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R. W. Nightingale, M. J. Aschwanden, D. Alexander (LMSAL), F. Reale, G. Peres (Univ. Palermo)
The temperature Te(s) and density structure ne(s) of active region loops in EUV observed with TRACE is modeled with a multi-thread model. The model loops are synthesized from the summed emission of many loop threads that have a distribution of maximum temperatures and that satisfy the steady-state Rosner-Tucker-Vaiana (RTV) scaling law, modified by Serio et al. for gravitational stratification (RTVSp). From model-fitting of the 171 and 195 Åfluxes of 41 loops, which have loop half lengths in the range of L=4-320 Mm, we find: (1) The EUV loops can be explained by near-isothermal loop threads in the temperature range of Te ~0.8-1.6 MK with substantially smaller temperature gradients than predicted by the RTVSp model, (2) the loop base pressure, p0 ~0.3±0.1 dyne cm-2, is independent of the loop length L, it agrees with the RTVSp model for the shortest loops, but exceeds the RTVSp model up to a factor of 35 for the largest loops, and (3) the pressure scale height is consistent with hydrostatic equilibrium for the shortest loops, but exceeds the temperature scale height up to a factor of ~3 for the largest loops. This work was supported by the TRACE project at LMSAL (contract NAS5-38099).
Ref.: Aschwanden,M.J., Nightingale,R.W., Alexander,D., Reale,F., and Peres,G. 2000, ApJ, subm., ``Evidence for Nonuniform Heating of Coronal Loops Inferred from Multi-Thread Modeling of TRACE Data'',
URL="ftp://sag.lmsal.com/pub/aschwand/2000_reale.ps.gz"
The author(s) of this abstract have provided an email address for comments about the abstract: nightingale@lmsal.com