# Accession Number:

## ADA170028

# Title:

## Thermal Stability of Static Coronal Loops. I. Effects of Boundary Conditions,

# Descriptive Note:

# Corporate Author:

## STANFORD UNIV CA CENTER FOR SPACE SCIENCE AND ASTROPHYSICS

# Personal Author(s):

# Report Date:

## 1985-11-15

# Pagination or Media Count:

## 11.0

# Abstract:

The authors investigate the linear stability of static coronal-loop models undergoing thermal perturbations. The effect of conditions at the loop base on the stability properties of the models is considered in detail. They consider the question of appropriate boundary conditions at the loop base and conclude that the most physical assumptions are that the temperature and density or pressure perturbations vanish there. However, if the base is taken to be sufficiently deep in the chromosphere, either several chromospheric scale heights or several coronal loop lengths in depth, then the effect of the boundary conditions on loop stability becomes negligible so that all physically acceptable conditions are equally appropriate. For example, one could as well assume that the velocity vanishes at the base. They calculate the growth rates and eigenmodes of static models in which a gravity is negligible throughout the loop, b the coronal heating is a relatively simple function, either constant per unit mass or per unit volume, and c the loop has a uniform cross- sectional area. It is found that all such models are unstable with a growth rate of the order of the coronal cooling time. The physical implications of these results for the solar corona and transition region are discussed. Keywords hydrodynamics. Author

# Descriptors:

# Subject Categories:

- Astrophysics