E-Print Archive

There are 1713 abstracts currently viewable.


Search:

Advanced Search
Options
Main Page Add New E-Print Submitter
Information
Feedback
News Help/FAQ About Preferences
Manage Key Phrase
Notification
Magnetic helicity accumulation and tilt angle evolution of newly emerging active regions View all abstracts by submitter

Shangbin Yang   Submitted: 2009-10-08 02:34

Context: It has been known for years that there is a general dominance of negative (positive) helicity of active regions (ARs) in the northern (southern) solar hemisphere. For a better understanding of the role of helicity in the evolution of active regions, it is necessary to know more about the accumulation of helicity during the emergence of active regions. In particular, different conclusions were drawn in the past about the relationship between the accumulated helicity and the writhe of active regions. Aims: We investigate the accumulation of helicity in newly emerging simple bipolar solar active regions. We also investigate the relation between the accumulated helicity and writhe. Methods: We obtain helicity accumulation by applying Fast Fourier Transforms (FFT) and local correlation tracking (LCT) to MDI data. We deduce the writhe of the active regions according to the evolution of the tilt angle between the connecting line of the weighting centers of opposite polarities in the ARs. Results: It is found that the accumulated helicity is proportional to the exponent of magnetic flux (|H| ∝ Φ^1.85) in the 58 selected newly emerged simple ARs. 74% of ARs have a negative (positive) helicity when the above defined tilt angle rotates clockwise (counter-clockwise). This means that the accumulated helicity and writhe have the same sign for most of the investigated ARs according to the tilt angle evolution of ARs. We also found that 56% (57.6%) of these ARs in the northern (southern) photosphere provide negative (positive) helicity to the corona in the course of the emergence of magnetic flux.

Authors: Yang, S.; Zhang, H.; Büchner, J.
Projects: SoHO-MDI

Publication Status: A&A (published)
Last Modified: 2009-10-08 07:40
Go to main E-Print page  Temporal comparison of nonthermal flare emission and magnetic-flux change rates  	 	Magnetic Helicity Exchange Between Neighboring Active Regions  Edit Entry  Download Preprint  Submitter's Homepage Delete Entry 

Key
Go to main E-Print pageGo to main E-Print page.
Previous AbstractPrevious Abstract.
Next AbstractNext Abstract.
Download PreprintDownload Preprint.
Submitter's HomepageSubmitters Homepage.
Edit EntryEdit Entry.
View All Abstracts By SubmitterView all abstracts by submitter.
Delete AbstractDelete abstract.

Latest Entries
Statistical properties of H -alpha flares in relation to sunspots and active regions in the cycle 23
Diagnostics of energetic electrons with anisotropic distributions in solar flares I. Hard X-rays bremsstrahlung emission
On the Correlation between Spectra of Solar Microwave Bursts and Proton Fluxes near the Earth
Sun-as-a-Star, Chromospheric Lines, 1974-2009
FORMATION OF TORUS-UNSTABLE FLUX ROPES AND ELECTRIC CURRENTS IN ERUPTING SIGMOIDS
Resolving the Azimuthal Ambiguity in Vector Magnetogram Data with the Divergence-Free Condition: Application to Discrete Data
Minima of Solar Cycles 22/23 and 23/24 as Seen in SOHO/CELIAS/SEM Absolute Solar EUV Flux
HINODE OBSERVATIONS OF COHERENT LATERAL MOTION OF PENUMBRAL FILAMENTS DURING A X-CLASS FLARE
EUV SpectroPhotometer (ESP) in Extreme Ultraviolet Variability Experiment
The effect of wave-particle interactions on low energy cutoffs in solar flare electron spectra
Heliospheric Current Sheet Distortions from Adjacent Outflowing Transients: Multi-spacecraft Observations
A detailed investigation of the properties of a Vlasov-Maxwell equilibrium for the force-free Harris sheet}
On the Relationship between Equilibrium Bifurcations and Ideal MHD Instabilities for Line-Tied Coronal Loops}
Coronal Mass Ejections and Global Coronal Magnetic Field Reconfiguration
Relationship Between a Coronal Mass Ejection-Driven Shock and a Coronal Metric Type II Burst
An Intriguing Chromospheric Jet Observed by Hinode: I. Fine Structure Kinematics and Evidence of Unwinding Twists
A Code for Automated Tracing of Coronal Loops Approaching Visual Perception
Large Amplitude Oscillations in Prominences
An Extension of the Theory of Kinematic MHD Models of Collapsing Magnetic Traps to 2.5D with shear flow and to 3D
Confirming a Seismologically Inferred Coronal Temperature

Related Pages
MSU Solar Physics.
Max Millennium Science Mail Archive.
Max Millennium Message of the Day Mail Archive.
Max Millennium Flare Catalog

Archive Maintainer
Alisdair Davey



© 2003 Solar Physics Group - Montana State University