AAS 200th meeting, Albuquerque, NM, June 2002
Session 20. Pre-eruptive Magnetic Structures
Oral, Monday, June 3, 2002, 10:00-11:30am, San Miguel

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[20.04] Photospheric Vertical Current Density and Overlying Atmospheric Activity in an Emerging Flux Region

M. K. Georgoulis, D. M. Rust, P. N. Bernasconi (The Johns Hopkins University Applied Physics Laboratory), B. Schmieder (Observatoire de Paris, France)

Using high-resolution vector magnetograms obtained by the balloon-borne Flare Genesis Experiment (FGE), we construct maps of the vertical current density in the emerging flux region NOAA 8844. The vertical current density has been decomposed into components that are field-aligned and perpendicular to the magnetic field, thus allowing a straightforward identification of force-free areas, as well as of areas where the force-free approximation breaks down. Small-scale chromospheric activity, such as H \alpha Ellerman bombs and Ultraviolet bright points in 1600 Å\;show a remarkable correlation with areas of strong current density. Simultaneous data of overlying coronal loops, observed by TRACE in the Extreme Ultraviolet (171 Å\;and 195 Å\;), have been carefully co-aligned with the FGE photospheric maps. We find that the footpoints of the TRACE loops always coincide with strong vertical currents and enhancements of the current helicity density. We also investigate whether the force-free approximation is valid on the photosphere during various evolutionary stages of the active region.

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Bulletin of the American Astronomical Society, 34
© 2002. The American Astronomical Soceity.