Evolutionary and flare-associated magnetic shear variations observed in a complex, flare-productive active region

Solar Physics ◽  
1993 ◽  
Vol 148 (2) ◽  
pp. 277-299 ◽  
Author(s):  
Ashok Ambastha ◽  
Mona J. Hagyard ◽  
E. A. West
Keyword(s):  
Active Region ◽  
Magnetic Shear

scholarly journals Distribution of magnetic shear angle in an emerging flux region

2010 ◽  
Vol 6 (S273) ◽  
pp. 347-350
Author(s):  
Sanjay Gosain
Keyword(s):  
High Resolution ◽  
Active Region ◽  
Shear Angle ◽  
Flux Emergence ◽  
Magnetic Shear

AbstractWe study the distribution of magnetic shear in an emerging flux region using the high-resolution Hinode/SOT SP observations. The distribution of mean magnetic shear angle across the active region shows large values near region of flux emergence i.e., in the middle of existing bipolar region and decreases while approaching the periphery of the active region.

Correlation between magnetic shear and magnetic tension in a solar active region

Solar Physics ◽  
1993 ◽  
Vol 144 (2) ◽  
pp. 315-322 ◽  
Author(s):  
P. Venkatakrishnan ◽  
R. S. Narayanan ◽  
N. D. N. Prasad
Keyword(s):  
Active Region ◽  
Solar Active Region ◽  
Magnetic Shear ◽  
Magnetic Tension

scholarly journals Evolution and decay of an active region: Magnetic shear, flare and CME activity

2000 ◽  
Vol 39 (1) ◽  
pp. 73-80
Author(s):  
L. van Driel-Gresztelyi ◽  
B. Thompson ◽  
S. Punkett ◽  
P. Démoulin ◽  
G. Aulanier
Keyword(s):  
Active Region ◽  
Michelson Doppler Imager ◽  
Magnetic Shear ◽  
Heliospheric Observatory ◽  
Doppler Imager

Desde abril de 1996 y hasta febrero de 1997, se observó en el disco solar un complejo de actividad. Este complejo exhibió su nivel más alto de actividad durante el nacimiento de la región activa (AR) 7978. Nuestro análisis se extiende a lo largo de seis rotaciones solares, desde la aparición de AR 7978 (julio de 1996) hasta el decaimiento y dispersión de su flujo (noviembre de 1996). Los datos en varias longitudes de onda provistas por los instrumentos a bordo del Solar and Heliospheric Observatory (SOHO) y del satélite japonés Yohkoh, nos permiten seguir la evolución de la región desde la fotosfera hasta la corona. Usando los magnetogramas del disco completo obtenidos por el Michelson Doppler Imager (SOHO/MDI) como condiciones de contorno, calculamos el campo magnético coronal y determinamos su apartamiento de la potencialidad ajustando las líneas de campo calculadas a los arcos observados en rayos X blandos. Discutimos la evolución de la torsión del campo magnético coronal y su probable relación con la actividad observada en forma de eyecciones de masa coronal (CMEs) y fulguraciones.

scholarly journals Evolution of twist-shear and dip-shear in flaring active region NOAA 10930

2010 ◽  
Vol 6 (S273) ◽  
pp. 212-215
Author(s):  
Sanjay Gosain ◽  
P. Venkatakrishnan
Keyword(s):  
Active Region ◽  
Potential Field ◽  
Vertical Plane ◽  
Field Vector ◽  
Shear Angle ◽  
Active Region Noaa ◽  
Magnetic Shear ◽  
Significant Drop ◽  
Region Noaa ◽  
The Difference

AbstractWe study the evolution of magnetic shear angle in a flare productive active region NOAA 10930. The magnetic shear angle is defined as the deviation in the orientation of the observed magnetic field vector with respect to the potential field vector. The shear angle is measured in horizontal as well as vertical plane. The former is computed by taking the difference between the azimuth angles of the observed and potential field and is called the twist-shear, while the latter is computed by taking the difference between the inclination angles of the observed and potential field and is called the dip-shear. The evolution of the two shear angles is then tracked over a small region located over the sheared penumbra of the delta sunspot in NOAA 10930. We find that, while the twist-shear shows an increasing trend after the flare the dip-shear shows a significant drop after the flare.

Activated Prominences; Mechanisms for Activation and Eruption

1979 ◽  
Vol 44 ◽  
pp. 307-313
Author(s):  
D.S. Spicer
Keyword(s):  
Pressure Gradient ◽  
Density Gradient ◽  
Current Density ◽  
Convective Instability ◽  
Tearing Mode ◽  
Magnetic Shear ◽  
Long Wavelength ◽  
Ideal Mhd ◽  
Gradient Change ◽  
Accelerated Particles

A possible relationship between the hot prominence transition sheath, increased internal turbulent and/or helical motion prior to prominence eruption and the prominence eruption (“disparition brusque”) is discussed. The associated darkening of the filament or brightening of the prominence is interpreted as a change in the prominence’s internal pressure gradient which, if of the correct sign, can lead to short wavelength turbulent convection within the prominence. Associated with such a pressure gradient change may be the alteration of the current density gradient within the prominence. Such a change in the current density gradient may also be due to the relative motion of the neighbouring plages thereby increasing the magnetic shear within the prominence, i.e., steepening the current density gradient. Depending on the magnitude of the current density gradient, i.e., magnetic shear, disruption of the prominence can occur by either a long wavelength ideal MHD helical (“kink”) convective instability and/or a long wavelength resistive helical (“kink”) convective instability (tearing mode). The long wavelength ideal MHD helical instability will lead to helical rotation and thus unwinding due to diamagnetic effects and plasma ejections due to convection. The long wavelength resistive helical instability will lead to both unwinding and plasma ejections, but also to accelerated plasma flow, long wavelength magnetic field filamentation, accelerated particles and long wavelength heating internal to the prominence.

Morphology of the flare-productive active region NOAA 9087

2020 ◽  
Vol 36 (3) ◽  
pp. 69-90
Author(s):  
S. N. Chornogor ◽  
◽  
N. N. Kondrashova ◽  
Keyword(s):  
Active Region ◽  
Active Region Noaa ◽  
Region Noaa

On-the-Fly Determination of Active Region Centers in Adaptive-Partitioning QM/MM

2020 ◽  
Author(s):  
Zenghui Yang
Keyword(s):  
Quantum Mechanics ◽  
Active Region ◽  
Molecular Mechanics ◽  
Active Regions ◽  
Available Energy ◽  
Adaptive Partitioning ◽  
Different Levels

Quantum mechanics/molecular mechanics (QM/MM) methods partition the system into active and environmental regions and treat them with different levels of theory, achieving accuracy and efficiency at the same time. Adaptive-partitioning (AP) QM/MM methods allow on-the-fly changes to the QM/MM partitioning of the system. Many of the available energy-based AP-QM/MM methods partition the system according to distances to pre-chosen centers of active regions. For such AP-QM/MM methods, I develop an adaptive-center (AC) method that allows on-the-fly determination of the centers of active regions according to general geometrical or potential-related criteria, extending the range of application of energy-based AP-QM/MM methods to systems where active regions may occur or vanish during the simulation.

Characteristics of Soft X-Ray Radiation of the Solar Active Region NOAA 1024 Registered by the PINGVIN-M Device in July 2009

2020 ◽  
Vol 60 (7) ◽  
pp. 936-941
Author(s):  
M. I. Savchenko ◽  
P. V. Vatagin ◽  
P. B. Dmitriev ◽  
M. G. Ogurtsov ◽  
E. M. Kruglov ◽  
...  
Keyword(s):  
Active Region ◽  
Solar Active Region ◽  
Active Region Noaa ◽  
X Ray ◽  
Region Noaa
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