Condensation Formation by Impulsive Heating in Prominences
Abstract
Our thermal nonequilibrium model for prominence formation provides an explanation for the well-observed presence of predominantly dynamic, cool, dense material suspended in the corona above filament channels. According to this model, condensations form readily along long, low-lying magnetic field lines when heating is localized near the chromosphere. Often this process yields a dynamic cycle in which condensations repeatedly form, stream along the field, and ultimately disappear by falling onto the nearest footpoint. Our previous studies employed only steady heating, as is consistent with some coronal observations, but many coronal heating models predict transient episodes of localized energy release (e.g., nanoflares). Here we present the results of a numerical investigation of impulsive heating in a model prominence flux tube and compare the outcome with previous steady-heating simulations. We find that condensations form readily when the average interval between heating events is less than the coronal radiative cooling time (~2000 s). As the average interval between pulses decreases, the plasma evolution more closely resembles the steady-heating case. The heating scale and presence or absence of background heating also determine whether or not condensations form and how they evolve. Our results place important constraints on coronal heating in filament channels and strengthen the case for thermal nonequilibrium as the process responsible for the plasma structure in prominences.
- Publication:
-
The Astrophysical Journal
- Pub Date:
- March 2008
- DOI:
- 10.1086/526335
- Bibcode:
- 2008ApJ...676..658K
- Keywords:
-
- Sun: corona;
- Sun: magnetic fields;
- Sun: prominences