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Title:
The Possible Ascent of a Closed Magnetic System through the Photosphere
Authors:
Lites, B. W.; Low, B. C.; Martinez Pillet, V.; Seagraves, P.; Skumanich, A.; Frank, Z. A.; Shine, R. A.; Tsuneta, S.
Publication:
Astrophysical Journal v.446, p.877 (ApJ Homepage)
Publication Date:
06/1995
Origin:
APJ; KNUDSEN
Astronomy Keywords:
SUN: ATMOSPHERE, SUN: CORONA, SUN: MAGNETIC FIELDS, SUN: PROMINENCES, SUN: SUNSPOTS
DOI:
10.1086/175845
Bibliographic Code:
1995ApJ...446..877L

Abstract

We present a comprehensive interpretation of the evolution of a small magnetic region observed during its entire disk passage. The vector magnetic field measurements from the Advanced Stokes Polarimeter, along with Halpha and magnetogram measurements from the Lockheed SOUP instrument operating at the Swedish Solar Observatory on La Palma, and soft X-ray images from the Yohkoh satellite support the hypothesis that we have observed the passage of a nearly closed magnetic system through the photosphere into the corona. The observations suggest that as the magnetic flux begins to emerge into the photosphere it shows a rather simple geometry, but it subsequently develops a small delta-sunspot configuration with a highly sheared vector field along the polarity inversion line running through it. At that stage, the vector field is consistent with a concave upward magnetic topology, indicative of strong electric currents above the photosphere. An Halpha prominence is found above this inversion line when the delta-sunspot is fully formed. These observed features and the sequence of events are interpreted in terms of a nearly closed magnetic system that rises through the photosphere into the corona as a result of magnetic buoyancy. The magnetic system persists in the corona well after the dark delta-sunspot has disappeared in the photosphere We suggest that this coronal structure is in quasi-static equilibrium with its buoyancy partially countered by the weight of the plasma trapped at the bottom of closed magnetic loops. The plausibility of such a scenario is demonstrated by a three-dimensional magnetostatic model of the emergence of a closed, spheroidal magnetic system in the corona, in which the Lorentz force arising from cross-field currents is balanced by the gravitational and pressure forces. This theoretical model carries many features in common with the observed morphology of our active region.

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