| Presentation Title: | Characterizing Chromospheric Condensation with High-cadence Si~{\sc IV} Observations from IRIS |
| Author(s): | Dana Longcope, Chunming Zhu, Willow Reed, Alysa Derks |
Abstract:
Chromospheric flare ribbons are believed to result from coronal magnetic energy released by reconnection and propagating down to the cooler, lower atmosphere. They offer an opportunity to study flare reconnection using chromospheric observations at a spatial and temporal resolution higher than typically available by direct coronal observation. Transient downflows, known as chromospheric condensations, often occur at the leading edge of a ribbon as a prompt response to the energy input. These have properties that have recently been shown to relate to the coronal energy release process driving them. We use a set of IRIS observations of flare ribbons, made at high cadence in the sit-and-stare mode, to identify and analyze a sample of 134 chromospheric condensation episodes. Quantitative analysis of this large sample shows the distribution of pre-flare chromospheric scale heights and flare energy fluxes. Scale heights fall primarily between 200 - 1,500 km. Clear chromospheric condensation appears to occur in only about one fifth of all ribbon pixels. This indicates that flare energy release is necessary but not sufficient for producing the characteristic form of chromospheric condensation. We find that condensation pixels form clusters averaging one arcsecond in extent, all undergoing similar and concurrent time evolution. This suggests that coronal reconnection, and associated energy release, occur in localized patches whose spatial extent maps to around one arcsecond in the chromosphere.