ANNIHILATION OF MAGNETIC HELICITY: A NEW MODEL OF SOLAR FLARE ONSET MECHANISM
Kanya Kusano Submitted: 2003-05-13 00:10
Although magnetic reconnection is believed
as a key process of solar flares,
the onset mechanism of flares remains as a long-standing problem.
In this paper, we propose a new model
that solar flares can be triggered by magnetic reconnection
to convert the oppositely-sheared field into the shear-free field.
This process can be understood as
the annihilation between magnetic helicities
of the different signs, and is consistent with the
recent results of the helicity observations.
Numerical simulation was carried out to examine the model, and
it indicates that, if the helicity is sharply reversed within
a magnetic arcade, reconnection quickly grows
at the helicity inversion layer, driving the explosive dynamics.
The explosive process appears as a result of the nonlinear instability,
which can grow faster than exponential function of time.
These results well support the annihilation-of-helicity model
as the flare onset mechanism.
Based on the results, we predict that
the coexistence of the positive and negative helicity is
crucial for the onset of flares.
Authors: K.Kusano, T.Yokoyama, T.Maeshiro, T.Sakurai
Publication Status: COSPAR, Adv. Space Research, in press
Last Modified: 2003-05-13 00:10