scholarly journals Origine des régions actives solaires ‘anormales’

1968 ◽  
Vol 35 ◽  
pp. 25-32 ◽  
Author(s):  
M. J. Martres
Keyword(s):  
Solar Activity ◽  
Active Region ◽  
Active Center ◽  
Active Regions ◽  
The West ◽  
Magnetic Inversion ◽  
Solar Active Regions ◽  
Western Side ◽  
Magnetic Inversion Line

Solar active regions are considered ‘anomalous’ when they belong to magnetic classes γ,βγ and βf-αf. The study of the solar activity of the region where, later on, these groups are born shows an evident correlation between the presence of an old active center and the complexity of the new active region.It is found that the complexity is greater if the old active center is younger, and the superposition better. We also observe that the birth of anomalous sunspots groups occurs much more frequently on the western side of the magnetic inversion line of the old center.When the birth of an active center occurs outside and on the West of the faculae, we observe the weakly anomalous groups βf-αf. The ‘perturbation’ decreases with distance and is extended at least to 10 heliographic degrees of the boundaries of the old faculae.

Numerical Short-Term Solar Activity Forecasting

2017 ◽  
Vol 13 (S335) ◽  
pp. 243-249 ◽  
Author(s):  
Huaning Wang ◽  
Yihua Yan ◽  
Han He ◽  
Xin Huang ◽  
Xinghua Dai ◽  
...  
Keyword(s):  
Solar Activity ◽  
Magnetic Fields ◽  
Solar Atmosphere ◽  
Magnetic Energy ◽  
Three Dimensional ◽  
Active Regions ◽  
Short Term ◽  
Solar Active Regions ◽  
Solar Eruptions ◽  
Dimensional Reconstruction

AbstractIt is well known that the energy for solar eruptions comes from magnetic fields in solar active regions. Magnetic energy storage and dissipation are regarded as important physical processes in the solar corona. With incomplete theoretical modeling for eruptions in the solar atmosphere, activity forecasting is mainly supported with statistical models. Solar observations with high temporal and spatial resolution continuously from space well describe the evolution of activities in the solar atmosphere, and combined with three dimensional reconstruction of solar magnetic fields, makes numerical short-term (within hours to days) solar activity forecasting possible. In the current report, we propose the erupting frequency and main attack direction of solar eruptions as new forecasts and present the prospects for numerical short-term solar activity forecasting based on the magnetic topological framework in solar active regions.

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 Transport of Magnetic Helicity and Dynamics of Solar Active Regions

2005 ◽  
Vol 13 ◽  
pp. 117-118 ◽  
Author(s):  
M. K. Georgoulis ◽  
B. J. LaBonte ◽  
D. M. Rust
Keyword(s):  
Time Series ◽  
Active Region ◽  
Lower Limit ◽  
Active Regions ◽  
Magnetic Helicity ◽  
Solar Active Regions ◽  
Linear Force

AbstractWe introduce a method to calculate the magnetic helicity density in a given active-region vector magnetogram, and a lower limit of it, based on a linear force-free (Iff) approximation. Moreover, we provide a lower limit of the total magnetic helicity in the active region (AR). A time series of magnetograms can be used to calculate the rate of helicity transport. The results can be then correlated with manifestations of the dynamical activity in ARs, such as flares and filament eruptions.

scholarly journals Observations of Solar Active Regions at 2 and 6 cm Wavelengths with 3 Arc Second Resolution

1980 ◽  
Vol 86 ◽  
pp. 105-108
Author(s):  
T. Velusamy ◽  
M. R. Kundu
Keyword(s):  
Fine Structure ◽  
Active Regions ◽  
Field Of View ◽  
Large Array ◽  
The West ◽  
Very Large Array ◽  
Group I ◽  
West Limb ◽  
Solar Active Regions ◽  
Sunspot Groups

We have used the Very Large Array of the NRAO to observe solar active regions at 2 and 6 cm wavelengths in May 1979. In this paper we present and discuss the fine structure components of a sunspot associated radio region observed with a resolution of 3″ arc on May 4 and 5, 1979. In this region (McMath 15974) there were two distinct groups of sunspots separated by about 3′ arc. Group I located towards the west limb contained two spots while Group II in the east was a complex containing several spots that emerged during the period of our observations. At 6 cm both the sunspot groups were within the primary beam whereas at 2 cm only Group I was within the field of view. The VLA observations were made at 6 and 2 cm alternating between them every 5 minuts. The region was mapped with a resolution of about 3″ x 3″ using 10 hours of synthesis data on each day.

Energy Balance and Structure Of Active Regions

1977 ◽  
Vol 36 ◽  
pp. 457-473 ◽  
Author(s):  
Frank Q. Orrall ◽  
Roger A. Kopp
Keyword(s):  
Solar Activity ◽  
Energy Balance ◽  
Active Region ◽  
Internal Structure ◽  
Solar Flares ◽  
Active Regions ◽  
Particle Emission ◽  
Space Astronomy ◽  
Coronal Bright Points ◽  
Definition Of

With the advent of radio and space astronomy it became necessary to extend the definition of a center of activity or active region (AR) originally proposed by L. d’Azambuja. At IAU Symposium 35, K.O. Klepenheuer (1968) defined an AR as “The totality of all observable phenomena preceding, accompanying and following the birth of sunspots, including radio-, X-, EUV-, and particle emission.” The recognition that there are other short-lived bipolar features with a distribution similar to that of active regions (ephemeral active regions) by Harveyet al. (1975) and their identification with coronal bright points by Golub et al. (1975) suggests that the definition will have to be extended further. Active regions manifest themselves in the photosphere as sunspots and faculae; in the chromosphere as the plage and its structures; in the corona as a coronal enhancement with a complex, often loop-like internal structure. (The termenhancementwas Introduced by Billings. The original termpermanent coronal condensation, introduced by Waldemeler, only referred to the very bright enhancements and was, moreover, often confused with hissporadic coronal condensations, a flareassodated phenomena. The termcoronal active regionhas, recently also been used for the coronal extension of the AR.) In keeping with the aims of this symposium the stress of this review will be on the chromosphere and corona. Active regions are especially Important as the site of most flare-associated phenomena. Here we shall be concerned with flares only as they affect the overall energy balance. Our concern is with the “quiet” active regions that cause the slowly varying components of solar activity and provide the ambiance within which solar flares occur.

scholarly journals Multifractal spectrum of solar active region NOAA 10960 in the Hα spectral line

2009 ◽  
Vol 5 (S264) ◽  
pp. 66-71 ◽  
Author(s):  
D. Batmunkh
Keyword(s):  
Active Region ◽  
Ccd Camera ◽  
Active Regions ◽  
Multifractal Spectrum ◽  
Astronomical Observatory ◽  
Active Region Noaa ◽  
Complicated Form ◽  
Multifractal Spectra ◽  
Solar Active Regions ◽  
Different Dimensions

AbstractWe obtained the Hα images of some solar active regions and prominences. Our astronomical observatory has the telescope-coronagraph which was equipped with the birefringent Halle Hα filter and CCD camera Apogee U4 (2048x2048 pixels). This paper presents multifractal spectra of images of some solar active regions in Hα line obtained with the coronagraph. The Pointwise Hoelder exponents (α) and Hausdorff spectrum fn(α) for a part of chromosphere with active region and without it, have been obtained. It is visible, that curves fn(α) for quiet and active regions of chromosphere differ very strongly. In particular, fn(α) for region with a sunspot and flare has very complicated form, and for region with filament the curves do not considerably differ from quiet chromosphere. The multifractal spectrum of quiet chromosphere shows that the quiet chromosphere is very well described by fractals with different dimensions. We analyze this result.

scholarly journals Variations of the total electronic concentration in the ionosphere in seismically active region

2021 ◽  
Vol 333 ◽  
pp. 02012
Author(s):  
Valentin Kashkin ◽  
Tatyana Rubleva ◽  
Konstantin Simonov ◽  
Andrey Zabrodin ◽  
Aleksey Kabanov
Keyword(s):  
Solar Activity ◽  
Active Region ◽  
Electron Concentration ◽  
Navigation System ◽  
Active Regions ◽  
Computational Technique ◽  
Total Electron ◽  
Catastrophic Earthquake ◽  
Electronic Concentration ◽  
Geodynamic Activity

In this work we studied the variations in the total electron concentration (TEC) obtained from measurements of the global navigation system GPS in the preparation zone for the 2010 catastrophic Chilean earthquake (Mw = 8.8) under calm background conditions at a minimum of 24 solar activity (SA) cycles. The analysis of the geodynamic activity and ionospheric TEC disturbances in the seismically active region of this catastrophic earthquake is carried out. A computational technique has been developed that can be used to study TEC variations over seismically active regions.

scholarly journals Average surface flows before the formation of solar active regions and their relationship to the supergranulation pattern

2019 ◽  
Vol 628 ◽  
pp. A37 ◽  
Author(s):  
A. C. Birch ◽  
H. Schunker ◽  
D. C. Braun ◽  
L. Gizon
Keyword(s):  
Simple Model ◽  
Active Region ◽  
Active Regions ◽  
Convergence Region ◽  
Near Surface ◽  
Surface Flows ◽  
Quiet Sun ◽  
Horizontal Flows ◽  
Solar Active Regions ◽  
Region Emergence

Context. The emergence of solar active regions is an important but poorly understood aspect of the solar dynamo. Aims. Knowledge of the flows associated with the rise of active-region-forming magnetic concentrations through the near-surface layers will help determine the mechanisms of active region formation. Methods. We used helioseismic holography and granulation tracking to measure the horizontal flows at the surface that precede the emergence of active regions. We then averaged these flows over about sixty emerging active regions to reduce the noise, selecting active regions that emerge into relatively quiet Sun. To help interpret the results, we constructed a simple model flow field by generating synthetic “emergence locations” that are probabilistically related to the locations of supergranulation-scale convergence regions in the quiet Sun. Results. The flow maps obtained from helioseismology and granulation tracking are very similar (correlation coefficients for single maps around 0.96). We find that active region emergence is, on average, preceded by converging horizontal flows of amplitude about 40 m s−1. The convergence region extends over about 40 Mm in the east-west direction and about 20 Mm in the north-south direction and is centered in the retrograde direction relative to the emergence location. This flow pattern is largely reproduced by a model in which active region emergence occurs preferentially in the prograde direction relative to supergranulation inflows. Conclusions. Averaging over many active regions reveals a statistically significant pattern of near-surface flows prior to emergence. The qualitative success of our simple model suggests that rising flux concentrations and supergranule-scale flows interact during the emergence process.

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