1,507 research outputs found
The Role of Helicity in Magnetic Reconnection: 3D Numerical Simulations
We demonstrate that conservation of global helicity plays only a minor role
in determining the nature and consequences of magnetic reconnection in the
solar atmosphere. First, we show that observations of the solar coronal
magnetic field are in direct conflict with Taylor's theory. Next, we present
results from three-dimensional MHD simulations of the shearing of bipolar and
multi-polar coronal magnetic fields by photospheric footpoint motions, and
discuss the implications of these results for Taylor's theory and for models of
solar activity. The key conclusion of this work is that significant magnetic
reconnection occurs only at very specific locations and, hence, the Sun's
magnetic field cannot relax completely down to the minimum energy state
predicted by conservation of global helicity.Comment: AGU LaTeX manuscript, 17 pages, 2 b-w figures, 4 color plate
The role of Vitamin D and Parathyroid Hormone in Cardiovascular Health
Visser, M. [Promotor]Brouwer, I.A. [Copromotor
Chirality of Intermediate Filaments and Magnetic Helicity of Active Regions
Filaments which form either between or around active regions (ARs) are called
intermediate filaments. In spite of various theoretical studies, the origin of
the chirality of filaments is still uncovered. We investigated how intermediate
filaments are related to their associated ARs, especially from the point of
view of magnetic helicity and the orientation of polarity inversion lines
(PILs). The chirality of filaments has been determined based on the
orientations of barbs observed in BBSO full-disk Halpha images taken during the
rising phase of solar cycle 23. The sign of magnetic helicity of ARs has been
determined using S/inverse-S shaped sigmoids from Yohkoh SXT images. As a
result, we have found a good correlation between the chirality of filaments and
the magnetic helicity sign of ARs. Among 45 filaments, 42 filaments have shown
the same sign as helicity sign of nearby ARs. It has been also confirmed that
the role of both the orientation and the relative direction of PILs to ARs in
determining the chirality of filaments is not significant, against a
theoretical prediction. These results suggest that the chirality of
intermediate filaments may originate from magnetic helicity of their associated
ARs.Comment: 13 pages, 7 figures, Accepted for Ap
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