Parametric Instabilities of Arc-Polarized Alfvén Waves Revisited

We revisit the parametric decay instability of arc-polarized Alfvén waves. Three dimensional magnetohydrodynamic (MHD) simulations show that the growth of decay instabilities of “shear” component of arc-polarized waves is in good agreement with linear growth rates of circularly polarized waves with effective value (root-mean-squared) amplitude. Daughter waves of the decay instability including “compressible” components of arc-polarized waves, whose frequency is twice as high as the shear component frequency, is also observed.