Formation of current layers in three-dimensional, inhomogeneous coronal magnetic fields by photospheric motions

1997 ◽  
Vol 102 (A10) ◽  
pp. 22285-22293 ◽  
Author(s):  
G. W. Inverarity ◽  
V. S. Titov
Keyword(s):  
Magnetic Fields ◽  
Three Dimensional ◽  
Coronal Magnetic Fields

scholarly journals Magnetism and the Invisible Man: The mysteries of coronal cavities

2013 ◽  
Vol 8 (S300) ◽  
pp. 139-146 ◽  
Author(s):  
Sarah Gibson
Keyword(s):  
Magnetic Field ◽  
Magnetic Fields ◽  
Interplanetary Space ◽  
Three Dimensional ◽  
Field Measurements ◽  
Coronal Magnetic Field ◽  
Magnetic Structures ◽  
Coronal Magnetic Fields ◽  
Multiple Wavelengths ◽  
The Magnetic Field

AbstractMagnetism defines the complex and dynamic solar corona. Twists and tangles in coronal magnetic fields build up energy and ultimately erupt, hurling plasma into interplanetary space. These coronal mass ejections (CMEs) are transient riders on the ever-outflowing solar wind, which itself possesses a three-dimensional morphology shaped by the global coronal magnetic field. Coronal magnetism is thus at the heart of any understanding of the origins of space weather at the Earth. However, we have historically been limited by the difficulty of directly measuring the magnetic fields of the corona, and have turned to observations of coronal plasma to trace out magnetic structure. This approach is complicated by the fact that plasma temperatures and densities vary among coronal magnetic structures, so that looking at any one wavelength of light only shows part of the picture. In fact, in some regimes it is the lack of plasma that is a significant indicator of the magnetic field. Such a case is the coronal cavity: a dark, elliptical region in which strong and twisted magnetism dwells. I will elucidate these enigmatic features by presenting observations of coronal cavities in multiple wavelengths and from a variety of observing vantages, including unprecedented coronal magnetic field measurements now being obtained by the Coronal Multichannel Polarimeter (CoMP). These observations demonstrate the presence of twisted magnetic fields within cavities, and also provide clues to how and why cavities ultimately erupt as CMEs.

Measurements of Three‐dimensional Coronal Magnetic Fields from Coordinated Extreme‐Ultraviolet and Radio Observations of a Solar Active Region Sunspot

2002 ◽  
Vol 574 (1) ◽  
pp. 453-466 ◽  
Author(s):  
Jeffrey W. Brosius ◽  
Enrico Landi ◽  
John W. Cook ◽  
Jeffrey S. Newmark ◽  
N. Gopalswamy ◽  
...  
Keyword(s):  
Active Region ◽  
Magnetic Fields ◽  
Extreme Ultraviolet ◽  
Three Dimensional ◽  
Solar Active Region ◽  
Radio Observations ◽  
Coronal Magnetic Fields

Particle Acceleration in a Three-Dimensional Model of Reconnecting Coronal Magnetic Fields

2006 ◽  
Vol 124 (1-4) ◽  
pp. 249-259 ◽  
Author(s):  
Peter J. Cargill ◽  
Loukas Vlahos ◽  
Rim Turkmani ◽  
Klaus Galsgaard ◽  
Heinz Isliker
Keyword(s):  
Particle Acceleration ◽  
Magnetic Fields ◽  
Three Dimensional ◽  
Dimensional Model ◽  
Three Dimensional Model ◽  
Coronal Magnetic Fields

Calculated Coronal Magnetic Fields and Their Comparison with the Coronal Structures as Observed during Five Solar Eclipses

1994 ◽  
Vol 144 ◽  
pp. 559-564
Author(s):  
P. Ambrož ◽  
J. Sýkora
Keyword(s):  
Magnetic Field ◽  
Solar Cycle ◽  
Magnetic Fields ◽  
Solar Corona ◽  
Coronal Magnetic Field ◽  
Coronal Magnetic Fields ◽  
Solar Eclipses ◽  
Coronal Structures

AbstractWe were successful in observing the solar corona during five solar eclipses (1973-1991). For the eclipse days the coronal magnetic field was calculated by extrapolation from the photosphere. Comparison of the observed and calculated coronal structures is carried out and some peculiarities of this comparison, related to the different phases of the solar cycle, are presented.

scholarly journals Can Multi-threaded Flux Tubes in Coronal Arcades Support a Magnetohydrodynamic Avalanche?

Solar Physics ◽  
2021 ◽  
Vol 296 (8) ◽  
Author(s):  
J. Threlfall ◽  
J. Reid ◽  
A. W. Hood
Keyword(s):  
Magnetic Fields ◽  
Three Dimensional ◽  
Coronal Loops ◽  
Flux Tubes ◽  
Single Thread ◽  
Mhd Instabilities ◽  
Mhd Instability ◽  
Mhd Simulations ◽  
Ideal Mhd ◽  
Model Geometry

AbstractMagnetohydrodynamic (MHD) instabilities allow energy to be released from stressed magnetic fields, commonly modelled in cylindrical flux tubes linking parallel planes, but, more recently, also in curved arcades containing flux tubes with both footpoints in the same photospheric plane. Uncurved cylindrical flux tubes containing multiple individual threads have been shown to be capable of sustaining an MHD avalanche, whereby a single unstable thread can destabilise many. We examine the properties of multi-threaded coronal loops, wherein each thread is created by photospheric driving in a realistic, curved coronal arcade structure (with both footpoints of each thread in the same plane). We use three-dimensional MHD simulations to study the evolution of single- and multi-threaded coronal loops, which become unstable and reconnect, while varying the driving velocity of individual threads. Experiments containing a single thread destabilise in a manner indicative of an ideal MHD instability and consistent with previous examples in the literature. The introduction of additional threads modifies this picture, with aspects of the model geometry and relative driving speeds of individual threads affecting the ability of any thread to destabilise others. In both single- and multi-threaded cases, continuous driving of the remnants of disrupted threads produces secondary, aperiodic bursts of energetic release.

scholarly journals Boundary Fitting Problems Associated with Coronal Magnetic Models

1974 ◽  
Vol 57 ◽  
pp. 89-91 ◽  
Author(s):  
Kenneth H. Schatten
Keyword(s):  
Magnetic Fields ◽  
Legendre Polynomial ◽  
Magnetic Monopole ◽  
Polynomial Fit ◽  
Coronal Magnetic Fields ◽  
Boundary Fitting

The calculation of coronal magnetic fields was first suggested by Gold (1958). Altschuler and Newkirk (1969) and Newkirk et al. (1968) used a Legendre polynomial fit to the photospheric observations of magnetic fields whereas Schatten (1968) with Wilcox and Ness (Schatten et al., 1969) use a magnetic monopole fit, first incorporated by Schmidt (1964).

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