Coronal Loops Heated by Turbulence-driven Alfvn Waves

Abstract

A two-fluid dynamic model of long-lived coronal loops is presented, whereby heating of the confined plasma is achieved by turbulence-driven Alfven waves. It is assumed that the nonthermal motions inferred from spectral line observations in the transition region are due to Alfven waves. It is also assumed that the turbulence is already fully developed when the waves are injected at the footpoint of the loop while the wave/turbulence energy is readily absorbed by the proton gas. The Coulomb coupling between protons and electrons subsequently heats the electron gas. The model produces a fairly uniform electron temperature in the coronal segment of the loop even though the heating is nonuniform. The model also reproduces electron densities of (1-4) × 109 cm-3, in the range inferred from observations, as well as a moderate flow speed around 10 km s-1 along the loop. The turbulence heating mechanism adopted in this Letter, however, cannot produce stable loops with temperatures T ≤ 1.3 × 106 K.