Models for solar magnetic loops. I. A simple theoretical model and diagnostic procedure

Abstract

In the present paper the quasi-static model of Landini & Monsignori Fossi (\cite{Landini75}) for coronal loops is improved and a simple diagnostic procedure is developed to compare the most important physical properties of the model with a set of spectral observations of loops such as those obtained by the CDS and SUMER instruments on SOHO. The model assumes quasi-static and isobaric conditions and solves the energy equation among radiative losses, a constant heating function and heat conduction. The model is allowed to have a variable loop section. To better match the latest observational results, an isothermal section of the loop is added at the top of the loop model; its effects on the diagnostic technique and on the shape of the unknown heating function are discussed. A numerical simulation is shown and the effect of the isothermal region is discussed. In a second paper (Brković et al. \cite{Brkovic01}, Paper II) the present model will be compared with observations from the SOHO satellite.