On the large-scale dynamics and magnetic structure of solar active regions

1987 ◽  
Vol 323 ◽  
pp. 368 ◽  
Author(s):  
James A. Klimchuk
Keyword(s):  
Magnetic Structure ◽  
Large Scale ◽  
Active Regions ◽  
Solar Active Regions

scholarly journals A study of the localization of flares in selected active regions

1968 ◽  
Vol 35 ◽  
pp. 318-325 ◽  
Author(s):  
M. J. Martres ◽  
R. Michard ◽  
I. Soru-Iscovici ◽  
T. Tsap
Keyword(s):  
Magnetic Fields ◽  
Magnetic Structure ◽  
Active Regions ◽  
The Other ◽  
Cooperative Study ◽  
Solar Active Regions

From the material gathered during the ‘Cooperative Study of Solar Active Regions’, we studied the flare locations in AR magnetic structure, and flare relations to changes in the magnetic fields and spot configurations. Besides a confirmation of previous results, we find that flares are often associated with two features of the spot configuration evolving in opposite senses, one growing, the other declining.

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.

Large-scale patterns formed by solar active regions during the ascending phase of cycle 21

1983 ◽  
Vol 265 ◽  
pp. 1056 ◽  
Author(s):  
V. Gaizauskas ◽  
K. L. Harvey ◽  
J. W. Harvey ◽  
C. Zwaan
Keyword(s):  
Large Scale ◽  
Active Regions ◽  
Solar Active Regions

scholarly journals Radio Wavelength Observations: Structure, Strength and Variability of Magnetic Fields in the Transition Region and the Solar Corona

1983 ◽  
Vol 102 ◽  
pp. 363-367
Author(s):  
Kenneth R. Lang
Keyword(s):  
Magnetic Field ◽  
Magnetic Structure ◽  
Longitudinal Magnetic Field ◽  
Active Regions ◽  
Coronal Loops ◽  
Solar Active Regions ◽  
Radio Wavelength ◽  
Structure Strength ◽  
Solar Bursts ◽  
The Magnetic Field

The 6 cm radiation of solar active regions marks the legs of dipolar loops which have their footpoints in lower-lying sunspots. The temperatures T ≈ 106K and longitudinal magnetic field strengths Hℓ ≈ 600 Gauss at heights h ≈ 4 × 109 cm above sunspot umbrae. The circularly polarized emission at 6 cm delineates the magnetic structure above sunspot penumbrae. The 20 cm radiation of solar active regions delineates the ubiquitous coronal loops previously detected at X-ray wavelengths. We infer semilengths L ≈ 5 × 109cm, maximum electron temperatures Te(max) ≈ 3 × 106K, emission measures and electron densities Ne ≈ 109cm−3 for the 20 cm bremsstrahlung. Future V.L.A. observations at 20 cm may be used to determine the magnetic field strength of coronal loops. Changes in temperature and magnetic structure before and during solar bursts are briefly discussed.

Radio Measurements of Coronal Magnetic Fields

1994 ◽  
Vol 144 ◽  
pp. 21-28 ◽  
Author(s):  
G. B. Gelfreikh
Keyword(s):  
Magnetic Field ◽  
Magnetic Fields ◽  
Solar Corona ◽  
Active Regions ◽  
High Sensitivity ◽  
Coronal Magnetic Field ◽  
Transverse Magnetic ◽  
Radio Sources ◽  
Radio Waves ◽  
Solar Active Regions

AbstractA review of methods of measuring magnetic fields in the solar corona using spectral-polarization observations at microwaves with high spatial resolution is presented. The methods are based on the theory of thermal bremsstrahlung, thermal cyclotron emission, propagation of radio waves in quasi-transverse magnetic field and Faraday rotation of the plane of polarization. The most explicit program of measurements of magnetic fields in the atmosphere of solar active regions has been carried out using radio observations performed on the large reflector radio telescope of the Russian Academy of Sciences — RATAN-600. This proved possible due to good wavelength coverage, multichannel spectrographs observations and high sensitivity to polarization of the instrument. Besides direct measurements of the strength of the magnetic fields in some cases the peculiar parameters of radio sources, such as very steep spectra and high brightness temperatures provide some information on a very complicated local structure of the coronal magnetic field. Of special interest are the results found from combined RATAN-600 and large antennas of aperture synthesis (VLA and WSRT), the latter giving more detailed information on twodimensional structure of radio sources. The bulk of the data obtained allows us to investigate themagnetospheresof the solar active regions as the space in the solar corona where the structures and physical processes are controlled both by the photospheric/underphotospheric currents and surrounding “quiet” corona.

On the nature of microwave pulsations from solar active regions

2003 ◽  
Vol 8 (5-6) ◽  
pp. 136-139
Author(s):  
G.B. Gelfreikh ◽  
◽  
Y.T. Tsap ◽  
Y.G. Kopylova ◽  
L.I. Tsvetkov ◽  
...  
Keyword(s):  
Active Regions ◽  
Solar Active Regions

A Study of the Evolution of Solar Active Regions for Improving Solar Flare Forecasts

1989 ◽  
Author(s):  
Patricia L. Bornmann ◽  
Darren Kalmbach ◽  
David Kulhanek ◽  
April Casale
Keyword(s):  
Solar Flare ◽  
Active Regions ◽  
Solar Active Regions
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