The Dynamical Properties of Twisted Ropes of Magnetic Field and the Vigor of New Active Regions on the Sun

1974 ◽  
Vol 191 ◽  
pp. 245 ◽  
Author(s):  
E. N. Parker
Keyword(s):  
Magnetic Field ◽  
Active Regions ◽  
The Sun ◽  
Dynamical Properties

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 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 Active regions and the interplanetary magnetic field

1968 ◽  
Vol 35 ◽  
pp. 390-394
Author(s):  
John M. Wilcox ◽  
Norman F. Ness ◽  
Kenneth H. Schatten
Keyword(s):  
Magnetic Field ◽  
Interplanetary Magnetic Field ◽  
Large Scale ◽  
Early Stage ◽  
Active Regions ◽  
The Sun ◽  
Sector Structure ◽  
Archimedean Spiral ◽  
Spiral Angle ◽  
Scale Evolution

The relation of solar active regions to the large-scale sector structure of the interplanetary field is discussed. In the winter of 1963–64 (observed by the satellite IMP-1) the plage density was greatest in the leading portion of the sectors and lesser in the trailing portion of the sectors. The boundaries of the sectors (places at which the direction of the interplanetary magnetic field changed from toward the Sun to away from the Sun, or vice versa) were remarkably free of plages. The very fact that since the first observations in 1962 the average interplanetary field has almost always had the property of being either toward the Sun or away from the Sun (along the Archimedean spiral angle) continuously for several days must be considered in the discussion of large-scale evolution of active regions. Using the observed interplanetary magnetic field at 1 AU and a set of reasonable assumptions the magnetic configuration in the ecliptic from 0·4 AU to 1·2 AU has been reconstructed. In at least one case a pattern emerges which appears to be related to the evolution of an active region from an early stage in which the magnetic lines closely couple the preceding and following halves of the region to a later stage in which the two halves of the region are more widely separated.

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.

scholarly journals Magnetic helicity ejections and coronal activity

2012 ◽  
Vol 8 (S294) ◽  
pp. 519-530 ◽  
Author(s):  
A. Nindos
Keyword(s):  
Magnetic Field ◽  
Physical Quantity ◽  
Coronal Mass Ejections ◽  
Active Regions ◽  
Magnetic Helicity ◽  
The Sun ◽  
Coronal Activity ◽  
Solar Eruptions ◽  
Ideal Tool ◽  
The Magnetic Field

AbstractMagnetic helicity quantifies the degree of linkage and/or twistedness in the magnetic field. It is probably the only physical quantity which is approximately conserved even in resistive MHD. This makes it an ideal tool for the exploration of the physics of solar eruptions. In this article, I discuss the sources of magnetic helicity injected into active regions and I point out that coronal mass ejections (CMEs) are probably necessary to remove at least part of the excess helicity produced in the Sun. I also discuss the importance of magnetic helicity in the overall coronal evolution that may lead to eruptions.

scholarly journals Protons associated with centres of solar activity and their propagation in interplanetary magnetic-field regions co-rotating with the Sun

1968 ◽  
Vol 35 ◽  
pp. 403-403
Author(s):  
C. Y. Fan ◽  
M. Pick ◽  
R. Ryle ◽  
J. A. Simpson ◽  
D. R. Smith
Keyword(s):  
Magnetic Field ◽  
Solar Activity ◽  
Interplanetary Magnetic Field ◽  
Active Regions ◽  
Alpha Particles ◽  
Western Hemisphere ◽  
Energy Spectra ◽  
The Sun ◽  
Long Term Storage ◽  
Proton Fluxes

The Pioneer-6 and Pioneer-7 space probes carried charged-particle telescopes which measure, for the first time, both the direction of arrival and differential energy spectra of protons and alpha particles. The intensity changes, directional distributions and energy spectra of proton fluxes associated with solar activity are investigated. The data were obtained in the beginning of the new solar cycle (no. 20), when it is possible to unambiguously associate proton-flux increases with specific solar active regions. The origin, possibly long-term storage, and propagation of these proton fluxes are investigated. It was observed that enhanced 0·6–13 MeV proton fluxes associated with specific active regions were present over heliographic longitude ranges as great as ~ 180°. These enhanced fluxes exhibit definite onsets and cut-offs which appear to be associated with the magnetic-sector boundaries observed by Ness on Pioneer-6. Discrete flare-produced intensity increases extending in energy to more than 50 MeV are observed, superposed on the enhanced flux. These increases displayed short transit times and short rise times. Both the enhanced and flare-produced fluxes propagate along the spiral interplanetary magnetic field from the Western hemisphere of the Sun. From these observations we are led to a model in which the magnetic fields from the active region are spread out over a longitude range of 100–180° in the solar corona. The existence of strong unidirectional anisotropies in the initial phases of flare-proton events implies that little scattering occurs between the Sun and spacecraft. However, the gradual approach to an isotropic flux at late times indicates that the decay phase is controlled by the interplanetary magnetic field.

scholarly journals Magnetic classification of active regions

1968 ◽  
Vol 35 ◽  
pp. 33-42 ◽  
Author(s):  
Sara F. Smith ◽  
Robert Howard
Keyword(s):  
Magnetic Field ◽  
Classification Scheme ◽  
Angular Resolution ◽  
Active Regions ◽  
The Sun ◽  
Statistical Relation ◽  
Equatorial Zone ◽  
Reversed Polarity ◽  
Flare Productivity

All the active regions observed on the Sun with the Mount-Wilson magnetograph between August 1959 and December 1962 have been given magnetic classifications in a system similar to the Mount-Wilson sunspot-classification scheme. The flare productivity of regions classified as unipolar, bipolar, and complex bipolar, as well as regions composed of multiple bipolar components has been studied. It has not been necessary to provide a classification corresponding to the γ class of sunspots. Although the relatively poor angular resolution employed in the magnetograms limits somewhat the accuracy of the data, it is clear that both complex bipolar regions and regions with multiple bipolar components produce more than three times the number of flares than the simple bipolar regions produce. The most flare-productive class of regions is the reversed polarity complex classification.The statistical relation of the spot magnetic-field classification to the classification of the corresponding plage fields has been studied and found to be poor for these data.The distribution of the magnetic regions in latitude shows that many of the regions with polarities reversed from the usual orientation are confined to the equatorial zone.

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