Properties of multistranded, impulsively heated hydrodynamic loop models

• Published in: Astronomy and astrophysics (Berlin) Vol. 552; pp. A17 - np
• Main Authors: Susino, R., Spadaro, D., Lanzafame, A. C., Lanza, A. F.
• Format: Journal Article
• Language: English
• Published: EDP Sciences 01.04.2013
• Subjects: Computer simulation; Density; Fluid flow; Heating; Hydrodynamics; Mathematical models; methods: numerical; Nanostructure; Strands; Sun: corona; Sun: UV radiation
• ISSN: 0004-6361; 1432-0746
• DOI: 10.1051/0004-6361/201116542

Aims. We investigate the capability of multistranded loop models subject to nanoflare heating to reproduce the properties recently observed in coronal loops at extreme ultraviolet (EUV) wavelengths. Methods. One-dimensional hydrodynamic simulations of magnetic loop strands were performed with an impulsive, footpoint-localised heating, with a moderate asymmetry between the two loop halves that was produced either by a sequence of identical nanoflares with a given cadence time tC or by a single energy pulse. The temporal evolution of the emission of a multistranded loop was modelled by simply combining the results of independent single-strand simulations, neglecting any spatial interaction among the strands, and was compared with TRACE and SDO/AIA light curves. The density excess with respect to hydrostatic equilibrium (the ψ factor) was evaluated with the filter-ratio technique. Results. Both loop models exhibit a density excess compared with hydrostatic equilibrium models, which agrees well with the observed values (1 ≲ ψ ≲ 12). However, in the single-pulse model the light curve and density excess maxima do not match. On the other hand, the models with a sequence of nanoflares predict strong emission at lower temperatures that cannot be reconciled with the available observations.