Modeling Evaporative Upflows Through a Flux Tube of Nonconstant Area
Abstract
Chromospheric evaporation is a long studied part of solar flares. Spectroscopic observations of flares typically show subsonic upflows. This contrasts with simulations which consistently predict supersonic evaporation flows. One possible explanation is that the actual flows occur though flux tubes which expand from confined photospheric sources to volume-filling coronal field. Very few flare simulations to date have accounted for this geometry, and run instead with flare loops of uniform cross section. It is well known that transonic flows are dramatically affected by their geoemetry, and can exhibit shocks under certain circumstances.To investigate this we created a simple model of the canopy of magnetic field. This exhibited the expected expansion but also showed some cases of over-expansion followed by constriction. The flow through those flux tubes will encounter a kind of chamber. We then used a one-dimensional isothermal hydrodynamics to model the flow of plasma through such a chamber. According to this simulation, there exists a set of inflow parameters that will generate a standing shock inside the chamber. This solution results in a sonic outflow from a supersonic inflow.
- Publication:
-
AAS/Solar Physics Division Abstracts #47
- Pub Date:
- May 2016
- Bibcode:
- 2016SPD....47.0629U