Numerical simulations of fast and slow coronal mass ejections |
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Tibor Toeroek Submitted: 2007-05-16 05:33
Solar coronal mass ejections (CMEs) show a large variety in their
kinematic properties. CMEs originating in active regions and accompanied
by strong flares are usually faster and accelerated more impulsively than
CMEs associated with filament eruptions outside active regions and weak
flares. It has been proposed more than two decades ago that there are two
separate types of CMEs, fast (impulsive) CMEs and slow (gradual) CMEs.
However, this concept may not be valid,
since the large data sets acquired in recent years do not show two distinct
peaks in the CME velocity distribution and reveal that both fast and slow
CMEs can be accompanied by both weak and strong flares. We present numerical
simulations which confirm our earlier analytical result that a flux-rope
CME model
permits describing fast and slow CMEs in a unified manner. We consider a
force-free coronal magnetic flux rope embedded in the potential field of
model bipolar and quadrupolar active regions. The eruption is driven by
the torus instability which occurs if the field overlying the flux rope
decreases sufficiently rapidly with height. The acceleration profile depends
on the steepness of this field decrease, corresponding to fast CMEs for rapid
decrease, as is typical of active regions, and to slow CMEs for gentle
decrease, as is typical of the quiet Sun. Complex (quadrupolar) active
regions lead to the fastest CMEs.
Authors: Toeroek T., Kliem B.
Projects: None
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Publication Status: Astronomische Nachrichten 328, No.8 (in press)
Last Modified: 2007-05-16 10:04
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