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Energy balance in the solar transition region. I - Hydrostatic thermal models with ambipolar diffusionThe energy balance in the lower transition region is analyzed by constructing theoretical models which satisfy the energy balance constraint. The energy balance is achieved by balancing the radiative losses and the energy flowing downward from the corona. This energy flow is mainly in two forms: conductive heat flow and hydrogen ionization energy flow due to ambipolar diffusion. Hydrostatic equilibrium is assumed, and, in a first calculation, local mechanical heating and Joule heating are ignored. In a second model, some mechanical heating compatible with chromospheric energy-balance calculations is introduced. The models are computed for a partial non-LTE approach in which radiation departs strongly from LTE but particles depart from Maxwellian distributions only to first order. The results, which apply to cases where the magnetic field is either absent, or uniform and vertical, are compared with the observed Lyman lines and continuum from the average quiet sun. The approximate agreement suggests that this type of model can roughly explain the observed intensities in a physically meaningful way, assuming only a few free parameters specified as chromospheric boundary conditions.
Document ID
Document Type
Reprint (Version printed in journal)
External Source(s)
Fontenla, J. M. (NASA Marshall Space Flight Center; Alabama, University Huntsville, United States)
Avrett, E. H. (NASA Marshall Space Flight Center Huntsville, AL, United States)
Loeser, R. (Harvard-Smithsonian Center for Astrophysics Cambridge, MA, United States)
Date Acquired
August 14, 2013
Publication Date
June 1, 1990
Publication Information
Publication: Astrophysical Journal, Part 1
Volume: 355
ISSN: 0004-637X
Subject Category
Funding Number(s)
Distribution Limits