AAS Meeting #194 - Chicago, Illinois, May/June 1999
Session 78. TRACE and Coronal Heating
Solar, Display, Wednesday, June 2, 1999, 10:00am-6:30pm, Southeast Exhibit Hall

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[78.06] TRACE and SVST Observations of an Active-Region Filament

A. A. van Ballegooijen, E. E. DeLuca (SAO)

In June 1998 the Transition Region and Coronal Explorer (TRACE) observed filaments and prominences in coordination with various ground-based solar observatories, including the Swedish Vacuum Solar Telescope (SVST) on La Palma. Here we present results for an active-region filament observed on June 21-22. This horse-shoe shaped filament had a "barb" that reached down from the filament spine to the chomosphere below. We use high-resolution images obtained at the SVST on June 21 from 18:03 to 19:04 UT to study the fine structure and dynamics of plasmas in the barb and other parts of the filament. The data consist of narrowband H\alpha images taken with the Lockheed Tunable Filtergraph operating at a cadence of 20 s. We present Doppler maps derived from these images.

The filament erupted six hours after the SVST observations. The eruption was observed with TRACE, which obtained images in Fe IX/X 171, Fe XII 195, Fe XV 284 and H I Ly\alpha. At the start of the event, a thin bright loop appears high above the filament at the location of the barb. We interpret this feature as the outline of a magnetic "bubble" which forms as a result of kink instability in the magnetic field that supports the filament. The bright loop appears to be due to particle acceleration and impulsive heating along certain field lines on the periphery of this magnetic structure. A few minutes later, the dark filament threads turn into emission and move outward, exhibiting a helical structure. We discuss the magnetic structure of the barb and its possible role in the filament eruption.

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