Alfvénic-turbulence-heated magnetic loops: Effects of lateral expansion and magnetic twist

Using a 1.5-dimensional two-fluid magnetic loop model in which loops are heated by Alfvénic turbulence, we explore the effects on the loop parameters of the varying cross-section and the magnetic twist. The introduced magnetic twist is set to be around the kink instability threshold for a curved loop. It is found that: (i) The lateral expansion, which takes place close to footpoints, can significantly influence the heating profile, leading to a significant footpoint plasma flow. When observed on disc, the corresponding footpoint blue/red shift may be found for upper transition region lines, (ii) The effects introduced by magnetic twist are twofold. Firstly, the twist-related force may contribute to the axial force balance. Secondly, the projection effect reduces the electron and proton thermal conductivities. The former is found to be of little significance; however, the latter gives rise to considerable changes compared to the untwisted case.