Observational evidence favors a resistive wave heating mechanism for coronal loops over a viscous phenomenon

¹ Department of Physics, University of Warwick, Coventry, CV4 7AL, UK e-mail: t.van-doorsselaere@warwick.ac.uk
² Centrum voor Plasma-Astrofysica, K.U.Leuven, Celestijnenlaan 200B, 3001 Leuven, Belgium

Received: 30 October 2006
Accepted: 2 June 2007

Abstract

Context.How coronal loops are heated to their observed temperatures is the subject of a long standing debate.

Aims.Observational evidence exists that the heating in coronal loops mainly occurs near the loop footpoints. In this article, analytically and numerically obtained heating profiles produced by resonantly damped waves are compared to the observationally estimated profiles.

Methods.To do that, the predicted heating profiles are fitted with an exponential heating function, which was also used to fit the observations. The results of both fits, the estimated heating scale heights, are compared to determine the viability of resonant absorption as a heating mechanism for coronal loops.

Results.Two results are obtained. It is shown that any wave heating mechanism (i.e. not just resonant absorption) should be dominated by a resistive (and not a viscous) phenomenon in order to accomodate the constraint of footpoint heating. Additionally it is demonstrated that the analytically and numerically estimated heating scale heights for the resonant absorption damping mechanism fit the observations very well.