Ring‐Diagram Analysis of the Structure of Solar Active Regions

Several techniques are used to study local areas in helioseismology, including time-distance helioseismology, acoustic imaging/holography, and ring diagram analysis. These techniques can be used to study flows, magnetic fields, and temperature inhomogeneities. The “local” area studied can be as small as a supergranule, or as large as the entire convection zone in the case of meridional circulation as studied by Giles and colleagues. Active regions have been studied with some interesting results, with complicated flow patterns below sunspots and detectable sound speed inhomogeneities in the 10 Mm below the spots. Another interesting result is the detection of sunspots on the back side of the Sun by Lindsey and Braun using the holography technique. A confirmation of their result using the time-distance technique is presented.

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Probing the Subsurface Structures of Active Regions with Ring-Diagram Analysis

Solar Physics ◽

10.1007/s11207-008-9213-9 ◽

2008 ◽

Vol 251 (1-2) ◽

pp. 439-451 ◽

Cited By ~ 26

Author(s):

Richard S. Bogart ◽

Sarbani Basu ◽

Maria Cristina Rabello-Soares ◽

H. M. Antia

Keyword(s):

Active Regions ◽

Subsurface Structures ◽

Ring Diagram ◽

Diagram Analysis

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Emerging Active Regions Studied with Ring‐Diagram Analysis

The Astrophysical Journal ◽

10.1086/523998 ◽

2008 ◽

Vol 672 (2) ◽

pp. 1254-1265 ◽

Cited By ~ 25

Author(s):

R. Komm ◽

S. Morita ◽

R. Howe ◽

F. Hill

Keyword(s):

Active Regions ◽

Ring Diagram ◽

Diagram Analysis

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Fractional Frequency Shifts of Local Helioseismic Modes With Magnetic Activity Using Ring-Diagram Analysis

Symposium - International Astronomical Union ◽

10.1017/s007418090021913x ◽

2001 ◽

Vol 203 ◽

pp. 215-218 ◽

Cited By ~ 1

Author(s):

B. Hindman ◽

D. Haber ◽

J. Toomre ◽

R. S. Bogart

Keyword(s):

Active Regions ◽

Magnetic Activity ◽

Doppler Velocity ◽

Velocity Data ◽

Frequency Shifts ◽

Ring Diagram ◽

High Degree ◽

Diagram Analysis ◽

Positive Frequency ◽

Full Disk

Using full-disk Doppler velocity data from MDI on SOHO, we have determined the central frequencies of high-degree p modes and f modes over a dense mosaic of localized regions on the sun using ring-diagram analyses (Haber et al. 2000). The motion of active regions as they rotate across the solar disk is well traced by changes in the central frequencies of the acoustic wave modes. Active regions appear as locations of large positive frequency shifts.

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Solar subsurface flows of active regions: flux emergence and flare activity

Proceedings of the International Astronomical Union ◽

10.1017/s1743921311015158 ◽

2010 ◽

Vol 6 (S273) ◽

pp. 148-152

Author(s):

Rudolf Komm ◽

Rachel Howe ◽

Frank Hill ◽

Kiran Jain

Keyword(s):

Spatial Scales ◽

Active Regions ◽

Flare Activity ◽

Near Surface ◽

Zonal Flows ◽

Global Oscillation Network Group ◽

Ring Diagram ◽

Subsurface Flows ◽

Vorticity Component ◽

Diagram Analysis

AbstractWe study the temporal variation of subsurface flows associated with active regions within 16 Mm of the solar surface. We have analyzed the subsurface flows of nearly 1000 active and quiet regions applying ring-diagram analysis to Global Oscillation Network Group (GONG) Dopplergram data. We find that newly emerging active regions are characterized by enhanced upflows and fast zonal flows in the near-surface layers, as expected for a flux tube rising from deeper layers of the convection zone. The subsurface flows associated with strong active regions are highly twisted, as indicated by their large vorticity and helicity values. The dipolar pattern exhibited by the zonal and meridional vorticity component leads to the interpretation that these subsurface flows resemble vortex rings, when measured on the spatial scales of the standard ring-diagram analysis.

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Radio Measurements of Coronal Magnetic Fields

International Astronomical Union Colloquium ◽

10.1017/s0252921100024933 ◽

1994 ◽

Vol 144 ◽

pp. 21-28 ◽

Cited By ~ 4

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.

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