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Diagnostics of electron-heated solar flare models. III - Effects of tapered loop geometry and preheatingA series of hydrodynamic numerical simulations of nonthermal electron-heated solar flare atmospheres and their corresponding soft X-ray Ca XIX emission-line profiles, under the conditions of tapered flare loop geometry and/or a preheated atmosphere, is presented. The degree of tapering is parameterized by the magnetic mirror ratio, while the preheated atmosphere is parameterized by the initial upper chromospheric pressure. In a tapered flare loop, it is found that the upward motion of evaporated material is faster compared with the case where the flare loop is uniform. This is due to the diverging nozzle seen by the upflowing material. In the case where the flare atmosphere is preheated and the flare geometry is uniform, the response of the atmosphere to the electron collisional heating is slow. The upward velocity of the hydrodynamic gas is reduced due not only to the large coronal column depth, but also to the increased inertia of the overlying material. It is concluded that the only possible electron-heated scenario in which the predicted Ca XIX line profiles agree with the BCS observations is when the impulsive flare starts in a preheated dense corona.
Document ID
19930031013
Document Type
Reprint (Version printed in journal)
External Source(s)
Authors
Emslie, A. G. (NASA Headquarters Washington, DC United States)
Li, Peng (California Univ. Berkeley, United States)
Mariska, John T. (U.S. Navy E.O. Hulburt Center for Space Research, Washington, United States)
Date Acquired
August 15, 2013
Publication Date
November 10, 1992
Publication Information
Publication: Astrophysical Journal, Part 1
Volume: 399
Issue: 2
ISSN: 0004-637X
Subject Category
SOLAR PHYSICS
Funding Number(s)
CONTRACT_GRANT: NAG5-500
CONTRACT_GRANT: NSF ATM-87-15195
CONTRACT_GRANT: NAGW-294
Distribution Limits
Public
Copyright
Other