On the role of transition region on the Alfvén wave phase mixing in solar spicules

Abstract

Alfvénic waves are thought to play an important role in coronal heating and solar wind acceleration. Here we investigate the dissipation of standing Alfvén waves due to phase mixing at the presence of steady flow and sheared magnetic field in the stratified atmosphere of solar spicules. The transition region between chromosphere and corona has also been considered. The initial flow is assumed to be directed along spicule axis, and the equilibrium magnetic field is taken 2-dimensional and divergence-free. It is determined that in contrast to propagating Alfvén waves, standing Alfvén waves dissipate in time rather than in space. Density gradients and sheared magnetic fields can enhance damping due to phase mixing. Damping times deduced from our numerical calculations are in good agreement with spicule lifetimes. Since spicules are short living and transient structures, such a fast dissipation mechanism is needed to transport their energy to the corona.

Mode coupling in solar spicule oscillations

“…In the considered conditions for a spicule, the values of all the presented parameters are (Murawski & Zaqarashvili 2010, Ebadi et al 2012, Fazel & Ebadi 2013): L = 6000 km (spicule length), a = 250 km (spicule radius), d = 0.2a = 50 km (inhomogeneous layer width), n e = 11.5 × 10…”