Static and dynamic solar coronal loops with cross-sectional area variations

ABSTRACT The Enthalpy Based Thermal Evolution of Loops approximate model for static and dynamic coronal loops is developed to include the effect a loop cross-sectional area which increases from base transition region (TR) corona. TR defined as part between top chromosphere location where thermal conduction changes an energy loss gain. There are significant differences constant due manner in reduced volume responds conductive enthalpy fluxes For with modest variation standard picture balance retained, corona being primarily heating losses corona, downward radiation space TR. As at apex increases, becomes thicker density larger. large areas, one radiation, playing increasingly unimportant role, thickness becoming fraction length. Approximate scaling laws derived that give agreement full numerical solutions density, but not temperature. non-uniform have higher peak temperature denser radiative cooling phase by order 50 per cent than case examples considered. They also show final rapid draining once approaches 1 MK. Although magnitude emission measure will be enhanced phase, there little change important observational diagnostic its dependence.