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Astron. Astrophys. 352, L99-L102 (1999)

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Letter to the Editor

New insight into transition region dynamics via SUMER observations and numerical modelling

L. Teriaca 1, J.G. Doyle 1, R. Erdélyi 2 and L.M. Sarro 3

1 Armagh Observatory, College Hill, Armagh BT61 9DG, Northern Ireland (lte,jgd@star.arm.ac.uk)
2 Space and Atmosphere Research Center, Department of Applied Mathematics, University of Sheffield, England (Robertus@sheffield.ac.uk)
3 Laboratorio de Astrofisica Espacial y Fisica Fundamental (LAEFF) INTA, 28080 Madrid, Spain

Received 11 October 1999 / Accepted 2 November 1999

Abstract

We explore the idea that the occurrence of nano-flares in a magnetic loop around the O VI formation temperature could explain the observed red-shift of mid-low transition region lines as well as the blue-shift observed in low coronal lines ([FORMULA]K). Observations are compared to numerical simulations of the response of the solar atmosphere to an energy perturbation of [FORMULA] ergs representing an energy release during magnetic reconnection in a 1-D semi-circular flux tube. The temporal evolution of the thermodynamic state of the loop is converted into C IV 1548, O VI 1032 and Ne VIII 770 line profiles in non-equilibrium ionization. Performing an integration over the entire period of simulations, a redshift of [FORMULA] is found in C IV , while a blue-shift of [FORMULA] and [FORMULA] were derived for O VI and Ne VIII , respectively, in reasonable agreement with observations.

Key words: Magnetohydrodynamics (MHD) – line: profiles – Sun: activity – Sun: corona – Sun: transition region – Sun: UV radiation

Send offprint requests to: L. Teriaca

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© European Southern Observatory (ESO) 1999

Online publication: December 2, 1999
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