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

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.

scholarly journals Sunspot Proper Motion and Flare Frequency

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).

scholarly journals The balance of magnetic fluxes in active regions

1968 ◽  
Vol 35 ◽  
pp. 47-49 ◽  
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.

scholarly journals Electric Currents in the Atmosphere of the Sun

1990 ◽  
Vol 138 ◽  
pp. 267-271
Author(s):  
V.I. Abramenko ◽  
S.I. Gopasyuk ◽  
M.B. Ogir
Keyword(s):  
Magnetic Field ◽  
Active Regions ◽  
The Sun ◽  
Proper Motions ◽  
Electric Currents ◽  
The Magnetic Field ◽  
Sunspot Groups

The structure of the magnetic field, proper motions of sunspots and electric currents have been studied and related to the evolution of sunspot groups. Further the height variations of the magnetic fluxes and electric currents in active regions have been explored.

Emergence of Twisted Magnetic Flux Related Sigmoidal Brightening

2000 ◽  
Vol 179 ◽  
pp. 263-264
Author(s):  
K. Sundara Raman ◽  
K. B. Ramesh ◽  
R. Selvendran ◽  
P. S. M. Aleem ◽  
K. M. Hiremath
Keyword(s):  
Magnetic Field ◽  
Magnetic Fields ◽  
Magnetic Flux ◽  
Ultra Violet ◽  
Active Regions ◽  
Morphological Properties ◽  
Energy Storage And Conversion ◽  
The Sun ◽  
X Rays ◽  
The Magnetic Field

Extended AbstractWe have examined the morphological properties of a sigmoid associated with an SXR (soft X-ray) flare. The sigmoid is cospatial with the EUV (extreme ultra violet) images and in the optical part lies along an S-shaped Hαfilament. The photoheliogram shows flux emergence within an existingδtype sunspot which has caused the rotation of the umbrae giving rise to the sigmoidal brightening.It is now widely accepted that flares derive their energy from the magnetic fields of the active regions and coronal levels are considered to be the flare sites. But still a satisfactory understanding of the flare processes has not been achieved because of the difficulties encountered to predict and estimate the probability of flare eruptions. The convection flows and vortices below the photosphere transport and concentrate magnetic field, which subsequently appear as active regions in the photosphere (Rust & Kumar 1994 and the references therein). Successive emergence of magnetic flux, twist the field, creating flare productive magnetic shear and has been studied by many authors (Sundara Ramanet al.1998 and the references therein). Hence, it is considered that the flare is powered by the energy stored in the twisted magnetic flux tubes (Kurokawa 1996 and the references therein). Rust & Kumar (1996) named the S-shaped bright coronal loops that appear in soft X-rays as ‘Sigmoids’ and concluded that this S-shaped distortion is due to the twist developed in the magnetic field lines. These transient sigmoidal features tell a great deal about unstable coronal magnetic fields, as these regions are more likely to be eruptive (Canfieldet al.1999). As the magnetic fields of the active regions are deep rooted in the Sun, the twist developed in the subphotospheric flux tube penetrates the photosphere and extends in to the corona. Thus, it is essentially favourable for the subphotospheric twist to unwind the twist and transmit it through the photosphere to the corona. Therefore, it becomes essential to make complete observational descriptions of a flare from the magnetic field changes that are taking place in different atmospheric levels of the Sun, to pin down the energy storage and conversion process that trigger the flare phenomena.

scholarly journals Solar and Stellar Dynamo Waves Under Asymptotic Investigation

1998 ◽  
Vol 167 ◽  
pp. 415-418
Author(s):  
Kirill M. Kuzanyan
Keyword(s):  
Magnetic Field ◽  
Temporal Distribution ◽  
Active Regions ◽  
Magnetic Activity ◽  
Dynamo Model ◽  
The Sun ◽  
Asymptotic Investigation ◽  
Spatio Temporal ◽  
Dynamo Wave ◽  
The Magnetic Field

AbstractThe main magnetic activity of the Sun can be visualised by Maunder butterfly diagrams which represent the spatio-temporal distribution of sunspots. Besides sunspots there are other tracers of magnetic activity, like filaments and active regions, which are observable over a wider latitudinal range of the Sun. Both these phenomena allow one to consider a complete picture of solar magnetic activity, which should be explained in the framework of one relatively simple model.A kinematic αѡ-dynamo model of the magnetic field’s generation in a thin convection shell with nonuniform helicity for large dynamo numbers is considered in the framework of Parker’s migratory dynamo. The obtained asymptotic solution of equations governing the magnetic field has a form of a modulated travelling dynamo wave. This wave propagates over the most latitudes of the solar hemisphere equatorwards, and the amplitude of the magnetic field first increases and then decreases with the propagation. Over the subpolar latitudes the dynamo wave reverses, there the dynamo wave propagates polewards and decays with latitude. Butterfly diagrams are plotted and analyzed.There is an attractive opportunity to develop a more quantitatively precise model taking into account helioseismological data on differential rotation and fitting the solar observational data on the magnetic field and turbulence, analyzing the helicity and the phase shift between toroidal and poloidal components of the field.

scholarly journals Joint Discussion 3 Solar active regions and 3D magnetic structure

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.

scholarly journals Magnetic field in active regions of the sun at coronal heights

2008 ◽  
Vol 4 (S257) ◽  
pp. 349-352
Author(s):  
V. M. Bogod ◽  
L. V. Yasnov
Keyword(s):  
Magnetic Field ◽  
Field Strength ◽  
Vertical Structure ◽  
Active Regions ◽  
Magnetic Flux Tube ◽  
Microwave Range ◽  
The Sun ◽  
Two Dimensional ◽  
Radio Waves ◽  
The Magnetic Field

AbstractA method is developed for estimation of the vertical structure of the magnetic field in active regions using multi-wave spectral-polarization measurements of radio waves which gives not only the dependence of magnetic field strength on height but also determines two-dimensional form of a magnetic flux tube, emitted in the microwave range of wavelengths.

scholarly journals Numerical Simulations of Large-scale Solar Magnetic Fields

1985 ◽  
Vol 38 (6) ◽  
pp. 999 ◽  
Author(s):  
CR DeVore ◽  
NR Sheeley Jr ◽  
JP Boris ◽  
TR Young Jr ◽  
KL Harvey
Keyword(s):  
Magnetic Field ◽  
Magnetic Flux ◽  
Large Scale ◽  
Sunspot Cycle ◽  
Active Regions ◽  
The Sun ◽  
Solar Magnetic Fields ◽  
Field Patterns ◽  
Large Scale Magnetic Field ◽  
The Magnetic Field

We have solved numerically a transport equation which describes the evolution of the large-scale magnetic field of the Sun. Data derived from solar magnetic observations are used to initialize the computations and to account for the emergence of new magnetic flux during the sunspot cycle. Our objective is to assess the ability of the model to reproduce the observed evolution of the field patterns. We discuss recent results from simulations of individual active regions over a few solar rotations and of the magnetic field of the Sun over sunspot cycle 21.

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