Solar Radio S-Component Variation with the Magnetic Field of Active Regions

AbstractAccording to an active region model proposed in the present paper, i.e. three-dimensional and continuous distributions of the three plasma parameters (electron temperature, electron density, and magnetic field) from the active region to the quiet region, and using the combined mechanisms of gyroresonance radiation and bremsstrahlung, we have researched the solar radio S-component (i.e. the slowly varying component or SVC) variation with the magnetic field of active regions.

Numerical simulation of helical jets at active region peripheries

Monthly Notices of the Royal Astronomical Society ◽

10.1093/mnras/stz2674 ◽

2019 ◽

Vol 490 (3) ◽

pp. 3679-3690 ◽

Cited By ~ 4

Author(s):

Peter F Wyper ◽

C Richard DeVore ◽

Spiro K Antiochos

Keyword(s):

Magnetic Field ◽

Active Region ◽

Three Dimensional ◽

Flux Rope ◽

Active Regions ◽

Quantitative Agreement ◽

Null Point ◽

Closed Field ◽

The Magnetic Field ◽

Bald Patch

ABSTRACT Coronal jets are observed above minority-polarity intrusions throughout the solar corona. Some of the most energetic ones occur on the periphery of active regions where the magnetic field is strongly inclined. These jets exhibit a non-radial propagation in the low corona as they follow the inclined field, and often have a broad, helical shape. We present a three-dimensional magnetohydrodynamic simulation of such an active-region-periphery helical jet. We consider an initially potential field with a bipolar flux distribution embedded in a highly inclined magnetic field, representative of the field nearby an active region. The flux of the minority polarity sits below a bald-patch separatrix initially. Surface motions are used to inject free energy into the closed field beneath the separatrix, forming a sigmoidal flux rope that eventually erupts producing a helical jet. We find that a null point replaces the bald patch early in the evolution and that the eruption results from a combination of magnetic breakout and an ideal kinking of the erupting flux rope. We discuss how the two mechanisms are coupled, and compare our results with previous simulations of coronal-hole jets. This comparison supports the hypothesis that the generic mechanism for all coronal jets is a coupling between breakout reconnection and an ideal instability. We further show that our results are in good qualitative and quantitative agreement with observations of active-region-periphery jets.

Quantum cascade lasers in magnetic field: An active region model

physica status solidi (b) ◽

10.1002/pssb.200461758 ◽

2005 ◽

Vol 242 (9) ◽

pp. 1812-1816 ◽

Cited By ~ 2

Author(s):

I. Savić ◽

V. Milanović ◽

D. Indjin ◽

Z. Ikonić ◽

V. D. Jovanović ◽

...

Keyword(s):

Magnetic Field ◽

Active Region ◽

Quantum Cascade Lasers ◽

Quantum Cascade ◽

Region Model ◽

Active Region Model ◽

Cascade Lasers

Joint Discussion 3 Solar active regions and 3D magnetic structure

Proceedings of the International Astronomical Union ◽

10.1017/s1743921307010071 ◽

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 ◽

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.

Sunspot Proper Motion and Flare Frequency

International Astronomical Union Colloquium ◽

10.1017/s0252921100034540 ◽

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).

Searching for failed eruptions interacting with overlying magnetic field

Proceedings of the International Astronomical Union ◽

10.1017/s1743921316000557 ◽

2015 ◽

Vol 11 (S320) ◽

pp. 221-223 ◽

Cited By ~ 1

Author(s):

Dominik Gronkiewicz ◽

Tomasz Mrozek ◽

Sylwester Kołomański ◽

Martyna Chruślińska

Keyword(s):

Magnetic Field ◽

Statistical Analysis ◽

Active Region ◽

Solar Flares ◽

Active Regions ◽

Automated Method ◽

Solar Eruptions ◽

Mass Ejection ◽

The Magnetic Field ◽

Flare Site

AbstractIt is well known that not all solar flares are connected with eruptions followed by coronal mass ejection (CME). Even strongest X-class flares may not be accompanied by eruptions or are accompanied by failed eruptions. One of important factor that prevent eruption from developing into CME is strength of the magnetic field overlying flare site. Few observations show that active regions with specific magnetic configuration may produce many CME-less solar flares. Therefore, forecasts of geoeffective events based on active region properties have to take into account probability of confining solar eruptions. Present observations of SDO/AIA give a chance for deep statistical analysis of properties of an active region which may lead to confining an eruption. We developed automated method which can recognize eruptions in AIA images. With this tool we will be able to analyze statistical properties of failed eruptions observed by AIA telescope.

Data-driven model of the solar corona above an active region

Astronomy and Astrophysics ◽

10.1051/0004-6361/201935385 ◽

2019 ◽

Vol 624 ◽

pp. L12 ◽

Cited By ~ 4

Author(s):

J. Warnecke ◽

H. Peter

Keyword(s):

Magnetic Field ◽

Active Region ◽

Extreme Ultraviolet ◽

Three Dimensional ◽

Data Driven ◽

Diffuse Emission ◽

Qualitative Level ◽

Induction Equation ◽

Hot Corona ◽

Aims. We aim to reproduce the structure of the corona above a solar active region as seen in the extreme ultraviolet (EUV) using a three-dimensional magnetohydrodynamic (3D MHD) model. Methods. The 3D MHD data-driven model solves the induction equation and the mass, momentum, and energy balance. To drive the system, we feed the observed evolution of the magnetic field in the photosphere of the active region AR 12139 into the bottom boundary. This creates a hot corona above the cool photosphere in a self-consistent way. We synthesize the coronal EUV emission from the densities and temperatures in the model and compare this to the actual coronal observations. Results. We are able to reproduce the overall appearance and key features of the corona in this active region on a qualitative level. The model shows long loops, fan loops, compact loops, and diffuse emission forming at the same locations and at similar times as in the observation. Furthermore, the low-intensity contrast of the model loops in EUV matches the observations. Conclusions. In our model the energy input into the corona is similar as in the scenarios of fieldline-braiding or flux-tube tectonics, that is, energy is transported to the corona through the driving of the vertical magnetic field by horizontal photospheric motions. The success of our model shows the central role that this process plays for the structure, dynamics, and heating of the corona.

The X-Ray Corona and the Photospheric Magnetic Field

10.1017/s0074180900022841 ◽

1971 ◽

Vol 43 ◽

pp. 397-412 ◽

Cited By ~ 35

Author(s):

A. S. Krieger ◽

G. S. Vaiana ◽

L. P. Van Speybroeck

Keyword(s):

Magnetic Field ◽

Neutral Line ◽

Three Dimensional ◽

Active Regions ◽

Grazing Incidence ◽

Magnetic Polarity ◽

Lower Corona ◽

X Ray ◽

Three Dimensional Configuration ◽

Soft X-ray (3–60 Å) photographs of the solar corona have been obtained on four flights of a rocket-borne grazing incidence telescope having a resolution of a few arc seconds. The configuration of the X-ray emitting structures in the corona has been compared to the magnetic field distribution measured by photospheric longitudinal magnetograms. The X-ray structures trace the three dimensional configuration of the magnetic field through the lower corona.Active regions in the corona take the form of tubular structures connecting regions of opposite magnetic polarity within the same or adjacent chromospheric active regions.Higher, larger structures link widely separated active regions into complexes of activity covering substantial fractions of the disk. The complexes are separated by areas of low average field in the photosphere. Interconnections across the solar equator appear to originate over areas of preceding polarity.Enhanced X-ray emission is observed, outside the active belt, over areas of enhanced general magnetic field. Bright point-like X-ray features are observed above bipolar areas in the general coronal field.Two, probably related, classes of X-ray features are associated with points of high field gradient along the longitudinal magnetic, ‘neutral line’. Both in the non-flaring active region and in flares the brightest emission is observed from one or more small line sources (at our present resolution). In flares this can account for a substantial fraction of the total soft X-ray emission of the flare.

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

10.1017/s0074180900021537 ◽

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 ◽

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.

The balance of magnetic fluxes in active regions

10.1017/s007418090002129x ◽

1968 ◽

Vol 35 ◽

pp. 47-49 ◽

Cited By ~ 2

Author(s):

Jan Olof Stenflo

Keyword(s):

Magnetic Field ◽

Solar Cycle ◽

Active Region ◽

Solar Surface ◽

Active Regions ◽

Basic Feature ◽

The Sun ◽

Magnetic Disturbance ◽

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.

An Attempt to Associate Observed Photospheric Motions with the Magnetic Field Structure and Flare Occurrence in an Active Region

10.1017/s0074180900022907 ◽

1971 ◽

Vol 43 ◽

pp. 435-442 ◽

Cited By ~ 8

Author(s):

M. J. Martres ◽

I. Soru-Escaut ◽

J. Rayrole

Keyword(s):

Magnetic Field ◽

Active Region ◽

Empirical Evidence ◽

Active Regions ◽

Field Structure ◽

Magnetic Field Structure ◽

Abrupt Changes ◽

We have tried to find empirical evidence for the role of photospheric motions in the building up of the flare productive magnetic patterns in Active Regions.The bright Hα faculae are associated with V∥ structures different from a classical Evershed flow and particularly ‘anomalous’ in the regions and periods of high flare occurrence. The flares observed occurred at ‘crossings’ of the lines V∥ = 0(V ≠ 0) and H∥ = 0 and at places where V∥ = 0 showed abrupt changes of direction. It is suggested that these anomalous V∥ structures are evidence of vortex motions.