Coronal loops heated by turbulence-driven Alfvén waves: A two fluid model

Institute of Mathematical and Physical Sciences, University of Wales, Aberystwyth, SY23 3BZ, UK e-mail: ijo98@aber.ac.uk

Received: 5 July 2004
Accepted: 8 February 2005

Abstract

We present the results of a thorough parameter study of coronal loop models in the aim to explore the mechanism behind coronal heating. The two-fluid coronal loops described in this paper have lengths from 10 Mm to 600 Mm and consist of protons and electrons. The loops are treated with our unique, self-consistent, steady state dynamic loop model to derive the basic parameters (as introduced by Li & Habbal 2003, ApJ, 598, L125). The only heating mechanism assumed is turbulently generated Alfvén waves that carry the necessary flux from the chromosphere to energize the coronal plasma through preferential heating of the proton gas. Strong Coulomb coupling allows energy to pass efficiently from protons to electrons. We have control over the independent variables, driving scale (l) and Alfvén amplitude (ξ), which influence the dissipation and flux of these resonant waves. We find “mapping” the loop parameter response to varying l with fixed ξ a useful tool to find where certain conditions for each loop length exist. From this, we are able to pin-point where the coldest solution lies. For a loop of  Mm, the coolest loops have a maximum temperature of  MK. We also focus on a  Mm loop and vary both l and ξ so we can compare results with existing work. From this parameter mapping we can categorise the loop heating profiles. Our model indicates the existence of footpoint, non-uniformly and quasi-uniformly heated profiles. There is also strong evidence to suggest the same mechanism may apply to hot, SXT loops.