MANIFESTATIONS OF TWO BRANCHES OF SOLAR ACTIVITY IN THE HELIOSPHERE AND GCR INTENSITY

This paper provides insight into heliospheric processes and galactic cosmic ray (GCR) modulation occurring due to the presence of two branches of solar activity in this solar layer. According to the topology of solar magnetic fields, these branches are called toroidal (active regions, sunspots, flares, coronal mass ejections, etc.) and poloidal (high-latitude magnetic fields, polar coronal holes, zonal unipolar magnetic regions, etc.). The main cause of different manifestations of the two branches on the solar surface and in the heliosphere — the layer at the base of the heliosphere in which the main energetic factor is the magnetic field — is formulated. In this case, the magnetic fields of the poloidal branch, which have a larger scale but a lower intensity, gain an advantage in penetrating into the heliosphere. A connection is shown between the poloidal branch and the heliospheric characteristics (solar wind velocity field, size of the heliosphere, form of the heliospheric current sheet, regular heliospheric magnetic field and its fluctuations) that, according to modern notions, determine GCR propagation in the heliosphere.

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Coronal Holes in Global Complexes of Activity

Advances in Astronomy ◽

10.1155/2015/438124 ◽

2015 ◽

Vol 2015 ◽

pp. 1-9

Author(s):

Vladimir N. Obridko ◽

Bertha D. Shelting

Keyword(s):

Magnetic Field ◽

Magnetic Fields ◽

Coronal Holes ◽

Active Regions ◽

Local Fields ◽

Magnetic Region ◽

Single Process ◽

Global And Local ◽

The Relationship ◽

The Magnetic Field

We propose a new concept that considers the global complexes of activity as a combination of global and local fields. Traditionally, the complexes of activity have been identified from observations of active regions (ARs). Here, we show that a complex of activity comprises both (AR) and coronal holes (CHs). Our analysis is based on observations of magnetic fields of various scales, SOHO/MDI data, and UV observations of CH. The analysis has corroborated the existence of complexes of activity that involve AR and equatorial CH. Both AR and CH are embedded in an extended magnetic region dominated by the magnetic field of one sign, but not strictly unipolar. It is shown that the evolution of CH and AR is a single process. The relationship between the fields of various scales in the course of a cycle is discussed.

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Emergence of Twisted Magnetic Flux Related Sigmoidal Brightening

International Astronomical Union Colloquium ◽

10.1017/s0252921100064630 ◽

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.

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The Origin and Dynamical Effects of the Magnetic Fields and Cosmic Rays in the Disk of the Galaxy

Symposium - International Astronomical Union ◽

10.1017/s0074180900004873 ◽

1970 ◽

Vol 39 ◽

pp. 168-183

Author(s):

E. N. Parker

Keyword(s):

Magnetic Field ◽

Cosmic Rays ◽

Magnetic Fields ◽

Dynamical Behavior ◽

Cosmic Ray ◽

Interested Reader ◽

Written Text ◽

The Galaxy ◽

Basic Ideas ◽

The Magnetic Field

The topic of this presentation is the origin and dynamical behavior of the magnetic field and cosmic-ray gas in the disk of the Galaxy. In the space available I can do no more than mention the ideas that have been developed, with but little explanation and discussion. To make up for this inadequacy I have tried to give a complete list of references in the written text, so that the interested reader can pursue the points in depth (in particular see the review articles Parker, 1968a, 1969a, 1970). My purpose here is twofold, to outline for you the calculations and ideas that have developed thus far, and to indicate the uncertainties that remain. The basic ideas are sound, I think, but, when we come to the details, there are so many theoretical alternatives that need yet to be explored and so much that is not yet made clear by observations.

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Nonlinear force-free modeling of magnetic fields in flare-productive active regions

Proceedings of the International Astronomical Union ◽

10.1017/s1743921316000387 ◽

2015 ◽

Vol 11 (S320) ◽

pp. 167-174

Author(s):

M. S. Wheatland ◽

S. A. Gilchrist

Keyword(s):

Magnetic Field ◽

Magnetic Fields ◽

Boundary Data ◽

Numerical Solutions ◽

Free Field ◽

Active Regions ◽

Coronal Magnetic Field ◽

Nonlinear Force ◽

The Magnetic Field ◽

Force Free Field

AbstractWe review nonlinear force-free field (NLFFF) modeling of magnetic fields in active regions. The NLFFF model (in which the electric current density is parallel to the magnetic field) is often adopted to describe the coronal magnetic field, and numerical solutions to the model are constructed based on photospheric vector magnetogram boundary data. Comparative tests of NLFFF codes on sets of boundary data have revealed significant problems, in particular associated with the inconsistency of the model and the data. Nevertheless NLFFF modeling is often applied, in particular to flare-productive active regions. We examine the results, and discuss their reliability.

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Oscillatory convection in strong magnetic fields and origin of active regions

Symposium - International Astronomical Union ◽

10.1017/s0074180900021410 ◽

1968 ◽

Vol 35 ◽

pp. 127-130 ◽

Cited By ~ 1

Author(s):

S. I. Syrovatsky ◽

Y. D. Zhugzhda

Keyword(s):

Magnetic Field ◽

Magnetic Fields ◽

Active Regions ◽

Oscillatory Convection ◽

Strong Magnetic Fields ◽

Various Boundary Conditions ◽

Convective Cells ◽

The Magnetic Field ◽

Polytropic Atmosphere

The convection in a compressible inhomogeneous conducting fluid in the presence of a vertical uniform magnetic field has been studied. It is shown that a new mode of oscillatory convection occurs, which exists in arbitrarily strong magnetic fields. The convective cells are stretched along the magnetic field, their horizontal dimensions are determined by radiative cooling. Criteria for convective instability in a polytropic atmosphere are obtained for various boundary conditions in the case when the Alfvén velocity is higher compared with the velocity of sound.The role of oscillatory convection in the origin of sunspots and active regions is discussed.

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Cyclotron Lines in the Spectra of Solar Flares and Solar Active Regions

International Astronomical Union Colloquium ◽

10.1017/s025292110003205x ◽

1989 ◽

Vol 104 (1) ◽

pp. 449-456

Author(s):

V. V. Zheleznyakov ◽

E. Ya. Zlotnik

Keyword(s):

Magnetic Field ◽

Magnetic Fields ◽

Cross Section ◽

Active Regions ◽

Kinetic Temperature ◽

Magnetic Tube ◽

Tube Cross Section ◽

Solar Active Regions ◽

Electron Gyrofrequency ◽

The Magnetic Field

AbstractIt was shown by Zheleznyakov and Zlotnik (1980a, b) that in complex configurations of solar magnetic fields (in hot loops above the active centres, in neutral current sheets in the preflare phase, in hot X-ray kernels in the initial flare phase) a system of cyclotron lines in the spectrum of microwave radiation is likely to be formed. Such a line was obtained by Willson (1985) in the VLA observations at harmonics of the electron gyrofrequency. This communication interprets these observations on the basis of an active region model in which thermal cyclotron radiation is produced by hot plasma filling the magnetic tube in the corona above a group of spots. In this model the frequency of the recorded 1658 MHz line corresponds to the third harmonic of electron gyrofrequency, which yields the magnetic field (196 + 4) G along the magnetic tube axis. The linewidth Af/f ∼ 0.1 is determined by the 10% inhomogeneity of the magnetic field over the cross-section of the tube; the line profile indicates the kinetic temperature distribution of electrons over the tube cross-section with the maximum value 4 x 106 K. Analysis shows that study of cyclotron lines can serve as an efficient tool for diagnostics of magnetic fields and plasma in the solar active regions and flares.

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THE STRUCTURE OF THE SOLAR WIND IN THE HELIOSPHERE DEPENDING ON THE PHASE OF THE SOLAR CYCLE: LARGE-SCALE DYNAMICS OF THE HELIOSPHERIC CURRENT SHEET

Journal of Oceanological Research ◽

10.29006/1564-2291.jor-2019.47(1).25 ◽

2019 ◽

Vol 47 (1) ◽

pp. 85-87

Author(s):

E.V. Maiewski ◽

R.A. Kislov ◽

H.V. Malova ◽

O.V. Khabarova ◽

V.Yu. Popov ◽

...

Keyword(s):

Magnetic Field ◽

Solar Wind ◽

Solar Activity ◽

Solar Cycle ◽

Current Sheet ◽

Heliospheric Current Sheet ◽

High Solar Activity ◽

The Sun ◽

High Latitudes ◽

The Magnetic Field

A stationary axisymmetric MHD model of the solar wind has been constructed, which allows us to study the spatial distribution of the magnetic field and plasma characteristics at radial distances from 20 to 400 radii of the Sun at almost all heliolatitudes. The model takes into account the changes in the magnetic field of the Sun during a quarter of the solar cycle, when the dominant dipole magnetic field is replaced by a quadrupole. Selfconsistent solutions for the magnetic and velocity fields, plasma concentration and current density of the solar wind depending on the phase of the solar cycle are obtained. It is shown that during the domination of the dipole magnetic component in the solar wind heliospheric current sheet (HCS) is located in the equatorial plane, which is a part of the system of radial and transverse currents, symmetrical in the northern and southern hemispheres. As the relative contribution of the quadrupole component to the total magnetic field increases, the shape of the HCS becomes conical; the angle of the cone gradually decreases, so that the current sheet moves entirely to one of the hemispheres. At the same time, at high latitudes of the opposite hemisphere, a second conical HCS arises, the angle of which increases. When the quadrupole field becomes dominant (at maximum solar activity), both HCS lie on conical surfaces inclined at an angle of 35 degrees to the equator. The model describes the transition from the fast solar wind at high latitudes to the slow solar wind at low latitudes: a relatively gentle transition in the period of low solar activity gives way to more drastic when high solar activity. The model also predicts an increase in the steepness of the profiles of the main characteristics of the solar wind with an increase in the radial distance from the Sun. Comparison of the obtained dependences with the available observational data is discussed.

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Active Phenomena in the Solar Atmosphere

Publications of the Astronomical Society of Australia ◽

10.1017/s1323358000014090 ◽

1975 ◽

Vol 2 (6) ◽

pp. 316-317

Author(s):

S.B. Pikel’ner

Keyword(s):

Magnetic Field ◽

Solar Activity ◽

Temperature Gradient ◽

Active Regions ◽

Convective Transport ◽

Short Description ◽

Photospheric Level ◽

The Magnetic Field ◽

Extended Review ◽

Main Factor

This paper gives a short description and interpretation of some solar magneto-hydrodynamical and plasma phenomena, based mainly on work by the writer and his collaborators (for an extended review see Kaplan et al. 1974).The magnetic field is considered as the main factor responsible for a number of manifestations of solar activity. At the photospheric level active regions are displayed as plages, i.e., bright areas, seen near the limb. This means that the temperature gradient in plages is smaller than in the undisturbed photosphere. The decrease in gradient is a result of an increase of convective transport of energy.

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3D model of magnetic fields evolution in dwarf irregular galaxies

Proceedings of the International Astronomical Union ◽

10.1017/s1743921311007344 ◽

2010 ◽

Vol 6 (S274) ◽

pp. 389-392

Author(s):

Hubert Siejkowski ◽

Marian Soida ◽

Katarzyna Otmianowska-Mazur ◽

Michał Hanasz ◽

Dominik J. Bomans

Keyword(s):

Magnetic Field ◽

Magnetic Fields ◽

Gravitational Potential ◽

Spiral Galaxies ◽

Cosmic Ray ◽

Dynamo Model ◽

Slow Rotation ◽

Irregular Galaxies ◽

Dwarf Irregular Galaxies ◽

The Magnetic Field

AbstractRadio observations show that magnetic fields are present in dwarf irregular galaxies (dIrr) and its strength is comparable to that found in spiral galaxies. Slow rotation, weak shear and shallow gravitational potential are the main features of a typical dIrr galaxy. These conditions of the interstellar medium in a dIrr galaxy seem to unfavourable for amplification of the magnetic field through the dynamo process. Cosmic-ray driven dynamo is one of the galactic dynamo model, which has been successfully tested in case of the spiral galaxies. We investigate this dynamo model in the ISM of a dIrr galaxy. We study its efficiency under the influence of slow rotation, weak shear and shallow gravitational potential. Additionally, the exploding supernovae are parametrised by the frequency of star formation and its modulation, to reproduce bursts and quiescent phases. We found that even slow galactic rotation with a low shearing rate amplifies the magnetic field, and that rapid rotation with a low value of the shear enhances the efficiency of the dynamo. Our simulations have shown that a high amount of magnetic energy leaves the simulation box becoming an efficient source of intergalactic magnetic fields.

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