platform.

Changes of space weather and space climate at Earth orbit: An update

We present an update of the changes in space weather/space climate at Earth orbit using sunspot number (SSN) timeline (1700–2018), geomagnetic indices aa/Ap, solar polar magnetic field, interplanetary magnetic field (IMF) and galactic cosmic ray (GCR) flux in the stratosphere at high latitudes. The Cycle 24 is close to solar minimum, expected in 2020. The baseline of aa index increases monotonically from 1900 to 1986 and declines steeply afterwards, solar polar magnetic field decreases systematically for the last three cycles (22–24) as do SSNs at cycle peaks. Livingston and Penn (2009) note a long term weakening of maximum magnetic field in sunspots since 1992. They expect SSNs for the Cycle 25 to peak at 7 (a steep decline in solar activity) leading to Maunder-like minimum, in contrast to prediction of several colleagues of a Dalton minimum. The North-South asymmetry in solar polar field is pronounced for the decay phase of cycles 23, 24, itseems to change sign after the Cycle 21. GCR flux in the stratosphere is greater that in 1965 and increasing, pointing to an enhanced radiation exposure in future for the passengers on transpolar flights, the astronauts on the space station as well as those travelling to and staying on the Moon and the Mars on prolonged missions; the assets in space would have to be hardened for safety from increased radiation. We speculate about the connection between the Earth climate and changes in solar activity, inferring that the science of the Earth climate change is not settled yet.

Magnetic flux participation in solar surface magnetism during solar cycle 24

This study aims at investigating surface magnetic flux participation among different types of magnetic features during solar cycle 24. State-of-the-art observations from SDO/HMI and Hinode/SOT are combined to form a unique database in the interval from April 2010 to October 2015. Unlike previous studies, the statistics presented in this paper are feature-detection-based. More than 20 million magnetic features with relatively large scale, such as sunspot/pore, enhanced and quiet networks, are automatically detected and categorized from HMI observations, and the internetwork features are identified from SOT/SP observations. The total flux from these magnetic features reaches 5.9×1022 Mx during solar minimum and 2.4×1023 Mx in solar maximum. Flux occupation from the sunspot/pore region is 29% in solar maximum. Enhanced and quiet networks contribute 18% and 21% flux during the solar minimum, and 50% and 9% flux in the solar maximum respectively. The internetwork field contributes over 55% of flux in the solar minimum, and its flux contribution exceeds that of sunspot/pore features in the solar maximum. During the solar active condition, the sunspot field increases its area but keeps constant flux density of about 150G, while the enhanced network follows the sunspot number variation showing increasing flux density and area, but the quiet network displays decreasing area and somewhat increasing flux density of about 6%. The origin of the quiet network is not known exactly, but is suggestive of representing the interplay between mean-field and local dynamos. The source, magnitude and possible importance of ‘hidden flux’ are discussed in some detail.

ДОСЛІДЖЕННЯ ЦИКЛІЧНОСТІ МАГНЕТИЗМУ СОНЦЯ В МЕЖАХ ТЕОРІЇ МАКРОСКОПІЧНОЇ МАГНІТОГІДРОДИНАМІКИ

Since the mid-70s of the last century, a new direction in theoretical studies of the evolution of the global magnetism of the Sun in the framework of macroscopic MHD has been launched at the Astronomical Observatory of the Taras Shevchenko National University of Kyiv. The paper presents the results of a study of the processes of generation and restructuring of a large-scale (global) magnetic field based on the αΩ-dynamo model, taking into account new turbulent effects discovered in the theory of macroscopic MHD and data of helioseismological experiments on the internal rotation of the Sun. It was established that a sharp radial gradient of turbulent velocity in the lower half of the solar convective zone (SCZ) leads to a change in the sign of the azimuthal component of the helicity parameter α, resulting in the formation of a relatively thin layer of negative α-effect near the bottom of the SCZ. It was found that the layer of negative α-effect, together with the sign of the radial gradient of the angular velocity, detected in helioseismological experiments, makes it possible to explain the direction of migration of dynamo-waves on the solar surface. The magnetic saturation of the α-effect (alpha-quenching) in the deep layers of the SCZ was calculated. An explanation of the protracted duration of the 23rd solar cycle of about 13 years is proposed. For this, we used the observed data on a significant increase of the annual module of the magnetic fields of sunspots in the 23rd cycle. The calculated north-south asymmetry of the structure of the global magnetic field provides an opportunity to explain the phenomenon of the seeming magnetic “monopole”, which is observed during reversal of polar magnetism. It was found that the values of turbulent electrical conductivity and turbulent magnetic permeability of the solar plasma are significantly less than the corresponding gas-kinetic parameters. Therefore, the turbulent dissipation of solar magnetic fields is enhanced by 4–9 orders of magnitude compared with classical ohmic dissipation. Macroscopic turbulent diamagnetism of solar plasma was investigated. It has been found that in the lower part of the SCZ, turbulent diamagnetism acts against magnetic buoyancy, thus fulfilling the role of “negative magnetic buoyancy”. As a result of the balance of the effects of magnetic buoyancy and turbulent diamagnetism, a layer of blocked magnetic field of magnitude ≈ 3000 G is formed in the depths of the SCZ. The turbulent advection of a magnetic field in an inhomogeneous plasma density of the SCZ was studied. It was found that in the lower half of the SCZ of the equatorial domain, turbulent advection is directed upwards. As a result of the combined action of magnetic buoyancy and turbulent advection, deep strong toroidal fields are carried to the surface of the Sun in the latitudinal “royal zone” of sunspots. The role of horizontal turbulent diamagnetism in ensuring the long-term stability of sunspots was noted. To explain the observed phenomenon of double maxima of the solar spot cycle, a scenario was developed containing the generation of a magnetic field in the tachocline at the bottom of the SCZ and subsequent removal of this magnetic field from the depth layers to the surface in the latitudinal “royal zone”. The role of the radial omega-effect in the radiant zone in explaining the observed asymmetry in the amplitude of two neighbouring 11-years sunspot cycles was noted.

Incorporating Surface Convection into a 3D Babcock–Leighton Solar Dynamo Model

Abstract The convective flows observed on the photosphere (e.g., supergranulation, granulation) play a key role in the Babcock–Leighton (BL) process to generate large-scale polar fields from sunspot fields. In most surface flux transport (SFT) and BL dynamo models, the dispersal and migration of surface fields are modeled as an effective turbulent diffusion. Recent SFT models have incorporated explicit, realistic convective flows in order to improve the fidelity of convective transport but, to our knowledge, this has not yet been implemented in previous BL models. We present the first kinematic 3D Flux-Transport/BL model to explicitly incorporate realistic convective flows based on solar observations. Though we describe a means to generalize these flows to 3D, we find that the kinematic small-scale dynamo action they produce disrupts the operation of the cyclic dynamo. The cyclic solution is found by limiting the convective flow to act only on the vertical radial component of the magnetic field. The results obtained are generally in good agreement with the observed surface flux evolution and with non-convective models that have a turbulent diffusivity of the order of 3 × 1012 cm2 s−1 (300 km2 s−1). However, we find that the use of a turbulent diffusivity underestimates the dynamo efficiency, producing weaker mean fields and a shorter cycle than in the convective models. Also, the convective models exhibit bands of mixed polarity in the polar regions that have no counterpart in solar observations, and the poleward migration speed of poloidal flux is determined mainly by the meridional flow and the vertical diffusion.