Astronomy and Astrophysics – Astronomy
Scientific paper
Mar 1996
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=1996apj...460..530p&link_type=abstract
Astrophysical Journal v.460, p.530
Astronomy and Astrophysics
Astronomy
60
Magnetohydrodynamics: Mhd, Sun: Prominences
Scientific paper
In a recent paper Martin and coworkers have discussed several striking facts about the structure of solar prominences and the filament channels in which they lie. They form two classes, called dextral and sinistral. In a dextral (sinistral) prominence, an observer viewing a prominence or filament channel from the positive-polarity side would see the magnetic field point to the right (left) along the axis of the filament channel, whereas an observer viewing from above would see the prominence feet bear off the axis to the right (left). Furthermore, dextral prominences dominate the northern hemisphere and sinistral the southern hemisphere, regardless of the cycle. Fibrils in the filament channels do not cross the prominence but usually stream from or to plagettes parallel to the prominence axis.
These pioneering observations suggest that there is a coherent organizational principle orchestrating the global nature of prominences, and they have led us to reexamine the standard paradigms of contemporary prominence theory, such as that (1) prominences form in a sheared force-free arcade, (2) formation is by radiative instability, (3) the prominence material is static, and (4) eruption occurs when the shear or twist is too great. We propose a new model which accounts for the above new observational features in a natural way, replaces many of the above paradigms, and explains the previously puzzling feet of a prominence. It is a dynamic model in which a prominence is maintained by the continual input of mass and magnetic flux. The correct global dextral and sinistral patterns for high-latitude east-west prominences (such as those in the polar crown) are created by an organizational principle that includes the combined effects of differential rotation on subphotospheric flux, its subsequent emergence by magnetic buoyancy, and its rearrangement by flux reconnection to form a filament channel with magnetic flux oriented along its axis. Continual emergence and reconnection creates a prominence as a flux tube along the filament channel axis and filled with cool plasma which is lifted up from the photosphere and chromosphere by the reconnection process. Prominences at low latitudes are in this model formed in a similar way, except that it is a general subphotospheric flow (rather than differential rotation) which acts and so may produce either dextral or sinistral structures, depending on the sense of the flow. The effect of neighboring plagettes in avoiding the prominence and making it snake its way along the filament channel is modeled. It is suggested that feet are short-lived structures caused by the interaction of nearby magnetic fragments with the prominence field and may represent either the addition or the extraction of mass from the prominence.
Mackay Duncan H.
Priest Eric R.
van Ballegooijen Adriaan A.
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