4 edition of Neutral-line magnetic shear and enhanced coronal heating in solar active regions found in the catalog.
Neutral-line magnetic shear and enhanced coronal heating in solar active regions
by National Aeronautics and Space Administration, National Technical Information Service, distributor in [Washington, DC, Springfield, Va
Written in English
|Other titles||Neutral line magnetic shear and enhanced coronal heating in solar active regions.|
|Statement||D.A. Falconer ... [et al.].|
|Series||NASA-TM -- 112520., NASA technical memorandum -- 112520.|
|Contributions||Falconer, David A. 1964-, United States. National Aeronautics and Space Administration.|
|The Physical Object|
much hotter than the photosphere. The mechanism or mechanisms heating the outer solar layers are not known, so this is known as the coronal heating problem. wTo di erent categories of theories have emerged: wave theories and magnetic reconnection theories. Both wave features and magnetic re-. Papers. Listed alphabetically by first author. Alexander, D., Gary, G. A., and Thompson, B.J., , "Analysis of Active Regions via 3D Rendering Techniques'', in.
To contribute to the understanding of heating and dynamic activity in boundary‐driven, low‐beta plasmas such as the solar corona, we investigate how an initially homogeneous magnetic field responds to random large‐scale shearing motions on two boundaries, by numerically solving the dissipative MHD equations, with resolutions ranging from 24 3 to by: direct and quantitative solar observations. The solar magnetic ﬁeld plays a critical role in controlling solar activity that ultimately aﬀects human life on Earth. There has been a long history of observing solar magnetic ﬁeld, especially that in a solar active region (AR; sunspot region).Author: Qiang Hu, Na Deng, Debi P. Choudhary, B. Dasgupta, Jiangtao Su.
During the solar minimum, when the Sun is at its least active, the solar wind1,2 is observed at high latitudes as a predominantly fast (more than kilometres per second), highly Alfvénic Cited by: The magnetic field in the corona is important for understanding solar activity. Linear polarization measurements inforbidden lines in the visible/IR provide information about coronal magnetic direction and topology.
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The magnetic shear is strong (shear angle greater than 45 °) in the white segments of the neutral lines and weak (shear angle less than 45 °) in the gray segments.
tures that are persistently bright over the part of the orbit during which the active region is observed by Yohkoh (typically minutes). From these results, we conclude that most persistent enhanced heating of coronal loops in active regions (1) requires the presence of a polarity inversion in the magnetic field near at least one of the loop footpoints, (2) is greatly aided by the presence of strong shear in the core magnetic field along that neutral line, and (3) is controlled by some variable process that acts in this magnetic by: From 27 orbits " worth of Yohkoh SXT images of the five active regions, we have obtained a sample of 94 persistently bright coronal features (bright in all images from a given orbit), 40 long (>20, km) neutral-line segments having strong magnetic shear throughout (shear angle greater than 45°), and 39 long neutral-line seg-ments having weak magnetic shear throughout (shear angle less than 45°).
A strong dependence of active-region (AR) coronal heating on the magnetic field is demonstrated by the strong correlation of AR X-ray luminosity with AR total magnetic flux (Fisher et al ApJ). AR X-ray luminosity is also correlated with AR length of strong-shear neutral line in the photospheric magnetic field (Falconer ).
These two whole-AR magnetic parameters are also correlated with Author: David Falconer, Sanjiv Tiwari, Amy Winebarger, Ron Moore.
•Falconer found that coronal X-ray luminosity was correlated with length of strong-shear, strong-field neutral line. •Fisher et al found that coronal X-ray luminosity was correlated with several magnetic parameters, many of these were correlated with each other.
The parameter with the best correlation was total magnetic flux. From these results, we conclude that most persistent enhanced heating of coronal loops in active regions: (1) requires the presence of a polarity inversion in the magnetic field near at least one of the loop footpoints; (2) is greatly aided by the presence of strong shear in the core magnetic field along that neutral line; and (3) is controlled by some variable process that acts in this magnetic environment.
We have also found from these active regions that the presence of a neutral line with strong magnetic shear is a favorable condition for strong heating. Large loops in the high coronal envelope of an active region are apparently selected for enhanced heating by the presence of such magnetic shear near a footpoint of the large loop.
Electric-current Neutralization, Magnetic Shear, and Eruptive Activity in Solar Active Regions Yang Liu1, Xudong Sun1, Tibor Török2, Viacheslav S.
Titov2, and James E. Leake3 1 W. Hansen Experimental Physics Laboratory, Stanford University, Stanford, CAUSA 2 Predictive Science Inc., Mesa Rim Road, SuiteSan Diego, CAUSACited by: 7. that most persistent enhanced heating of coronal loops in active regions (1) requires the presence of a polarity inversion in the magnetic Ðeld near at least one of the loop footpoints, (2) is greatly aided by the presence of strong shear in the core magnetic Ðeld along that neutral line.
The physical conditions that determine whether or not solar active regions (ARs) produce strong flares and coronal mass ejections (CMEs) are not yet well understood.
Here we investigate the association between electric-current neutralization, magnetic shear along polarity inversion lines (PILs), and eruptive activity in four ARs; two emerging and two well-developed ones. Cited by: 7. Coronal Heating. A number of mechanisms have been proposed to explain coronal heating, The two most commonly proposed mechanisms are wave heating (ion-cyclotron waves) and micro-flare (or nano-flare) heating.
This page is under active construction. Return later for more entries. Radio Emissions from Solar Active Regions 9 F or free-free emissions, the degree of circular polarization can b e deter- mined easily and it depends only on the line-of-sight magnetic ﬁeld and.
Get this from a library. Neutral-line magnetic shear and enhanced coronal heating in solar active regions. [David A Falconer; United States. National Aeronautics and Space Administration.;]. The present Letter is aimed at the study of properties of the current and magnetic shear in solar active regions.
The distribution of the magnetic shear and current provides information on the Author: Hongqi Zhang. Topology of Magnetic Field and Coronal Heating in Solar Active Regions: Authors: Force-free magnetic fields can be computed by making use of a new numerical technique, in which the fields are represented by a boundary integral equation based on a specific Green's function.
The reconstruction of 3-D magnetic field in active region NOAA. Abstract. The photospheric vector magnetic fields, Hα and soft X-ray images of AR were simultaneously observed with the Solar Flare Telescope at Mitaka and the Soft X-ray Telescope of Yohkoh on Octo, when there was no important activity in this region.
Taking the observed photospheric vector magnetic fields as the boundary condition, 3D magnetic fields above the Cited by: Falconer et al. () believe that a kind of hybrid heating process including classes (a) and (b) is a viable possibility for some of these coronal features.
They found that the heating of BCFs in solar active regions, namely enhanced coronal heat- TOPOLOGY OF MAGNETIC FIELD AND CORONAL HEATING, II Figure 1.
Introduction. The heating of the solar corona by small, impulsive heating events appears to date to a discussion by Gold , and the subsequent more quantitative proposal of Levine [2,3] that small coronal current sheets were responsible for the uent analysis of Skylab data led to a quasi-consensus that the X-ray corona could be understood in terms of steady heating and Cited by:  From a sample of 17 vector magnetograms of 12 bipolar active regions we have recently found (1) that a measure of the overall nonpotentiality (the overall twist and shear in the magnetic field) of an active region is given by the strong shear length L SS, the length of the portion of the main neutral line on which the observed transverse fields is strong (> Guass (G)) and strongly Cited by: From magnetic fields and coronal heating observed in flares, active regions, quiet regions, and coronal holes, we propose that exploding sheared core magnetic fields are the drivers of most of the dynamics and heating of the solar atmosphere, ranging from the largest and most powerful coronal mass ejections and flares, to the vigorous microflaring and coronal heating in active regions Cited by: 4.
Magnetic fields play a crucial role in heating the outer atmospheres of the Sun and Sun-like stars, but the mechanisms by which magnetic energy in Cited by: L. P. Chitta et al.: Energetics of magnetic transients in a solar active region plage Fig. 2. Evolution of the magnetic transients in a plage region.
The region covered by the panels in each row shows the SST line-of-sight magnetic ﬁeld map (saturated at 50G) and is Cited by: 4.1. Introduction. The concept of magnetic reconnection goes back to Giovanelli () in solar flare studies.
Since solar flares are explosive in nature and powered by magnetic energy, it is expected that the reconnection responsible for flares must have taken place in the corona in order to account for the rapid magnetic energy by: 5.