Simulations of Thermal Nonequilibrium in Raining Null-Point Topologies
Abstract
Coronal heating and the origins of slow solar wind remain central open questions of solar physics. The recent discovery of raining null-point topologies allows study of regions that hold implications for both questions. We present observations from SDO AIA that show persistent coronal condensations in null-point topologies formed by decaying active regions located near coronal hole boundaries. Coronal rain - catastrophically-cooled plasma precipitating along flux tubes - can be used as a tracer of several physical processes to provide insight into local heating and cooling dynamics. The rain forms in two observationally-distinct ways: along the lower spine and null, and within the closed loops under the fan surface. The former is attributed to interchange reconnection, while the latter is due to thermal nonequilibrium (TNE). TNE is caused by height-dependent footpoint heating, which creates a runaway cooling affect far from the loop base and triggers condensation. Using the one-dimensional HYDrodynamic and RADiation solver code (HYDRAD, Bradshaw & Mason 2003), we model asymmetric flux tubes with a large expansion factor where the loop apex occurs near the null point. A broad parameter study of heating scale heights and heating rates show the ranges within which rain could occur, and point to highly restricted coronal heating scale heights in the decaying active regions. This study provides predictions for Parker Solar Probe and Solar Orbiter observations.
- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2019
- Bibcode:
- 2019AGUFMSH53B3381A
- Keywords:
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- 2164 Solar wind plasma;
- INTERPLANETARY PHYSICS;
- 2169 Solar wind sources;
- INTERPLANETARY PHYSICS;
- 7509 Corona;
- SOLAR PHYSICS;
- ASTROPHYSICS;
- AND ASTRONOMY;
- 7863 Turbulence;
- SPACE PLASMA PHYSICS