34th Solar Physics Division Meeting, June 2003
Session 4 Corona II
Poster, Monday, June 16, 2003, 3:30-5:00pm, Mezzanine

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[4.14] Effects of nonuniform flux tube area on prominence formation through thermal nonequilibrium

J. T. Karpen (NRL), S. E. M. Tanner (ICSI, George Mason Univ.), S. K. Antiochos (NRL)

We have developed a dynamic model of prominence formation in which steady but unequal footpoint heating causes a dynamic cycle of chromospheric evaporation, condensation, motion, and destruction (Antiochos et al. 1999a, 2000; Karpen et al. 2001, 2002). We have performed 1D hydrodynamic simulations with varying geometries and other properties to determine the limits of this mechanism under solar conditions. In previous studies we identified several key parameters that dictate the existence and characteristics of this cyclic process: the ratio of loop length to heating scale height, the loop apex height, the heating asymmetry, and dip depth. For those idealized calculations, the cross-sectional area of the flux tube was assumed to be constant. On the Sun, however, we expect the flux tube areas to be highly nonuniform, narrowing where the flux is constrained by stronger adjacent fields and expanding where neighboring fields are weaker.

To determine the effects of varying cross-sectional area on the evaporation and condensation processes at the core of our prominence formation model, we performed a set of 1D calculations with ARGOS, our 1D hydrodynamic code with adaptive mesh refinement. Representative field lines capable of supporting prominence condensations were selected from the 3D sheared-arcade model of the prominence magnetic field (DeVore & Antiochos 2000); the flux tube area was measured at intervals along these field lines and fit by a smooth analytic function suited for our computational approach. For comparison, ``control" loops also were set up with the same 1D loop geometry but with constant cross-section. As in our earlier calculations, these field lines were subjected to steady, localized heating at the footpoints and subsequent developments were monitored. Results from this study will be presented in the context of our previous studies and compared with prominence observations, as a critical test of our model.

This work was supported by NASA and ONR.

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Bulletin of the American Astronomical Society, 35 #3
© 2003. The American Astronomical Soceity.