ASYMMETRY IN APPEARANCE OF THE LEADING AND FOLLOWING POLARITIES IN THE PHOTOSPHERIC MAGNETIC FIELD AT THE EARLY STAGE OF ACTIVE REGION FORMATION

We study the evolution of the photospheric magnetic field at the early stage of active region development. We use data on longitudinal component of the magnetic field and line-of-sight velocities from SOHO/MDI and SDO/HMI. The visual inspection of 48 cases of birth of active regions and the detailed analysis of the magnetic flux dynamics in 4 active regions have shown that at the time of emergence of a new magnetic field, the field of the following polarity is the first to be detected in the photosphere. The flux asymmetry of the leading and following polarities persists for several tens of minutes. The observed asymmetry of magnetic fluxes supports the results of the numerical simulation of emergence of the active region magnetic field in the upper layers of the convective zone, which has been carried out by Rempel and Cheung [2014].

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Joint Discussion 3 Solar active regions and 3D magnetic structure

Proceedings of the International Astronomical Union ◽

10.1017/s1743921307010071 ◽

2006 ◽

Vol 2 (14) ◽

pp. 139-168

Author(s):

Debi Prasad Choudhary ◽

Michal Sobotka

Keyword(s):

Magnetic Field ◽

Active Region ◽

Large Scale ◽

Focal Point ◽

Active Regions ◽

Theoretical Modelling ◽

Solar Chromosphere ◽

Origin And Evolution ◽

Solar Active Regions ◽

The Magnetic Field

AbstractKeeping in view of the modern powerful observing tools, among othersHinode(formerlySOLAR-B),STEREOand Frequency-Agile Solar Radiotelescope, and sophisticated modelling techniques, Joint Discussion 3 during the IAU General Assembly 2006 focused on the properties of magnetic field of solar active regions starting in deep interior of the Sun, from where they buoyantly rise to the coronal heights where the site of most explosive events are located. Intimately related with the active regions, the origin and evolution of the magnetic field of quiet Sun, the large scale chromospheric structures were also the focal point of the Joint Discussion. The theoretical modelling of the generation and dynamics of magnetic field in solar convective zone show that the interaction of the magnetic field with the Coriolis force and helical turbulent convection results in the tilts and twists in the emerging flux. In the photosphere, some of these fluxes appear in sunspots with field strengths up to about 6100 G. Spectro-polarimetric measurements reveal that the line of sight velocities and magnetic field of these locations are found to be uncombed and depend on depth in the atmosphere and exhibit gradients or discontinuities. The inclined magnetic fields beyond penumbra appear as moving magnetic features that do not rise above upper photospheric heights. As the flux rises, the solar chromosphere is the most immediate and intermediary layer where competitive magnetic forces begin to dominate their thermodynamic counterparts. The magnetic field at these heights is now measured using several diagnostic lines such as CaII854.2 nm, HI656.3 nm, and HeI1083.0 nm. The radio observations show that the coronal magnetic field of post flare loops are of the order of 30 G, which might represent the force-free magnetic state of active region in the corona. The temperatures at these coronal heights, derived from the line widths, are in the range from 2.4 to 3.7 million degree. The same line profile measurements indicate the existence of asymmetric flows in the corona. The theoretical extrapolation of photospheric field into coronal heights and their comparison with the observations show that there exists a complex topology with separatrices associated to coronal null points. The interaction of these structures often lead to flares and coronal mass ejections. The current MHD modelling of active region field shows that for coronal mass ejection both local active region magnetic field and global magnetic field due to the surrounding magnetic flux are important. Here, we present an extended summary of the papers presented in Joint Discussion 03 and open questions related to the solar magnetic field that are likely to be the prime issue with the modern observing facilities such asHinodeandSTEREOmissions.

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Fast downflows in a chromospheric filament

Proceedings of the International Astronomical Union ◽

10.1017/s174392131900992x ◽

2019 ◽

Vol 15 (S354) ◽

pp. 454-457

Author(s):

K. Sowmya ◽

A. Lagg ◽

S. K. Solanki ◽

J. S. Castellanos Durán

Keyword(s):

Magnetic Field ◽

Active Region ◽

Magnetic Fields ◽

Velocity Component ◽

Field Vector ◽

Line Of Sight ◽

Plasma Velocity ◽

Supersonic Velocities ◽

Slow Velocity ◽

The Magnetic Field

AbstractAn active region filament in the upper chromosphere is studied using spectropolarimetric data in He i 10830 Å from the GREGOR telescope. A Milne-Eddingon based inversion of the Unno-Rachkovsky equations is used to retrieve the velocity and the magnetic field vector of the region. The plasma velocity reaches supersonic values closer to the feet of the filament barbs and coexist with a slow velocity component. Such supersonic velocities result from the acceleration of the plasma as it drains from the filament spine through the barbs. The line-of-sight magnetic fields have strengths below 200 G in the filament spine and in the filament barbs where fast downflows are located, their strengths range between 100 - 700 G.

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Sunspot Proper Motion and Flare Frequency

International Astronomical Union Colloquium ◽

10.1017/s0252921100034540 ◽

1995 ◽

Vol 151 ◽

pp. 45-46

Author(s):

G. Csepura ◽

L. Győri ◽

A.A. Galal

Keyword(s):

Magnetic Field ◽

Active Region ◽

Proper Motion ◽

Active Regions ◽

Field Configuration ◽

Flare Activity ◽

Magnetic Field Configuration ◽

Spot Group ◽

The Magnetic Field ◽

Flare Frequency

Flare activity of solar active regions is generally believed to depend on a sheared configuration of magnetic fields (Hagyard et al. 1984). There are cases when the shear necessary for a flare can be attributed to the emergence of a new flux in the spot group (Wang 1992). But, perhaps, a newly born active region can also influence the magnetic field configuration in a nearby active region (Poleto et al. 1993, Gesztelyi et al. 1993). In this paper we are interested primarily in the influence of a newly emerging spot group on a nearby one.The three neighbouring active regions NOAA AR 6412(B-C), 6413(A) and 6415(D) have been studied between 13-22 December 1990. White-light pictures for studying sunspot proper motion and area evolution were taken at Gyula Observing Station (Hungary), Debrecen Heliophysical Observatory (Hungary) and Helwan Observatory (Egypt). Times and positions of the flares were taken from the Solar Geophysical Data (No. 558, part 1, February 1991).

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Searching for failed eruptions interacting with overlying magnetic field

Proceedings of the International Astronomical Union ◽

10.1017/s1743921316000557 ◽

2015 ◽

Vol 11 (S320) ◽

pp. 221-223 ◽

Cited By ~ 1

Author(s):

Dominik Gronkiewicz ◽

Tomasz Mrozek ◽

Sylwester Kołomański ◽

Martyna Chruślińska

Keyword(s):

Magnetic Field ◽

Statistical Analysis ◽

Active Region ◽

Solar Flares ◽

Active Regions ◽

Automated Method ◽

Solar Eruptions ◽

Mass Ejection ◽

The Magnetic Field ◽

Flare Site

AbstractIt is well known that not all solar flares are connected with eruptions followed by coronal mass ejection (CME). Even strongest X-class flares may not be accompanied by eruptions or are accompanied by failed eruptions. One of important factor that prevent eruption from developing into CME is strength of the magnetic field overlying flare site. Few observations show that active regions with specific magnetic configuration may produce many CME-less solar flares. Therefore, forecasts of geoeffective events based on active region properties have to take into account probability of confining solar eruptions. Present observations of SDO/AIA give a chance for deep statistical analysis of properties of an active region which may lead to confining an eruption. We developed automated method which can recognize eruptions in AIA images. With this tool we will be able to analyze statistical properties of failed eruptions observed by AIA telescope.

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The proper motions of sunspots and the magnetic field of active regions

Symposium - International Astronomical Union ◽

10.1017/s0074180900021537 ◽

1968 ◽

Vol 35 ◽

pp. 211-213

Author(s):

G. V. Kuklin

Keyword(s):

Magnetic Field ◽

Active Region ◽

Proper Motion ◽

Active Regions ◽

The Sun ◽

Proper Motions ◽

The Magnetic Field

According to our program of sunspot proper motion investigations (Kuklin and Syklen, 1966) we study the interdependence of the sunspot proper motions inside the group and the magnetic field of the whole group or active region. This aspect of the dynamics of matter in disturbed regions of the Sun was not considered practically up to the last time.

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The balance of magnetic fluxes in active regions

Symposium - International Astronomical Union ◽

10.1017/s007418090002129x ◽

1968 ◽

Vol 35 ◽

pp. 47-49 ◽

Cited By ~ 2

Author(s):

Jan Olof Stenflo

Keyword(s):

Magnetic Field ◽

Solar Cycle ◽

Active Region ◽

Solar Surface ◽

Active Regions ◽

Basic Feature ◽

The Sun ◽

Magnetic Disturbance ◽

The Magnetic Field

According to modern theories of the solar cycle, active regions on the Sun are caused by a magnetic disturbance penetrating the solar surface from below. Sunspots, filaments, flares and other conspicuous events in an active region seem to be only secondary phenomena, the basic feature being the magnetic field itself.

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An Attempt to Associate Observed Photospheric Motions with the Magnetic Field Structure and Flare Occurrence in an Active Region

Symposium - International Astronomical Union ◽

10.1017/s0074180900022907 ◽

1971 ◽

Vol 43 ◽

pp. 435-442 ◽

Cited By ~ 8

Author(s):

M. J. Martres ◽

I. Soru-Escaut ◽

J. Rayrole

Keyword(s):

Magnetic Field ◽

Active Region ◽

Empirical Evidence ◽

Active Regions ◽

Field Structure ◽

Magnetic Field Structure ◽

Abrupt Changes ◽

The Magnetic Field

We have tried to find empirical evidence for the role of photospheric motions in the building up of the flare productive magnetic patterns in Active Regions.The bright Hα faculae are associated with V∥ structures different from a classical Evershed flow and particularly ‘anomalous’ in the regions and periods of high flare occurrence. The flares observed occurred at ‘crossings’ of the lines V∥ = 0(V ≠ 0) and H∥ = 0 and at places where V∥ = 0 showed abrupt changes of direction. It is suggested that these anomalous V∥ structures are evidence of vortex motions.

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Solar Radio S-Component Variation with the Magnetic Field of Active Regions

International Astronomical Union Colloquium ◽

10.1017/s0252921100029225 ◽

1993 ◽

Vol 141 ◽

pp. 275-278

Author(s):

Ren-Yang Zhao

Keyword(s):

Magnetic Field ◽

Active Region ◽

Solar Radio ◽

Three Dimensional ◽

Active Regions ◽

Plasma Parameters ◽

Region Model ◽

Temperature Electron ◽

Active Region Model ◽

The Magnetic Field

AbstractAccording to an active region model proposed in the present paper, i.e. three-dimensional and continuous distributions of the three plasma parameters (electron temperature, electron density, and magnetic field) from the active region to the quiet region, and using the combined mechanisms of gyroresonance radiation and bremsstrahlung, we have researched the solar radio S-component (i.e. the slowly varying component or SVC) variation with the magnetic field of active regions.

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Numerical simulation of helical jets at active region peripheries

Monthly Notices of the Royal Astronomical Society ◽

10.1093/mnras/stz2674 ◽

2019 ◽

Vol 490 (3) ◽

pp. 3679-3690 ◽

Cited By ~ 4

Author(s):

Peter F Wyper ◽

C Richard DeVore ◽

Spiro K Antiochos

Keyword(s):

Magnetic Field ◽

Active Region ◽

Three Dimensional ◽

Flux Rope ◽

Active Regions ◽

Quantitative Agreement ◽

Null Point ◽

Closed Field ◽

The Magnetic Field ◽

Bald Patch

ABSTRACT Coronal jets are observed above minority-polarity intrusions throughout the solar corona. Some of the most energetic ones occur on the periphery of active regions where the magnetic field is strongly inclined. These jets exhibit a non-radial propagation in the low corona as they follow the inclined field, and often have a broad, helical shape. We present a three-dimensional magnetohydrodynamic simulation of such an active-region-periphery helical jet. We consider an initially potential field with a bipolar flux distribution embedded in a highly inclined magnetic field, representative of the field nearby an active region. The flux of the minority polarity sits below a bald-patch separatrix initially. Surface motions are used to inject free energy into the closed field beneath the separatrix, forming a sigmoidal flux rope that eventually erupts producing a helical jet. We find that a null point replaces the bald patch early in the evolution and that the eruption results from a combination of magnetic breakout and an ideal kinking of the erupting flux rope. We discuss how the two mechanisms are coupled, and compare our results with previous simulations of coronal-hole jets. This comparison supports the hypothesis that the generic mechanism for all coronal jets is a coupling between breakout reconnection and an ideal instability. We further show that our results are in good qualitative and quantitative agreement with observations of active-region-periphery jets.

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