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Session 2 - Everything Else.
Display session, Friday, June 27
Ballroom C, Chair: Richard Canfield

[2.68] Magnetic Compression in Current Sheets for Generating the Coronal Temperature Structure and Wind Acceleration

L. J. November (Southwest Research Institute)

A magnetostatic model for current sheets between oppositely directed potential fields predicts positive and negative pressure fluctuations, demonstrating the power of the static magnetic field to modify the ambient gas pressure. The predicted gas pressure fluctuations are consistent with our observation of 1-5 Mm dark and bright threads, made at the July 11 1991 eclipse made with the Canada-France-Hawaii Telescope (November and Koutchmy 1996). The remarkable property that dark threads are fully evacuated structures indicates that the static magnetic field is doing work on the overall ambient gas outside of the dark threads and current-sheet regions. It is straightforward to characterize the radial pressure function with an added term that contains the normal radial ambient magnetic-field variation. In the photosphere the gas pressure is dominated by the nominal atmosphere which we take as a polytrope in this demonstration of the effect. However the exponentially decaying polytropic form is soon overtaken by the magnetic pressure term. The modified atmosphere exhibits the salient features of the quiet solar atmosphere: a chromospheric temperature rise, a sharp transition region 1000 to 3000 km above the photosphere, and a 1.5-2.5 M^\circK corona whose radial variation closely agrees with coronal temperature observations. In addition the model can account for spreading of fields, a magnetic canopy in the chromosphere, a static outward wind acceleration, and provides an explanation for prominences as topologically isolated magnetically unmodified atmospheres.

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