Definitions
Name |
Cause |
Physical Process |
Spectroscopic Signature |
---|---|---|---|
Core dimming |
Mass loss |
Ejection of emitting plasma from corona |
Simultaneous drop of multiple emission lines, with roughly the same percentage decrease |
Thermal dimming |
Temperature evolution |
Heating raises lower ionization states (e.g. a fraction of Fe IX becomes Fe X), cooling does the opposite |
Heating: Emission loss in lines with lower formation temperatures with roughly simultaneous emission gain in lines with higher formation temperatures. Cooling: reverse of above |
Obscuration dimming |
Obscuration |
Dim feature (e.g. filament) moves between observing location and bright feature (e.g. flare arcade) |
Drop of emission lines proportional to their absorption cross section in the obscuring material. Also apparent in EUV images |
Global dimming? |
Waves |
Shocks propagate globally, causing compression/rarefaction of plasma |
Apparent in EUV images, especially using difference movies |
Doppler shift dimming |
Doppler shift |
Fast moving plasma causes Doppler shift of emissions, which could start to shift outside instrument bandpass |
Doppler shift is seen in spectral measurements (e.g. EVE) |
This is a good place to have the debate about names and the expected spectroscopic signatures. It'd be best to use the comment section below until we reach a consensus, and then we can update the table.