Radiatively-driven downdrafts and redshifts in transition region lines. I. Reference model.
Abstract
We show that downdrafts driven by radiatively-cooling subarcsecond perturbations in the solar transition region can produce significant UV line redshifts consistent with those frequently observed on the solar disk, and, by extension, with those more recently observed on stars. We model in detail the thermo-hydrodynamic evolution of a non-linear isobaric spherical condensation inside an initially hydrostatic atmosphere, stratified both in density and temperature, and with initial conditions typical of a solar active region. We study the evolution of the atmosphere both neglecting the effect of magnetic fields and taking it into account by forcing conduction and motions to be only along the vertical direction. The synthesis of emitted flux and effective speed in four UV lines from model results shows the presence of intense redshifted components at speeds between 5 and 10km/s.
- Publication:
-
Astronomy and Astrophysics
- Pub Date:
- December 1996
- Bibcode:
- 1996A&A...316..215R
- Keywords:
-
- STARS: ATMOSPHERES;
- SUN: TRANSITION REGION;
- SUN: UV RADIATION;
- ULTRAVIOLET: STARS