More
or less isotropic or symmetrical dimmings and coronal waves extending throughout
a significant part of the disk (e.g.,
Thompson et al., 1998, 1999, 2000; Zarro et al., 1999; Klassen et al.,
2000; Warmuth et al., 2001).
Complicated GSM (near the sycle maximum):
--
Large-scale (global) EUV dimmings have a pronounced anisotropic
character and extend along some narrow lengthy structures (channels).
--
Characteristics of the canalized dimmings: depletion - up to 50%;
development time - a few tens of minutes; life time - several hours;
propagation speed - a few hundreds of km/s.
--
Bright coronal (EIT) wave either are not observed at all or they are
anisotropic also propagating inside a limited sector of the disk.
Sometimes
dimming waves take place instead of bright coronal waves.
Identification with coronal structures (preliminary remarks)Canalized dimmings outlines significant pre-event coronal features:
-- EUV emitting structures between remote (transequatorial) ARs (e.g., Khan and
Hudson, 2000);
-- some large-scale emitting chains (see Chertok, 2000);
-- boundaries of the large-scale magnetic fluxes;
-- H-alpha filament channels;
-- CH boundaries (see Thompson et al., 1998).
Canalized dimmings are closely associated with strong disturbance (perhaps of MHD wave character) and restructuring (opening) of the large-scale magnetic fields involved in the CME process in the complicated GSM.
