Large-scale Solar Magnetic Field Research Articles

The nature of strong temblors on earth and large coronal mass ejections on the Sun: Summer 2012

It was discovered that the dates of the earthquakes of the summer 2012, being ordered in accordance with the corresponding Carrington rotations (CR) of the Sun nos. 2123–2127, form four discrete isolated groups, with a 30-day periodicity of the earthquakes in each group. On the Sun, the moments of the earthquakes correspond to four groups of the discrete Carrington longitudes (CL) of the four-sector structure of the large-scale open solar magnetic field (LOSMF). Close to each time of occurrence of the earthquake, the strong coronal mass ejections (CME) of Halo and Particle Halo types were identified. It was unexpectedly discovered that the occurrence times of the earthquakes and the onsets of CMEs are approximately synchronous, either keeping slightly ahead or lagging somewhat behind each other. This means that the earthquakes and CMEs are governed by a common external factor. The hypothesis that this could have been caused by the influence of Jupiter is supported by the discovered phenomenon of the eclipse of Jupiter by the Sun in May–June 2012, when the Sun occurred between Jupiter and the Earth and a significant decline in the magnitudes of the quakes was detected on the Earth.

Dynamics of the large-scale open solar magnetic field and its specific features in the zone of the main active longitudes in 2006–2012

The dynamics of the absolute global values (Φ) of the large-scale open solar magnetic field (LOSMF) fluxes at an interval of one solar rotation in 2006–2012 has been studied based on the Wilcox Solar Observatory data and using the ISOPAK original package for modeling the solar magnetic field. The reference points and the duration of the final quasi-biennial interval in cycle 23 (January 2006–May 2007; 17 months) and the phases of the cycle 24 minimum (May 2007–November 2009; 30 months), growth (November 2009–May 2012; 30 months), and the beginning of the maximum (May 2012–January 2013) have been determined. It has been indicated that the absolute values (Φ) decreased sharply at the beginning of the minimum, growth, and the maximum phases to ∼(2, 1.25, 0.75) × 1022 Mx, respectively. During the entire minimum phase, LOSMF corotated super-quasi-rigidly westward in the direction of solar rotation; at the beginning of the growth phase, this field started corotating mostly eastward. The LOSMF polarity reversal in the current cycle 24 started in May–June 2012 (CR 2123–2124), when fields of southern polarity rushed from the Sun’s southern hemisphere toward the north. The statement that the solar cycle is a continuous series of quasi-biennial LOSMF intervals is confirmed. In particular, the minimum and growth phases are characterized by opposite LOSMF rotation directions, i.e., super-quasi-rigid corotation (twisting) and detwisting, with identical duration at least in cycle 24.

Large-scale solar magnetic field mapping: I.

This article focuses on mapping the Sun’s large-scale magnetic fields. In particular, the model considers how photospheric fields evolve in time. Our solar field mapping method uses Netlogo’s cellular automata software via algorithms to carry out the movement of magnetic field on the Sun via agents. This model's entities consist of two breeds: blue and red agents. The former carry a fixed amount of radially outward magnetic flux: 1023 Mx, and the latter, the identical amount of inward directed flux. The individual agents are distinguished, for clarity, by various shades of blue and red arrows whose orientation indicates the direction the agents are moving, relative to the near-steady bulk fluid motions. The fluid motions generally advect the field with the well known meridional circulation and differential rotation. Our model predominantly focuses on spatial and temporal variations from the bulk fluid motions owing to magnetic interactions. There are but a few effects that agents have on each other: i) while at the poles, field agents are connected via the Babcock - Leighton (B - L) subsurface field to other latitudes. This allows them to undertake two duties there: A) the B - L subsurface field spawns the next generation of new magnetic field via new agents, and B) the B - L subsurface field attracts lower-latitude fields via the “long-range” magnetic stress tension; ii) nearby agents affect each other’s motion by short-range interactions; and iii) through annihilation: when opposite field agents get too close to each other, they disappear in pairs. The behavior of the agents’ long- and short-range magnetic forces is discussed within this paper as well as the model's use of internal boundary conditions. The workings of the model may be seen in the accompanying movies and/or by using the software available via SpringerPlus’ website, or on the NetlogoTM community website, where help is readable available, and should all these fail, some help from the author.Electronic supplementary materialThe online version of this article (doi:10.1186/2193-1801-2-21) contains supplementary material, which is available to authorized users.

Relationship between cyclic variations in the velocity and occurrence frequency of coronal mass ejections and cyclic changes in the structure of the large-scale solar magnetic field

This paper investigates the relationship between cyclic variations in the velocity of coronal mass ejections and cyclic changes in the structure of the large-scale solar magnetic field (LSSMF) in solar cycle 23, using the effective solar multipole index as a parameter of the characteristic dimensions of LSSMF structural elements. Cyclic variations in the velocity and frequency of coronal mass ejections are found to resemble cyclic changes in the effective solar multipole index. It is suggested that cyclic changes in the maximum velocity of coronal mass ejections are associated with different conditions for the formation of complexes of active regions connected by coronal arch structures, the energy of which is the main source of energy (velocity) for coronal mass ejections. The study leads to some suggestions about the possible site of initiation of coronal mass ejections.

Solar dynamo model with nonlocal alpha-effect and diamagnetic pumping

AbstractSunspot data and large-scale solar magnetic field data are used to demonstrate the operation of the Babcock-Leighton mechanism on the Sun. A dynamo model is developed that employs jointly a nonlocal alpha-effect of the Babcock-Leighton type and diamagnetic downward pumping. The pumping concentrates magnetic fields to the base of the convection zone. The magnetic cycle period, equatorial symmetry of the generated fields, their meridional drift, and the polar-to-toroidal field ratio obtained in the model agree with observations.

Height stratification of solar magnetic fields in cycle 23

The radial component Br of magnetic field was calculated in the potential approximation and the synoptic maps of Br for several heights in the Solar atmosphere were constructed based on observations of the photospheric magnetic field made on the old magnetograph at the US Kitt Peak National Observatory and on the new SOLIS magnetograph at the US National Solar Observatory for cycle 23 (the years 1997–2009). Parameters of large-scale structures of magnetic field with positive and negative polarities were determined at seven heights in the Sun’s atmosphere—from the photosphere (H = Ro) to H = 2.5 Ro (Ro is the Solar radius). The processes of polar reversal for polar fields and changing of the sector structure of the field at middle latitudes were observed. Characteristic lifespans and rotations were ascertained. The general picture of variations of the large-scale solar magnetic field during cycle 23 was put forward. Two types of boundaries of large magnetic structures at various heights were identified.

The solar magnetic field since 1700

We have used semi-synthetic records of emerging sunspot groups based on sunspot number data as input for a surface flux transport model to reconstruct the evolution of the large-scale solar magnetic field and the open heliospheric flux from the year 1700 onward. The statistical properties of the semi-synthetic sunspot group records reflect those of the observed Royal Greenwich Observatory photoheliographic results. These include correlations between the sunspot numbers and sunspot group latitudes, longitudes, areas and tilt angles. The reconstruction results for the total surface flux, the polar field, and the heliospheric open flux (determined by a current sheet source surface extrapolation) agree well with the available observational or empirically derived data and reconstructions. We confirm a significant positive correlation between the polar field during activity minimum periods and the strength of the subsequent sunspot cycle, which has implications for flux transport dynamo models for the solar cycle. Just prior to the Dalton minimum, at the end of the 18th century, a long cycle was followed by a weak cycle. We find that introducing a possibly “lost” cycle between 1793 and 1800 leads to a shift of the minimum of the open flux by 15 years which is inconsistent with the cosmogenic isotope record.

Crossing Filaments

Solar filaments show the position of large scale polarity inversion lines and are used for the reconstruction of large-scale solar magnetic field structure on the basis of H{\alpha} synoptic charts for the periods when magnetographic measurements were not available. Sometimes crossing filaments are seen in H{\alpha} filtergrams. We analyze daily H{\alpha} filtergrams from the archive of Big Bear Solar Observatory for the period of 1999-2003 to find crossing and interacting filaments. A number of examples are presented and filament patterns are compared with photospheric magnetic field distributions. We have found that all crossing filaments reveal quadrupolar magnetic configurations of the photospheric field and presume the presence of null points in the corona.

Laws of the Evolution of Large-Scale Magnetic Fields in the Sun by Observations Data

On the basis of the observations data the evolution of large-scale solar magnetic fields during three solar cycles was investigated and the general picture of changing the solar cycles of weak photospheric and strong (in active regions) fields was determined. It has been found that in addition to significant differences in the evolution of weak and strong magnetic fields there is a close relationship of their behavior in the separated out strength intervals, if the growth rate of the total flow field is considered as a characteristic for comparing. At present there is no well-reasoned theoretical explanation of the found in the article connection, and the problem of its interpretation is a subject of a separate research.

Displacement of large-scale open solar magnetic fields from the zone of active longitudes and the heliospheric storm of November 3–10, 2004: 2. “Explosion” of singularity and dynamics of sunspot formation and energy release

A more detailed scenario of one stage (August–November 2004) of the quasibiennial MHD process “Origination ... and dissipation of the four-sector structure of the solar magnetic field” during the decline phase of cycle 23 has been constructed. It has been indicated that the following working hypothesis on the propagation of an MHD disturbance westward (in the direction of solar rotation) and eastward (toward the zone of active longitudes) with the displacement of the large-scale open solar magnetic field (LOSMF) from this zone can be constructed based on LOSMF model representations and data on sunspot formation, flares, active filaments, and coronal ejections as well as on the estimated contribution of sporadic energy release to the flare luminosity and kinetic energy of ejections: (1) The “explosion” of the LOSMF singularity and the formation in the explosion zone of an anemone active region (AR), which produced the satellite sunspot formation that continued west and east of the “anemone,” represented a powerful and energy-intensive source of MHD processes at this stage. (2) This resulted in the origination of two “governing” large-scale MHD processes, which regulated various usual manifestations of solar activity: the fast LOSMF along the neutral line in the solar atmosphere, strongly affecting the zone of active longitudes, and the slow LOSMF in the outer layers of the convection zone. The fronts of these processes were identified by powerful (about 1031 erg) coronal ejections. (3) The collision of a wave reflected from the zone of active longitudes with the eastern front of the hydromagnetic impulse of the convection zone resulted in an increase in LOSMF magnetic fluxes, origination of an active sector boundary in the zone of active longitudes, shear-convergent motions, and generation and destabilization of the flare-productive AR 10696 responsible for the heliospheric storm of November 3–10, 2004.

The solar cycle from data on the large-scale surface magnetic field and solar-dynamo theory

Latitude-time (butterfly) diagrams of the large-scale solar magnetic field differ appreciably from the butterfly diagrams for sunspots. Tilted features corresponding to waves propagating from the middle latitudes to the equator are virtually absent from the diagrams for the large-scale magnetic field. The latitude-time diagram of the 22-year solar cycle based on data for the large-scale surface field appears as a checkerboard pattern rather than a traveling wave. Solutions describing similar behavior for the poloidal magnetic field are found for Parker’s solar-dynamo equations. These solutions agree with observations especially well if meridional circulation is added to the two sources generating the magnetic-field in this dynamo-differential rotation and mirror-asymmetric convection.

Displacement of large-scale open solar magnetic fields from the zone of active longitudes and the heliospheric storm of November 3–10, 2004: 1. The field dynamics and solar activity

The dynamics of the large-scale open field and solar activity at the second stage of the MHD process, including the origination and disappearance of the four-sector structure during the decline phase of cycle 23 (the stage when the blocking field is displaced from the main zone of active longitudes), has been considered. Extremely fast changes in the scales of one of new sectors (from an extremely small sector (“singularity”) to a usual sector that originated after the uniform expansion (“explosion”) of singularity with a “kick” into the zone of active longitudes, westward motion of the MHD disturbance front in the direction of solar rotation, and formation of an active quasi-rigidly corotating sector boundary responsible for the heliospheric storm of November 2004) have been detected in the field dynamics. It has been indicated that a very powerful group of sunspots AR 10656 (which disappeared after the explosion) with an area of up to 1540 ppmh (part per million hemisphere), a considerable deficit of the external energy release, and zero geoeffectiveness in spite of the closeness to the Earth helioprojection existed within singularity. It has been assumed that the energy escaped from this group with effort owing to the interaction between coronal ejections and narrow sector walls (singularity), and a considerable part of the energy was released in the outer layers of the convective zone, as a result of which singularity exploded and this explosion was accompanied by the above effects in the large-scale field and solar activity.

Superconcentration of photospheric sources of the large-scale open solar magnetic field in the main zone of active longitudes, blocking of differential rotation, and origination of the four-sector structure: 2. Geoeffectiveness

The effectiveness of the series of powerful heliospheric storms, originated during the decline phase of cycle 23 owing to the superconcentration of the open field photospheric sources in the main zone of active longitudes, has been studied. The geoeffectiveness of the storm of July 16—27, 2004, was closely related to the origination of the four-sector structure and depended on the destabilization of two activity centers weakly and strongly geoeffective with ARs 10649 and 10652. The first center was localized in one of the new sectors; the second center, in the western surroundings of the zone of active longitudes. The departure of coronal mass ejections from AR 10649 was substantially hindered: they were completely absent after the series of powerful X-ray flares, and a rare phenomenon of “sunquake” was observed: shock waves did not reach the Earth in spite of its favorable position. The Earth was strongly shielded by new sector boundaries from coronal ejections from AR 10652 with a gradual weakening and disappearance of this region, as a result of which the cascade of three near-Earth storms with an increasing power and Ap, indices of 52, 154, and 186 originated. Rare phenomena in AR 10649 and the cascade of solar—terrestrial heliospheric storms made the storm of July 16— 27 a unique phenomenon in cycle 23, and a short-term prediction of its geoeffectiveness was impossible.

An advective solar-type dynamo without the $\sf \alpha$ effect

<i>Context. <i/> Most solar and stellar dynamo models use the scenario where the magnetic field is generated by the interplay between differential rotation (the <i>Ω<i/> effect) and a mean electromotive force due to helical turbulent convection flows (the <i>α<i/> effect). There are, however, turbulent dynamo mechnisms that may complement the <i>α<i/> effect or may be an alternative to it.<i>Aims. <i/>We investigate models of solar-type dynamos where the <i>α<i/> effect is completely replaced by two other turbulent dynamo mechanisms, namely the effect and the shear-current effect, which both result from an inhomogeneity of the mean magnetic field.<i>Methods. <i/> We studied axisymmetric mean-field dynamo models containing differential rotation, the and shear-current effects, and a meridional circulation. The model calculations were carried out using the rotation profile of the Sun as obtained from helioseismic measurements and radial profiles of other quantities according to a standard model of the solar interior.<i>Results. <i/>Without meridional flow, no satisfactory agreement of the models with the solar observations can be obtained. With a sufficiently strong meridional circulation included, however, the main properties of the large-scale solar magnetic field, namely, its oscillatory behavior, its latitudinal drift towards the equator within each half cycle, and its dipolar parity with respect to the equatorial plane, are correctly reproduced.<i>Conclusions. <i/> We have thereby constructed the first mean-field models of solar-type dynamos that do not use the <i>α<i/> effect.

Superconcentration of photospheric sources of the large-scale open solar magnetic field in the main zone of active longitudes, differential rotation blocking, and origination of the four-sector structure. 1. The field and solar activity dynamics

The phenomena of superconcentration of the large-scale field photospheric sources in the main zone of active longitudes, blocking of regular differential rotation by these sources, and origination of the four-sector structure of the solar magnetic field during the decline phase of cycle 23 have been considered in more detail and taking into account the polar correction. It has been indicated that superconcentration was formed due to the penetration of photospheric sources into the zone from the western surroundings of this zone and owing to the generation of the large-scale field in the zone itself. The dynamics of a blocking-induced complex MHD disturbance with reflected from the zone and reconnecting photospheric sources of negative and positive polarity, respectively, and the transformation of the bisector structure into the four-sector one have been considered. It has been indicated that the dynamics of this MHD disturbance was responsible for that of associated solar activity: the generation of sunspot groups, appearance of flares, and, finally, origination of a powerful heliospheric storm and the solar-terrestrial extrastorm of July 22–27, 2004.

Large-scale patterns and ‘active longitudes’

AbstractThe following aspects of the physics of large-scale solar magnetic fields are discussed: structure of large-scale fields (LSF) and connection with local fields; dynamo and origin of LSF; LSF cycle variation; meridional circulation and LSF; rotation of LSF; fine structure of the field in quiet regions and the concept of the pebble-shaped field; active longitudes, their manifestation in various solar indices, and dependence on the power of solar activity.

MHD nature of the origination, dynamics, geoeffectiveness, and disappearance of the four-sector structure of the solar magnetic field during the cycle 23 decline phase

The MHD nature of the origination, dynamics, geoeffectiveness, and disappearance of the four-sector structure of the solar magnetic field during the cycle 23 decline phase has been established. A prolonged ordered MHD process including the chain of the interrelated phenomena (unknown before this study), which begin and end in one of the main zones of active longitudes and are responsible for the above nature of the four-sector structure, has been detected as a result of the simulation of the large-scale open solar magnetic field and an analysis of the dynamics of this field fluxes. These phenomena are as follows: the extreme concentration of the photospheric field sources of the same sign in the zone of active longitudes; blocking of regular differential rotation by these sources; origination of a nonstationary MHD disturbance in the form of a four-sector structure, traveling in the direction of solar rotation at a nearly Alfven velocity; upset of blocking, displacement of blocking sources from the zone, and their shearing motion relative to a traveling MHD disturbance; deceleration and dissipation of a four-sector MHD disturbance; and reconstruction of a bisector structure. The interactions during this process, which lasted from May 2004 to December 2005, were accompanied by the generation of an ordered succession of heliospheric and solar-terrestrial disturbances including the series of nine extrastorms that were observed from July 2004 to September 2005 and were the last storms in the finished cycle 23 of solar activity.

Anomalies in the evolution of global and large-scale solar magnetic fields as the precursors of several upcoming low solar cycles

Anomalies in the solar magnetic fields of various scales are studied. The polar magnetic field strength is shown to have decreased steadily during the last three solar cycles. This is because the increase in the dipole magnetic moment observed from 1915 to 1976 has changed into a decrease in the last three cycles. At the same time, the medium scale magnetic fields (like those of isolated coronal holes) have been unusually strong in the last cycle. As a result, the tilt of the heliospheric current sheet is still about 30°. The large effective contribution from the medium scale fields to the total energy of the large-scale fields is also confirmed by our calculations of the effective multipolarity index. The aa-index at the cycle minima is correlated with the height of the succeeding maxima. The set of data considered may be indicative of the possible approach of a sequence of low solar cycles.

Intersector disbalance of the large-scale open solar magnetic field fluxes, active and passive boundaries, and solar-terrestrial extrastorms

The dynamics (from rotation to rotation) of the absolute values of the large-scale open solar magnetic field fluxes in the four-sector field structure has been considered for the first time, using CRs 2032–2035 in July–October 2005 as examples. An important role of the ratio of the fluxes at the eastern and western sector boundaries (Φ E /Φ W ) is confirmed. As in the cases of the two-sector structure, Φ E /Φ W > 1 is typical of active rigidly corotating boundaries with intense sunspot formation, flares, and interplanetary and geomagnetic disturbances. A remarkable property of the considered structure was the presence of a rapidly increasing flux in an initially narrow sector and the flux interaction with a stable rigidly corotating sector in the zone of the main active longitudes, which caused an unexpectedly strong geoeffective long-range action of flares near the corresponding active boundary.

Beginning of the new solar cycle (cycle 24) in the large-scale open solar magnetic field

It is proposed to determined minimums of the 11-year solar cycles based on a minimal flux of the large-scale open solar magnetic field. The minimal fluxes before the finished cycle 23 (Carrington rotation CR 1904) and the started cycle 24 (CR 2054, April 2007) were equal to 1.8 × 1022 and 1.2 × 1022 μs, respectively. The long-term tendency toward an approach to a deep minimum of solar activity is confirmed. On the assumption that magnetic flux variations from minimums to maximums are proportional to each other, the anticipated value of the maximal Wolf number during cycle 24 is estimated as Wmax = 80.