scholarly journals An Assessment of Magnetic Conditions for Strong Coronal Heating in Solar Active Regions by Comparing Observed Loops with Computed Potential Field Lines

2000 ◽  
Vol 528 (2) ◽  
pp. 1004-1014 ◽  
Author(s):  
D. A. Falconer ◽  
G. A. Gary ◽  
R. L. Moore ◽  
J. G. Porter
Keyword(s):  
Potential Field ◽  
Active Regions ◽  
Coronal Heating ◽  
Solar Active Regions ◽  
Field Lines

scholarly journals Evidence for Open Field Lines from Active Regions: Short Communication

1980 ◽  
Vol 91 ◽  
pp. 261-261
Author(s):  
K. V. Sheridan
Keyword(s):  
Open Field ◽  
Subject Matter ◽  
Short Communication ◽  
Active Regions ◽  
Theoretical Physics ◽  
University Of Colorado ◽  
Solar Active Regions ◽  
The Subject ◽  
Field Lines ◽  
Sydney Australia

A paper that has considerable relevance of the subject matter of this symposium is the following: “Evidence for Extreme Divergence of Open Field Lines from Solar Active Regions,” by G. A. Dulk (Division of Radiophysics, CSIRO, Sydney, Australia and Department of Astro-Geophysics, University of Colorado, Boulder, Colorado), D. B. Melrose (Department of Theoretical Physics, University of Sydney, Australia) and S. Suzuki (Division of Radiophysics, CSIRO, Sydney, Australia).

scholarly journals Neutral‐Line Magnetic Shear and Enhanced Coronal Heating in Solar Active Regions

1997 ◽  
Vol 482 (1) ◽  
pp. 519-534 ◽  
Author(s):  
D. A. Falconer ◽  
R. L. Moore ◽  
J. G. Porter ◽  
G. A. Gary ◽  
T. Shimizu
Keyword(s):  
Neutral Line ◽  
Active Regions ◽  
Coronal Heating ◽  
Magnetic Shear ◽  
Solar Active Regions

scholarly journals Low Brightness Temperature in Microwaves at Periphery of Some Solar Active Regions

2017 ◽  
Vol 54 (3) ◽  
pp. 58-67
Author(s):  
B. I. Ryabov ◽  
D. A. Bezrukov ◽  
J. Kallunki
Keyword(s):  
Brightness Temperature ◽  
Open Field ◽  
Active Regions ◽  
Source Surface ◽  
The Sun ◽  
Coronal Emission ◽  
Field Source ◽  
Wavelet Space ◽  
Solar Active Regions ◽  
Field Lines

AbstractThe microwave regions with low brightness temperature are found to overlap the regions of the depressed coronal emission and open field lines at the periphery of two solar active regions (ARs). The imaging microwave observations of the Sun with the Nobeyama Radio heliograph at 1.76 cm, the MRO-14 radio telescope of Metsähovi Radio Observatory at 0.8 cm, and the RT-32 of Ventspils International Radio Astronomy Centre in the range 3.2-4.7 cm are used. To reduce the noise in the intensity distribution of the RT-32 maps of the Sun, one wavelet plane of “à trous” wavelet space decomposition is subtracted from each map. To locate the open-field regions, the full-Sun coronal magnetic fields with the potential field source surface (PFSS) model for RSS= 1.8 Rʘare simulated. We conclude that the revealed LTRs present narrow coronal hole-like regions near two ARs and imply an extra investigation on the plasma outflow.

Evidence for Extreme Divergence of Open Field Lines from Solar Active Regions

1979 ◽  
Vol 3 (6) ◽  
pp. 375-379 ◽  
Author(s):  
G. A. Dulk ◽  
D. B. Melrose ◽  
S. Suzuki
Keyword(s):  
Magnetic Field ◽  
Open Field ◽  
Interplanetary Space ◽  
Active Regions ◽  
Type Iii ◽  
Solar Active Regions ◽  
Field Lines ◽  
Type V ◽  
Open Magnetic Field

In this paper we review the evidence on the structure of the open magnetic field lines that emerge from solar active regions into interplanetary space. The evidence comes mainly from the measured sizes, positions and polarization of Type III and Type V bursts, and from electron streams observed from space. We find that the observations are best interpreted in terms of a strongly-diverging field topology, with the open field lines filling a cone of angle ~60°.

scholarly journals Coronal heating and flaring in QSLs

2010 ◽  
Vol 6 (S273) ◽  
pp. 233-241 ◽  
Author(s):  
Guillaume Aulanier
Keyword(s):  
Magnetic Field ◽  
Magnetic Energy ◽  
Free Field ◽  
Active Regions ◽  
Coronal Heating ◽  
Small Scale ◽  
Flux Tubes ◽  
Solar Instruments ◽  
Field Lines ◽  
New Generation

AbstractQuasi-Separatrix Layers (QSLs) are 3D geometrical objects that define narrow volumes across which magnetic field lines have strong, but finite, gradients of connectivity from one footpoint to another. QSLs extend the concept of separatrices, that are topological objects across which the connectivity is discontinuous. Based on analytical arguments, and on magnetic field extrapolations of the Sun's coronal force-free field above observed active regions, it has long since been conjectured that QSLs are favorable locations for current sheet (CS) formation, as well as for magnetic reconnection, and therefore are good predictors for the locations of magnetic energy release in flares and coronal heating. It is only up to recently that numerical MHD simulations and solar observations, as well as a laboratory experiment, have started to address the validity of these conjectures. When put all together, they suggest that QSL reconnection is involved in the displacement of EUV and SXR brightenings along chromospheric flare ribbons, that it is related with the heating of EUV coronal loops, and that the dissipation of QSL related CS may be the cause of coronal heating in initially homogeneous, braided and turbulent flux tubes, as well as in coronal arcades rooted in the slowly moving and numerous small-scale photospheric flux concentrations, both in active region faculae and in the quiet Sun. The apparent ubiquity of QSL-related CS in the Sun's corona, which will need to be quantified with new generation solar instruments, also suggests that QSLs play an important role in stellar's atmospheres, when their surface radial magnetic fields display complex patterns.

scholarly journals Diagnostics of Coronal Heating in Solar Active Regions

2004 ◽  
Vol 219 ◽  
pp. 478-482 ◽  
Author(s):  
A. Fludra ◽  
J. Ireland
Keyword(s):  
Magnetic Flux ◽  
Flux Density ◽  
Average Power ◽  
Active Regions ◽  
Coronal Heating ◽  
Magnetic Flux Density ◽  
Line Intensities ◽  
Solar Active Regions ◽  
The Relationship ◽  
Coronal Diagnostic Spectrometer

We study the relationship between EUV spectral line intensities and the photospheric magnetic field in solar active regions, using magnetograms from SOHO-MDI and EUV spectra of the Fe XVI 360.8 Â line (2 × 106 K) and the O V 629.7 A line (220,000 K) from the Coronal Diagnostic Spectrometer on SOHO, recorded for several active regions. We overlay and compare spatial patterns of the O V emission and the magnetic flux concentrations, with a 4″ x 4″ spatial resolution, and search for a relationship between the local O V line intensity and the photospheric magnetic flux density in each active region. While this dependence exhibits a certain amount of scatter, it can be represented by a power law fit. The average power index from all regions is 0.7 ± 0.2. Applying static loop models, we derive the dependence of the heating rate on the magnetic flux density, Eh ∝ B0.8, and compare it to the dependence predicted by the coronal heating models.

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