LARGE-SCALE PHENOMENA AT THE SUN ASSOCIATED
WITH FILAMENT ERUPTIONS OUTSIDE ACTIVE
I. M. Chertok, V. V. Grechnev, A. M. Uralov
Considering
the 12.09.1999 event as an example, we analyze manifestations of large-scale disturbances
associated with coronal mass ejections (CMEs) caused by filament eruptions
outside of active regions. The analysis is based on H-alpha
filtergrams, extreme ultraviolet and soft X-ray images
as well as coronagraphic data. The filament eruption occurred in relatively
weak magnetic fields, but it was accompanied by larger-scale phenomena than
flare events do. The eruption was followed by the development in several hours
of a large-scale arcade, whose bases were expanding flare-like ribbons. The
volume of the event was bounded by an “EIT wave”, which was quasi-stationary at
the solar surface, and expanded above the limb. The event was not impulsive;
thus, the “EIT wave” above the limb was a magnetic structure, which we
identified as a frontal structure of a CME based on the coincidence of their
shapes, structural details, and kinematics. Within the area of the event, three
kinds of dimmings were observed, whose nature was (a) plasma evacuation, (b)
plasma heating and its subsequent evacuation, and (c) absorption of emissions
in a system of filaments activated by the eruption. The fact that a dimming
appeared due to the plasma heating was revealed from soft X-ray data, whereas
four EIT channels did not demonstrate this. Thus, a question arises about the
correctness of some conclusions drawn previously from EIT data only. Transformations
of magnetic fields due to the eruption occurred also inside a stationary coronal
hole adjoining the area of the event. A CME expands self-similarly, with a rapidly
decreasing acceleration, that is not taken into account by a polynomial fit, which
is widely used.