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C. R. DeVore, S. K. Antiochos (Naval Research Laboratory), G. Aulanier (Observatoire de Meudon)
It has long been known that pairs of filaments near each other on the Sun's disk sometimes come into contact and interact. Under favorable conditions, the two structures apparently link up to form a single, larger filament. When conditions are unfavorable, on the other hand, the filaments appear to avoid each other and retain their distinct identities. Recent ground-based observational studies have shown that a key requirement for linkage to occur is that the two filaments possess the same chirality, or handedness.
We have performed detailed numerical experiments of pairs of interacting filaments within the sheared-arcade model. In this model, the filament plasma resides in the magnetic hammock formed in a strongly sheared field held down by an overlying arcade. We considered four cases: like or unlike chirality of the two filaments, and like or unlike polarity of the vertical magnetic fields at their approaching ends. Only the case of like chirality and unlike polarity produces any significant reconfiguration. The magnetic structure is substantially modified, with reconnected field lines extending over the entire combined length of the filaments. Low, closed arcade fields form in the reconnection zone, forcing the newly linked filament fields above them to rise and form a magnetic 'aneurysm.' Our simple, bipolar configuration relaxes to a new equilibrium, consistent with those cases in which the linked structure is observed to persist stably after the interaction has passed. In the much more complex magnetic environment of the solar corona, on the other hand, newly linked filaments with such aneurysms sometimes are observed to erupt promptly and violently. The removal of the restraining arcade fields, by reconnection with the external field of the corona, is likely necessary for eruption to occur.
This research was supported by NASA and ONR.
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Bulletin of the American Astronomical Society, 34
© 2002. The American Astronomical Soceity.